```

[Federal Register Volume 81, Number 251 (Friday, December 30, 2016)]
[Rules and Regulations]
[Pages 96572-96701]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 2016-30246]

[[Page 96571]]

Vol. 81

Friday,

No. 251

December 30, 2016

Part II

Department of Transportation

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 Federal Aviation Administration

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14 CFR Parts 21, 23, 35, et al.

Revision of Airworthiness Standards for Normal, Utility, Acrobatic, and 
Commuter Category Airplanes; Final Rule

Federal Register / Vol. 81 , No. 251 / Friday, December 30, 2016 / 
Rules and Regulations

[[Page 96572]]

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DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Parts 21, 23, 35, 43, 91, 121, and 135

[Docket No.: FAA-2015-1621; Amdt. Nos. 21-100, 23-64, 35-10, 43-49, 91-
346, 121-378, and 135-136]
RIN 2120-AK65

Revision of Airworthiness Standards for Normal, Utility, 
Acrobatic, and Commuter Category Airplanes

AGENCY: Federal Aviation Administration (FAA), DOT.

ACTION: Final rule.

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SUMMARY: The FAA amends its airworthiness standards for normal, 
utility, acrobatic, and commuter category airplanes by replacing 
current prescriptive design requirements with performance-based 
airworthiness standards. These standards also replace the current 
weight and propulsion divisions in small airplane regulations with 
performance- and risk-based divisions for airplanes with a maximum 
seating capacity of 19 passengers or less and a maximum takeoff weight 
of 19,000 pounds or less. These airworthiness standards are based on, 
and will maintain, the level of safety of the current small airplane 
regulations, except for areas addressing loss of control and icing, for 
which the safety level has been increased. The FAA adopts additional 
airworthiness standards to address certification for flight in icing 
conditions, enhanced stall characteristics, and minimum control speed 
to prevent departure from controlled flight for multiengine airplanes. 
This rulemaking is in response to the Congressional mandate set forth 
in the Small Airplane Revitalization Act of 2013.

DATES: Effective August 30, 2017.

ADDRESSES: For information on where to obtain copies of rulemaking 
documents and other information related to this final rule, see ``How 
To Obtain Additional Information'' in the SUPPLEMENTARY INFORMATION 
section of this document.

FOR FURTHER INFORMATION CONTACT: For technical questions concerning 
this action, contact Lowell Foster, Regulations and Policy, ACE-111, 
Federal Aviation Administration, 901 Locust St., Kansas City, MO 64106; 
telephone (816) 329-4125; email lowell.foster@faa.gov.

SUPPLEMENTARY INFORMATION: All sections of part 23 contain revisions, 
except the FAA did not make any changes to the following sections: 
23.1457, Cockpit Voice Recorders, 23.1459, Flight Data Recorders, and 
23.1529, Instructions for Continued Airworthiness. Sections 23.1459 and 
23.1529 were changed to align the cross references with the rest of 
part 23. The three sections otherwise remain unchanged relative to the 
former regulations.

Authority for This Rulemaking

    The FAA's authority to issue rules on aviation safety is found in 
Title 49 of the United States Code. Subtitle I, Section 106 describes 
the authority of the FAA Administrator. Subtitle VII, Aviation 
Programs, describes in more detail the scope of the agency's authority.
    This rulemaking is promulgated under the authority described in 
Subtitle VII, Part A, Subpart III, Section 44701. Under that section, 
the FAA is charged with promoting safe flight of civil airplanes in air 
commerce by prescribing minimum standards required in the interest of 
safety for the design and performance of airplanes. This regulation is 
within the scope of that authority because it prescribes new 
performance-based safety standards for the design of normal, utility, 
acrobatic, and commuter category airplanes.
    Additionally, this rulemaking addresses the Congressional mandate 
set forth in the Small Airplane Revitalization Act of 2013 (Pub. L. 
113-53; 49 U.S.C. 44704 note) (SARA). Section 3 of SARA requires the 
Administrator to issue a final rule to advance the safety and continued 
development of small airplanes by reorganizing the certification 
requirements for such airplanes under part 23 to streamline the 
approval of safety advancements. SARA directs that the rule address 
specific recommendations of the 2013 Part 23 Reorganization Aviation 
Rulemaking Committee (Part 23 ARC).

Table of Contents

I. Overview of Final Rule
II. Background
    A. Statement of the Problem
    B. History
    C. Summary of the NPRM
III. Discussion of the Public Comments and Final Rule
    A. Delayed Effective Date
    B. Overview of Comments
    C. General Public Comments
    D. Part 23, Airworthiness Standards
    1. Legacy Rules
    a. Cockpit Voice Recorders (Sec.  23.1457)/Flight Data Recorders 
(Sec.  23.1459)
    b. Instructions for Continued Airworthiness (Sec.  23.1529)
    2. Subpart A--General
    3. Subpart B--Flight
    4. Subpart C--Structures
    5. Subpart D--Design and Construction
    6. Subpart E--Powerplant
    7. Subpart F--Equipment
    8. Subpart G--Flightcrew Interface and Other Information
    E. Miscellaneous Amendments (Sec. Sec.  21.9, 21.17, 21.24, 
21.35, 21.50, 21.101, Appendix E to Part 43, and 91.323)
    1. Production of Replacement and Modification Articles (Sec.  
21.9)
    2. Designation of Applicable Regulations (Sec.  21.17)
     3. Issuance of Type Certificate: Primary Category Aircraft 
(Sec.  21.24)
    4. Flight Tests (Sec.  21.35)
    5. Instructions for Continued Airworthiness and Manufacturer's 
Maintenance Manuals Having Airworthiness Limitations Sections (Sec.  
21.50)
    6. Designation of Applicable Regulations (Sec.  21.101)
    7. Special Federal Regulations 23 (SFAR No. 23)
    8. Altimeter System Test and Inspection (Appendix E to Part 43)
    9. Increased Maximum Certification Weights for Certain Airplanes 
Operated in Alaska (Sec.  91.323)
    10. Additional Emergency Equipment (Sec.  121.310)
    11. Additional Airworthiness Requirements (Sec.  135.169)
IV. Regulatory Notices and Analyses
    A. Regulatory Evaluation Summary
    B. Initial Regulatory Flexibility Determination
    C. International Trade Impact Assessment
    D. Unfunded Mandates Assessment
    E. Paperwork Reduction Act
    F. International Compatibility and Cooperation
    G. Environmental Analysis
    H. Regulations Affecting Intrastate Aviation in Alaska
V. Executive Order Determination
    A. Executive Order 13132, Federalism
    B. Executive Order 13211, Regulations That Significantly Affect 
Energy Supply, Distribution, or Use
VI. How To Obtain Additional Information
    A. Rulemaking Documents
    B. Comments Submitted to the Docket
    C. Small Business Regulatory Enforcement Fairness Act
Appendix 1 to the Preamble--Current to Proposed Regulations Cross-
Reference Table
Appendix 2 to the Preamble--Abbreviations and Acronyms Frequently 
Used in This Document

I. Overview of Final Rule

    This rule amends Title 14, Code of Federal Regulations (14 CFR) 
part 23 by replacing current prescriptive design requirements with 
performance-based airworthiness standards. It maintains the level of 
safety associated with current part 23 except for areas addressing loss 
of control and icing where a higher level of safety is established, 
provides greater flexibility to applicants seeking certification of 
their airplane designs, and facilitates

[[Page 96573]]

faster adoption of safety enhancing technology in type-certificated 
products while reducing regulatory time and cost burdens for the 
aviation industry and FAA. This final rule also reflects the FAA's 
safety continuum philosophy,\1\ which balances an acceptable level of 
safety with the societal burden of achieving that level of safety, 
across the broad range of airplane types certificated under part 23.
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    \1\ The FAA's safety continuum philosophy is that one level of 
safety is not appropriate for all aviation.
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    This final rule allows the use of consensus standards accepted by 
the Administrator as a means of compliance to part 23's performance-
based regulations. The use of these FAA-accepted consensus standards as 
a means of compliance will streamline the certification process. 
However, consensus standards are one means, but not the only means, of 
showing compliance to the performance-based standards of part 23. 
Applicants, individuals, or organizations also have the option to 
propose their own means of compliance as they do today.
    In this final rule, the FAA adopts additional airworthiness 
standards to address certification for flight in icing conditions and 
enhanced stall characteristics to prevent inadvertent departure from 
controlled flight. Manufacturers that choose to certify an airplane for 
flight in Supercooled Large Drops (SLD) \2\ must demonstrate safe 
operations in SLD conditions. For those manufacturers who choose 
instead to certify an airplane with a prohibition against flight in SLD 
conditions, this final rule will require a means for detecting SLD 
conditions and showing the airplane can safely avoid or exit such 
conditions.
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    \2\ SLD conditions include freezing drizzle and freezing rain, 
which contain drops larger than those specified in appendix C to 
part 25, and can accrete aft of leading edge ice protection systems.
---------------------------------------------------------------------------

    This final rule adopts additional airworthiness standards to 
address enhanced stall characteristics to prevent loss of control 
(LOC). This final rule requires applicants to use new design approaches 
and technologies to improve airplane stall characteristics and pilot 
situational awareness to prevent LOC accidents.
    Additionally, this final rule also streamlines the process for 
design approval holders applying for a type design change, or for a 
third party modifier applying for a supplemental type certificate 
(STC), to incorporate new and improved equipment in part 23 airplanes. 
The revised part 23 standards are much less prescriptive; therefore, 
the certification process for modifications is simplified. 
Certification of an amended type certificate (TC) or STC under this 
final rule requires fewer special conditions or exemptions, lowering 
costs and causing fewer project delays.
    This final rule also revises 14 CFR part 21, ``Certification 
Procedures for Products and Articles,'' to simplify the approval 
process for low-risk articles. Specifically, it amends Sec.  21.9 to 
allow FAA-approved production of replacement and modification articles 
for airplanes certificated under part 23, using methods not listed in 
Sec.  21.9(a). This will reduce constraints on the use of non-required, 
low-risk articles, such as carbon monoxide detectors and weather 
display systems.
    Lastly, this final rule removes Special Federal Regulation No. 23 
(SFAR No. 23) and contains conforming amendments to 14 CFR parts 21, 
35, 43, 91, and 135. These conforming amendments align part 23 
references to the part 23 rules contained in this final rule.
    The FAA has analyzed the benefits and costs associated with this 
rule. This rule responds to the Small Airplane Revitalization Act of 
2013 (SARA) and to industry recommendations for performance-based 
standards. This rule reduces new certification processing by 
streamlining new certification processing. In addition, this rule 
improves safety by adding stall characteristic, stall warnings, and 
icing requirements. The following table summarizes the benefit and cost 
analysis, showing the estimated cost is substantially less than the 
benefits resulting from the combined value of the safety benefits and 
the cost savings. The following table shows these results.

                      Estimated Benefits and Costs
                            [2015 $ Millions]
------------------------------------------------------------------------
                                                       Safety benefits +
                                    Stall & spin +      cost savings =
                                      other costs       total benefits
------------------------------------------------------------------------
Total...........................  $0.8 + $3.1 = $3.9  $17.9 + $9.9 =
                                                       $27.8.
Present value at 7%.............  $0.8 + $3.1 = $3.9  $6.1 + $4.9 =
                                                       $11.0.
Present value at 3%.............  $0.8 + $3.1 = $3.9  $11.1 + $7.1 =
                                                       $18.3.
------------------------------------------------------------------------
* These numbers are subject to rounding error.

    Accordingly, the FAA has determined that the rule will be cost 
beneficial.

II. Background

A. Statement of the Problem

    The range of airplanes certificated under part 23 is diverse in 
terms of performance capability, number of passengers, design 
complexity, technology, and intended use. Currently, certification 
requirements of part 23 airplanes are determined by reference to a 
combination of factors, including weight, number of passengers, and 
propulsion type. The resulting divisions (i.e., normal, utility, 
acrobatic, and commuter categories) historically were appropriate 
because there was a clear relationship between the propulsion and 
weight of the airplane and its associated performance and complexity.
    Technological developments have altered the dynamics of that 
relationship. For example, high-performance and complex airplanes now 
exist within the weight range that historically was occupied only by 
light and simple airplanes. The introduction of high-performance, 
lightweight airplanes required subsequent amendments of part 23 to 
include more stringent and demanding standards--often based on the part 
25 requirements for larger transport category airplanes--to ensure an 
adequate level of safety for airplanes under part 23. The unintended 
result is that some of the more stringent and demanding standards for 
high-performance airplanes now apply to the certification of simple and 
low-performance airplanes. Because of this increased complexity, it 
takes excessive time and resources to certify new part 23 airplanes.

B. History

    In 2008, the FAA initiated the Part 23 Certification Process Study 
(CPS) \3\ to review part 23. Collaborating with industry, the CPS 
team's challenge was

[[Page 96574]]

to determine the future of part 23, given products at the time and 
anticipated future products. The team identified opportunities for 
improvements by examining the entire life cycle of a part 23 airplane, 
including operations and maintenance. The CPS recommended reorganizing 
part 23 using criteria focused on performance and design complexity. 
The CPS also recommended the FAA implement general airworthiness 
requirements, with the means of compliance defined in industry 
consensus standards.
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    \3\ See docket number FAA-2015-1621.
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    In 2010, following the publication of the CPS, the FAA held a 
series of public meetings to seek feedback concerning the findings and 
recommendations. Overall, the feedback was supportive of, and in some 
cases augmented, the CPS recommendations.
    One notable difference between the CPS findings and the public 
feedback was the public's request that the FAA revise part 23 
certification requirements for simple, entry-level airplanes. Over the 
past two decades, part 23 standards have become more complex as 
industry has generally shifted towards correspondingly complex, high-
performance airplanes. This transition has placed an increased burden 
on applicants seeking to certificate smaller, simpler airplanes. Public 
comments requested that the FAA focus on reducing the costs and time 
burden associated with certificating small airplanes by restructuring 
the requirements based on risk. The risk exposure for most simple 
airplane designs is typically low, because of the small number of 
occupants.
    On August 15, 2011, the Administrator chartered the Part 23 ARC to 
consider the following CPS recommendations:
     Recommendation 1.1.1--Reorganize part 23 based on airplane 
performance and complexity, rather than the existing weight and 
propulsion divisions.
     Recommendation 1.1.2--Certification requirements for part 
23 airplanes should be written on a broad, general, and progressive 
level, segmented into tiers based on complexity and performance.
    The ARC's recommendations took into account the Federal Aviation 
Modernization and Reform Act of 2012 (Pub. L. 112-95) (FAMRA), which 
requires the Administrator, in consultation with the aviation industry, 
to assess the airplane certification and approval process. The purpose 
of the ARC's assessment was to develop recommendations for streamlining 
and reengineering the certification process to improve efficiency, 
reduce costs, and ensure the Administrator can conduct certifications 
and approvals in a manner that supports and enables the development of 
new products and technologies and the global competitiveness of the 
United States aviation industry.\4\ FAMRA also directed the 
Administrator to consider the recommendations from the CPS.\5\
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    \4\ Public Law 112-95, section 312(c).
    \5\ Public Law 112-95, section 312(b)(6).
---------------------------------------------------------------------------

    ARC membership represented a broad range of stakeholder 
perspectives, including U.S. and international manufacturers, trade 
associations, and foreign civil aviation authorities (FCAAs).
    The ARC noted the prevailing view within industry was that the only 
way to reduce the program risk, or business risk, associated with the 
certification of new airplane designs was to avoid novel design 
approaches and testing methodologies. Under existing part 23, the 
certification of new and innovative products frequently requires the 
FAA's use of equivalent level of safety (ELOS) findings, special 
conditions, and exemptions. These take time, resulting in uncertainty 
and high project costs. The ARC emphasized that although industry needs 
to develop new airplanes designed to use new technology, current 
certification costs inhibit the introduction of new technology. The ARC 
identified prescriptive certification requirements as a major barrier 
to installing safety[hyphen]enhancing modifications in the existing 
fleet and to producing newer, safer airplanes.
    The ARC also examined the harmonization of certification 
requirements between the FAA and FCAAs, and the potential for such 
harmonization to improve safety while reducing costs. Adopting 
performance-based safety regulations that facilitate international 
harmonization, coupled with internationally accepted means of 
compliance, could result in both significant cost savings and the 
enabling of safety-enhancing equipment installations. The ARC 
recommended that internationally accepted means of compliance should be 
reviewed and voluntarily accepted by the appropriate aviation 
authorities, in accordance with a process established by those 
authorities. Although each FCAA would be capable of rejecting all or 
part of any particular means of compliance, the intent would be to have 
FCAA participation in the creation of the means of compliance to ease 
acceptance of the means of compliance.
    Based on the ARC recommendations and in response to FAMRA, the FAA 
initiated rulemaking on September 24, 2013. Subsequently, on November 
27, 2013, Congress passed the SARA, which requires the FAA to issue a 
final rule revising the certification requirements for small airplanes 
by--
     Creating a regulatory regime that will improve safety and 
decrease certification costs;
     Setting safety objectives that will spur innovation and 
technology adoption;
     Replacing prescriptive rules with performance-based 
regulations; and
     Using consensus standards to clarify how safety objectives 
may be met by specific designs and technologies.
    The FAA has determined that the performance-based-standards 
component of this final rule complies with the FAMRA and the SARA 
because it will improve safety, reduce regulatory compliance costs, and 
spur innovation and the adoption of new technology. This final rule 
will replace the weight-and propulsion-based prescriptive airworthiness 
standards in part 23 with performance- and risk-based airworthiness 
standards for airplanes with a maximum seating capacity of 19 
passengers or less and a maximum takeoff weight of 19,000 pounds or 
less. The standards will maintain or increase the level of safety 
associated with the current part 23, while also facilitating the 
adoption of new and innovative technology in general aviation (GA) 
airplanes.

C. Summary of the NPRM

    On March 7, 2016, the FAA issued a notice of proposed rulemaking 
(NPRM) proposing to revise part 23 in response to the SARA.\6\ In the 
NPRM, the FAA proposed to--
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    \6\ See 81 FR 13452.
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     Establish a performance-based regulatory regime; and
     Add new certification standards for LOC and icing.
    On May 3-4, 2016, the FAA held a public meeting to discuss the 
NPRM, hear the public's questions, address any confusion, and obtain 
information relevant to the final rule under consideration.\7\ The 
meeting notice and the transcripts are both in the docket. The FAA 
considered comments made at the public meeting along with comments 
submitted by the public to docket number FAA-2015-1621.
---------------------------------------------------------------------------

    \7\ See 81 FR 20264.
---------------------------------------------------------------------------

    The comment period closed on May 13, 2016.

III. Discussion of the Public Comments and Final Rule

A. Delayed Effective Date

    The FAA has decided it is necessary to delay the effective date of 
this final

[[Page 96575]]

rule for 8 months, until August 30, 2017.
    This final rule establishes a new performance-based system that 
will require additional training for both FAA and industry engineers, 
as noted in the NPRM regulatory evaluation summary. Several commenters 
expressed concern with the need for additional training and guidance in 
order to implement the new performance-based standards. The FAA finds 
that a delayed effective date will alleviate these concerns.
    Delaying the effective date will provide the FAA time to conduct 
the training necessary to implement this rule in a consistent manner. 
Additionally, the delayed effective date provides the FAA with 
sufficient time to develop guidance materials to ensure the FAA and 
industry have sufficient information to implement the new performance-
based standards consistently and correctly. Furthermore, while 
compliance with part 23, amendment 23-62 will remain a means of 
compliance with this final rule, a delayed effective date will allow 
industry time to develop new means of compliance and will facilitate 
the development of harmonized means of compliance among the FAA, 
industry, FCAAs.

B. Overview of Comments

    The FAA received 692 comments. Of the 692 comments, individuals 
submitted approximately 30 comments and industry and other foreign 
authorities submitted the remaining comments. The General Aviation 
Manufacturers Association (GAMA); Aircraft Electronics Association 
(AEA); Experimental Aircraft Association (EAA); and Aircraft Owners & 
Pilots Association (AOPA) (hereafter ``the Associations'') collected 
comments from their membership and presented these jointly. The vast 
majority of commenters overwhelmingly supported the proposed changes 
and provided constructive feedback so the FAA could clarify the safety 
intent in various sections of this rule.
    The FAA did not receive comments on the proposed changes to the 
following sections. These sections are adopted as proposed, and the 
explanations for the changes from the former regulations are contained 
in the NPRM.

 Sec.  23.1515, ``Instructions for continued airworthiness''
 Sec.  35.1, ``Applicability''
 Sec.  35.37, ``Fatigue limits and evaluation''
 Sec.  91.205, ``Powered civil aircraft with standard category 
U.S. airworthiness certificates: Instrument and equipment 
requirements''
 Sec.  91.313, ``Restricted category civil aircraft: Operating 
limitations''
 Sec.  91.531, ``Second in command requirements''
 Sec.  121.310, ``Additional Emergency equipment''
 Sec.  135.169, ``Additional airworthiness requirements''

C. General Public Comments

1. Rule Organization and Numbering
    In the NPRM, the FAA proposed a new organization and numbering 
scheme for part 23. Appendix 1 to the NPRM preamble contains a cross-
reference table detailing how the current regulations are addressed in 
the proposed part 23 regulations.
    The FAA received several comments suggesting the FAA change the 
regulation numbering scheme for proposed part 23. Commenters expressed 
concern that confusion or undue complexity would result because the 
proposed part 23 regulations do not correlate by section number to the 
former part 23 regulations. Commenters also noted that certain sections 
of the proposed rule would have shared the same section numbers as 
former part 23 regulations but would have contained completely 
different content.
    To avoid confusion, EASA proposed a new numbering system for 
Certification Specification 23 (CS 23) \8\ and part 23, where the new 
regulations would not share numbers with the former regulations to 
emphasize the difference in content between these two sets of 
regulations. EASA suggested the numbering for subpart A begin at Sec.  
23.2000, for subpart B at Sec.  23.2100, and so on, with the 
regulations numbers increasing by incremental steps of 5, i.e., 
Sec. Sec.  23.2005, 23.2010, and so on.
---------------------------------------------------------------------------

    \8\ EASA published an Advance Notice of Proposed Amendment (A-
NPA) 2015-06 on March 27, 2015, which set forth EASA's concept for 
its proposed reorganization of Certification Specification 23 (CS-
23). EASA also published a Notice of Proposed Amendment (NPA) 2016-
05 on June 27, 2016.
---------------------------------------------------------------------------

    The FAA agrees that the proposed numbering scheme would have caused 
confusion and undue complexity. The FAA has considered EASA's 
recommended new numbering scheme for part 23 and adopts it in the final 
rule. This recommendation harmonizes the numbering of part 23 and CS 23 
and provides new part 23 with a unique numbering scheme to avoid any 
confusion with former part 23. The FAA has determined the new numbering 
scheme also alleviates concerns about situations in which a 
certification basis would contain a former part 23 rule and a new part 
23 rule sharing the same section number, but different subject-matter.
    The FAA did not propose to change or renumber Sec. Sec.  23.1457, 
23.1459, and 23.1529; therefore, these sections remain as legacy rules 
in the new part 23.\9\
---------------------------------------------------------------------------

    \9\ The prescriptive requirements of Sec. Sec.  23.1457, 
23.1459, and 23.1529 are consistent in substance and numbering 
across parts 23, 25, 27, and 29.
---------------------------------------------------------------------------

    Air Tractor, Inc. (Air Tractor) suggested that the FAA retain 
former part 23, amendment 23-62, and create a new part (e.g., part 22) 
for the proposed performance-based regulations. It also suggested that 
proposed appendix A should remain appendix G to avoid over-writing 
existing appendix A.
    The FAA notes Air Tractor's recommendation to retain former part 23 
and to create a new 14 CFR part for the proposed regulations. However, 
this regulation is a rewrite of part 23 by replacing the prescriptive 
design requirements with performance-based airworthiness requirements, 
and the creation of an additional part would result in unnecessary 
confusion and overlap. However, the FAA will accept the use of the 
prescriptive means of compliance contained in former part 23 as one way 
to show compliance with new part 23. This will not apply to the 
sections containing new requirements, such as Sec. Sec.  23.2135, 
23.2150, and 23.2165 (proposed in the NPRM as Sec. Sec.  23.200, 
23.215, and 23.230). In addition, the FAA is issuing a policy statement 
identifying the means by which the FAA has addressed errors, findings 
of ELOS to various provisions of former part 23, and special 
conditions. This policy should be considered in defining means of 
compliance based on former part 23.
    The FAA also considered Air Tractor's recommendation to not rename 
appendix G. As proposed in the NPRM, the FAA removed appendixes A 
through F. However, the FAA is renaming former appendix G to part 23, 
as appendix A to part 23--Instructions for Continued Airworthiness, 
because this final rule is a complete rewrite and beginning the 
appendices at G instead of A may cause confusion.
    The following table identifies each requirement, its previously-
proposed section in the NPRM, and its corresponding section in this 
final rule.

[[Page 96576]]

----------------------------------------------------------------------------------------------------------------
                  NPRM                                Title                             Final rule
----------------------------------------------------------------------------------------------------------------
                                               Subpart A--General
----------------------------------------------------------------------------------------------------------------
Sec.   23.1.............................  Applicability and definitions  Sec.   23.2000.
Sec.   23.5.............................  Certification of normal        Sec.   23.2005.
                                           category airplanes.
Sec.   23.10............................  Accepted means of compliance.  Sec.   23.2010.
----------------------------------------------------------------------------------------------------------------
                                                Subpart B--Flight
----------------------------------------------------------------------------------------------------------------
                                                   Performance
----------------------------------------------------------------------------------------------------------------
Sec.   23.100...........................  Weight and center of gravity.  Sec.   23.2100.
Sec.   23.105...........................  Performance data.............  Sec.   23.2105.
Sec.   23.110...........................  Stall speed..................  Sec.   23.2110.
Sec.   23.115...........................  Takeoff performance..........  Sec.   23.2115.
Sec.   23.120...........................  Climb requirements...........  Sec.   23.2120.
Sec.   23.125...........................  Climb information............  Sec.   23.2125.
Sec.   23.130...........................  Landing......................  Sec.   23.2130.
----------------------------------------------------------------------------------------------------------------
                                             Flight Characteristics
----------------------------------------------------------------------------------------------------------------
Sec.   23.200...........................  Controllability..............  Sec.   23.2135.
Sec.   23.205...........................  Trim.........................  Sec.   23.2140.
Sec.   23.210...........................  Stability....................  Sec.   23.2145.
Sec.   23.215...........................  Stall characteristics, stall   Sec.   23.2150.
                                           warning, and spins.
Sec.   23.220...........................  Ground and watering handling   Sec.   23.2155.
                                           characteristics.
Sec.   23.225...........................  Vibration, buffeting, and      Sec.   23.2160.
                                           high-speed characteristics.
Sec.   23.230...........................  Performance and flight         Sec.   23.2165.
                                           characteristics requirements
                                           for flight in icing
                                           conditions.
----------------------------------------------------------------------------------------------------------------
                                              Subpart C--Structures
----------------------------------------------------------------------------------------------------------------
Sec.   23.300...........................  Structural design envelope...  Sec.   23.2200.
Sec.   23.305...........................  Interaction of systems and     Sec.   23.2205.
                                           structures.
----------------------------------------------------------------------------------------------------------------
                                                Structural Loads
----------------------------------------------------------------------------------------------------------------
Sec.   23.310...........................  Structural design loads......  Sec.   23.2210.
Sec.   23.315...........................  Flight load conditions.......  Sec.   23.2215.
Sec.   23.320...........................  Ground and water load          Sec.   23.2220.
                                           conditions.
Sec.   23.325...........................  Component loading conditions.  Sec.   23.2225.
Sec.   23.330...........................  Limit and ultimate loads.....  Sec.   23.2230.
----------------------------------------------------------------------------------------------------------------
                                             Structural Performance
----------------------------------------------------------------------------------------------------------------
Sec.   23.400...........................  Structural strength..........  Sec.   23.2235.
Sec.   23.405...........................  Structural durability........  Sec.   23.2240.
Sec.   23.410...........................  Aeroelasticity...............  Sec.   23.2245.
----------------------------------------------------------------------------------------------------------------
                                                     Design
----------------------------------------------------------------------------------------------------------------
Sec.   23.500...........................  Structural design............  Sec.   23.2250.
Sec.   23.505...........................  Protection of structure......  Sec.   23.2255.
Sec.   23.510...........................  Materials and processes......  Sec.   23.2260.
Sec.   23.515...........................  Special factors of safety....  Sec.   23.2265.
----------------------------------------------------------------------------------------------------------------
                                         Structural Occupant Protection
----------------------------------------------------------------------------------------------------------------
Sec.   23.600...........................  Emergency conditions.........  Sec.   23.2270.
----------------------------------------------------------------------------------------------------------------
                                       Subpart D--Design and Construction
----------------------------------------------------------------------------------------------------------------
Sec.   23.700...........................  Flight control systems.......  Sec.   23.2300.
Sec.   23.705...........................  Landing gear systems.........  Sec.   23.2305.
Sec.   23.710...........................  Buoyancy for seaplanes and     Sec.   23.2310.
                                           amphibians.
----------------------------------------------------------------------------------------------------------------
                                      Occupant System Design and Protection
----------------------------------------------------------------------------------------------------------------
Sec.   23.750...........................  Means of egress and emergency  Sec.   23.2315.
                                           exits.
Sec.   23.755...........................  Occupant physical environment  Sec.   23.2320.
----------------------------------------------------------------------------------------------------------------
                                         Fire and High-Energy Protection
----------------------------------------------------------------------------------------------------------------
Sec.   23.800...........................  Fire protection..............  Sec.   23.2325.
Sec.   23.805...........................  Fire protection in designated  Sec.   23.2330.
                                           fire zones and adjacent
                                           areas.
Sec.   23.810...........................  Lightning protection.........  Sec.   23.2335.
----------------------------------------------------------------------------------------------------------------

[[Page 96577]]

 
                                              Subpart E--Powerplant
----------------------------------------------------------------------------------------------------------------
Sec.   23.900...........................  Powerplant installation......  Sec.   23.2400.
Sec.   23.905...........................  Propeller installation.......  not adopted.
Sec.   23.910...........................  Powerplant installation        Sec.   23.2410.
                                           hazard assessment.
Sec.   23.915...........................  Automatic power or thrust      Sec.   23.2405.
                                           control systems.
Sec.   23.920...........................  Reversing systems............  Sec.   23.2420.
Sec.   23.925...........................  Powerplant operational         Sec.   23.2425.
                                           characteristics.
Sec.   23.930...........................  Fuel system..................  Sec.   23.2430.
Sec.   23.935...........................  Powerplant induction and       Sec.   23.2435.
                                           exhaust systems.
Sec.   23.940...........................  Powerplant ice protection....  Sec.   23.2415.
Sec.   23.1000..........................  Powerplant fire protection...  Sec.   23.2440.
----------------------------------------------------------------------------------------------------------------
                                              Subpart F--Equipment
----------------------------------------------------------------------------------------------------------------
Sec.   23.1300..........................  Airplane level systems         Sec.   23.2500.
                                           requirements.
Sec.   23.1305(a)(1)....................  Function and installation....  Sec.   23.2505
Sec.   23.1305(a)(3),(b),(c)............  Installation and operation...  Sec.   23.2605.
Sec.   23.1310..........................  Flight, navigation, and        Sec.   23.2615.
                                           powerplant instruments.
Sec.   23.1315..........................  Equipment, systems, and        Sec.   23.2510.
                                           installations.
Sec.   23.1320..........................  Electrical and electronic      Sec.   23.2515.
                                           system lightning protection.
Sec.   23.1325..........................  High-intensity Radiated        Sec.   23.2520.
                                           Fields (HIRF) protection.
Sec.   23.1330..........................  System power generation,       Sec.   23.2525.
                                           storage, and distribution.
Sec.   23.1335..........................  External and cockpit lighting  Sec.   23.2530.
Sec.   23.1400..........................  Safety equipment.............  Sec.   23.2535.
Sec.   23.1405..........................  Flight in icing conditions...  Sec.   23.2540.
Sec.   23.1410..........................  Pressurized system elements..  Sec.   23.2545.
Sec.   23.755(a)(3).....................  Equipment containing high-     Sec.   23.2550.
                                           energy rotors.
Sec.   23.1457..........................  Cockpit voice recorders......  Sec.   23.1457.
Sec.   23.1459..........................  Flight data recorders........  Sec.   23.1459.
----------------------------------------------------------------------------------------------------------------
                              Subpart G--Flightcrew Interface and Other Information
----------------------------------------------------------------------------------------------------------------
Sec.   23.1500..........................  Flightcrew interface.........  Sec.   23.2600.
New.....................................  Installation and operation...  Sec.   23.2605.
Sec.   23.1505..........................  Instrument markings, control   Sec.   23.2610.
                                           markings and placards.
New.....................................  Flight, navigation, and        Sec.   23.2615.
                                           powerplant instruments.
Sec.   23.1510..........................  Airplane flight manual.......  Sec.   23.2620.
Sec.   23.1515..........................  Instructions for continued     Sec.   23.1529.
                                           airworthiness.
----------------------------------------------------------------------------------------------------------------
                                                   Appendices
----------------------------------------------------------------------------------------------------------------
Appendix A to Part 23...................  Instructions for Continued     Appendix A to Part 23.
                                           Airworthiness.
----------------------------------------------------------------------------------------------------------------

2. Level of Safety
    In the NPRM, the FAA proposed amendments to part 23 to create an 
adaptive regulatory environment that could quickly embrace new safety-
enhancing technologies and potentially increase the level of safety.
    Wipaire, Inc. (Wipaire) viewed the proposal as allowing new and 
emerging technologies an effective means of certification, but one 
which offered little economic and certification relief to currently-
established methods and technologies.
    An individual commenter noted that the proposal would allow 
industry to push new techniques, materials, procedures, and targets 
without being hindered by the prescriptive requirements of former part 
23. However, the commenter stated that the proposal could allow subpar 
designs to exist before the data suggests a failure in compliance.
    The National Transportation Safety Board (NTSB), while recognizing 
consensus standards provide ``a collaborative framework for standards 
development,'' commented on a situation where, in its view, consensus 
standards did not provide adequate protection from catastrophic 
aerodynamic flutter. The NTSB expressed concern that design standards 
important for safety consideration may be overlooked, and it encouraged 
the FAA to refine its methodology.
    The FAA understands the concerns over the level of safety required 
by the performance standards. However, by leveraging the expertise of 
consensus standards organizations and FAA specialists in determining 
whether those standards are acceptable, those means of compliance 
should provide at least the same level of safety as under the former 
process.
    The FAA will continue to be responsible for determining that 
proposed airplane designs meet the applicable standards and ensuring 
that the proposed standards provide at least the same level of safety 
as did the former standards. Under new part 23, the first time an 
applicant presents a new proposal for a means of compliance, the FAA 
will require sufficient time and resources to determine whether it 
does, in fact, meet the objectives of those standards. This is the same 
process as under the former prescriptive standards. However, once the 
proposed means of compliance is determined to meet these standards, the 
approval process becomes more efficient. The FAA will no longer be 
required to issue special conditions (or other formal processes) to 
approve the means of compliance each time it is proposed, but can 
accept those means of compliance immediately as it is proposed.

[[Page 96578]]

3. Accommodating Hybrid and Electric Propulsion
    In the NPRM, the FAA recognized that historical general design and 
performance assumptions may not be valid today. The FAA noted that 
former part 23 did not account for airplanes equipped with new 
technologies, such as electric propulsion systems, which may have 
features entirely different from piston and turbine engines. The FAA 
therefore proposed new regulations based on airplane performance and 
potential risk.
    With respect to allowing new technologies, the Associations and 
Zee.Aero Inc. (Zee) were particularly concerned with the accommodation 
of alternative engines. The Associations stated that hybrid and 
electric propulsion is one of the near-term significant technological 
developments which absolutely must be accommodated into the new part 23 
regulations structure.
    Zee also commented on the advancements in hybrid and electric 
propulsion. Zee noted that new hybrid propulsion, control, and airframe 
configurations are already beginning to blur the lines between the 
traditional airplane categories. Zee questioned whether the FAA intends 
to continue to maintain strict airplane categories and create a new 
``category'' every time a new unique category configuration emerges. 
Lastly, Zee noted that Sec.  21.17(b) currently captures such airplane 
and wondered whether that section would become the norm for those 
cases.
    The regulations adopted in this final rule do allow for alternative 
types of propulsion. The FAA does not intend to continue to use Sec.  
21.17(b) for unique category airplanes. The FAA plans to shift these 
unique airplanes from Sec.  21.17(b) to part 23. Unique airplane that 
more closely resemble rotorcraft may be treated differently.
4. Impact of Rule on FAA Engineers and Designated Engineering 
Representatives (DERs)
    In the NPRM, the FAA proposed changes to part 23 that would 
eliminate the workload of exemptions, special conditions, and ELOS 
findings necessary to certificate new part 23 airplanes. The NPRM did 
not specifically address the role of Designated Engineering 
Representatives (DERs) in the proposed process.
    Several commenters addressed the impacts of the proposed rule 
changes on FAA engineers and DERs.
    NetJets Association of Shared Aircraft Pilots (NJASAP) and Kestrel 
Aircraft Company (Kestrel) expressed concern that the process intended 
to streamline technological adoption may significantly increase the 
FAA's workload. Kestrel contended the increased workload for FAA 
engineers will create certification bottlenecks at the Aircraft 
Certification Offices (ACOs) as their staff work to understand and 
implement the changes.
    The FAA recognizes workload during the transition to the new system 
may increase temporarily for industry and the FAA. Under the former 
part 23, the FAA had a workload of exemptions, special conditions, and 
ELOS findings necessary to certificate new part 23 airplanes. However, 
the FAA has determined in the long term, the workload for industry and 
the FAA will be less than the workload under former part 23. As 
estimated in the NPRM's regulatory evaluation summary, there will be 
savings resulting from streamlining the certification process by 
reducing the issuance special conditions, exemptions, and ELOS 
findings. The NPRM and final rule regulatory evaluation provides 
details for these cost savings and the methodology the FAA employed to 
estimate the cost savings.
    Other commenters expressed concerns about how the DER process will 
fit in with the new regulations. Air Tractor questioned whether DERs 
will find compliance with accepted means of compliance. The National 
Air Traffic Controls Association (NATCA) asked whether DERs will issue 
acceptance statements or approvals. NATCA asked how the FAA will change 
the designee policy and asked whether the FAA intends to accept or 
approve the standards. Textron Aviation (Textron) requested 
clarification of the FAA's transition plan regarding Organization 
Designation Authorization (ODA) and DER delegations, in particular 
regarding continuity of authority from the old amendments to the new.
    In response to concerns regarding the role of the DERs and ODA 
engineers, the FAA is developing transition training for the FAA 
engineers, ODA engineers, and the DERs. The FAA is also reviewing the 
relevant orders and policies for needed changes, but does not expect 
changes to the basic certification process as the FAA engineers and 
industry designees will still be responsible for finding compliance to 
the requirements in part 23. Furthermore, the FAA is developing a 
change management plan that will include formal training for both FAA 
engineers and staff and industry designees. Under existing policies and 
processes, designees must demonstrate the capability to make correct 
determinations of compliance with particular regulations before they 
are authorized to do so. This is unchanged by this rule. To the extent 
an applicant uses previously-accepted methods of compliance for which 
the designee has demonstrated such capability, the FAA may delegate 
compliance findings. If an applicant is proposing a new method of 
compliance, the designee's authority may be limited to only 
recommending a finding of compliance.
    Kestrel contended standardization among ACOs would likely decrease 
due to lack of clearly-defined criteria and that divergent 
certification expectations would exacerbate existing issues of 
inconsistent application and interpretation of requirements.
    While this final rule adopts high-level performance standards, the 
FAA intends to ensure consistent application through the process for 
determining the acceptability of their means of compliance. The FAA's 
certification standards staff will determine whether proposed consensus 
standards are acceptable and, if so, will publish a notice of 
availability of those standards in the Federal Register. The FAA will 
also maintain a publicly-available list of consensus standards that 
have been found to be acceptable as methods of compliance.\10\ For 
methods of compliance submitted by individual applicants, the FAA will 
continue to use the existing issue paper process, which includes full 
coordination with the standards staff to ensure standardization. The 
FAA recognizes the importance of having an internationally accepted 
means of compliance for part 23 airplanes. The FAA believes once there 
are internationally accepted means of compliance available, 
manufacturers may be reluctant to bypass these harmonized means to 
develop their own, unless they have an innovative process or new 
technology not already addressed. In either case, the FAA's processes 
should ensure flexibility and transparency to the extent permitted 
without violating proprietary interests of entities developing methods 
of compliance. Allowing for innovation and new technology is a major 
goal of this rule.
---------------------------------------------------------------------------

    \10\ As discussed in the NPRM, the FAA will have a similar 
process for determining whether a previous acceptance of a method of 
compliance should be rescinded, based on new information or service 
experience.
---------------------------------------------------------------------------

    In response to NTSB's concerns about new technology, the FAA finds 
that shifting compliance emphasis to industry consensus standards is 
critical to ensuring the safety of new

[[Page 96579]]

technology. This shift will allow the FAA to leverage technical experts 
from across the aerospace industry and from outside the traditional 
aerospace industry to develop standards for new technologies.\11\
---------------------------------------------------------------------------

    \11\ National Transportation Safety Board, Auxiliary Power Unit 
Battery Fire, Japan Airlines Boeing 787-8, JA829J, Boston, 
Massachusetts, January 7, 2013, AIR-14/01 (Washington, DC: NTSB, 
2014).
---------------------------------------------------------------------------

5. Necessity of Training
    In the NPRM's regulatory evaluation, the FAA assumed that FAA and 
industry part 23 certification engineers would require additional 
training as a result of this rule.
    Some commenters expressed concern with training needs required by a 
new system. Kestrel noted the proposed rule would increase the workload 
of DERs, primarily because they will require additional training and 
FAA coordination to ensure proper understanding and implementation of 
the new certification process. NATCA noted the significant changes to 
part 23 will necessitate training of all FAA engineers, DERs, and ODA 
engineers. In particular, NATCA said designees and ODAs cannot be 
authorized to find compliance to part 23 until trained or demonstrated 
competence. NATCA recommended the FAA amend its delegation and ODA 
policy documents to reflect the changes to part 23 and implement 
training as soon as possible.
    The NTSB expressed concern about increased demand on FAA engineers 
to evaluate new technologies as a result of the proposed changes to 
part 23. It suggested the FAA may face challenges similar to those 
encountered with the certification of the lithium-ion batteries in the 
Boeing 787, including insufficient guidance and education to ensure 
compliance with applicable requirements. The NTSB pointed to several 
safety recommendations it issued to the FAA in the wake of a lithium-
ion battery incident in a Boeing 787 in 2013, which centered around 
developing and providing adequate written guidance and training to 
certification engineers.
    The FAA agrees guidance and training are necessary and has delayed 
the effective date of this rule in order to complete the training 
development and implementation for ACOs, DERs, and industry. The FAA 
will continue to review orders and policies for needed changes.
6. Need for Revised or New Agency Guidance and Directives
    The FAA proposed Advisory Circular (AC) 23.10,\12\ Accepted Means 
of Compliance, to provide applicants guidance on the process of 
submitting proposed means of compliance to the FAA for consideration by 
the Administrator. The FAA also indicated in the NPRM that it would 
provide guidance as it determines what satisfies the performance-based 
standards.
---------------------------------------------------------------------------

    \12\ See docket number FAA-2015-1621.
---------------------------------------------------------------------------

    NATCA requested the FAA publish new or revised Orders and policy 
documents for public review and comment prior to the issuance of the 
final rule. For example, how would a certification engineer recognize 
what is a ``good compliance showing'' to a new part 23 requirement and 
how would that engineer explain the compliance showing to an authorized 
representative of the Administrator. Also, how would a certification 
engineer minimize or avoid allegations from an applicant that the 
engineer is being inequitable in the application of the new part 23 
requirement compared to how the requirements have been applied to other 
applicants.
    NATCA noted applicants often use legal processes for approval of 
type design changes to obtain less expensive or extensive certification 
requirements for a design proposal, and that the ``number of seats'' 
has been used previously to finesse operating requirements 
applicability. NATCA questioned whether the FAA will permit this under 
new part 23 as established by the airplane certification levels and 
whether there will be any check or limitation or safety judgment made 
on this potential use of new part 23. NATCA requested the FAA publish 
an Order or policy addressing this issue.
    One commenter was concerned the FAA will eventually leave the task 
of developing ACs for means of compliance to consensus bodies and 
individual applicants and opposed a system where public domain guidance 
must be purchased from a private entity. The commenter suggested that 
even if the FAA decides to discontinue updating its guidance, it should 
retain control and continue to permit the use of its existing guidance 
as well as provide a list of guidance with its status.
    The FAA agrees with NATCA that updated guidance is needed and is in 
the process of reviewing current orders and policies and will use 
existing processes to implement those changes. The FAA also recognizes 
the potential that some applicants will attempt to ``finesse'' the 
applicability of requirements for higher airplane certification levels 
by limiting the maximum passenger capacity of their proposed designs. 
This potential is inherent in any attempt to establish different levels 
of safety based on the concept of the ``safety continuum.'' The 
disincentive for such finessing is the reduction of functionality, and 
therefore profitability, of the resulting design.
    The FAA will continue to use all applicable ACs associated with 
part 23. Applicants will need to use the cross-reference table in this 
final rule preamble because the ACs will continue to reference the 
former section numbers. The FAA will expand the guidance in these ACs 
to better address the range of part 23 airplanes identified in industry 
consensus standard documents. The FAA has no plans to cancel the 
current ACs because they are still needed for older airplane 
modifications; therefore, the applicable ACs will still be available to 
applicants. Consensus standards bodies will develop means of compliance 
with the new regulations. The FAA will continue to develop ACs, as 
needed, to provide guidance to the public on what means of compliance 
would be acceptable. These functions are distinct, but complementary.
7. Inconsistent Language
    In the NPRM, the FAA proposed to remove prescriptive design 
requirements and replace them with performance-based airworthiness 
standards.
    Some commenters expressed concern with the lack of concreteness in 
the proposed regulations. Transport Canada stated the standards 
required the definition of a safety objective to clarify the meaning of 
some terms. The National Agricultural Aircraft Association (NAAA) was 
concerned the proposed regulations could result in inconsistent 
interpretations. NATCA viewed the rules as too ``stripped down'' for 
non-experienced people and commented that the use of ``vague'' terms 
would make it difficult to apply the new rules. Air Tractor contended 
the proposed rules consolidated existing requirements into fewer 
``general'' or ``vaguely'' worded rules.
    Other commenters addressed perceived inconsistencies in the 
language of the proposed revisions to part 23. The Associations noted 
some of the proposed rules focused on the applicant while others 
focused on the airplane.\13\ These commenters observed

[[Page 96580]]

it is important that the language of part 23 does not contradict part 
21, which establishes the procedures for obtaining design approvals. 
The commenters recommended the FAA adopt the regulatory language used 
elsewhere in the airworthiness standards, which impose requirements on 
the airplane design.
---------------------------------------------------------------------------

    \13\ For example, some of the proposed rules stated ``the 
applicant must show'' or ``the applicant must demonstrate,'' while 
others stated ``the airplane must.''
---------------------------------------------------------------------------

    The FAA recognizes the final rule uses high-level performance 
standards, and in some cases, the requirements are not tightly 
specified. However, the FAA finds that tight specification is not 
needed as this final rule is consistent with the safety objectives of 
the former prescriptive standards. The cross-reference table in this 
final rule identifies what sections of this final rule are intended to 
meet the safety objectives of the former regulations. Because this 
final rule is intended to achieve at least the same level of safety as 
the former regulations, this comparison may be used as a guide to the 
various levels of acceptable risk associated with each section.
    In response to the comment raised by GAMA and others, part 21 
imposes obligations on applicants for design approvals; therefore, the 
references to the applicant in this final rule are consistent.
8. Need for Additional Provisions in Part 23
    NATCA recommended the FAA add several provisions to part 23, 
including a requirement about loss of propeller or propeller control, 
provisions defining the levels of software certification needed, 
requirements that address impact protection from unmanned aircraft 
systems (UAS), and provisions about the introduction of new 
technologies.
    The FAA considered NATCA's comments; however, the FAA declines to 
adopt NATCA's recommendations at this time. The FAA is not adding 
requirements about loss of propeller or propeller control and 
provisions defining the levels of software needed because these are 
more appropriately addressed in means of compliance. The FAA also finds 
it unnecessary to include specific provisions about the introduction of 
new technologies because all the regulations in new part 23 are 
intended to allow the introduction of new technologies. Furthermore, it 
would be outside the scope of this rulemaking to add requirements 
addressing impact protection from UAS.
9. Development of Standards
    In the NPRM, the FAA described how industry groups associated with 
the Part 23 ARC discussed the development of consensus standards and 
how the ARC selected ASTM as the appropriate organization to initiate 
this effort.
    NATCA expressed concerns the FAA was relinquishing standardization 
and stated the FAA needed to articulate an expected minimum technology 
maturity level.
    The FAA's process for reviewing applicant's submissions to verify 
compliance with the safety standards will address NATCA's concern 
regarding technology. This review process will not change from the way 
the FAA currently reviews an applicant's regulatory compliance. One of 
the purposes of this rule is to provide greater flexibility to 
applicants in showing they meet the objectives of the safety standards, 
and thus ``standardization'' in the strictest sense goes against this 
purpose. Similarly, with respect to minimum technology level, another 
purpose of this rule is to spur innovation and technology adoption. 
Therefore, requiring a certain technology maturity level would 
contradict that purpose.
10. Restricted Category Agricultural Airplanes
    In the NPRM, the FAA did not specifically address single-engine 
agricultural airplanes.
    The NAAA commented that AC 21.25-1, Issuance of Type Certificate: 
Restricted Category Agricultural Airplanes, is currently used by the 
FAA to determine which part 23 certification requirements should not be 
part of an airplane's TC under Sec.  21.25. NAAA questioned how the 
requirements found inappropriate for single-engine agricultural 
airplanes in AC 21.25-1 will influence the certification process.
    The FAA notes the cross reference table located in this final rule 
correlates the sections referenced in AC 21.25-1 with the new 
regulations and associated means of compliance. Long term, the FAA 
recommends NAAA work with the FAA to develop means of compliance 
specific to restricted category agricultural airplanes.
11. International Cooperation Efforts
    In the NPRM, the FAA indicated the part 23 rulemaking was a 
harmonization project between the FAA and EASA. EASA published an 
Advance Notice of Proposed Amendment (A-NPA) 2015-06 on March 27, 2015, 
which set forth EASA's concept for its proposed reorganization of CS 
23. The FAA received several comments on harmonization.
    Garmin International (Garmin) and Agencia Nacional De Aviacao Civil 
Brazil (ANAC) commented on the significant differences between the NPRM 
and EASA's A-NPA. Garmin encouraged the FAA and EASA to resolve all 
differences before publishing their final regulations. Textron stressed 
the importance of harmonizing rule language with other major global 
certification authorities because a lack of harmonization would call 
into question whether one set of consensus standards would be adequate 
to achieve certifications worldwide. Textron expressed disappointment 
that the FAA's NPRM and EASA's A-NPA were not better aligned prior to 
publication. Textron explained the goal should be 100 percent 
harmonization with no exceptions. Garmin and Textron both commented on 
the significant costs that non-harmonized regulations would have on the 
industry.
    EASA commented on the importance of using, as much as possible, the 
same text in CS 23 and part 23. EASA explained, however, that CS 23 was 
more of a technical standard, while proposed part 23 addressed the 
applicant's responsibility. To better align with CS 23, EASA suggested 
that the FAA require ``the applicant's design'' to meet certain 
requirements rather than ``the applicant.''
    Optimal Aerodynamics Ltd (Optimal) recognized the harmonization 
efforts that have taken place, but sought reassurance from the FAA that 
revisions to part 23 would not lead to greater differences with other 
CAA's certification standards. Assuming CS 23 aligns with part 23, 
Optimal asked if it would be possible to base compliance on EASA's 
revised CS 23 when applying to the FAA for certification under new part 
23.
    The FAA agrees that harmonization with EASA's standards is 
important. While identical language is not the goal, the FAA has worked 
closely with EASA to ensure the same basic requirements for part 23 and 
CS 23 in order that both authorities can accept the same set of 
industry means of compliance. For example, as discussed previously, 
references to the applicant's obligations (``the applicant must'') are 
consistent with part 21 and with EASA's counterpart requirement that 
applicants ``show'' compliance. To further this effort, the FAA has met 
with EASA,\14\ received comments from EASA, and submitted comments on 
EASA's A-NPA. EASA incorporated many of the

[[Page 96581]]

FAA's comments on its A-NPA into its Notice of Proposed Amendment 
(NPA), published on June 23, 2016. In addition, the FAA incorporated 
many of EASA's comments to the NPRM into this final rule, such as 
including two new sections in Subpart G.
---------------------------------------------------------------------------

    \14\ See docket number FAA-2015-1621-0062.
---------------------------------------------------------------------------

12. Part 23 ARC Recommendations and the Existing Fleet
    As previously discussed in more detail, the FAA chartered the Part 
23 ARC in 2011 to consider the reorganization of part 23 based on 
airplane performance and complexity and to investigate the use of 
consensus standards. The Part 23 ARC's recommendations were published 
in 2013 and are available in the docket.
    Textron, Garmin, and several individuals commented on those ARC 
recommendations that were not proposed in the NPRM. In particular, 
these commenters requested the FAA adopt changes to 14 CFR part 21, 
``Certification Procedures for Products and Articles''; part 43, 
``Maintenance, Preventive Maintenance, Rebuilding, and Alteration''; 
and part 91, ``General Operating and Flight Rules''; as recommended by 
the ARC. These comments related to type certification procedures and 
airplane maintenance and operations. Similarly, several commenters 
requested the FAA adopt the ARC's recommendation to establish a 
``Primary Non-Commercial Category'' (PNC), which also would have 
required revisions to part 21.
    Several individual commenters noted that regulations applicable to 
existing airplanes make it difficult and expensive to implement safety 
improvements on those airplanes. These commenters questioned whether 
this rulemaking will address those issues.
    While the FAA recognizes the commenters' concerns regarding the 
need to minimize the certification process burden, the FAA is not 
making additional changes to parts 21 or 43 because they are outside 
the scope of this rulemaking. The intent of this rulemaking is to 
remove the prescriptive design requirements from part 23 and replace 
them with performance-based airworthiness requirements. The FAA is, 
however, contemplating a future rulemaking that would make additional 
changes to part 21.\15\
---------------------------------------------------------------------------

    \15\ The Part 21 SMS ARC published its recommendation reports 
(appendix A-G and appendix H-P) on January 14, 2015. Copies can be 
downloaded from the FAA Advisory and Committee site at http://www.faa.gov/regulations_policies/rulemaking/committees/documents/.
---------------------------------------------------------------------------

    The FAA also considers the commenters' recommendations to create a 
PNC category for aging General Aviation (GA) airplanes to be outside 
the scope of the NPRM. The FAA did not propose to create a PNC category 
for aging GA airplanes, as the ARC recommended, because it is also out 
of scope of this rulemaking. However, the FAA is working to address the 
ARC recommendations that focused on the existing fleet and part 21 
processes.
    With respect to the existing fleet, the FAA does not expect the 
revisions to part 23 to provide immediate benefits to older airplanes. 
However, when an owner of an older airplane applies for a change to the 
airplane's TC in accordance with Sec.  21.101, the applicant may choose 
to use the more flexible performance-based standards. In addition, as 
discussed later, the revision to Sec.  21.9 will enable expedited 
approval of certain parts that will benefit the existing fleet.
13. Impacts of the Proposed Rule on the Existing Fleet and on Open/
Active Projects
    The FAA received several comments on impacts to the existing fleet 
and on open/active projects.
    Kestrel and Garmin asked how, under the proposed rule, the FAA will 
address active projects, derivative airplanes and changes to existing 
models. Kestrel noted Sec.  21.101 requires regulatory compliance with 
the latest amendment while permitting certification on a case-by-case 
basis to an earlier amendment for changes to existing models and 
derivative airplanes. Kestrel noted it is common for applicants to 
receive significant compliance credit on the basis of ``similarity/
identicality.'' Kestrel asked how the FAA would grant permission for an 
applicant for a derivative airplane to certify entirely to a previous 
amendment.
    As discussed in the NPRM, the applicant has the option of using 
former part 23, amendment 23-62, as a means of compliance with new part 
23 (except in the areas where this final rule raises the level of 
safety, as discussed previously). Since the new rule, combined with 
this accepted means of compliance, is identical to the former part 23 
requirements (with exceptions noted in this preamble), methods of 
showing compliance--including ``similarity/identicality''--are not 
affected for changes to existing airplane models. Furthermore, Sec.  
21.101 only requires regulatory compliance with the latest amendment 
for airplanes weighing more than 6,000 pounds. Section 21.101 also 
provides relief for airplanes weighing more than 6,000 pounds when the 
change is not significant or when compliance with a later amendment 
would not contribute materially to the level of safety or would be 
impractical
    Garmin requested more details on the changes the FAA believes would 
streamline the process for design approval and lower costs and project 
delays. Garmin also asked the FAA to clarify how existing special 
conditions, ELOS findings, and exemptions would be handled if an 
applicant wants to ``step up'' to the new amendment.
    The FAA has determined the cost and time savings will result from 
the greater flexibility afforded by this final rule to both applicants 
and the FAA to find compliance for innovative new technologies. For 
traditional designs, the FAA expects applicants will be able to use the 
new part 23 in the same way older Civil Air Regulation, part 3 (CAR 3) 
airplanes are modified using former part 23 regulations. The FAA will 
still find compliance with the regulations, and since the new 
regulations allow greater flexibility by relying on accepted means of 
compliance, there should be little need for special conditions, ELOS 
findings, or exemptions, all of which require additional cost and time.
    An individual and Air Tractor expressed concern over third-party 
modifiers of airplanes who were not part of the original certification 
process. The commenters suggested a third-party modifier could propose 
its own means of compliance and regard it as proprietary, which may 
conflict with the means of compliance used in the original basis of 
certification. The commenters were concerned an STC or field approval 
could become more difficult and create more work for the FAA.
    The FAA notes the situation raised by the commenters currently 
exists with proprietary means of compliance, and this will not change 
with the new performance-based regulations. As under the former 
regulations, STC applicants will continue to be required to demonstrate 
that their changes, and areas affected by the changes, comply with the 
applicable regulations. The FAA anticipates no increased potential for 
conflict with the original design.
    NATCA recommended the FAA make changes to the general definitions 
of 14 CFR 1.1 concurrently with the part 23 rewrite, including revising 
the definition of ``consensus standard'' because it applies to more 
than Light-Sport Aircraft (LSA), adding the definition of ``proprietary 
standard,'' and reconciling the differences between the International 
Civil Aviation Organization (ICAO) airplane categories and the new 
definitions in part 23.
    The FAA has determined there is no need to define the terms, 
``consensus

[[Page 96582]]

standard'' and ``proprietary standard'' in this final rule. The current 
definition of ``consensus standard,'' by its terms, applies only to 
LSA. For purposes of this final rule, ``consensus standard'' has the 
meaning established in SARA, as discussed previously. The FAA does not 
use the term ``proprietary standard'' in the regulations adopted by 
this final rule. Finally, the FAA notes the definitions of the 
categories need to remain the same because this final rule does not 
change their applicability to the existing fleet of airplanes. Also, 
the difference between the ICAO airplane standards and part 23 
categories is based on weight and this rule does not affect that 
difference.
    While NJASAP supported the LOC In-Flight and SLD safety 
enhancements, it stated runway excursions are another significant risk. 
NJASAP supported requiring secondary or emergency braking systems and 
recommended a requirement for powerplant reversing systems to be 
installed on all level 3 and 4 high-speed airplanes to help reduce the 
top three accident types. For the goal of reducing loss-of-control 
accidents, NJASAP supported--along with other aerodynamic 
improvements--the FAA requiring a device that gives a trained pilot 
immediate feedback on the status of the airplane's wing. NJASAP 
recommended level 3 high-speed airplanes be included in the safety 
enhancements required for level 4 airplanes because they will be flying 
similar missions, and Original Equipment Manufacturers (OEMs) will 
target the level 3 certification category and stop certifying as many 
level 4 airplanes.
    The FAA finds that requiring emergency braking systems and 
powerplant reversing systems is beyond the scope of this rulemaking and 
would add additional costs. Requiring a device that gives a trained 
pilot immediate feedback on the status of the wing is also beyond the 
scope of this rulemaking, but a device like this could be used (and the 
FAA encourages its use) as part of the low-speed stall protection. 
Furthermore, the design specific nature of these recommendations is 
inconsistent with the FAA's goal of performance-based requirements in 
this rule revision. The new rule structure will allow for these 
alternative devices.
    The FAA considered NJASAP's recommendation that level 3 airplanes 
be included in the level 4 safety enhancements because of levels 3 and 
4 airplanes' similar missions. In this final rulemaking, the FAA 
retains the traditional approach of drawing safety distinctions based 
on airplane capacity and operational risk.
    The NTSB commented on the proposed rule's focus on qualitative 
design methodologies, but recommends the use of both quantitative and 
qualitative design methodologies as the FAA has done historically. The 
NTSB pointed to proposed Sec. Sec.  23.305 and 23.1315 and the 
continued reliance on the requirements of former Sec.  23.1309, which 
only addresses the effects of single failures. The NTSB contended that 
the consideration of multiple failures should be required in the 
revised part 23 when active systems may potentially be used in 
commercial operations and the airplane may be more complex.
    The FAA's intent in this rule is to maintain the current level of 
safety. The FAA is currently engaged in rulemaking for transport 
airplanes to address the NTSB's concerns. Depending on the outcome of 
that rulemaking, the FAA may consider similar rulemaking for part 23 in 
the future.
14. Legal Issues
    In the NPRM, the FAA proposed to accept consensus standards as a 
means of compliance with the new part 23 performance-based regulations. 
Abbott Aerospace SEZC, Ltd. (Abbott) and Kestrel questioned the 
legality of using ASTM as a means of compliance.
    Abbott stated the proposed change is illegal as the new ASTM 
standards constitute de facto law despite being labelled ``advisory'' 
and are the only realistic path to certify an airplane. Abbott claimed 
this mislabeling will lead to confusion and cause industry to incur the 
cost of purchasing the ASTM standards under the belief that they 
constitute law and that compliance is mandatory.
    Kestrel also questioned the legality of relinquishing FAA guidance 
to a private entity and of using ASTM as the single standards body. 
Kestrel opposed handing over public domain guidance to a private entity 
for creation of its own standards, which will be provided back to the 
industry for a fee. Kestrel suggested the FAA retain control and 
continue to permit the use of its existing guidance.
    In light of the comments, the FAA reviewed its approach to use 
consensus standards as means of compliance with this rule. On November 
27, 2013, the President of the United States signed SARA whereby 
Congress mandated the FAA use consensus standards to clarify how safety 
objectives may be met by specific designs and technologies. SARA also 
requires the FAA to comply with the ``National Technology Transfer and 
Advancement Act of 1995'' (NTTAA), which directs Federal agencies to 
use voluntary consensus standards in lieu of government-mandated 
standards when practicable. This rulemaking also complies with the 
Office of Management and Budget (OMB) Circular A-119, ``Voluntary 
Consensus Standards,'' which provides guidance on how to comply with 
NTTAA. OMB Circular A-119 specifically addresses the issues raised by 
the commenters and establishes the policy that agencies should consider 
cost to regulated entities of using consensus standards as one factor 
in determining whether those standards are ``reasonably available.'' 
The FAA has considered the cost of ASTM standards and determined, for 
purposes of this rulemaking, ASTM standards are reasonably available 
because the interested parties have access to them through their normal 
course of business and the price is low enough that interested parties 
can easily purchase them.
    In addition, ASTM will not create de facto law nor be the single 
standard-setting body, or custodian of public domain documents. The FAA 
expects to accept means of compliance from individuals, companies, and 
other standards bodies, including ASTM. While the use of a previously 
accepted means of compliance will likely expedite the certification 
process, no applicant will be required to use ASTM or any other means 
of compliance. Instead, an applicant may propose its own means of 
compliance for acceptance, or demonstrate compliance to the new rule by 
using the prescriptive provisions in former part 23 and supporting 
guidance--all of which will remain publically available. As discussed 
in the NPRM, the long-term benefit and cost reduction provided by this 
rule is that it will allow the introduction of new technologies without 
the formal processes that currently increase certification costs and 
inhibit innovation.
    The American Association of Justice (AAJ) commented that the new 
part 23 performance standards should not preempt state tort law because 
state tort law functions as a necessary adjunct to federal regulations 
that impose only minimum standards of care. AAJ urged the FAA to avoid 
any language that could allow the new standards to be construed as 
preempting state law for defectively designed or produced airplane, or 
characterizing the standards beyond what is authorized by the Federal 
Aviation Act.
    AAJ's comment regarding preemption of state tort law in aviation 
cases was

[[Page 96583]]

not a topic of this rulemaking. Rather, it is the subject of current 
litigation in federal court regarding interpretation of the FAA's 
enabling legislation. The outcome of that litigation is neither the 
subject of this rulemaking, nor will this rulemaking affect that 
outcome. However, as noted by the Supreme Court in previous litigation, 
it is the applicant's obligation to comply with airworthiness 
standards; the FAA cannot guarantee such compliance.
15. Regulatory Evaluation
    The FAA received comments from five commenters (four companies and 
one individual) on the summary of the regulatory evaluation published 
as part of the NPRM. In the NPRM regulatory evaluation, the FAA 
requested that commenters include data supporting their comments, but 
no commenter submitted any cost or benefit data with its comments.
a. General
    Kestrel stated that all applicants will benefit from decreased 
certification costs and hopes the cost savings are tangible and can be 
realized in a short time frame; however, Kestrel anticipates an 
increased workload after the rule is adopted to train its personnel on 
the new standards. Abbott, Air Tractor, and one individual commenter 
characterized the cost benefit analysis as incomplete.
    In the NPRM, the FAA stated that if the proposed rule saves only 
one human life--for example, by improving stall characteristics and 
stall warning--that alone would result in the benefits outweighing the 
costs of the rule change. Air Tractor characterized this statement as 
``vacuous.'' Air Tractor went on to comment that its industry places a 
high value on protecting human life and expends enormous energy, 
talent, and resources to protect it.
    The FAA intended this statement as a simplified break-even analysis 
of the likely benefits of the proposed rule. It was not intended to 
replace the costs and benefits detailed in the regulatory evaluation. 
The complete regulatory evaluation, located in the docket, is more 
comprehensive than the summary that appears in the NPRM preamble and 
contains the estimates provided to the agency by industry.\16\
---------------------------------------------------------------------------

    \16\ See Docket Number FAA-2015-1621.
---------------------------------------------------------------------------

    Abbott stated there was no clear indication of how the proposed 
change would reduce net cost or expedite the certification process. 
Abbott concluded there were ``potential significant additional'' costs 
created by the proposed rule, but no obvious or defined cost reduction. 
Abbott characterized the proposed regulations as having an unknown cost 
impact and stated these unknown costs represent a yet-unassessed and 
unavoidable cost for airplane developers. Abbott also stated that any 
additional cost the proposed rule places on industry that is not offset 
by cost reduction elsewhere does harm to the industry.
    The FAA notes that under the proposed rule, applicants may choose 
to use an industry consensus standard, the former part 23 standards 
(available at no cost), or its own means of compliance accepted by the 
Administrator. The FAA presumes an applicant will use these options to 
make the best economic choices given the circumstances of design and 
development for its product. Such choices are an inherent strength of a 
performance-based standard, but cannot effectively be analyzed for 
costs or benefits, especially if a design encompasses new technology 
that was never subject to the former regulation. Similarly, the FAA 
cannot predict the viability of the products or the financial health of 
an unknown start-up company under a regulation that allows for, but 
does not require, its products be used in any airplane design.
b. Impact on Small Entities
    Air Tractor commented the FAA's analysis of the proposed rule 
impact on small entities did not include Air Tractor and Thrush 
Aircraft (Thrush).
    Air Tractor was concerned that data from only 5 entities was used 
in the regulatory flexibility analysis. It noted the FAA should have 
included every company that has active manufacturing activities and the 
data used were non-representative of the overall industry. Air Tractor 
also indicated the inclusion of Thrush and itself would have doubled 
the number of employees and annual revenues represented in the 
analysis. Additionally, Air Tractor believed the FAA should have also 
included the TC holders of small airplanes that are no longer being 
manufactured but require TC support and STC holders that certificate 
products to the part 23 standards.
    Finally, Air Tractor concluded that the omission of non U.S.-owned 
entities that ``operate'' in the United States presented a ``distorted 
view of the true impact'' of the proposed rule on the general aviation 
industry in the United States.
    The FAA conducted its analysis in accordance with the ``Small 
Business Regulatory Flexibility Act.'' For each regulatory flexibility 
analysis, an agency is required to provide a description of and, where 
feasible, an estimate of the number of small entities to which its 
proposed rule would apply. Many, if not most, small entities do not 
provide publically available information such as employment data that 
would allow an agency to determine if a business qualifies as a small 
entity under the guidelines of the Small Business Administration (SBA). 
Nor is there publicly available revenue data for these entities that 
make it possible to determine the burden of a proposed or final rule on 
these entities. The FAA does not have the authority or the means to 
require any entity to report its employment or revenue data. 
Accordingly, the FAA does not have the requisite knowledge of every 
company that still has active manufacturing activities that might be 
subject to the proposed rule.
    The small business entities the FAA used in its analysis had 
provided data on their employment and revenue either through the 
regulations of U.S. DOT Form 41, the Securities and Exchange 
Commission, or through news releases that the entities made public. 
Neither Air Tractor nor Thrush have such data on record, and Air 
Tractor did not provide employment or revenue data for itself as part 
of its comment.
    The five entities examined as part of the FAA's analysis qualified 
as small entities under the SBA criteria and were either actively 
manufacturing airplane or were under new ownership and had publically 
announced they were working toward setting up an airplane manufacturing 
line that would be subject to part 23. Airplanes previously 
certificated under part 23 will not be affected by the regulations 
affecting new certifications, so TC holders of operating airplanes who 
are not actively seeking some certification are not appropriately 
excluded from the analysis. The same holds true for STC holders that 
used the part 23 standards in effect at the time of these airplane 
original certifications.
    The regulatory flexibility analysis conducted for the proposed rule 
did not include any non-U.S. entities because, similar to the domestic 
firms referenced above, the employment and revenue information required 
for the analysis was not publicly available.
c. Icing
    Textron stated that although the FAA identified a need for improved 
certification standards for operation in severe icing conditions, it 
did not provide a cost benefit analysis to show that part 23 airplanes 
would benefit from them.
    The FAA did conduct a cost benefit analysis of the icing 
requirement. Flying into icing is risky and the ARC identified part 23 
airplane icing

[[Page 96584]]

accidents. The FAA contacted industry, and some Part 23 ARC members 
indicated to the FAA that the new rule and standards reflect current 
industry practices for detecting and exiting icing conditions. 
Additionally, the rule to certify that the airplane can operate safely 
in SLD is voluntary. When compliance is voluntary, or no change in 
industry practice will occur from a new regulation, the FAA determines 
the rule to be minimal cost. This determination was made in the initial 
regulatory impact analysis and is made in the final regulatory impact 
analysis.
    In the NPRM, the FAA proposed that for a part 23 airplane to be 
certificated to fly in known icing conditions, an applicant would have 
to demonstrate operation in the icing conditions defined in part 25 
appendix C. This requirement did not change from the former part 23 
requirements. As a safety matter, for many years airplanes currently 
certificated under part 23 have demonstrated the ability to detect and 
safely exit from freezing rain and freezing drizzle conditions.
    The standards and requirements for the various icing certification 
levels were discussed extensively with the Part 23 Icing ARC (Icing 
ARC) and the Part 23 ARC. The new rule and standards for detecting and 
exiting freezing drizzle and freezing rain are consistent with and 
include significant parts of the Icing ARC's recommendations.
d. Part 23 Limitation
    Textron recommended the FAA change the limitation on part 23 
airplanes from its proposed gross takeoff weight limit of 19,000 pounds 
(maintaining the current part 23 limit) to a maximum payload limitation 
of 6,000 pounds. Textron stated the change would have a dramatic 
positive impact on the potential costs and benefits of the proposed 
change.
    This change is beyond the scope of this rulemaking for the FAA to 
consider. This change was not proposed by the FAA and would be a 
fundamental change to part 23 that could potentially affect 
certification of airplanes under part 25.
e. Reporting and Recordkeeping Requirements
    The FAA stated it expected minimal new reporting and recordkeeping 
requirements would result from the proposed rule and requested comments 
on this finding. The FAA received no comments on reporting or 
recordkeeping requirements.
    Therefore, the FAA adopts the regulations as proposed, and will 
make no change to the regulatory evaluation regarding the reporting and 
recordkeeping requirements.
16. Out of Scope Statement
    Several commenters requested changes to regulations or to existing 
FAA processes and guidance materials that are not directly related to 
this rulemaking. The FAA is not addressing these comments specifically 
because they are beyond the scope of this rulemaking.

D. Part 23, Airworthiness Standards

1. Legacy Rules
a. Cockpit Voice Recorders (Sec.  23.1457)/Flight Data Recorders (Sec.  
23.1459)
    In the NPRM, the FAA proposed to use the same cockpit voice 
recorder (CVR) and flight data recorder (FDR) standards that exist in 
former Sec. Sec.  23.1457 and 23.1459. The proposed rule included 
revised references to other sections of proposed part 23, but no 
substantive changes to those standards.
    The NTSB stated it is pleased the NPRM retained the needed 
prescriptive design standards in proposed Sec. Sec.  23.1457 and 
23.1459. The NTSB added it would be appropriate for the FAA to include 
a requirement for image recorders, which it described in its Safety 
Recommendation A-13-12, dated May 6, 2013.
    The FAA considered the NTSB's request to add requirements for image 
recorders. No functional or operational requirements to record images 
has ever been proposed or evaluated for costs and benefits. Any such 
requirements would constitute significant rulemaking and require public 
participation, and therefore exceeds the scope of this rule.
    EASA and the Associations stated the CVR and FDR requirements stem 
from ICAO annex 6 requirements, which are already based upon EUROCAE 
industry standards ED-155; ED-112A, ``MOPS for Crash Protected Airborne 
Recorder System;'' and ED-155, ``MOPS Lightweight Flight Recording 
Systems.'' They suggested the FAA redraft the regulations to be more 
performance-based and number the regulations in accordance with any new 
numbering scheme, and change the references from the operating 
regulations as soon as practical.
    The interplay between operation and certification regulations 
remains the reason for carrying the current standards unchanged into 
the new part 23. Redrafting them to objective standards, as suggested 
by EASA and the Associations could result in varying data sets between 
operators without any discernible benefit for such variation. Changing 
the standards only for part 23 airplanes certificated after a 
particular date would also require significant changes to the 
regulations under which the airplanes operate, adding complication 
without any noted benefit.
    NJASAP supported the FAA's decision to maintain the current 
standards for cockpit voice recorders (Sec.  23.1457), noting that 
removing the current prescriptive requirements could hinder the conduct 
of future accident investigations. NJASAP did not comment on Sec.  
23.1459, ``Flight data recorders''.
    Commenters opposed to retaining the standards generally 
characterized them as too prescriptive. While accepting the need to 
maintain the numbering system to align with other regulations, EASA 
found the unchanged content to be detailed, design specific, and not 
providing the safety intent. The EASA-suggested language referenced 
recorder systems with more generalized statements regarding 
installation and technical specifications. BendixKing stated that it 
``seems binary'' that the ``specifics are invoked'' only ``if recording 
is required.'' It also noted that the standards use approximately 1,000 
words when 100 would be adequate in stating the safety intent. It 
concluded the requirement as written will hurt safety in the future by 
either retarding the technology or creating an environment where 
manufacturers will avoid recording. BendixKing included the identical 
comment for both recorder sections.
    The primary use of both CVRs and FDRs is for accident 
investigation. Over the past 30 years, the FAA has worked with the NTSB 
to adopt and refine the specific requirements that document both 
flightcrew communication and the functions of airplane that form the 
basis for airplane accident and incident investigation. The FAA adopted 
the first significant flight data recorder upgrades in 1997 and made a 
concerted effort to standardize the operational and certification 
requirements across the operating and certification parts. The primary 
requirements for recording voice and data are not contained in the 
certification regulations, but in the operating regulations. When an 
airplane is required by an operating rule to record voice or flight 
data, the operating rule references back to the standards for the 
equipment in the certification part that applies to the airplane. This 
is true for large and small airplanes and for helicopters.
    Airplane certification requirements do not align perfectly with 
operating regulations. A part 23 airplane may be operated under part 91 
or 135; therefore,

[[Page 96585]]

the requirement to have and use CVRs and FDRs may differ depending on 
how the airplane is operated. But the standards for the equipment--when 
required--do not differ, and are intended to function the same way 
regardless of the airplane's certification basis. This consistency is 
central to the needs of the NTSB and all investigative bodies. It makes 
the design, certification, and function of the equipment standard for 
the industry as a whole. The FAA last amended the recorder regulations 
in 2008 to reflect investigative experience with the functions of newer 
recorder and flight management tools.
    Therefore, the FAA finds it appropriate to retain these well-known 
requirements. The current integration of the operating and 
certification regulations is well established and functioning as 
intended. The need for investigative data following accidents and 
incidents is not forecasted to change. The commenters did not specify 
which of the current requirements were inappropriate or unnecessary, 
but merely expressed general concerns that the standards might inhibit 
safety in future designs. The FAA has long acknowledged the safety 
intent of flight recorders in providing investigators with the tools to 
recognize trends and malfunctions following accident and incidents. 
Consistency in the equipment and data that come from the equipment 
remains the goal.
    BendixKing's observation that the certification rules are invoked 
only when ``recording is required'' is accurate. As explained, the 
certification requirements for installation and use of this equipment 
are only effective when required by an operating rule. Once required, 
all the equipment must function to the same standards. The fact that 
recording is required under different operating regulations, and the 
certification regulations referenced in those operating regulations, is 
the reason for not changing them for one certification part. If an 
airplane is not required by operational rule to record voice or data, 
then the specificity of the certification regulations is not an issue. 
The commenters did not include proposed design or functional changes 
for new airplane that might affect the requirements as stated. If a 
novel design is proposed in the future that affects recorder function, 
before approval, the FAA would coordinate with the applicant to ensure 
such design features meet the needs of accident and incident 
investigation.
    Textron commented on proposed Sec.  23.1457(c), which retains the 
current language requiring each CVR to be installed so that specified 
communications are recorded on a separate channel. The regulation 
currently and as proposed specifies four separate channels--the first 
channel for the first pilot, the second channel for the second pilot, 
the third channel at the cockpit-mounted area microphone, and the 
fourth channel for the third and fourth crewmembers. Textron commented 
that these CVR channel assignments are a ``legacy'' from magnetic tape 
recorders and there is no physical effect of such assignment on current 
solid-state recorders. Textron stated the current channel assignments 
are different and, therefore, paragraph (c) language should be revised 
to allow for flexibility in channel assignment or be aligned with the 
assignments manufacturers currently use. In addition, Textron noted 
that a proposed rule of EASA does not specify channels, but instead 
references the more detailed requirement of an ASTM standard.
    Textron's comment--that the requirement for separate channels does 
not reflect the reality of currently-manufactured equipment--is limited 
in its view. While the regulation does require separated recording of 
different voice communication channels, the rule is flexible enough to 
avoid the issue raised by Textron. Regardless of an applicant's CVR 
channel numbering scheme, the regulation is satisfied if the CVR is 
designed to record audio sources on dedicated channels. This remains 
the FAA's policy on this regulation, which includes Textron's products 
already installed in airplanes that meet the former regulation.
    An individual commenter noted the proposed rule seemed to 
anticipate an onboard storage system that must withstand a crash.\17\ 
The commenter suggested that because recordings may not be stored 
onboard in the future, but rather wirelessly transmitted to the ground 
or a satellite, the FAA should revise the provision to reflect this 
possibility rather than ``locking in old technology.''
---------------------------------------------------------------------------

    \17\ See docket number FAA-2015-1621-0083. The comment was 
referenced as ``23.1457 Flight Data recorder.'' Section 23.1457 
covers cockpit voice recorders, while 23.1459 addresses flight data 
recorders. It is unclear if the comment addressed one or both 
sections, but the FAA's response would not change since both require 
crash protected recording devices.
---------------------------------------------------------------------------

    The FAA is aware that, at some point in the future, recordings may 
no longer need to be stored on board airplane. The FAA participates in 
international working groups that monitor these technology trends. 
There are many technical and legal issues attached to wireless 
transmission of voice and data communications. A change to allow such 
transmission and storage would affect several parts of the CFR and the 
functions of the NTSB, which were not proposed or discussed as part of 
this rulemaking.
b. Instructions for Continued Airworthiness (Sec.  23.1529)
    In the NPRM, the FAA proposed to relocate the requirements for 
Instructions for Continued Airworthiness from Sec.  23.1529 to proposed 
Sec.  23.1515. The FAA also proposed to remove appendixes A through F, 
and rename Appendix G to Part 23--Instructions for Continued 
Airworthiness, as Appendix A to Part 23--Instructions for Continued 
Airworthiness.
    Upon further consideration, the FAA has decided to retain the 
requirements for Instructions for Continued Airworthiness in Sec.  
23.1529. A change to Sec.  23.1529 would affect many other parts and 
guidance documents, which reference the section. Because of the new 
numbering scheme in part 23, Sec.  23.1529 is located in the ``Legacy 
Regulations'' section of the final rule. The appendix for Instructions 
for Continued Airworthiness is now located in Appendix A to Part 23, as 
proposed.
2. Subpart A--General
a. Applicability and Definitions (Proposed Sec.  23.1/Now Sec.  
23.2000)
    In the NPRM, proposed Sec.  23.1 (now Sec.  23.2000) would have 
prescribed airworthiness standards for issuance of type certificates, 
and changes to those certificates, for airplanes in the normal 
category. It also would have deleted references to utility, acrobatic, 
commuter category airplanes. Proposed Sec.  23.1 also would have 
included definitions for the following terms specific to part 23: 
Continued safe flight and landing, designated fire zone, and empty 
weight.
    Air Tractor asked why it was necessary to use the term ``category'' 
if there is only one ``normal'' category.
    The FAA notes that there is a need to retain the concept of 
different categories because other parts of the FAA's regulations, 
including the certification and operating rules, set certain 
requirements based on an airplane's category.
    An individual commenter opposed the elimination of the utility 
category as related to spin training for existing airplanes. The 
commenter would support elimination of the utility category if there 
would be a reevaluation of the airplanes allowed to be used for spin 
training. This

[[Page 96586]]

commenter also questioned whether the proposed change would result in a 
revision and reformatting of the current Type Certificate Data Sheet 
(TCDS) and whether the airplane would be considered not airworthy until 
re-placarded to conform to the new standards.
    This rule does not affect the category of existing airplanes, nor 
does it require the TCDS be revised or reformatted. Airplanes currently 
certified in the utility category for spin training retain that 
capability under this new rule. Furthermore, the airworthiness of the 
existing fleet will not be affected by this rule.
    An individual commenter recommended the FAA clarify whether the 
term ``continued safe flight and landing'' would not consider weather, 
environmental, or surface conditions in the event of a forced landing.
    The FAA agrees that it should clarify that in the event of a forced 
landing, the definition of ``continued safe flight and landing'' does 
not include consideration of weather, environmental, or surface 
conditions beyond those already taken into account by the FAA's 
operating rules. The FAA expects that a pilot will conduct his or her 
flight within the FAA's operating rules and the airplane's normal 
operating envelope, and finds doing so will help ensure the pilot has 
safe landing options. The FAA's intent was to maintain the existing 
level of safety for small airplanes. Historically, single-engine and 
light twin-engine airplanes have been required to have characteristics 
that minimized the resulting hazards when a loss of engine forced an 
off-airport landing. The requirements for larger, multiengine part 23 
airplanes are based on the requirement to continue flight back to an 
airport after the loss of an engine. This rule retains this requirement 
as it applies to part 23 airplanes that cannot maintain altitude after 
a critical loss of thrust. The FAA will provide additional 
clarification in guidance. It is not appropriate for the FAA to 
establish airworthiness standards for ``continued safe flight and 
landing'' that would require all airplane designs to account for 
extreme conditions--such as mountainous terrain--and extreme weather, 
because pilots who decide to fly over dangerous terrain or in weather 
have chosen to greatly reduce their options for safe landing.
    The FAA proposed including a definition of ``designated fire zone'' 
that was flexible enough to capture both the historical understanding 
of fire zones and those areas in airplanes that incorporate novel 
design concepts that merit the increased safety measures. However, the 
FAA finds including a definition of ``designated fire zone'' will cause 
confusion and result in less flexibility. Rather than include a 
definition, the FAA will maintain the same understanding as the 
historical use of the term ``fire zone,'' a well-understood term that 
has been in use for decades and generally includes the areas of an 
airplane in which a powerplant, or some portion thereof, resides. 
Accordingly, the FAA will remove the definition from the rule and will 
determine which areas are designated fire zones in the specific means 
of compliance. Furthermore, specific sections of the new rule have 
added the term ``fire zone'' back into the rule so there is a clear 
link to means of compliance.
    EASA commented the proposed definition of ``empty weight'' is too 
design specific and should be eliminated. EASA noted future 
technological developments would necessitate changes and future 
rulemakings, which is at odds with the objective to make objective 
rules change resistant for the next 20 years.
    The FAA agrees the definition of ``empty weight'' is too design 
specific because the list of traditional features included may not 
apply to all airplanes in the future. Accordingly, the FAA deletes the 
definition from the final rule and will rely on means of compliance to 
address the requirements for each airplane. This will allow the FAA to 
capture the appropriate features for new propulsion systems and 
configurations without losing the means of compliance for traditional 
airplanes.
    Air Tractor recommended the FAA provide a definition for ``minimum 
flying weight'' that would include the weight of the necessary crew and 
the minimum fuel required for legal operation for the lightest equipped 
airplane that complies with type design requirements. It asserted there 
is no point in the FAA certifying an airplane as safe for operation 
below the minimum weight at which the airplane can be operated.
    The FAA finds Air Tractor's recommended definition of ``minimum 
flying weight'' is not an appropriate substitute for empty weight. 
Empty weight is used to provide a baseline for an airplane; 
establishing a ``minimum flying weight'' would not work for that 
purpose.
    Embraer suggested the FAA include definitions for ``Aircraft Power 
Unit,'' ``Fuel,'' ``Critical lightning strike,'' and ``Fuel system'' in 
proposed Sec.  23.1(b).
    The FAA notes Embraer's suggestion to add definitions to proposed 
Sec.  23.1(b); however, these definitions are addressed in their 
respective subparts. The terms ``Aircraft Power Unit,'' ``Fuel,'' and 
``Fuel System'' are addressed in subpart E, and the term ``Critical 
lightning strike'' is addressed in subpart D. Furthermore, adding these 
definitions could lead to more confusion than clarification.
b. Certification of Normal Category Airplanes (Proposed Sec.  23.5/Now 
Sec.  23.2005)
    In the NPRM, proposed Sec.  23.5 (now Sec.  23.2005) would have 
applied certification in the normal category to airplanes with a 
passenger-seating configuration of 19 or less and a maximum 
certificated takeoff weight of 19,000 pounds or less. Proposed Sec.  
23.5 would have also established certification levels based on the 
passenger seating configuration and airplane performance levels based 
on speed. Proposed Sec.  23.5 also would have established a ``simple'' 
airplane classification.
Normal Category
    Air Tractor and Textron questioned the imposition of a weight-based 
limitation for certification in the ``normal'' category in proposed 
Sec.  23.5(a). Both commenters indicated that tying the applicability 
of part 23 to a maximum takeoff weight of 19,000 pounds would not meet 
the FAA's objective of replacing the current weight and propulsion 
divisions in small airplane regulations with performance- and risk-
based divisions. Air Tractor also commented there was no basis for 
weight differentiation between normal and transport category airplanes 
on the FAA's safety continuum and suggested it would be more consistent 
to only use certification levels and speed categories. Air Tractor 
further suggested that applicants should be free to decide between 
certification under part 23 and certification under ``the greater 
rigor'' of part 25. Textron recommended the FAA replace the 19,000-
pound maximum takeoff weight limit with a 6,000-pound maximum payload 
limit.
    The FAA notes Air Tractor's and Textron's comments to extend the 
scope of the normal category. However, these comments are beyond the 
scope of this rulemaking. The NPRM proposed to replace the prescriptive 
airworthiness standards of part 23 with performance-based standards, 
not to change the scope of applicability of part 23.
    Textron recommended the FAA include considerations for airplane 
functional or system complexity as a determining factor in 
certification requirements.

[[Page 96587]]

    The FAA notes this rule already considers system complexity during 
certification. The requirements applicable to an airplane depend on 
reliable indicators of complexity--the airplane's designed cruising 
speed or maximum operating limit speed, and the maximum number of 
passengers. The airworthiness standards accommodate all degrees of 
complexity, which will specifically be addressed in accepted means of 
compliance.
Airplane Certification and Performance Levels
    NATCA opposed the FAA's proposal to create certification and 
performance levels based on passenger capacity and airspeed in proposed 
Sec.  23.5(b) and (c). NATCA noted that this approach was not 
consistent with how some foreign authorities with whom the United 
States has bilateral agreements ``bucket'' airplane classifications, 
including EASA, which classifies certification levels based on weight.
    The FAA is not required to use the same metrics to classify 
airplanes as its bilateral partners. For example, Article 15 of the 
Agreement between the United States of America and the European Union 
on Cooperation in the Regulation of Civil Aviation Safety expressly 
reserves the authority for the United States to determine the level of 
protection it considers appropriate for civil aviation safety and to 
make changes to its regulations, procedures, and standards. 
Additionally, foreign authorities, including EASA, have been involved 
in the FAA's part 23 rulemaking effort since its inception with the 
Part 23 ARC. All foreign authorities involved in the part 23 
reorganization effort agreed on the need to eliminate the divisions in 
part 23 based on weight and propulsion. Furthermore, the FAA's actions 
are consistent with EASA's actions.
    NATCA also contended the FAA should retain a weight criterion 
because it relates to crash energy.
    The FAA notes the risk associated with operating a 19,000-pound, 
level 1, low-speed airplane is accounted for in this rule by directly 
addressing the technologies installed on the airplane. For example, an 
airplane approved for instrument flight rules (IFR) has to meet the 
reliability requirements for IFR, regardless of level. Also, the FAA's 
operating rules mitigate the airplane's operational risk.
    NATCA also asked the FAA to clarify that an applicant would not 
qualify for a lower certification level simply by removing seats and to 
publish guidance on determining certification levels.
    The FAA notes, as set forth in Sec.  23.5 (now Sec.  23.2005), an 
airplane's certification level depends only on its maximum passenger 
seating configuration. This number does not include flightcrew. The 
maximum passenger seating capacity is known during the certification 
process; therefore, the airplane must comply with the standards 
applicable to that certification level. An airplane operator's decision 
to remove a passenger seat after certification does not affect the 
standards applicable to that airplane.
    NATCA also recommended the FAA review the proposed part 23 
certification levels to incorporate LSA and primary category airplane 
and create equivalent regulations as necessary.
    The FAA notes that NATCA's suggestion is beyond the scope of this 
rulemaking. This rulemaking's purpose is to replace prescriptive design 
requirements of part 23 with performance-based standards, not expand 
the scope of part 23's applicability. The LSA and primary category 
certification processes exist as separate certification paths for 
airplane that qualify as either a LSA or primary airplane.
    NATCA further commented by asking--
     Whether the intent is for airplane models with multiple 
configurations to have each configuration listed on the TCDS;
     Whether there can be dual or more categories on one TC; 
and
     Whether an airplane can be moved between levels and speed 
definitions during operational usage and, if so, whether this needs to 
be captured as different options on the TCDS.
    In response to NATCA's question regarding multiple configurations, 
the FAA notes that if an airplane model has multiple configurations, 
the applicant will have to accept as the certification basis the 
requirements of the most stringent certification and performance levels 
available in the configuration list. If the applicant chooses not to 
comply with the most stringent requirements applicable to the 
configurations, the applicant will have to address each model 
individually on the TCDS. With respect to the number of categories on a 
TC, the FAA is eliminating the commuter, utility, and acrobatic 
airplane categories in part 23 for the reasons explained in the NPRM. 
Therefore, airplanes certified under new part 23 have only one 
category: normal.
    Lastly, with respect to NATCA's question regarding airplanes moving 
between certification levels and speed definitions, an applicant either 
accepts the most stringent certification basis or addresses each model 
individually on the TCDS or by an STC. In order to move to a higher 
level, it will be necessary to recertify the airplane to the higher-
level standard.
    NJASAP supported the proposal to use passenger capacity and 
airspeed to establish airplane certification and performance levels, 
but expressed concerns the methodology may go too far in generalizing a 
very diverse group of airplanes.
    The FAA understands NJASAP's concern, but notes the certification 
and performance levels are used to replace the weight and propulsion 
divisions in the former requirements. The levels are general to allow 
the accepted means of compliance to more accurately address the various 
technical differences.
    Kestrel supported the FAA's proposed airplane certification levels, 
but expressed concern with the impact of migrating the Airplane Classes 
in former Sec.  23.1309 (I, II, III, IV) \18\ to the proposed combined 
airplane certification and performance levels. Kestrel noted that 
Airplane Classes were currently used in the System Safety Analysis 
process to establish allowable quantitative probabilities. Kestrel 
asked the FAA to specify what the expected allowable quantitative 
probabilities would be for each of the eight possible combinations of 
certification and performance levels (i.e., low-speed levels 1-4 and 
high-speed levels 1-4).
---------------------------------------------------------------------------

    \18\ These Classes are described in AC 23.1309-1E, paragraph 15.
---------------------------------------------------------------------------

    The FAA notes that there is no direct connection between the 
systems-based airplane classes from AC 23.1309-1E \19\ and the airplane 
certification and performance levels in Sec.  23.2005, which apply to 
all subparts. The airplane classes reflect the safety continuum concept 
in that it may be acceptable for simpler airplanes or airplanes at 
lower certification levels to have a higher probability of failure for 
equipment. The airplane's certification level is strictly based on the 
number of passenger seats. The different means of compliance will 
address the safety continuum.
---------------------------------------------------------------------------

    \19\ The Airplane Class Levels from former Sec.  23.1309 are 
still addressed in subpart F of this rule.
---------------------------------------------------------------------------

    Air Tractor commented generally that it does not see a big 
difference in the certification effort required by the different 
certification and performance levels. Air Tractor suggested there could 
be a difference in required levels of safety for equipment, but 
indicated it was impossible to tell because the FAA had not yet defined 
the levels of

[[Page 96588]]

safety.\20\ Air Tractor suggested the FAA codify the required levels of 
safety because the rule preamble would not be given the weight of law.
---------------------------------------------------------------------------

    \20\ Air Tractor pointed out proposed Sec.  23.1300.
---------------------------------------------------------------------------

    The FAA acknowledges that Air Tractor is correct in that there 
could be a difference in the required levels of safety between two 
airplanes based on the FAA's safety continuum philosophy. Differences 
in products and their associated risks justifies using different levels 
of safety. While the high-level performance requirements are the same 
for all products, the required level of safety is best addressed using 
means of compliance so that each project is assigned the appropriate 
level of safety. Although language in the preamble does not supersede 
the language of the regulation itself, the preamble is evidence of the 
FAA's contemporaneous understanding of its proposed rules, and may 
serve as a source of evidence concerning contemporaneous agency 
intent.\21\
---------------------------------------------------------------------------

    \21\ Wyoming Outdoor Council v. U.S. Forest Service, 165 F.3d 
43, 53 (D.C. Cir. 1999).
---------------------------------------------------------------------------

    Several commenters questioned the meaning of ``passengers'' as used 
in the descriptions of certification levels in proposed Sec.  23.5(b), 
particularly for airplanes that may require 1 or 2 crew depending on 
operating regulations.
    The FAA elects to use the term ``passenger'' to align with the 
operating rules, and because passenger count has historically 
correlated to risk tolerance. The term ``passenger'' excludes 
``flightcrew'' members. The FAA recognizes the concerns over confusion 
because the ARC discussed this issue at length and it was again 
discussed within the FAA. Based on these discussions, the FAA finds 
``passenger'' is the most appropriate term. As one of the commenters 
noted, the ``crew'' could include one or more ``occupants.'' Part 23 
airplanes can include special use airplanes that may require multiple 
flightcrew members, but have no provisions for passengers. Part 23 is 
also used for airplanes that carry no ``flightcrew'' or ``passengers'' 
today (i.e., unmanned aircraft systems), and may also address airplanes 
with passengers and no flightcrew in the future. For airplanes that 
require different numbers of flightcrew for different operations, the 
applicant must use the smallest number of flightcrew required for any 
operation, which is typically one, the most conservative number. The 
FAA finds the approach proposed Sec.  23.5 (now Sec.  23.2005) will 
allow the most flexibility, least confusion, and focus on risk 
tolerance, which aligns part 23 with the operating rules.
    Several organizations commented specifically on the proposed 
airspeed limits for the low-speed and high-speed performance levels 
established in proposed Sec.  23.5(c). NATCA suggested the use of 
design cruising speed (VC) and maximum operating limit speed 
(VMO/MMO) may not be appropriate for untrained 
persons, and recommended the FAA either define those terms or use more 
common measurements. NATCA also commented that the FAA needs to clarify 
what ``speed'' means (i.e., cruise speed versus some other speed 
standard). NATCA expressed concerns over the use of ``common'' terms 
versus speeds used for certification, which are also used in 
operations.
    The FAA notes both VC and VMO are defined in 
14 CFR 1.2. VC means design cruising speed and 
VMO/MMO means maximum operating limit speed. The 
FAA finds that VC, VMO, and MMO are 
appropriate for engineering determinations as they relate to structural 
speeds as well as flight-testing speeds. Furthermore, the FAA clearly 
states these are calibrated speeds, which typically are used in 
certification.
    Transport Canada commented specifically on the parameters for the 
low-speed performance level in proposed Sec.  23.5(c)(1). In 
particular, Transport Canada said VC and VMO 
should both be less than 250 Knots Calibrated Airspeed (KCAS) for an 
airplane to qualify as low speed. Therefore, Transport Canada concluded 
the phrase ``VC or VMO'' in this provision should 
actually read ``VC and VMO''.
    The FAA agrees with Transport Canada concerning the use of ``and'' 
versus ``or'' and revises the rule accordingly.
    Air Tractor contended that the parenthetical references to 
MMO limits in proposed Sec.  23.5(c)(1) and (c)(2) are 
confusing because they are not clear if these values represent either 
new absolute constraints, or if they are intended to provide an 
approximate context for what 250 KCAS might mean at some higher 
altitude. Air Tractor noted that Mach 0.6 corresponds to 250 KCAS at 
about 23,400 feet in a standard atmosphere, but wondered what 
performance level would be assigned to an airplane with a VC 
of 250 KCAS and an MMO of 0.65.
    Garmin commented that some airplanes do not have a MMO, 
but have a maximum speed of more than Mach 0.6. For example, Garmin 
noted an airplane with a VMO of 240 KCAS up to its certified 
ceiling of 35,000 feet and no MMO would be classified as a 
low-speed airplane but will actually be going Mach 0.71 at 35,000 feet. 
Garmin recommended the FAA revise the low-speed and high-speed 
performance levels to remove MMO from parentheticals, 
clarify that a low-speed airplane must have a VC or 
VMO equal to or less than 250 KCAS and a MMO less 
than or equal to Mach 0.6, and that a high-speed airplane is anything 
that does not qualify as low speed.
    The FAA agrees that the proposed rule was unclear and revises the 
final rule to clarify that MMO is one of the criteria, not 
an approximation of the KCAS cutoff. Accordingly, an airplane must 
satisfy all of the VC, VMO, and MMO 
requirements to qualify as low speed. If an airplane does not satisfy 
all three, then it is considered a high-speed airplane. After further 
review, the FAA determined that VC and VMO are 
not directly parallel because VC is a structural speed and 
VMO is a performance speed. For this reason, the FAA 
replaces VC with VNO. VMO historically 
was a performance value used by turbine-powered airplanes while 
VNO historically was a performance value used by piston-
powered airplanes. By replacing VC with VNO, the 
values now reflect parallel operational speeds.
    ANAC commented that the FAA should use stall speed instead of 
VMO and MMO to define performance levels because 
it would help address loss of control and prevent an applicant from 
arbitrarily limiting an airplane's VMO and MMO 
below the airplane's capabilities to avoid more stringent certification 
standards. ANAC asked the FAA to elaborate on the connection between an 
airplane's VMO and MMO and takeoff risk.
    The FAA does not agree that stall speed is the best parameter to 
use for determining performance levels. Although an airplane's top 
speed generally has been aerodynamically limited to a multiple of stall 
speed that varied depending on propulsion, this is not true for all 
airplanes and does not provide the necessary flexibility to address 
airplanes that incorporate new technology. For example, there are 
airplanes in development that have very low-stall speeds--the airplane 
can land and takeoff in very little space, or even vertically--but may 
have VNO or VMO greater than 250 KCAS, making 
them a high-performance airplane.
Simple Airplane Classification
    The FAA proposed to define ``simple'' airplanes to recognize the 
entry-level airplane. Simple airplanes would have been limited to 
airplane designs that allow no more than one passenger, are limited to 
VFR operations, and have a low top speed and a low stall speed.

[[Page 96589]]

The FAA asked for comments concerning the value of creating a simple 
airplane sublevel given that a simple airplane would have 
characteristics very similar to a certification level 1, low-speed 
airplane.
    ICON, Transport Canada, BendixKing, NATCA, and two individual 
commenters supported the inclusion of a separate ``simple'' airplane 
classification. However, Zee and the Associations commented that the 
FAA should not create a ``simple'' airplane classification, and that 
each of the proposed certification and performance levels should stand 
on its own based solely on performance and complexity of operations. 
The commenters against inclusion of a ``simple'' category contended 
that it was more appropriate to address this sort of classification in 
the means of compliance.
    The FAA has decided not to adopt a ``simple'' airplane 
classification. The FAA finds the addition of a simple category does 
not produce benefits over those already provided by the new rule. The 
FAA finds it is more appropriate to address the requirements for a 
level 1, low-speed airplanes. Additionally, in the NPRM, the FAA 
proposed allowing simple airplanes to use non-type-certificated engines 
and propellers to allow those airplanes to use electric propulsion. The 
FAA can achieve the same flexibility by approving electronic propulsion 
as part of an airframe for a level 1, low-speed airplane; therefore, 
the FAA revises the propulsion requirements in this rule to provide 
that flexibility.
Airplanes Certified for Aerobatics
    The FAA proposed to eliminate the acrobatic airplane category in 
part 23, but still allow a normal category airplane to be approved for 
aerobatics provided the airplane was certified to address the factors 
affecting safety for the defined limits for that kind of operation.
    Velica S.A.S. (Velica) recommended the FAA define ``aerobatic 
category'' in proposed Sec.  23.5 to include airplanes without any 
maneuver restrictions, other than those shown to be necessary as a 
result of required flight tests.
    For the reasons explained in the NPRM, the FAA removed the 
acrobatic category from part 23. The FAA agrees with Velica that the 
limitations for an airplane certified for aerobatics should be based on 
flight tests, but believes more specificity is warranted. Therefore, 
the FAA will require airplanes certified for aerobatics to comply with 
the limitations established under subpart G of part 23 in this rule.
c. Accepted Means of Compliance (Proposed Sec.  23.10/Now Sec.  
23.2010)
    In the NPRM, proposed Sec.  23.10 (now Sec.  23.2010) would have 
required an applicant to show the FAA how it would demonstrate 
compliance with this part using a means of compliance, which may 
include consensus standards accepted by the Administrator. Proposed 
Sec.  23.10 would have also required a person requesting acceptance of 
a means of compliance to provide the means of compliance to the FAA in 
a form and manner specified by the Administrator. Proposed Sec.  23.10 
would have created flexibility for applicants in developing means of 
compliance and also specifically identify consensus standards as a 
means of compliance the Administrator may find acceptable.
General Comments
    The Associations recommended the FAA revise paragraph (a) to 
require an applicant to ``comply'' with part 23, rather than ``show the 
FAA how it will demonstrate compliance'' with part 23, using a means of 
compliance. The Associations also recommended revising paragraph (b) to 
require an acceptable means of compliance to be in a form and manner 
specified by the Administrator.
    The Associations also argued that, without these changes, the 
proposed rule could have been interpreted as requiring each applicant 
to come to agreement with the FAA on acceptable means of compliance for 
each certification project, when it appears the FAA intends to issue 
acceptance of methods of compliance in, for example, standards that are 
already deemed acceptable. The commenters also noted that part 21 does 
not currently require a showing of compliance in all cases. The 
commenters stated that today, and potentially more so in the future, 
the FAA may accept compliance through demonstration or even a statement 
of compliance. The commenters contended the above-referenced revisions 
to proposed Sec.  23.10 are necessary to ensure the designs meeting 
part 23 can continue to fully utilize part 21.
    The FAA agrees with the commenters that proposed Sec.  23.10(a) 
(now Sec.  23.2010(a)) may have had the unintended result of requiring 
applicants to get approval from the FAA for each means of compliance 
even when the FAA had already accepted a means of compliance. This 
would have been counter to the FAA's intention that a means of 
compliance, once accepted by the FAA, may be used for future 
applications for certification unless formally rescinded. The FAA 
adopts the commenters' recommendation for paragraph (a).
    The FAA does not adopt recommendation for paragraph (b) however, 
because it would not meet the intent of the requirement. Paragraph (b) 
addresses the situation in which an applicant proposes its own means of 
compliance, either as an alternative to an accepted means of compliance 
or as a new means of compliance for new technology. The FAA intended 
paragraph (b) to require applicants requesting acceptance of a means of 
compliance to do so in a form and manner specified by the FAA, not to 
require already-accepted means of compliance to be documented in a form 
and manner specified by the FAA. In light of the comment, the FAA 
revises the proposed rule language to clarify that paragraph (b) 
applies to applicants who are requesting FAA review and acceptance of a 
proposed means of compliance.
    Air Tractor questioned the need for a new rule specifying that all 
means of compliance must be accepted by the FAA and asked whether an 
applicant would need to obtain FAA approval for each means of 
compliance at the beginning of the process or any time prior to showing 
compliance.
    This final rule is necessary because Congress directed the FAA to 
issue a rule that replaces the prescriptive requirements of part 23 
with performance-based regulations.\22\ This change means that 
applicants for a TC may use any number of unique design elements to 
attempt to comply with the performance-based requirements but only the 
FAA can accept these as means of compliance because the FAA is 
responsible for finding that an airplane satisfies the performance-
based requirements in part 23 before issuing a TC. Although the means 
of compliance process is not new, the FAA adopts Sec.  23.2010 to make 
the process clear to all applicants and to highlight that applicants 
have the opportunity to develop alternative approaches to complying 
with the part 23 performance-based requirements. While an applicant is 
not required to obtain FAA acceptance of means of compliance at the 
beginning of the certification process, it is advisable to seek 
acceptance as soon as possible, or preferably before, to mitigate the 
risk of having to redesign the airplane should the FAA not accept the 
means of compliance.
---------------------------------------------------------------------------

    \22\ Small Airplane Revitalization Act of 2013 (Pub. L. 113-53, 
49 U.S.C. 44704 note).
---------------------------------------------------------------------------

    NATCA commented the FAA should require the accepted means of

[[Page 96590]]

compliance be included on the published certification basis so products 
can be standardized and post-TC modifiers can know the certification 
basis used for the underlying product. NATCA also commented that 
maintenance personnel returning an airplane back to service will need 
access to adequate documentation on how an airplane is compliant with 
the rule so they can verify the airplane remains compliant. Assuming 
the standards are listed, NATCA asked the FAA to clarify how they would 
be listed in the airplane certification basis.
    The FAA partially agrees with NATCA's concerns. Because many of the 
detailed requirements are no longer in part 23 and will move to means 
of compliance, it may be hard to know how an applicant showed 
compliance. That said, many means of compliance today are proprietary, 
and modifiers and maintenance personnel have no way of knowing what the 
original manufacturer did to show compliance. The FAA is working with 
its project support personnel to determine how much of the means of 
compliance information needs to be listed on the FAA TCDS to address 
concerns relating to post-TC modifiers and maintenance personnel. This 
information will be included in the training currently being developed 
for the ACO engineers and industry designees.
    NATCA also recommended the FAA permit design change applicants to 
use their own alternate means of compliance to gain approval rather 
than relying on the original means of compliance used for the 
underlying TC. NATCA suggested this would be in line with the FAA's 
statements that it is open to a means of compliance without preferring 
one over the other.
    This option is currently permitted and will continue to be 
permitted under the new part 23. Applicants requesting a change to type 
design may propose their own means of compliance rather than using the 
original means of compliance. However, the FAA will review the request 
depending on the complexity of the design change or the alternative 
means of compliance. While this is the current process, AC 23.2010 
provides guidance on how to submit a proposed means of compliance to 
part 23 for FAA acceptance.
    NATCA asked the FAA to clarify how the certification basis would be 
handled for industry consensus standards. NATCA also asked whether an 
applicant must at least partially use industry consensus standards, or 
whether an applicant may choose not to use consensus standards at all. 
Finally, NATCA asked if an applicant could get a part 23 TC by only 
using the standards in ACs. Air Tractor suggested the FAA revise 
proposed Sec.  23.10 to mention that the standards included in ACs are 
an accepted means of compliance.
    The FAA notes that the certification basis will be the same as it 
is today: Applicants must show compliance with part 23. An applicant 
may choose not to use any consensus standards, or a combination of 
consensus standards and other means of compliance, as long as the 
applicant's proposed means of compliance complies with part 23 and is 
accepted by the Administrator. The FAA finds it unnecessary to revise 
the proposed rule language as Air Tractor suggested. An applicant may 
already use ACs as means of compliance to part 23, where applicable, 
under Sec.  23.2010.
Use of Applicant-Proposed Means of Compliance
    Air Tractor contended the use of applicant-proposed means of 
compliance standards would lead to a significant loss in transparency 
of the certification process, as individual applicants may choose to 
make both the results and the process of showing compliance a matter of 
proprietary intellectual property. ANAC commented that the FAA should 
establish a method to publicize information about approved means of 
compliance that are not part of a consensus standard. To preserve 
proprietary information, ANAC recommended the FAA only publish 
summaries as it currently does for exemptions, special conditions, and 
ELOS findings. NATCA questioned how the FAA will handle proprietary 
specifications within a certification basis, arguing it is not in the 
public interest to have ``secret'' certification requirements. NATCA 
recommended the certification basis be published in the Federal 
Register for public comment. NATCA also recommended the certification 
basis for proprietary information be ``explicitly identified'' on the 
TCDS or STC. Finally, NATCA asked the FAA to clarify whether the FAA 
will publish FAA issue papers when an applicant uses an applicant-
proposed means of compliance and, if so, noted that several FAA orders 
and policies would need to be revised.
    The FAA has a responsibility to protect an applicant's proprietary 
information, including a proprietary means of compliance. As such, the 
FAA will not make the proprietary portions of applicant-proposed means 
of compliance publicly available. The FAA plans to address applicant-
proposed means of compliance as it does today, by summarizing the 
information. The FAA will identify the certification basis (i.e., the 
applicable airworthiness standards) on the TCDS or STC as is done 
today. The FAA has not published, and does not plan to publish, the 
certification basis or FAA issue papers in the Federal Register for 
public comment. Each applicant's certification basis is based on part 
23 and is agreed to between the applicant and the FAA. The FAA is not 
required to elicit public comment on proposed means of compliance.
    Garmin asked whether the FAA will accept portions of a previously 
accepted means of compliance, or whether an applicant must use that 
entire means of compliance. Garmin recommended the FAA revise proposed 
Sec.  23.10 (now Sec.  23.2010) to permit whole or partial 
implementation of a previously-accepted means of compliance or, 
alternatively, ensure AC 23.10 permits this.
    The FAA agrees with Garmin and points out that this is acceptable 
today. The FAA can be flexible in accepting mixed, partial, or entire 
means of compliance from industry consensus standards as applicable to 
the specific product. The FAA recognizes that new product innovations 
will make this flexibility more important in the future. An industry 
consensus standard can state that, for credit in meeting that standard, 
the applicant has to meet the entire set of requirements. But the FAA 
may tailor acceptable consensus standards based on what is appropriate 
for the intended function.
Use of Current Part 23 as Means of Compliance
    Embraer recommended the FAA revise proposed Sec.  23.10(a) (now 
Sec.  23.2010(a)) to acknowledge that an applicant may use the 
prescriptive requirements in former part 23 as an alternate means of 
compliance. Kestrel asked whether the FAA will require issue papers to 
permit the use of these former prescriptive requirements.
    In the NPRM, the FAA noted it will accept the use of the 
prescriptive means of compliance contained in former part 23 as 
alternate means of compliance, except for those sections where the 
level of safety has increased specifically for stall characteristics 
and icing protection. The FAA does not need to codify this decision to 
retain this flexibility and is therefore not revising the proposed 
language for Sec.  23.10. For applicants relying on satisfaction of the 
prescriptive requirements in former part 23, amendment 23-62, as a 
means of compliance, the FAA will only require the G-1 certification 
basis issue paper to list the means of compliance as ``amendment 23-
62''.

[[Page 96591]]

    NATCA asked whether the FAA will permit an applicant to use older 
prescriptive regulations, such as Aeronautics Bulletin, amendment 7a, 
``Airworthiness Requirements for Aircraft''; CAR 3; and previous 
versions of part 23, as a means of compliance. If not, NATCA asked the 
FAA to clarify why those regulations are not appropriate and acceptable 
for the proposed design.
    The FAA will consider the use of the older, prescriptive 
regulations in cases where it is appropriate for the airplane in 
question. There have been instances where applicants have approached 
the FAA with projects to ``remake'' new versions of vintage airplanes. 
The FAA has allowed and will continue to allow the use of 
appropriately-selected design standards on vintage airplanes. However, 
applicants wanting to use this approach should expect to use newer 
industry practices where the old standards and practices have, over 
time, not proven to meet the minimum acceptable safety standard for 
that class of airplane in part 23.
Manner in Which Applicant Must Present Means of Compliance
    Textron asked how the FAA will document the acceptance of a non-
industry standard means of compliance and whether acceptance of a 
Project-Specific Certification Plan (PSCP) is adequate proof of the 
FAA's acceptance of the means of compliance.
    The FAA plans to include information on the acceptance of non-
consensus standards on its Small Airplane Directorate Web site. The G-1 
issue paper and agreement on the certification basis and compliance 
checklist will suffice. PSCP acceptance is adequate proof of FAA 
acceptance of a means of compliance if a G-1 issue paper is not used.
    Textron also asked whether there would be a system set-up similar 
to repair specifications where an applicant could have pre-defined 
methods for making certain changes to its products, and whether there 
would be a method for the FAA to accept deviations to the accepted 
standards.
    The Part 23 ARC did not consider and the NPRM did not propose 
repair specification; therefore, it is beyond the scope of this 
rulemaking effort.
    Air Tractor and Kestrel contended the process proposed by draft AC 
23.10--which states that an applicant should list the means of 
compliance and consensus standards they intend to use to show 
compliance with part 23 in a certification plan or compliance 
checklist--is premature and would slow the certification process. The 
details of an airplane's design are often incomplete when an 
application is submitted and it can take years to obtain FAA acceptance 
of a PSCP. Air Tractor suggested that establishing a means of 
compliance during the process of negotiating the PSCP should be limited 
to picking one or more of the following: Analysis, tests, design 
review, physical inspection, etc. Air Tractor also commented that a 
requirement for the FAA to review and approve of particular methods 
before the analysis can be presented would be new for most regulations. 
It would also require a new level of required response from the FAA 
that would drastically slow the process of either establishing the 
certification plan or showing compliance. Air Tractor also questioned 
how this requirement compares with the FAA and Industry Guide to 
Product Certification.
    The FAA finds that including the means of compliance in the PSCP or 
the compliance checklist will not alter the current practice for new 
technology because some of the compliance requirements may not be known 
at the time of application. This initial uncertainty means the agreed 
compliance may remain as a draft during the development and 
certification process until the specific means of compliance are 
determined and agreed upon. This may be a common issue with new 
technology during the first few years after the new part 23 is 
implemented. It will take some time to get accepted means of compliance 
into consensus standards, resulting in these means of compliance being 
developed during the project. In the long term, the new approach should 
shorten the time needed for an applicant to get FAA agreement on its 
means of compliance.
    Finally, the FAA clarified the intent of the form and manner of the 
means of compliance. The FAA does not intend to ``specify'' the form 
and manner of means of compliance; the form and manner only need to be 
``acceptable.''
3. Subpart B--Flight
a. Weight and Center of Gravity (Proposed Sec.  23.100/Now Sec.  
23.2100)
    In the NPRM, proposed Sec.  23.100 (now Sec.  23.2100) would have 
required an applicant to determine weights and centers of gravity that 
provide limits for the safe operation of the airplane. Additionally, it 
would have required an applicant to show compliance with each 
requirement of this subpart at each combination of weight and center of 
gravity within the airplane's range of loading conditions using 
tolerances acceptable to the Administrator. Proposed Sec.  23.100 would 
have also required the condition of the airplane at the time of 
determining its empty weight and center of gravity be well defined and 
easily repeatable.
    The Associations recommended a clarifying change to proposed Sec.  
23.100(a) that would require the applicant to determine limits for 
weights and centers of gravity that provide for the safe operation of 
the airplane, rather than determine weights and centers of gravity that 
provide limits.
    The FAA adopts the Associations clarifying change. Accordingly, 
Sec.  23.2100(a) now requires the applicant to determine limits for 
weights and centers of gravity that provide for the safe operation of 
the airplane.
    Additionally, the Associations recommended changing proposed Sec.  
23.100(b) to require the applicant to comply with each requirement of 
subpart B at critical combinations of weight and center of gravity. The 
commenters explained that it is appropriate to demonstrate compliance 
at critical combinations of weight and center of gravity, but showing 
compliance at each combination ``would present an infinite matrix of 
test points.''
    The FAA also adopts the Associations recommended change to proposed 
Sec.  23.100(b) (now Sec.  23.2100(b)). While proposed Sec.  23.100(b) 
could have been interpreted to require an infinite matrix of test 
points, this was not the FAA's intent. Accordingly, Sec.  23.2100(b) 
now requires the applicant to comply with each requirement of subpart B 
at critical combinations of weight and center of gravity within the 
airplane's range of loading conditions using tolerances acceptable to 
the Administrator.
    The Associations also stated that the determination of empty weight 
and center of gravity in proposed Sec.  23.100(c) is ``somewhat 
confusing and potentially unnecessary.'' The commenters suggested 
clarifying changes that would replace ``empty weight'' with ``weight'' 
and delete ``well'' and ``easily repeatable,'' thereby requiring the 
condition of the airplane at the time of determining its weight and 
center of gravity to be defined. Similarly, Textron recommended 
deleting the terms ``well'' and ``easily'' from proposed Sec.  
23.100(c) because they are vague and subject to interpretation.
    The FAA is retaining the terms ``well defined'' and ``easily 
repeatable'' in Sec.  23.2100(c). In the NPRM, the FAA explained 
proposed Sec.  23.100 would capture the safety intent of Sec.  23.29. 
Section 23.29 has contained the terms

[[Page 96592]]

``well defined'' and ``easily repeated'' since it was published in 
amendment 23-0 \23\ with no challenges. Furthermore, ``easily'' is an 
important modifier for ``repeatable'' because it ensures that the 
condition of the airplane at the time of determining its empty weight 
and center of gravity is not hard for a mechanic to reproduce.
---------------------------------------------------------------------------

    \23\ 29 FR 17955, December 18, 1964.
---------------------------------------------------------------------------

    The FAA also retains the term ``empty weight'' in Sec.  23.2100(c). 
Determining empty weight is fundamental to baselining an airplane. 
Removing this term would leave the weight value for baseline open to 
any weight between empty to gross weight. The ambiguity of not defining 
the baseline weight would create confusion and problems.
b. Performance Data (Proposed Sec.  23.105/Now Sec.  23.2105)
    In the NPRM, proposed Sec.  23.105 (now Sec.  23.2105) would have 
required--
     An airplane to meet the performance requirements of this 
subpart in various conditions based on the airplane's certification and 
performance levels for which certification is requested;
     An applicant to develop the performance data required by 
this subpart at various altitudes and at high temperatures, while also 
accounting for losses due to atmospheric conditions, cooling needs, and 
other demands on power sources; and
     The procedures used for determining takeoff and landing 
distances to be executed consistently by pilots of average skill in 
atmospheric conditions expected to be encountered in service.
    EASA and the Associations stated that some designs may have 
performance limitations at low temperatures rather than high 
temperatures, such as batteries in electric propulsion systems. The 
commenters recommended revising the proposed language to require 
performance data for low temperatures that can be expected during 
operation, if those low temperatures could have a negative effect on 
performance.
    The FAA agrees proposed Sec.  23.105(b) (now Sec.  23.2105(b)) 
should account for possible performance degradation due to the effect 
of cold temperatures on electric propulsion systems. Proposed Sec.  
23.105 was intended to capture the safety intent of former Sec.  23.45, 
which required the determination of performance data in various 
conditions that could negatively affect performance. Historically, 
propulsion systems were gas powered and negatively affected by high 
temperatures, which resulted in a corresponding negative effect on 
performance. This explains why former Sec.  23.45 required the 
determination of performance data at a temperature from standard to 30 
degrees Celsius above standard, as performance degradations 
historically resulted from operation at high temperatures.
    As stated in the NPRM, the FAA intended the proposal to account for 
airplanes equipped with new technologies, such as electric propulsion 
systems. Additionally, the FAA intended proposed Sec.  23.105(b) to 
account for various conditions that could affect airplane performance. 
However, proposed Sec.  23.105(b) would only have accounted for 
performance degradations that could result from the operation of 
systems at high temperatures, as the proposed language reflected former 
Sec.  23.45. Because cold temperatures, rather than high temperatures, 
may have a negative performance effect on an electric propulsion system 
or a hybrid system, the FAA revises the proposed language to account 
for performance degradations at low temperatures. The FAA also removes 
the prescriptive language that would have required the determination of 
performance data at a temperature from standard to 30 degrees Celsius.
    Section 23.2105(b)(2) now requires the applicant to develop 
performance data at temperatures above and below standard day 
temperature that are within the range of operating limitations, if 
those temperatures could have a negative effect on performance. This 
requirement is consistent with the NPRM as it replaces the prescriptive 
design requirements from the regulation with performance-based 
airworthiness standards that accommodate new technologies, such as 
electric and hybrid propulsion systems. Additionally, Sec.  
23.2105(b)(2) more accurately reflects the safety intent of former 
Sec.  23.45 because it requires the development of performance data in 
conditions that could negatively affect performance, including 
conditions that account for new technologies.
    As a general matter, under Sec.  23.2105(b)(2), an applicant 
seeking certification of a gas-powered propulsion system must develop 
performance data at temperatures above standard that are within the 
airplane's operating limitations, because high temperatures could have 
a negative effect on the airplane's performance. Alternatively, an 
applicant seeking certification of an electric or hybrid propulsion 
system must develop performance data at temperatures both above and 
below standard that are within the airplane's operating limitations, if 
these temperatures could have a negative effect on performance.
    Garmin pointed out that limited airflow in a climb configuration 
may cause non-propulsion systems to overheat during long hot climbs, 
requiring a different climb speed or configuration for system cooling 
than addressed in proposed Sec.  23.105(b). Garmin recommended the FAA 
include the phrase ``other essential equipment'' in addition to 
propulsion cooling in paragraph (b)(2).
    The Associations similarly suggested that there may be some cases 
where the performance of equipment other than the propulsion system may 
drive cooling requirements for hot conditions. The commenters 
recommended revising the proposed language to include cooling 
requirements for these equipment, in situations other than climb.
    The FAA understands the concerns of Garmin and the Associations, 
for paragraph (b)(2) to address cooling requirements for more than the 
propulsion system. However, subpart B--including Sec.  23.2105--is 
intended to address airplane performance. Therefore, Sec.  23.2105 
should only address systems that affect airplane performance. For 
example, Sec.  23.2105 may apply to avionics that also control 
propulsion, or flight controls and lift systems needed to develop 
repeatable airplane performance. Traditional avionics that do not 
affect performance are addressed in subpart F, which contains 
requirements for equipment. Therefore, the FAA is not adopting the 
phrase ``other essential equipment'' because it may be interpreted to 
include systems that do not affect performance, such as oxygen or 
navigation systems. This would be a new requirement that has not been 
identified as a safety need, increasing the scope and possibly the cost 
of this rule. For the same reasons, the FAA is not expanding the scope 
of the rule to include cooling requirements for equipment other than 
propulsion systems, in situations other than climb.
    Nevertheless, in light of the comments, the FAA acknowledges there 
may be systems associated with propulsion that are necessary for 
consistent performance, such as batteries or engine controllers, that 
could be affected by temperature. Section 23.2105 should address these 
types of systems. Therefore, Sec.  23.2105(b)(2) will apply to systems 
associated with electric or other propulsion systems if those systems 
could negatively affect performance at temperatures above or below 
standard.

[[Page 96593]]

c. Stall Speed (Proposed Sec.  23.110/Now Sec.  23.2110)
    In the NPRM, proposed Sec.  23.110 (now Sec.  23.2110) would have 
required an applicant to determine the airplane stall speed or the 
minimum steady flight speed for each flight configuration used in 
normal operations, accounting for the most adverse conditions for each 
flight configuration, with power set at idle or zero thrust.
    The Associations recommended removing the proposed requirement for 
power to be set at idle or zero thrust for each determination to enable 
the introduction of new technologies such as distributed propulsion 
with reliable electric power. The commenters explained that proposed 
Sec.  23.110 must account for distributed lift systems because the 
concept of distributed lift along a wing may be used to facilitate low-
speed handling, and reliable systems of this type may dictate 
operational stall speeds. The commenters asserted their recommended 
change would ensure that distributed propulsion, with an appropriate 
reliability level, could be used in a landing condition accounting for 
a lower stall speed based upon the effects of this equipment.
    The FAA agrees that proposed Sec.  23.110 (now Sec.  23.2110) 
should account for distributed propulsion systems used for thrust, 
flight controls, and high lift systems. However, the rule must define a 
thrust level for standardization because stall speeds are important to 
the development of the performance-based speeds. The FAA finds it 
appropriate to require traditional designs to determine stall speeds 
and minimum steady flight speeds with power set at idle or zero thrust. 
Accordingly, Sec.  23.2110(a) now requires the power to be set at idle 
or zero thrust for propulsion systems used primarily for thrust. To 
accommodate distributed propulsion systems, the FAA is adding new Sec.  
23.2110(b), which requires a nominal thrust for propulsion systems used 
for thrust, flight control, and/or high-lift systems. These changes 
will allow Sec.  23.2110 to accommodate the new technologies identified 
by the commenters.
    Additionally, the FAA revises the proposed rule language to clarify 
the ``stall speed or minimum steady flight speed determination'' must 
account for the most adverse conditions for each flight configuration. 
This change is consistent with the proposed rule, which would have 
required ``each determination'' to account for the most adverse 
conditions for each flight configuration, because ``each 
determination'' referred to the ``stall speed or minimum steady flight 
speed determination.''
d. Takeoff Performance (Proposed Sec.  23.115/Now Sec.  23.2115)
    In the NPRM, proposed Sec.  23.115 (now Sec.  23.2115) would have 
required an applicant to determine airplane takeoff performance, which 
would have included the determination of ground roll and initial climb 
distance to 50 feet, accounting for stall speed safety margins, minimum 
control speeds, and climb gradients. Proposed Sec.  23.115 would have 
also required the takeoff performance determination to include 
accelerate-stop, ground roll and initial climb to 50 feet, and net 
takeoff flight path, after a sudden critical loss of thrust for levels 
1, 2, and 3 high-speed multiengine airplanes, multiengine airplanes 
with a maximum takeoff weight greater than 12,500 pounds, and level 4 
multiengine airplanes.
    The Associations suggested the FAA revise proposed Sec.  23.115 to 
capture the performance-based standards at a ``higher objective based 
level'' because the proposed section was too detailed and prescriptive. 
Textron recommended the FAA adopt language similar to EASA's A-NPA 
2015-06, which leaves determination of detailed standards appropriate 
to airplanes with different certification and performance levels to the 
means of compliance standards.
    The FAA disagrees with the comment, because it is important to 
ensure the consistency of takeoff performance data across part 23 
airplanes. This consistency aids private pilots, who often operate a 
variety of part 23 airplanes, in determining the airports from which 
they may operate.
    Several commenters recommended the FAA remove the 12,500-pound 
cutoff in proposed Sec.  23.115(c).
    The FAA agrees and removes the weight discriminator from the rule 
language. Although the FAA proposed to remove the commuter category, 
along with weight- and propulsion-based certification divisions, and to 
replace them with divisions based on risk and performance, the FAA also 
proposed to require multiengine airplanes with a maximum takeoff weight 
of more than 12,500 pounds to comply with the increased takeoff 
performance requirements in paragraph (c). Proposed paragraph (c) was 
intended to ensure that larger business jets carrying fewer than 10 
passengers, which would have been considered commuter category under 
the former rule, were captured under the takeoff performance 
requirements because these airplanes would not necessarily fall under 
level 4. The FAA recognizes that applying paragraph (c) to multiengine 
airplanes with a maximum takeoff weight of more than 12,500 pounds is 
redundant. Those airplanes, which are equivalent to airplanes under the 
former commuter category, are captured by applying paragraph (c) to 
levels 1, 2, and 3 high-speed multiengine airplanes and to all level 4, 
multiengine airplanes. Furthermore, while paragraph (c) does not apply 
to levels 1, 2 and 3 low-speed multiengine airplanes, the FAA may issue 
special conditions if there is a configuration that presents a higher-
than-anticipated risk.
    Several commenters objected to requiring the determination of 
takeoff performance for all airplanes to include the determination of 
initial climb distance to 50 feet above the takeoff surface. The 
commenters noted that under the former rule, takeoff distance for 
commuter category airplanes and multiengine jets weighing more than 
6,000 pounds required the initial climb distance be calculated using 35 
feet above the takeoff surface. Textron recommended the FAA revise 
proposed Sec.  23.115(b) to apply the 50-feet-above-takeoff-surface 
requirement only to single-engine airplanes and levels 1, 2, and 3 low-
speed multiengine airplanes rather than to all airplanes. Textron also 
recommended revising proposed Sec.  23.115(c)(2) from ``50 feet'' to 
``35 feet'' above the takeoff surface, noting the 35-foot standard has 
been demonstrated as safe for the classes of airplane to which it has 
been applied.
    The FAA agrees with the commenters and revises proposed Sec.  
23.115(b) (now Sec.  23.2115(b)) to require only single-engine 
airplanes and levels 1, 2, and 3 low-speed, multiengine airplanes to 
include the distance required to climb to a height above 50 feet when 
calculating takeoff performance. The FAA is also changing the altitude 
for the initial climb in Sec.  23.2115(c)(2) to 35 feet. The service 
history of airplanes that would be classified as levels 1, 2, and 3 
high-speed multiengine airplanes and level 4 multiengine airplanes 
under this rule, which were certified using a 35-feet-initial-climb 
requirement, has been sufficiently safe to support the proposition that 
the 35-feet requirement provides an adequate level of safety for high-
speed multiengine airplanes and level 4 airplanes.
    The Associations suggested revising proposed Sec.  23.115(b) and 
(c) to require takeoff performance to include the determination of 
``ground roll distance required to takeoff,'' rather than ``ground 
roll.''
    The FAA notes using ``ground roll distance required to takeoff'' is 
not necessary for clarity. The term ``ground

[[Page 96594]]

roll'' in the context of takeoff is well-understood.
    Several commenters recommended revising proposed Sec.  23.115(b) to 
include two subparagraphs in what the FAA interprets as an effort to 
clarify that the applicant must provide two distances, one for ground 
roll and another for the distance required for the initial climb to 50 
feet.
    The FAA finds it unnecessary to reorganize paragraph (b) as the 
commenters proposed. The format, as proposed and adopted, is 
sufficiently clear.
    The Associations suggested the FAA revise the proposed rule 
language in proposed Sec.  23.115(c)(1) to require the takeoff 
performance determination to include the distance determination of ``an 
aborted take-off at critical speed,'' rather than ``accelerate-stop.''
    The FAA agrees that ``accelerate-stop'' is not as clear a 
description of the objective of the maneuver as ``aborted take-off at 
critical speed''. Therefore, the FAA revises paragraph Sec.  
23.2115(c)(1) to reflect the commenters' recommendation.
    Embraer recommended the FAA provide special consideration--
including freezing the certification bases--for previously-approved 
light jets with certification bases that include special conditions 
measuring the takeoff distance as the distance required to takeoff and 
climb to a height of 35 feet above the takeoff surface. Embraer feared 
the potential cost associated with an upgrade or modification.
    The FAA finds a special consideration unnecessary. There is already 
a process, prescribed by Sec.  21.101(b), that allows applicants for a 
change to a TC to show that the change complies with an earlier 
amendment of a regulation if the newer requirement would not contribute 
materially to the level of safety of the product or would be 
impractical.
    ANAC recommended the FAA make it clear that takeoff airspeed and 
procedures must be determined. The FAA disagrees with ANAC's comment as 
such a change would be redundant with what we proposed for Sec.  23.105 
(now Sec.  23.2105).
e. Climb Requirements (Proposed Sec.  23.120/Now Sec.  23.2120)
    In the NPRM, proposed Sec.  23.120 (now Sec.  23.2120) would have 
required an applicant to demonstrate various minimum climb performances 
out of ground effect, depending on the airplane's certification level 
and performance capability.
    In light of comments received, the FAA revises proposed Sec.  
23.120 (now Sec.  23.2120) by withdrawing paragraphs (b)(4), (b)(5), 
and (c)(1), and renumbering paragraphs (c)(2) and (c)(3) as (c)(1) and 
(c)(2) respectively. This section discusses these changes in more 
detail.
    Textron commented that regulations have historically applied to the 
airplane, not to the applicant, with demonstration of compliance 
through flight testing. Textron recommended the FAA offer alternative 
rule language that reflected its comment. The Associations similarly 
recommended the FAA change the opening of proposed Sec.  23.120 to 
focus on the design rather than the applicant. These commenters also 
recommended re-designating the opening as paragraph (a).
    The FAA notes that, historically, the airplane-specific 
requirements focused on the airplane, and the part 21 certification 
requirements were targeted more to the applicant. Many sections in this 
rulemaking effort tried to include applicant accountability, which was 
why the proposed rule focused on the ``applicant.'' However, based on 
the comments received, the FAA revises the proposed language throughout 
this rule by removing ``applicant'' where the requirement is more 
logically based on the airplane.
    Textron commented on the proposal to apply discriminators based on 
weight divisions and detailed quantitative climb criteria conflicted 
with the stated intent of the rulemaking to remove weight-based 
divisions and develop standards reflecting the diversity of future 
airplane designs. Textron recommended the FAA adopt language similar to 
proposed CS 23.120, which leaves determination of detailed standards 
appropriate to airplanes with different certification and performance 
levels to means of compliance. The Associations recommended the FAA 
make the calculation of performances more general, to facilitate the 
use of standard means of compliance, which may exist in consensus-based 
standards. An individual commenter similarly stated the 
prescriptiveness of proposed Sec.  23.120 was contrary to the stated 
objective of the proposal. The commenter stated the text of proposed 
Sec.  23.120 would be more appropriate as a standard rather than a 
rule. The commenter recommended that the FAA use the language of 
proposed Sec.  23.125, which would have required the determination of 
climb performance in certain conditions and configuration, in proposed 
Sec.  23.120. The commenter also noted the current version of the ASTM 
standard for climb requirements already fully covers the language of 
proposed Sec.  23.120.
    In response to Textron's comment, the FAA revises proposed Sec.  
23.120 so it no longer contains weight divisions. Instead, the 
requirements of this section are based on certification levels, 
performance levels, and number of engines. Section 23.2120 does, 
however, contain quantitative climb criteria. On this topic, the FAA 
did not adopt the EASA proposed CS 23.120 language as recommended by 
Textron. While the idea of removing all climb gradient requirements was 
discussed in the Part 23 ARC, the FAA finds it is not in the best 
interest of safety to eliminate all required climb gradients. 
Therefore, the FAA is including the minimum climb gradients in this 
performance-based rule. But, the FAA consolidated the climb gradient 
requirements of former part 23 to simplify the requirement. The FAA 
finds doing so will maintain the former level of safety while reducing 
the certification burden. The FAA acknowledges the ASTM means of 
compliance contain the climb gradients in more detail than required 
from the requirements of this section. However, the ASTM means of 
compliance has not been accepted by the FAA as of the publication of 
this rule.
    The FAA finds that, while removing as many prescriptive 
requirements as possible is important for creating a performance-based 
rule, some requirements should remain because they have been proven 
over decades of service and are already based on performance. The FAA 
finds the climb requirements are one such case.
    In response to the comment that the FAA should use the language of 
proposed Sec.  23.125 (now Sec.  23.2125) in proposed Sec.  23.120 (now 
Sec.  23.2120), the FAA notes that Sec.  23.2125 only requires the 
performance information be determined for the airplane flight manual 
(AFM). There is no minimum climb gradient in Sec.  23.2125 as with 
Sec.  23.2120. The Part 23 ARC discussed this issue at length with the 
objective of defining a clear, minimum performance-based metric that 
would allow the prescriptive climb gradients to move to means of 
compliance. The climb gradients in former Sec. Sec.  23.65 through 
23.77 came from early CAR 3 and have been in place for more than half a 
century, with the exception of some commuter category requirements, 
which came from early part 25. Since the FAA has established 
measureable gradients, any alternative approach would need to maintain 
the same gradients to provide an equivalent level of safety as the 
former climb requirements. The ARC considered numerous options, but in 
every case the proposed metric was subjective such that the FAA may be

[[Page 96595]]

required to evaluate various other climb gradient schemes against the 
former climb gradients, when the intent was to maintain the former 
climb gradients. Finally, the FAA determined keeping the prescriptive 
climb gradients from the former rules remains the best approach. 
Furthermore, supporting this position, the FAA could not envision new 
and novel configurations that could not meet these climb gradients, but 
would offer the same level of safety. All the new and novel 
configurations that have been shared with the FAA have performance that 
will meet or exceed the minimum gradients proposed in the NPRM. For 
these reasons the FAA is retaining the proposed language.
    Furthermore, it may not have been clear in the NPRM that the FAA 
intended proposed Sec.  23.120 to address the required minimum climb 
gradients in former Sec. Sec.  23.63, 23.65, 23.67, and 23.77, and 
proposed Sec.  23.125 (now Sec.  23.2125) to address the required 
publication of the measured performance in former Sec. Sec.  23.66, 
23.69, and 23.71. Therefore, the FAA is not including language similar 
to proposed Sec.  23.125 (now Sec.  23.2125) in Sec.  23.2120, because 
Sec.  23.2120 includes required climb gradients, not information 
requirements.
    Textron stated that proposed Sec.  23.120(a) would have applied to 
the all engines operating (AEO) takeoff climb and that a common 
terminology should be used. Textron recommended the FAA replace the 
undefined phrase ``initial climb configuration'' in proposed paragraph 
(a) with the unambiguous phrase ``takeoff configuration'', and remove 
the phrase ``at takeoff'' from proposed paragraph (a)(2). Textron also 
recommended the FAA remove the phrase ``at sea level'' from proposed 
paragraph (a)(1) because the FAA already proposed Sec.  23.105 to 
require an airplane, unless otherwise prescribed, to meet the 
performance requirements of this subpart in still air and standard 
atmospheric conditions at sea level for all airplanes.
    The FAA notes that replacing ``initial climb configuration'' with 
``takeoff configuration'' would require the design to comply with the 
required minimum climb performance out of ground effect, with all 
engines operating and in the ``takeoff configuration''. The FAA finds 
that this change would be more stringent than the former regulations. 
Former Sec.  23.65(a) allowed for the climb to be demonstrated with the 
landing gear retracted, and former Sec.  23.65(b) allowed for the climb 
to be demonstrated with the landing gear retracted if it could be 
retracted in 7 seconds. While normalizing both former regulations might 
appear relieving for airplanes certified as complying with former Sec.  
23.65(b),\24\ the FAA finds that most airplanes designed in the past 2 
decades incorporated landing gear that retracted in less than seven 
seconds. Therefore, the FAA is retaining the phrase ``initial climb 
configuration'' in paragraph (a).
---------------------------------------------------------------------------

    \24\ Former Sec.  23.65(b) applied to normal, utility, and 
acrobatic category reciprocating engine-powered airplane of more 
than 6,000 pounds maximum weight, single-engine turbine, and 
multiengine turbine airplanes of 6,000 pounds or less maximum weight 
in the normal, utility, and acrobatic category.
---------------------------------------------------------------------------

    The FAA agrees with Textron's recommendation to delete ``at sea 
level'' from proposed Sec.  23.120(a)(1). The FAA proposed the term 
because it was part of former Sec.  23.65(a). As Textron noted, 
however, proposed Sec.  23.105(a) (now Sec.  23.2105(a)) would have 
already required an airplane to meet the performance data of subpart B, 
including Sec.  23.2120, in still air and atmospheric conditions at sea 
level for all airplanes. It is therefore unnecessary for paragraph 
(a)(1) to require a climb gradient ``at sea level'' of 8.3 percent for 
landplanes and 6.7 percent for seaplanes and amphibians. However, the 
FAA is not deleting ``at takeoff'' as recommended by Textron. The 
agency is aligning the new rule with former Sec.  23.65 by using 
``after takeoff'' instead of ``at takeoff.'' This requirement is 
indirectly addressed in Sec.  23.2105(b); however, as proposed, the 
language was not clear as to intent. By including the term ``after 
takeoff'', this requirement reinforces the meaning of ``ambient 
atmospheric conditions'' in Sec.  23.2105(b).
    The Associations and Transport Canada noted that proposed Sec.  
23.120(a) did not address climb performance for level 4 airplanes. 
Transport Canada stated the FAA should specify all engine operating 
climb gradient requirements for level 4 airplanes. The Associations 
stated the climb gradient requirements for level 4 airplanes should be 
the same as the requirement for high-speed level 1 and 2 airplanes and 
level 3 airplanes.
    The FAA considered the comments and in response, revises proposed 
Sec.  23.120(a) to include an all engines operating climb requirement 
for level 4 single-engine airplanes. The former climb requirements 
required all airplanes with 10 or more passengers to have multiple 
engines and meet the commuter category climb requirements, which were 
focused on the ability to climb after an engine failure. These one-
engine-inoperative climb requirements were extensive. The philosophy 
was that if the airplane could meet the climb requirements after one 
engine failed, it would have more-than-adequate performance with all 
engines operating. This is why there were no all engine operating climb 
requirements for commuter category airplanes. The FAA agrees with and 
continues this philosophy in the new rule for multiengine airplanes 
designed for 10 or more passengers, which are level 4 airplanes under 
this rule. However, because the new rule eliminates the commuter 
category and allows for single-engine airplanes to carry 10 or more 
passengers, there is now a need for single-engine level 4 airplanes to 
have an all engines operating climb requirement.
    The FAA agrees with the Associations that the climb gradient 
requirements for level 4 single-engines airplanes should be the same as 
the requirement for levels 1 and 2 high-speed airplanes and level 3 
airplanes. This was an oversight in the NPRM and the FAA is correcting 
it in this final rule. Accordingly, Sec.  23.2120(a)(2) now requires 
levels 1 and 2 high-speed airplanes, all level 3 airplanes, and level 4 
single-engine airplanes to demonstrate, with all engines operating and 
in the initial climb configuration, a climb gradient at takeoff of 4 
percent. This revision is a logical outgrowth of the notice because, as 
noted by the commenters, there is no basis for distinguishing between 
level 3 and level 4 airplanes for this requirement.
    Transport Canada commented that the FAA should consider and 
validate whether a 4 percent climb gradient for high-performance 
airplanes with all engines operating is sufficient. For example, an 
airplane climbing at 100 knots (approximately 400 feet per minute) may 
be acceptable for a level 1 airplane, but not for anything larger. 
Transport Canada noted that proposed paragraph (a)(2) may govern more 
frequently, because the all-engine climb capability driven by the one-
engine-inoperative requirements has been reduced in proposed paragraph 
(b)(3). Transport Canada also noted that, given the increasing 
probability of airplanes with more than 4 engines, it may be more 
effective to increase the all-engine climb gradient in proposed 
paragraph (a)(2).
    The FAA considered Transport Canada's comments, but notes the 
intent with this section was to maintain the level of safety in former 
part 23. Section 23.2120(b) requires the same climb gradient--4 
percent--as was required for similar airplanes by former part 23. The 
FAA notes that requiring more stringent climb requirements is beyond 
the scope of this rulemaking.

[[Page 96596]]

    Textron made several comments to proposed Sec.  23.120(b). Textron 
stated the word ``the'' should replace the word ``a'' when referring to 
critical loss of thrust. For proposed Sec.  23.120(b)(1), Textron 
suggested referring to climb gradient the same way as in proposed Sec.  
23.120(a)(2). Textron also recommended changing ``configuration'' to 
``configurations'' in proposed paragraph (b)(1) because one airplane 
may have multiple takeoff and approach configurations. Textron and 
Kestrel requested clarification regarding the single-engine 
crashworthiness requirements referred to in proposed Sec.  
23.120(b)(1). Kestrel asked whether those requirements will be 
established in the rule or based on an associated standard.
    Regarding Textron's comment on the use of the word ``the'' in the 
phrase ``the critical loss of thrust,'' the term ``the'' would assume 
that everyone knows what that critical loss of thrust is. While that 
may be true for traditional configurations, it may not be true for 
future configurations. Therefore, the FAA is keeping the proposed 
phrase ``a critical loss of thrust.'' However, the FAA agrees with 
Textron concerning multiple configurations and revises the rule to 
align the reference to the climb gradient in Sec. Sec.  23.2120(a)(2) 
and 23.2120(b)(1) for clarity.
    In response to Kestrel and Textron, Sec.  23.2120(b)(1) contains a 
requirement addressing airplanes that do not meet the single-engine 
crashworthiness requirements of proposed Sec.  23.600, ``Emergency 
conditions'' (now Sec.  23.2270). Section 23.2120(b)(1) is intended to 
capture the intent of former Sec.  23.67(a)(1), which required 
airplanes with VSO of more than 61 knots to maintain a 
steady climb gradient of at least 1.5 percent. Sixty-one knots was a 
historic stall speed limit for single-engine airplanes and for that 
reason, it was used as a division between multiengine airplanes that 
could climb after the loss of one engine and other multiengine 
airplanes that could not maintain altitude after the loss of one 
engine. These former requirements assumed that the airplane only had 
two engines. The FAA is not using the 61 knot stall speed division in 
this new rule the way it was used in former Sec.  23.562, ``Emergency 
landing dynamic conditions'', for crashworthiness requirements. 
Instead, the FAA is basing these new regulations on actual stall speed. 
The new regulations should, over time, allow several alternatives to 
address occupant protection. For this reason, and because the FAA did 
not intend to increase the level of safety over the former 
requirements, the FAA is using the phrase ``single-engine 
crashworthiness.''
    Textron asserted that to obtain the best takeoff performance in 
high and hot conditions, it can be advantageous to use lesser flap 
settings to improve climb capability after takeoff. However, the 
proposed climb requirements--defined only in terms of the approach 
configuration--would have eliminated this capability, and would not 
have reflected the former part 23 standards. Textron suggested the FAA 
revise the proposed rule language in paragraph (b)(3) to require 
multiengine level 3 high-speed airplanes and level 4 airplanes to 
determine the climb gradients for weight, altitude, and temperature 
combinations appropriate for takeoff in the takeoff configuration.
    The FAA notes that the reason for using the ``approach 
configuration'' was not that it reflected an actual configuration, but 
that it was more conservative than using the ``takeoff configuration.'' 
The FAA elected to consolidate the climb requirements from four 
configurations into one configuration. To do so, the FAA had to make 
some assumptions. The major assumption used in consolidating the climb 
requirements was that if the airplane could meet the second segment 
climb gradient at 400 feet, then it should meet the other traditional 
requirements and would provide an acceptable level of safety. However, 
to provide a margin of safety in case one of the other conditions was 
slightly more critical, the FAA elected to apply the discontinued 
approach flap configuration, which is ``approach'' flaps, for this 
requirement.
    Transport Canada commented it would be more conservative to require 
the four-engine climb gradient of 2.6 percent in proposed Sec.  
23.120(b)(3), rather than the two-engine climb gradient of 2 percent.
    The FAA explained in the NPRM that the climb gradient associated 
with the loss of one engine for a two-engine airplane has provided an 
acceptable safety history for this class of airplane. The historical 
three- and four-engine climb gradients were based on part 25 
regulations regarding gas engine technology, and may not be appropriate 
for distributed electric propulsion configurations or designs. For this 
reason, using those historical values may end up with a more 
conservative approach than intended. This would increase the 
requirements from the former part 23 regulations, which is outside the 
scope of this rulemaking.
    Several commenters recommended the FAA either delete, clarify, or 
re-write proposed Sec.  23.120(b)(4) and (5) because the intent of 
those paragraphs is unclear.
    The FAA agrees that proposed Sec.  23.120(b)(4) and (b)(5) are 
confusing. The FAA intended the conditions in paragraphs (b)(4) and 
(b)(5) to apply to the determinations required by paragraph (b). 
However, because Sec.  23.2105(a) requires an airplane to meet the 
performance data of subpart B for these 2 conditions, paragraphs (b)(4) 
and (b)(5) are redundant and confusing. For this reason, the FAA 
withdraws paragraphs (b)(4) and (b)(5).
    An individual commented that all multiengine airplanes should be 
able to climb after an engine failure. The commenter stated this 
performance is affordable and the FAA should not permit poor 
performance because a manufacturer wants to refurbish a decades-old 
design and produce it.
    The FAA notes that adding the requirement for all-multiengine 
airplanes to be able to climb after an engine failure is beyond the 
scope of this rulemaking. The FAA finds that the current level of 
safety in former part 23 regarding climb performance for multiengine 
airplanes following an engine failure is adequate.
    The Associations recommended the FAA revise the proposed rule 
language to require the applicant to demonstrate a climb gradient of 3 
percent during balked landing ``without creating undue pilot 
workload.'' The commenters also recommended the FAA rewrite proposed 
Sec.  23.120(c) to include a general requirement for the applicant to 
determine, as applicable, climb and descent performance for all engines 
operating; following a critical loss of thrust on take-off; and after a 
critical loss of thrust during the enroute phase of flight.
    The FAA originally determined that adding the phrase ``without 
creating undue pilot workload'' in this requirement was redundant with 
proposed Sec.  23.105(c); however, proposed Sec.  23.105(c) only 
addressed takeoff and landing distances. The FAA also recognizes that 
many of the part 23 fatal accidents happen on go-arounds or balked 
landings and are attributable, at least in part, to high-pilot 
workload. For this reason, the FAA is adding ``without creating undue 
pilot workload'' to Sec.  23.2120(c).
    The FAA also addresses the commenters' recommendation to include a 
general requirement for the applicant to determine, as applicable, 
climb and descent performance for all engines operating; following a 
critical loss of thrust on take-off; and after a critical loss of 
thrust during the enroute

[[Page 96597]]

phase of flight in Sec.  23.2125(a)(2) and (a)(3).
    Textron and Transport Canada also commented on proposed Sec.  
23.120(c). Textron stated that it is unclear why takeoff power is 
specified for the balked landing, but not for any other minimum climb 
performance requirements. Textron recommended changing the word 
``configuration'' to ``configurations'' in proposed Sec.  23.120(c)(3) 
because an airplane might have multiple landing configurations.
    The FAA agrees with Textron that the reference to takeoff power was 
not needed. Therefore, the FAA deletes the reference from proposed 
Sec.  23.120(c) (now Sec.  23.2120(c)). The FAA also agrees with 
Textron's recommendation to change ``configuration'' to 
``configurations'' and makes this change in Sec.  23.2120(c).
    Transport Canada asked that the FAA justify the reduction in the 
required landing climb gradients from 3.3 percent to 3 percent.
    The FAA notes that former Sec.  23.77, which governed balked 
landings, required a 3.3 percent gradient for piston airplanes weighing 
less than 6,000 pounds; a 2.5 percent gradient for piston engine and 
single-engine turbine-powered airplanes over 6,000 pounds and for 
multiengine turbine-powered airplanes weighing 6,000 pounds or less; 
and a 3.2 percent gradient for multiengine turbine-powered airplanes 
weighing over 6,000 pounds and commuter category airplanes. The FAA is 
simplifying the former requirement by taking the average of the three 
climb gradients. The FAA did not receive any negative comments 
concerning the decrease or increase in climb gradient requirements, so 
the FAA adopts the language as proposed.
f. Climb Information (Proposed Sec.  23.125/Now Sec.  23.2125)
    In the NPRM, proposed Sec.  23.125 (now Sec.  23.2125) would have 
required an applicant to determine the climb performance for--
     All single-engine airplanes;
     Level 3 multiengine airplanes, after a critical loss of 
thrust on takeoff in the initial climb configuration; and
     All multiengine airplanes, during the enroute phase of 
flight with all engines operating and after a critical loss of thrust 
in the cruise configuration.
    Proposed Sec.  23.125 would have also required an applicant to 
determine the glide performance of the airplane after a complete loss 
of thrust for single-engine airplanes.
    Transport Canada commented that proposed Sec.  23.125(a) appears to 
lack the concept of determining climb performance at each approved 
weight, altitude, and temperature. Additionally, Transport Canada 
stated it is unclear why proposed Sec.  23.125(a)(2) applies only to 
level 3 multiengine airplane. Transport Canada recommended the FAA 
require the determination of climb performance following a critical 
loss of thrust on take-off in the initial climb configuration for all 
multiengine airplanes at each weight, altitude, and temperature.
    The FAA agrees with Transport Canada that proposed Sec.  23.125(a) 
would not have expressly required the determination of climb 
performance at each approved weight, altitude, and temperature. The FAA 
intended proposed Sec.  23.105(a)--which would have required levels 1 
and 2 high-speed airplanes and level 3 airplanes to provide performance 
data in ambient atmospheric conditions within the operating envelope--
to capture this requirement. To comply with the requirement in proposed 
Sec.  23.105(a) to ``meet the performance requirements'' of subpart B, 
an applicant would have had to make these determinations anyway. 
However, after considering Transport Canada's comment, the FAA revises 
the proposed language to make clear that Sec.  23.125(a)(2) (now Sec.  
23.2125(a)(2)) requires the determination of climb performance at each 
weight, altitude, and ambient temperature within the operating 
limitations. This change is consistent with the NPRM, which explained 
that proposed Sec.  23.125 was intended to capture the safety intent of 
former Sec. Sec.  23.66 and 23.69. Both of these sections required the 
determination to be made at each weight, altitude, and ambient 
temperature within the airplane operating limitations.
    The FAA agrees that Sec.  23.2125(a)(2) should apply to more than 
level 3 multiengine airplanes; however, it should not apply to all 
multiengine airplanes. Section 23.2125(a)(2) captures the safety intent 
of former Sec.  23.66, which applied only to reciprocating engine-
powered airplanes of more than 6,000 pounds maximum weight and turbine 
engine-powered airplanes. Under the new performance-based regulations, 
the equivalent airplanes--considering the intent of former Sec.  
23.66--are levels 1 and 2 high-speed multiengine airplanes and all 
level 3 airplanes. Therefore, the FAA revises the proposed rule 
language to include levels 1 and 2 high-speed multiengine airplanes in 
addition to level 3 multiengine airplanes, to maintain the same level 
of safety as former Sec.  23.66. However, because former Sec.  23.66 
did not apply to commuter-category airplanes--which were considered the 
equivalent of level 4 multiengine airplanes--Sec.  23.2125(a)(2) should 
not apply to all multiengine airplanes as doing so would make the rule 
more stringent than former Sec.  23.66.
    Textron noted the continuous reference to ``a critical loss of 
thrust'' in proposed Sec.  23.125 and recommended the FAA refer to it 
as ``the critical loss of thrust.'' The FAA understands Textron's 
comment; however, the term ``the critical loss of thrust'' assumes 
there is a critical loss of thrust and that it is a known, finite 
condition for all multiengine airplanes. This may not be the case. The 
phrase ``a critical loss of thrust'' allows for the possibility that 
there is no critical loss of thrust or that different airplane 
configurations would have different critical loss of thrust conditions 
based on a specific configuration.
    Textron recommended deleting the undefined phrase ``initial climb 
configuration'' from proposed Sec.  23.125. Textron also recommended 
the FAA not require multiengine airplanes to be in the cruise 
configuration during the determination of climb performance in the 
enroute phase of flight. Textron explained that while the enroute phase 
of flight is typically associated with a ``clean'' airplane 
configuration, the applicant should be free to define this 
configuration.
    The FAA agrees with Textron's intent, but does not accept Textron's 
recommendations. The FAA is requiring the airplane to be in the 
``initial climb configuration'' in Sec.  23.2125(a)(2) and the ``cruise 
configuration'' in Sec.  23.2125(a)(3). However, the FAA is not 
defining ``initial climb configuration'' because a definition would be 
prescriptive and inflexible for new configurations, which would be 
contrary to this performance-based regulation. Paragraphs (a)(2) and 
(a)(3) capture the safety intent of former Sec. Sec.  23.66 and 23.69, 
respectively. Former Sec. Sec.  23.66 and 23.69 contained prescriptive 
requirements pertaining to the takeoff and enroute configurations, 
which were based on airplane designs over the past half-century. The 
FAA finds the new rules should include traditional configurations, but 
be flexible enough for new configurations in the future. These new 
configurations may be different from what was traditionally required in 
part 23 due to a unique propulsion, high lift, and/or flight control 
configuration. Therefore, Sec.  23.2125(a)(2) and (a)(3) specify the 
configuration conditions in a performance-based manner that allows 
flexibility for the applicant to define what the configuration is in 
means of compliance.

[[Page 96598]]

    Furthermore, based on another comment from Textron, the FAA deletes 
unnecessary text in paragraph (b) and moves the phrase ``single engine 
airplanes'' in the same paragraph to make the rule language of Sec.  
23.2125(b) read consistently with Sec.  23.2125(a).
g. Landing (Proposed Sec.  23.130/Now Sec.  23.2130)
    In the NPRM, proposed Sec.  23.130 (now Sec.  23.2130) would have 
required an applicant to determine the landing distance for standard 
temperatures at each weight and altitude within the operational limits 
for landing. The landing distance determination would start from a 
height of 50 feet (15 meters) above the landing surface, require the 
airplane to land and come to a stop (or for water operations, reach a 
speed of 3 knots) using approach and landing speeds, configurations, 
and procedures which allow a pilot of average skill to meet the landing 
distance consistently and without causing damage or injury. Proposed 
Sec.  23.130 would have required these determinations for standard 
temperatures at each weight and altitude within the operational limits 
for landing.
    Transport Canada stated proposed Sec.  23.130 should require the 
landing performance to account for stall speed safety margins and 
minimum control speeds to maintain consistency with the take-off 
requirements in proposed Sec.  23.115 (now Sec.  23.2115) and to ensure 
the same level of safety as former part 23.
    The FAA agrees the landing requirements of proposed Sec.  23.130 
(now Sec.  23.2130) should expressly account for stall speed safety 
margins and minimum control speeds consistent with the takeoff 
performance requirements of proposed Sec.  23.115 (now Sec.  23.2115). 
Proposed Sec.  23.130(b) would have generally required the 
determination of approach and landing speeds. As explained in the NPRM, 
the FAA intended proposed Sec.  23.130 to capture the safety intent of 
former Sec.  23.73, which required the reference landing approach speed 
to account for minimum control speed (VMC) and 
VS1. The FAA's intention to account for stall speed safety 
margins and minimum control speed, which would ensure the same level of 
safety as former Sec.  23.73, was not clear in the proposed rule 
language. Accordingly, the FAA is adding language to paragraph Sec.  
23.2115(b) to clarify that an applicant must account for stall speed 
safety margins and minimum control speeds when determining the approach 
and landing speeds, configurations, and procedures.
    Several commenters recommended clarifying changes to proposed Sec.  
23.130. The Associations recommended deleting the phrases ``the 
following'' and ``for landing'' in the introductory paragraph. Textron 
recommended various changes to proposed Sec.  23.130(b), such as 
replacing ``meet'' with ``achieve,'' specifying that the landing 
distance is determined in proposed paragraph (a), and replacing 
``causing damage or injury'' with ``endangering the airplane and its 
occupants.''
    The FAA deletes the phrase ``for landing'' from the introductory 
paragraph of Sec.  23.2130. This phrase is unnecessary because the 
section is about landing distance. However, the FAA retains the phrase 
``the following'' for clarity. For Sec.  23.2130(b), the FAA agrees 
that requiring a pilot of average skill ``to meet the landing 
distance'' is unclear, but will not replace the term ``meet'' because 
changing one word would not make the regulation any clearer. Instead, 
the FAA revises the language in Sec.  23.2130(b) to require a pilot of 
average skill ``to land within the published landing distance'' and 
finds it unnecessary to specify in Sec.  23.2130(b) that the landing 
distance is determined in Sec.  23.2130(a). Lastly, the FAA retains the 
proposed language ``causing damage or injury'' because the commenter's 
recommended change is vague and could cause the regulations to be 
interpreted more stringently.
    BendixKing suggested adding language to proposed Sec.  23.130(a) 
that would require the speed of 3 knots for water operations to be 
relative to the surface in calm atmospheric conditions. Alternatively, 
the Associations recommended removing entirely the requirement for 
water operations to reach a speed of 3 knots. The commenters agreed 
that the term ``stop'' would differ for water and land operations, but 
asserted that the difference is not as simple as stating 3 knots. The 
commenters stated the appropriate method of compliance for determining 
a stop for seaplanes or amphibians should be contained in accepted 
standards.
    The FAA agrees with the commenters and removes from the proposed 
rule language the requirement for water operations to reach a speed of 
3 knots. The speed of 3 knots originated from AC 23-8C, which addresses 
water operations. Former Sec.  23.75, the predecessor to Sec.  23.130, 
required the airplane to come to a complete stop, and left the surface 
type undefined. The FAA intended to clarify rule language by specifying 
the speed of 3 knots to differentiate between land and water 
operations. However, in light of the comments, the proposed language 
added confusion and failed to allow the flexibility necessary for water 
operations. The FAA agrees with the commenters that the 3-knot 
reference is more appropriate as guidance. Accordingly, Sec.  
23.2130(a) now requires the applicant to determine the distance 
required to land and come to a stop, starting at a height of 50 feet 
above the landing surface. This change removes the need to address 
whether the speed of 3 knots must be relative to the surface in calm 
atmospheric conditions. The information necessary to comply with Sec.  
23.2130(a) will be addressed in means of compliance.
    NJASAP said that wet runway data, as well as contaminated runway 
data, should be available for airplane certified to land under the 
conditions set forth in proposed Sec.  23.130(a). NJASAP also suggested 
the FAA adopt concepts from the Takeoff and Landing Performance 
Assessment (TALPA) ARC. NJASAP pointed out that airplanes certified 
under part 135 fly in all weather conditions. Finally, NJASAP stated 
that runway excursions are a documented risk for these airplanes and 
this opportunity offers an additional enhancement.
    While the FAA supports the NJASAP recommendation to make wet runway 
data available, doing so should not be a requirement. The TALPA ARC was 
primarily a part 25 effort targeting transport operations, not small 
airplane operations. The FAA is not adopting the TALPA ARC 
recommendations because they exceed former part 23 requirements and are 
therefore outside the scope of this rulemaking. The FAA recommends that 
NJASAP work with industry to add wet runway conditions to the industry 
consensus standards as possible means of compliance for airplanes used 
in part 135 operations.
    ANAC recommended the FAA require the landing procedures to allow 
for a safe landing, or a transition to a balked landing configuration, 
as this would cover the intent of former Sec.  23.75.
    The FAA agrees that proposed Sec.  23.130 (now Sec.  23.2130) 
should address the safe transition to the balked landing conditions. 
The FAA intended proposed Sec.  23.130 to capture the safety intent of 
former Sec. Sec.  23.73 and 23.75. Former Sec.  23.75 required a safe 
transition to the balked landing conditions of former Sec.  23.77 from 
the conditions that existed at the 50-foot height. The balked landing 
conditions are now contained in Sec.  23.2120(c), which captures the 
safety intent of former Sec.  23.77. To ensure Sec.  23.2130 contains 
the same level of safety as former Sec.  23.75, the FAA revises the 
proposed rule language to require an

[[Page 96599]]

applicant to determine the approach and landing speeds, configurations, 
and procedures that allow for a safe transition to the balked landing 
conditions specified in part 23.
    The Associations also recommended the FAA clarify the introductory 
sentence of proposed Sec.  23.130 by deleting ``each.'' The FAA agrees 
with this comment. Requiring determinations to be made at ``each'' 
combination of weight and altitude within the operational limits could 
be interpreted as requiring an infinite matrix of test points, which 
was not the FAA's intent. Rather than requiring the applicant to 
determine landing performance at ``each'' combination of weight and 
altitude within the operational limits, the FAA is requiring the 
determinations to be made at ``critical combinations'' of weight and 
altitude. This change is consistent with the change the FAA made to 
Sec.  23.2100(b).
h. Controllability (Proposed Sec.  23.200/Now Sec.  23.2135)
    In the NPRM, proposed Sec.  23.200 (now Sec.  23.2135) would have 
required--
     The airplane to be controllable and maneuverable, without 
requiring exceptional piloting skill, alertness, or strength, within 
the operating envelope, at all loading conditions for which 
certification is requested. This would have included during low-speed 
operations, including stalls, with any probable flight control or 
propulsion system failure, and during configuration changes;
     The airplane to be able to complete a landing without 
causing damage or serious injury, in the landing configuration at a 
speed of VREF minus 5 knots using the approach gradient 
equal to the steepest used in the landing distance determination;
     VMC not to exceed VS1 or 
VS0 for all practical weights and configurations within the 
operating envelope of the airplane for levels 1 and 2 multiengine 
airplanes that cannot climb after a critical loss of thrust; and
     An applicant to demonstrate those aerobatic maneuvers for 
which certification is requested and determine entry speeds.
    Kestrel questioned whether proposed Sec.  23.200, which is intended 
to capture the requirements of former Sec.  23.145, would be 
interpreted to include the former requirement to show the airplane can 
pitch nose downward when approaching stall, thus avoiding or recovering 
from stall, or, alternatively, whether the FAA found that requirement 
to be too prescriptive, representing only one possible means of 
compliance with the proposed controllability requirements.
    The FAA intended proposed Sec.  23.200 (now Sec.  23.2135) to 
capture the safety intent of the former controllability Sec. Sec.  
23.141 through 23.157 and allow for other possible means of compliance 
appropriate to new or innovative designs. Therefore, proposed Sec.  
23.200 was not related only to former Sec.  23.145 and was not intended 
to capture the specific requirements of former Sec.  23.145, but did 
intend to capture its broader safety intent. The former requirement 
referenced by the commenter is prescriptive and provides a means of 
compliance for traditional configuration airplanes. Because it is 
possible for novel configurations and control schemes in the future to 
need different means of compliance, the FAA finds that the prescriptive 
language from former Sec.  23.145 is more appropriate as means of 
compliance.
    Textron commented on proposed Sec.  23.200(a)(2). Textron pointed 
out that former Sec.  23.143(a) and the proposal from the Part 23 ARC 
referenced ``all flight phases,'' which better captures the general 
intent of former Sec.  23.143(a). Additionally, Textron stated that 
proposed Sec.  23.215 addresses stall characteristics, making the stall 
aspect of proposed Sec.  23.200(a)(2) redundant. Textron recommended 
the FAA maintain language similar to former part 23 by replacing the 
phrase ``low-speed operations, including stalls,'' with ``all flight 
phases.''
    The FAA agrees with Textron. The FAA's intent in proposed Sec.  
23.200(a) (now Sec.  23.2135(a)) was to capture the safety intent of 
former Sec.  23.143, which required the airplane to be safely 
controllable and maneuverable during all phases of flight. The FAA 
agrees that the phrase ``all flight phases'' better captures the safety 
intent of former Sec.  23.143(a). Additionally, upon further review, 
the language of proposed Sec.  23.200(a)(2) is confusing because, while 
the FAA proposed to add requirements to essentially avoid the stall 
maneuver in proposed Sec.  23.215, proposed Sec.  23.200(a)(2) would 
have required controllability in the stall. While this is a desirable 
and recommended condition, the FAA does not want to add confusion. The 
stall requirements belong in proposed Sec.  23.215 (now Sec.  23.2150). 
For these reasons, the FAA adopts Textron's recommendation.
    Textron also commented on proposed Sec.  23.200(a)(3). Textron 
noted that former Sec.  23.143 and the proposal from the Part 23 ARC 
did not address failures other than a response to a sudden engine 
failure. Textron also noted that proposed Sec.  23.1315 already covers 
general airplane system or equipment failures. Textron claimed the 
requirements of proposed Sec.  23.200(a)(3) could be interpreted as 
requiring demonstration of all probable flight control and propulsion 
failures in a flight-test environment, which the commenter said would 
not be practical or safe. Textron recommended maintaining the 
traditional scope of former subpart B controllability requirements, 
which included normal operations and, for multiengine airplanes, the 
response to critical loss of thrust, and using the methods employed for 
proposed Sec.  23.1315 to evaluate responses to other failures.
    In light of Textron's comment, the FAA finds it necessary to 
clarify that Sec.  23.2135(a)(3) applies to ``reversible,'' which were 
traditionally mechanical flight controls, not ``irreversible'' flight 
controls. The FAA's intent in proposed Sec.  23.200(a) was to capture 
the safety intent of former Sec. Sec.  23.145(e) and 23.147(c), which 
required applicants to address mechanical control system failures. 
Historically, these requirements targeted control cable failures or 
push-pull tube disconnects. Former subpart F, which contained 
requirements on equipment, addressed powered- and computer-controlled 
flight control systems. Under this final rule, subpart F continues to 
address equipment, such as powered- and computer-controlled flight 
control systems, and Sec.  23.2135 addresses mechanical control system 
failures, which is consistent with former Sec. Sec.  23.145(e) and 
23.147(c).
    The Associations and EASA also addressed proposed Sec.  
23.200(a)(3).\25\ The Associations recommended the FAA delete the word 
``any'' from the phrase ``any probable flight control or propulsion 
system failure.'' EASA recommended the FAA replace the word 
``probable'' with ``likely,'' to avoid creating ambiguity with 
probability definitions.
---------------------------------------------------------------------------

    \25\ EASA actually referred to proposed Sec.  23.200(a)(4) in 
its comment, but the FAA assumes EASA meant to refer to proposed 
Sec.  23.200(a)(3), which is where the term ``probable'' is used.
---------------------------------------------------------------------------

    The FAA agrees the term ``any'' does not add value compared to the 
potential for confusion coming from an absolute qualifier. The FAA 
therefore deletes the word ``any'' in Sec.  23.2135(a)(3).
    The FAA also agrees the term ``probable'' has specific meaning 
relative to systems. Furthermore, the FAA expects a transition from 
mechanical flight controls to computer-controlled flight control 
systems, which are covered under the requirements in subpart F. Because 
the term ``probable''

[[Page 96600]]

has the potential to create confusion between the flight test 
requirements of subpart B and the systems requirements of subpart F, 
the FAA is using the term ``likely,'' rather than ``probable,'' which 
will reduce the potential for confusion while maintaining the intent of 
the requirement. For more detailed discussion on the use of ``likely'', 
please refer to the discussion on proposed Sec.  23.205 (now Sec.  
23.2140).
    The Associations commented on proposed Sec.  23.200(b), stating 
that it does not account for preferred technologies, such as angle of 
attack indicators, for executing safe approach and landing procedures. 
The commenters recommended proposed paragraph (b) require the airplane 
to complete a safe landing when following the landing procedures; 
providing a safe margin below Vref or above angle of attack. 
EASA recommended removing the configuration details and specific speed 
margin from proposed Sec.  23.200(b) because future designs would not 
be able to comply with them.
    The FAA agrees with these comments. The FAA intended proposed Sec.  
23.200(b) (now Sec.  23.2135(b)) to capture the safety intent of former 
Sec.  23.153 for control during landings. The FAA agrees that 
specifying a prescriptive speed of Vref minus 5 knots, which 
former Sec.  23.153 required, may not be appropriate for entry-level 
airplanes with very-low landing speeds and may not even apply to new 
configurations. The FAA therefore removes this prescriptive speed. 
Instead, the FAA is requiring a reasonable margin below Vref 
or above approach angle of attack, as recommended by the Associations. 
This change from what was proposed is consistent with the safety intent 
of former Sec.  23.153 as it requires a safe speed margin and it 
accounts for entry-level airplanes and new technology. The FAA also 
deletes the phrase ``equal to the steepest used in the landing distance 
determination'' and replaces it with ``steepest approved'' approach 
gradient procedures as this is clarifying.
    Textron recommended proposed Sec.  23.200(b) be modified to require 
the airplane to land without ``endangering the airplane and its 
occupants,'' rather than to land without ``causing damage or serious 
injury.''
    The FAA finds that Textron's recommendation does not capture the 
safety intent of former Sec.  23.153, which required safe completion of 
a landing. However, in light of Textron's comment, the FAA is 
clarifying the term ``damage.'' As proposed in the NPRM, the rule would 
not have allowed any damage, no matter how trivial. This was not the 
intent of former Sec.  23.153. The FAA intended to capture the safety 
intent of former Sec.  23.153 in proposed Sec.  23.200(b) (now Sec.  
23.2135(b)); therefore, the FAA revises the proposed rule language by 
defining the damage that could be accepted during demonstration. 
Section 23.2135(b) now requires the airplane to be able to complete a 
landing without causing ``substantial'' damage or serious injury. 
Substantial damage is defined in 49 CFR part 830 as requiring major 
repairs and effectively preclude the use of the airplane for its 
intended purpose.
    Textron also noted that proposed Sec.  23.200 would not have 
required VMC to be determined. ANAC and Textron recommended 
the FAA require VMC to be determined, because it must be 
accounted for in the determination of takeoff performance. Textron 
recommended adding a new paragraph to proposed Sec.  23.200. Textron 
recommended the new paragraph state VMC is the calibrated 
airspeed at which, following the sudden critical loss of thrust, it is 
possible to maintain control of the airplane. For multiengine 
airplanes, the applicant must determine VMC for each flight 
configuration used in takeoff and landing operations.
    The FAA agrees the rule should require VMC to be 
determined. Proposed Sec.  23.200 was intended to capture the safety 
intent of former Sec.  23.149, which defined and required the 
determination of VMC. The FAA is adding language to Sec.  
23.2135(c) that is consistent with former Sec.  23.149, but removes the 
prescriptive requirements of former Sec.  23.149, such as the specific 
configuration requirements. Section 23.2135(c) now states that 
VMC is the calibrated airspeed at which, following the 
sudden critical loss of thrust, it is possible to maintain control of 
the airplane. Section 23.2135(c) also requires the applicant to 
determine VMC, if applicable, for the most critical 
configurations used in the takeoff and landing operations. The FAA is 
requiring the applicant to determine VMC in the most 
``critical'' configurations rather than in ``each'' configuration 
because requiring the determination at each configuration would present 
an infinite number of test points. Additionally, the FAA added the 
phrase ``if applicable'' to the rule language because there are 
multiengine airplanes that do not have a VMC.
    ANAC recommended proposed Sec.  23.200(c) be written in a less 
prescriptive manner to allow for different technology solutions. ANAC 
stated that proposed Sec.  23.200(c) should contain only the safety 
objective stated in the NPRM. For example, proposed Sec.  23.200 should 
have stated that an airplane should not depart controlled flight at low 
speeds above stall as a result of asymmetric thrust.
    The Associations stated that while proposed Sec.  23.200(c) 
represented a potential solution to the typical accident scenario 
involving loss of control in multiengine airplanes, which are unable to 
climb on a single engine, there are other solutions that may be better 
depending on the design of the airplane. The commenters noted that 
instead of assuring VMC is below the stall speed, solutions 
might include envelope protection, increased awareness of the loss of 
control condition, or automatic-power response. To ensure the rule 
allows the best solution for a particular design, the commenters 
recommended the FAA not adopt proposed Sec.  23.200(c). Instead, the 
commenters recommended the section on loss of control, proposed Sec.  
23.215, require multi-engine airplanes, not certified for aerobatics, 
not have a tendency to suffer a loss of control after a likely critical 
loss of thrust. Several other commenters also expressed concerns about 
proposed Sec.  23.200(c) and made similar recommendations.
    As explained in the NPRM, the critical safety issue that the FAA 
intended proposed Sec.  23.200(c) to address was the loss of control 
caused by asymmetric thrust. The FAA recognized in the NPRM concerns 
regarding the effectiveness of the proposed requirement in addressing 
loss of control caused by asymmetric thrust and requested comments on 
the proposal. In light of the comments received, the FAA is not 
adopting proposed Sec.  23.200(c). The FAA agrees with ANAC and the 
Associations that the rule should allow for different technologies as 
design solutions to the identified safety issue. The FAA also agrees 
that Sec.  23.2150 should include the requirement to address this loss 
of control issue. Therefore, the FAA adopts less prescriptive language 
similar to that recommended by the commenters, which is consistent with 
the intent of proposed Sec.  23.200(c). This will allow for alternative 
design solutions. Section 23.2150(c) now requires levels 1 and 2 
multiengine airplanes, not certified for aerobatics, to not have a 
tendency to inadvertently depart controlled flight from thrust 
asymmetry after a critical loss of thrust.
    The Associations and EASA recommended the FAA apply this 
requirement to all multiengine airplanes, rather than only levels 1 and 
2. The FAA is not adopting this recommendation. As explained in the 
NPRM, the FAA does not have the accident history data to support it. 
The FAA encourages manufacturers of levels

[[Page 96601]]

3 and 4 multiengine airplanes to incorporate safety features that 
prevent inadvertent departure as with levels 1 and 2 multiengine 
airplanes.
    ICON commented an airplane designed in accordance with proposed 
Sec.  23.200(c) would require less skill and presence of mind during an 
emergency, resulting in better safety.
    While the FAA is not adopting proposed Sec.  23.200(c), new Sec.  
23.2150(c) achieves the safety objective of proposed Sec.  23.200(c).
    Transport Canada noted the reason for requiring VMC to 
be less than the stall speed is to avoid loss of control following an 
engine failure. Transport Canada suggested an airplane designed with a 
large enough rudder to meet this requirement may be more prone to 
inadvertent spin entries. Transport Canada recommended requiring all 
multiengine airplane to have a positive climb gradient following an 
engine failure.
    As explained in the NPRM, while the Part 23 ARC discussed the 
option that all multiengine airplanes have guaranteed climb performance 
after a critical loss of thrust, the FAA ultimately rejected this 
option because it could impose a significant cost on the production of 
training airplanes.
i. Trim (Proposed Sec.  23.205/Now Sec.  23.2140)
    In the NPRM, proposed Sec.  23.205 (now Sec.  23.2140) would have 
required the airplane to maintain longitudinal, lateral, and 
directional trim under various conditions, depending on the airplane's 
certification level, without allowing residual forces to fatigue or 
distract the pilot during likely emergency operations, including a 
critical loss of thrust on multiengine airplanes.
    EASA commented the text of proposed Sec.  23.205 failed to take 
into account residual forces for lateral and directional control for 
those level 1, 2, and 3 airplanes with ground-adjustable trim tabs.
    The FAA agrees with EASA that while the FAA addressed ground-
adjustable trim tabs for level 1, 2, and 3 airplanes, the proposed rule 
failed to account for residual forces in lateral and directional axes. 
The FAA intended for proposed Sec.  23.205 to maintain the level of 
safety found in former Sec.  23.161. Former Sec.  23.161(a), which 
applied generally to all airplanes and to lateral, directional, and 
longitudinal trim, stated that it must be possible to ensure the pilot 
will not be unduly fatigued or distracted by the need to apply residual 
control forces exceeding those for prolonged application of former 
Sec.  23.143(c) in normal operations of the airplane. In light of 
EASA's comment, the FAA recognizes that proposed Sec.  23.205 (now 
Sec.  23.2140) would only have prohibited residual control forces from 
fatiguing or distracting the pilot during likely emergency conditions. 
The FAA agrees with EASA that the rule should account for residual 
control forces in lateral and directional axes for levels 1, 2, and 3 
airplanes. However, to maintain the same level of safety as former 
Sec.  23.161, the rule should also account for residual control forces 
in longitudinal axes and should apply generally to levels 1, 2, 3, and 
4 airplanes. Accordingly, the FAA is adding the requirement for 
residual control forces not to fatigue or distract the pilot during 
normal operations of the airplane to Sec.  23.2140(c). This requirement 
is consistent with former Sec.  23.161(a).
    Textron noted that the reference ``normal operations'' would 
require all level 4 airplanes to be able to trim in all three axes from 
obstacle height to obstacle height. Textron contended that would seem 
to increase the burden from the former requirements in Sec.  23.161, at 
least regarding lateral and directional trim.
    The FAA considered Textron's comment, but is retaining the 
reference to ``normal operations'' in proposed Sec.  23.205(a)(2) (now 
Sec.  23.2140(a)(2)). While Sec.  23.2140(a)(2) could be interpreted 
more stringently than former Sec.  23.161(b)(2), the FAA never intended 
the proposed language to increase the burden from the previous 
requirements. Former Sec.  23.161 required lateral and directional trim 
for commuter category airplanes, which are the equivalent of level 4 
airplanes, at all speeds from 1.4VS1 to the lesser of 
VH or VMO/MMO. The objective of the 
proposed rule was to allow the prescriptive requirements of former 
Sec.  23.161 to be addressed in means of compliance. While specific 
speeds such as 1.4VS1 are appropriate as the lower speed 
limit for defining ``normal operations'' for traditional configurations 
of level 4 airplanes, it may not fit new airplanes with novel 
propulsion, high lift, and flight control system configurations. For 
this reason, the FAA finds the proposed language of ``normal 
operations'' best addresses the top-level safety requirement of former 
Sec.  23.161(b)(2) while allowing the appropriate speed range to be 
addressed in means of compliance.
    In reference not only to this section, but also to its use 
throughout the proposed rule, ANAC commented that the term ``likely'' 
is not precise and should be clarified or replaced with more precise 
terms such as ``probable'', ``remote'', or ``not extremely 
improbable.''
    The FAA infers that ANAC recommended using a quantitative term, 
such as ``probable,'' because it is defined in guidance material. While 
the FAA agrees with ANAC's comment that the term ``likely'' is not 
precise, the FAA intends to allow some imprecision for the objective of 
providing performance-based standards that are sufficiently flexible to 
accommodate new technologies. The term ``likely'' was chosen to mean a 
reasonable expectation based on the existing conditions. This is 
consistent with the former usage of the term throughout part 23. 
Clarification of what should or should not be considered likely for a 
particular rule will be provided in the means of compliance.
    Textron recommended deleting the qualifying term ``likely'' from 
proposed Sec.  23.205(c) because it would be subject to interpretation. 
Textron also recommended adding abnormal operations to those operations 
during which residual control forces must not fatigue or distract the 
pilot. Lastly, Textron recommended a few editorial changes, including 
adding the term ``control'' to residual forces.
    While Textron took exception to the word ``likely'' to describe 
emergency operations, the FAA finds the term to be appropriate in this 
case. Deleting the qualifier ``likely'' could actually lead to more 
stringent interpretations of the requirement. The term ``likely'' 
bounds the requirement within rational and probable emergencies. Simply 
using the term ``emergency'' could be construed as requiring an 
applicant to address any possible emergency regardless of how 
improbable it is.
    The FAA agrees with Textron concerning the addition of abnormal 
operations. Former Sec.  23.161 referenced the specific condition of an 
engine failure, which would have been based on traditional engine 
configuration on the wing. Looking ahead, that failure condition could 
be considered an abnormal and/or an emergency operation depending on 
the number of engines, location, and control of the engines. 
Furthermore, there may be other types of failures where trim would be 
important. For these reasons, the FAA finds that addressing the 
situation using the performance-based terms of ``abnormal'' and 
``emergency'' is appropriate and consistent with the objective of 
providing performance-based standards that are sufficiently flexible to 
accommodate new technologies.
    The FAA also agrees with Textron's recommendation to add 
``control'' to

[[Page 96602]]

residual forces. The FAA notes that former Sec.  23.161 referenced 
``residual control forces,'' not ``residual forces.'' This was an 
oversight in the NPRM. Accordingly, Sec.  23.2140(c) now prohibits 
residual control forces from fatiguing or distracting the pilot during 
likely abnormal or emergency operations.
    The Associations and Textron recommended streamlining the proposed 
rule language by moving a phrase that appeared twice in proposed Sec.  
23.205(a)(1) and (2) to a single, earlier reference in proposed Sec.  
23.205(a).
    The FAA agrees with the commenters and has adopted their 
recommendation. Section 23.2140(a) now requires the airplane to 
maintain lateral and directional trim without further force upon, or 
movement of, the primary flight controls or corresponding trim controls 
by the pilot, or the flight control system, under the conditions 
specified in paragraphs (a)(1) and (a)(2). This marks a change from 
what was proposed in the NPRM in that paragraph (a) no longer addresses 
longitudinal trim. The FAA removed the reference to longitudinal trim 
in paragraph (a) because longitudinal trim is addressed by paragraph 
(b).
    Furthermore, the FAA is adding language to paragraph (b) that 
requires the longitudinal trim to be maintained without further force 
upon, or movement of, the primary flight controls or corresponding trim 
controls by the pilot, or the flight control system, under the 
conditions specified in paragraphs (b)(1) through (b)(4). This 
requirement, which is consistent with the intent of the NPRM, ensures 
Sec.  23.2140(b) maintains the same level of safety as former Sec.  
23.161. Former Sec.  23.161(a) required each airplane to meet the trim 
requirements of former Sec.  23.161 after being trimmed and without 
further pressure upon, or movement of, the primary flight controls or 
their corresponding trim controls by the pilot or the automatic pilot. 
This requirement applied generally to lateral, directional, and 
longitudinal trim.
j. Stability (Proposed Sec.  23.210/Now Sec.  23.2145)
    In the NPRM, proposed Sec.  23.210 (now Sec.  23.2145) would have 
required airplanes not certified for aerobatics to have the following 
in normal operations: (1) Static longitudinal, lateral, and directional 
stability, and (2) dynamic short period and combined lateral 
directional stability. Proposed Sec.  23.210 would have also required 
airplanes not certified for aerobatics to provide stable control force 
feedback throughout the operating envelope. Additionally, proposed 
Sec.  23.210 would have precluded any airplane from exhibiting any 
divergent stability characteristic so unstable as to increase the 
pilot's workload or otherwise endanger the airplane and its occupants.
    Kestrel suggested removing the phrase ``in normal operations'' from 
proposed Sec.  23.210(a)(1) because it could be interpreted to mean 
that static stability is not required in abnormal operations.
    The FAA understands Kestrel's concern with the phrase ``in normal 
operations'' in the proposed language. However, the FAA intended 
proposed Sec.  23.210(a) (now Sec.  23.2145(a)) to capture the safety 
intent of the stability sections in former part 23, which did not 
require demonstrations in abnormal or emergency conditions. Former 
Sec.  23.171 required an airplane to show static stability in ``any 
condition normally encountered in service,'' which the FAA considers to 
be normal operations. The former requirements have provided an 
acceptable level of safety. The FAA adopts the proposed language in 
Sec.  23.2145(a)(1) as proposed.
    Optimal stated that proposed Sec.  23.210(a)(2) appears to require 
that all lateral modes be stable, implying that airplane need to be 
spirally stable. This commenter indicated that most airplane have 
divergent spiral modes and therefore could not meet this requirement as 
proposed.
    The FAA agrees with Optimal that the proposed requirement could be 
interpreted as including spiral mode. The FAA intended proposed Sec.  
23.210(a)(2) to capture the short period and Dutch-roll stability that 
former part 23 required. ``Combined lateral-directional oscillations'' 
means ``Dutch roll.'' The FAA revises the language in Sec.  
23.2145(a)(2) to replace ``combined lateral-directional stability'' 
with ``Dutch roll'' stability.
    ANAC suggested including the terms ``adequate'' or ``appropriate'' 
to qualify dynamic stability in proposed Sec.  23.210(a)(2).\26\ ANAC 
stated that requiring only a showing of stability may allow for the 
interpretation that ``marginally stable'' is acceptable, while current 
part 23 has minimum damping factors prescribed.
---------------------------------------------------------------------------

    \26\ ANAC actually addressed this comment to Sec.  23.205(a)(2), 
but it appears it was supposed to address Sec.  23.210(a)(2).
---------------------------------------------------------------------------

    The FAA agrees with ANAC that requiring only stability without a 
qualifier could allow for interpretations outside of the prescriptive 
standards of former part 23. However, the FAA does not agree with 
qualifying stability in Sec.  23.2145(a)(2). Under the new part 23, 
applicants will have to propose a means of compliance. While this is a 
significant change from the former part 23, the language in Sec.  
23.2145(a)(2) will enable the FAA to accept the current prescriptive 
limits as a means of compliance. Alternatively, if a new technology 
requires something different, the FAA can accept what is appropriate.
    NJASAP suggested the ``Dutch roll'' characteristic on the EMB505 
airplane is close to the language used in proposed Sec.  23.210(b). 
NJASAP sought to ensure any stability system used to comply with this 
section is not so dependent on Global Positioning System (GPS) 
technology that its loss or interruption could cause the electronic 
augmentation system to fail.
    NJASAP's comment is outside the scope of this section as the FAA 
proposed Sec.  23.210 (now Sec.  23.2145) to include requirements for 
flight controls, not for their underlying systems. The FAA notes, 
however, that flight control systems used to comply with this section 
must also meet the system requirements of subpart F, which adequately 
address the commenter's concern.
k. Stall Characteristics, Stall Warning, and Spins (Proposed Sec.  
23.215/Now Sec.  23.2150)
    In the NPRM, proposed Sec.  23.215 (now Sec.  23.2150) would have 
required an airplane to have controllable stall characteristics in 
straight flight, turning flight, and accelerated turning flight with a 
clear and distinctive stall warning that provides sufficient margin to 
prevent inadvertent stalling. Proposed Sec.  23.215 would have allowed 
for alternative approaches to meeting this requirement for levels 1 and 
2 airplanes and level 3 single-engine airplanes, not certified for 
aerobatics, in order to avoid a tendency to inadvertently depart 
controlled flight. Proposed Sec.  23.215 would have also required 
airplanes certified for aerobatics to have controllable stall 
characteristics and the ability to recover within one and one-half 
additional turns after initiation of the first control action from any 
point in a spin, not exceeding six turns or any greater number of turns 
for which certification is requested while remaining within the 
operating limitations of the airplane. Proposed Sec.  23.215 would have 
also precluded airplanes certified for aerobatics from having spin 
characteristics that would result in unrecoverable spins due to pilot 
disorientation or incapacitation or any use of the flight or engine 
power controls.
    Garmin commented that while the proposal contained a lengthy 
discussion about requirements to improve the

[[Page 96603]]

airplane's resistance to departing controlled flight, proposed Sec.  
23.215(a) would only have required the airplane to have controllable 
stall characteristics in straight, turning and accelerated flight. 
Garmin stated there was no mention of flight characteristics related to 
control usage at the stall that does not precisely and correctly 
control the stall. As an example, Garmin noted an applicant can comply 
with the rule and have an airplane that is controllable through a stall 
if flown correctly, but if not flown correctly, can enter an 
uncontrollable spin if the airplane is allowed to stall while not 
precisely coordinated. Garmin recommended the FAA change either the 
rule or the preamble to be consistent with each other.
    The FAA acknowledges the NPRM preamble discussion may have been 
unclear. The FAA only intended proposed Sec.  23.215(b) (now Sec.  
23.2150(b) to improve an airplane's resistance to departing controlled 
flight. This increase in level of safety applied only to the smaller 
part 23 airplanes, not all part 23 airplanes. Furthermore, the FAA 
intended for proposed Sec.  23.215(a) to capture the safety intent of 
former Sec. Sec.  23.201 and 23.203. Garmin's example will continue to 
be true for airplanes not required to meet Sec.  23.2150(b). The FAA 
notes that Sec.  23.2150(a) will not include requirements related to 
conditions and control usage at the stall. While former Sec. Sec.  
23.201 and 23.203 included these requirements, the FAA finds they are 
better addressed in means of compliance.
    The FAA notes the details from these former rules will be addressed 
in the means of compliance and will remain essentially unchanged, 
especially for larger, higher-performance airplanes. The reason is that 
the accident history of the larger airplanes does not warrant the 
change. The means of compliance for the level 1 and 2 airplanes and 
level 3 single-engine airplanes is expected to allow for more 
alternative approaches from what is acceptable today to meet the higher 
level of safety in this rule.
    Textron and the Associations commented that Sec.  23.215(b) should 
not require multiengine airplanes to not have a tendency to 
inadvertently depart controlled flight. The commenters explained that 
loss of control accidents involving multiengine airplanes result mostly 
from pilots failing to maintain directional control following a 
critical loss of thrust. Textron noted that this concern is being 
addressed by proposed Sec.  23.200(c), which proposes new requirements 
for airplanes that cannot climb after a critical loss of thrust. 
Textron also noted former Sec.  23.221 was not a requirement for 
multiengine airplanes and that proposed Sec.  23.215(b) would have 
represented a significant new burden with no safety justification.
    The Associations stated it believed loss of control accidents 
predominately involve single-engine airplanes, or multiengine airplanes 
during a critical loss of thrust event. The Associations recommended 
that the FAA revise proposed Sec.  23.215 to ensure the loss of control 
requirements are applied in a manner that will maximize safety while 
being applied in an efficient manner. The Associations specifically 
recommended the FAA revise proposed Sec.  23.215 to require multiengine 
airplanes, not certified for aerobatics, to not have a tendency to 
suffer a loss of control after a likely critical loss of thrust. This 
would be an alternative to adopting proposed Sec.  23.200(c). The 
Associations also recommended the FAA revise the proposed Sec.  
23.215(b) to require single-engine airplanes, not certified for 
aerobatics, to not have a tendency to inadvertently depart controlled 
flight.
    The FAA agrees that proposed Sec.  23.215(b) (now Sec.  23.2150(b)) 
should apply only to single-engine airplanes. The FAA proposed to apply 
paragraph (b) to level 1 and 2 multiengine airplanes in an attempt to 
address the loss of control accidents in light multiengine airplanes 
that can occur after an engine failure if the pilot does not maintain a 
safe single-engine speed. However, as noted by Textron, the FAA 
proposed Sec.  23.200(c) to address this safety issue by requiring that 
Vmc not exceed Vs1 or Vso. In light of 
the comments, the FAA recognizes it is more appropriate to address the 
loss of control issue for light multiengine airplanes in Sec.  23.2150 
rather than Sec.  23.2135 because it is redundant to address the issue 
in both sections. The FAA revises Sec.  23.2150(b) in this final rule 
to reflect that it only applies to single-engine airplanes in all 
certification levels to be consistent with former Sec.  23.221. While 
the FAA did not propose in the NPRM that level 4 single-engine 
airplanes would be subject to this requirement, extending this 
requirement to such airplanes is a logical outgrowth from the proposal 
because the same safety benefit applies regardless of certification 
level. Also, the FAA finds no valid technical basis for excluding level 
4 airplanes from this requirement. The airplane categories in former 
part 23 did not provide for certification of single-engine airplanes 
with passenger capacities greater than nine; however, it is possible 
that applicants may seek approval for such an airplane in the future. 
In such cases, these airplanes will have the same level of safety as 
smaller single-engine airplanes.
    As discussed in the preamble discussion of Sec.  23.2135, the FAA 
is withdrawing proposed Sec.  23.200(c) and adding a new Sec.  
23.2150(c). Paragraph (c) requires levels 1 and 2 multiengine 
airplanes, not certified for aerobatics, to not have a tendency to 
inadvertently depart controlled flight from thrust asymmetry after a 
critical loss of thrust. The FAA finds that paragraphs (b) and (c), as 
revised, more accurately reflect the FAA's intent regarding the 
prevention of loss of control accidents in both single and multi-engine 
airplanes.
    EASA commented that proposed Sec.  23.215(b) would not have 
provided the flexibility needed for future designs. EASA recommended 
the FAA allow levels 1 and 2 airplanes and level 3 single-engine 
airplanes not certified for aerobatics to meet one of three 
alternatives: (1) Not to have the tendency to inadvertently depart 
controlled flight; (2) have a benign behavior when departing controlled 
flight; or (3) have a system preventing departure from controlled 
flight.
    While the FAA understands EASA's recommended approach, Sec.  
23.2150(b) and (c) contain the most significant safety improvements in 
this rulemaking effort. Any departure from controlled flight is likely 
to result in a fatal accident unless an experienced pilot demonstrating 
spins in an aerobatic airplane intentionally does it. Allowing levels 1 
or 2 airplanes or level 3 single-engine airplanes to have a benign 
behavior when departing controlled flight would not meet the FAA's 
safety objective for airplanes that are not certified for aerobatics. 
The FAA notes that an airplane that can depart controlled flight with 
benign behavior can inadvertently depart controlled flight. 
Furthermore, having a system that prevents departure from controlled 
flight may be a means of compliance for Sec.  23.2150(b). Therefore, 
the FAA finds it inappropriate to offer it as an alternative in the 
regulation.
    The FAA did not intend Sec.  23.2150(b) to be absolute in that 
``spin resistance'' is the only way to meet the rule. An airplane using 
enhanced stall warnings and envelope protection could be very difficult 
to depart from controlled flight and comply with Sec.  23.2150(b). That 
same airplane, with some effort, could be made to spin (depart 
controlled flight) and have good recovery capability and still--because 
of the stall characteristics and the enhanced warning and systems 
protection--comply with the new requirement. The

[[Page 96604]]

FAA is working on means of compliance that will allow numerous 
combinations of airframe and systems approaches to complying with the 
new requirement so that applicants have alternative ways to comply with 
the regulation. Furthermore, this approach will encourage the 
development of new innovative technology that targets resistance to 
departure from controlled flight.
    Several commenters took issue with the proposed requirement in 
Sec.  23.215(b) that certain airplanes must not have a tendency to 
inadvertently depart controlled flight. Air Tractor, Optimal, and an 
individual commenter noted the proposal does not define this phrase. 
The individual commenter asked whether this phrase includes proper use 
of flight controls, improper use of flight controls, conditions beyond 
and per former Sec.  23.221(a)(2) for spin resistance. Air Tractor 
stated it would be difficult to prove an airplane meets this 
requirement.
    The FAA purposely used language that would allow flexibility in 
showing compliance. The FAA recognizes the lack of clear, detailed 
requirements may increase the difficulty of proving that the airplane 
meets this requirement. However, the FAA finds providing clear, 
detailed requirements would prevent the acceptance of alternative 
approaches to this safety problem. It could also prevent the use of new 
technology, which would discourage the development of even newer 
technology. As explained in the NPRM, the FAA envisions numerous 
alternative approaches to meeting this requirement, ranging from a 
stick pusher to full spin resistance. The FAA is relying on industry to 
develop acceptable means of compliance beyond these two acceptable 
approaches for this requirement, should industry fully leverage the 
flexibility the FAA built into the rule. The FAA is also relying on 
industry to incorporate new technologies into the airplane to address 
stall-based accidents. Currently, the ASTM committee is maturing an 
innovative approach that incorporates many of the variables associated 
with stall characteristics to prevent inadvertent departures from 
controlled flights.
    Air Tractor expressed concern that it may not be able to comply 
with the intent of the proposed requirement because its airplanes are 
designed to operate close to the ground and sometimes close to a stall. 
According to Air Tractor, if it were to add some kind of substantial 
departure resistance to prevent inadvertent stalls resulting in a 
departure from controlled flight, as described in the NPRM, this 
modification could potentially increase pilot fatigue significantly.
    The FAA notes that Air Tractor's airplanes are certified in 
restricted category and have the latitude to modify the part 23 
requirements where necessary. For example, as Air Tractor pointed out, 
its airplanes are designed to operate close to the ground and sometimes 
close to a stall. For this reason, Air Tractor did not have to meet the 
one-turn spin requirement from former part 23 as specified on TCDS 
Number A19SW. However, because Air Tractor's airplanes are operated 
close to the ground and sometimes close to a stall, characteristics or 
features that prevent inadvertent departure would be desirable, unless 
these characteristics or features add control forces that fatigue the 
pilot or reduce maneuverability. The FAA finds these issues apply only 
to a small subset of airplanes and can be addressed most efficiently 
and effectively in the certification context, rather than by revising 
the regulatory text. Optimal expressed concern with unintended 
consequences that may result from imposing departure from controlled 
flight resistance requirements. Specifically, it questioned whether 
proposed Sec.  23.215(b) can be satisfied without compromising other 
aspects of the airplane's performance and handling.
    The FAA notes that, historically, when only using traditional 
mechanical controls, there are performance and handling tradeoffs that 
can come from imposing departure resistance requirements. This is one 
reason the FAA has been reluctant to push for departure resistant 
characteristics in the past. However, the development, availability, 
and cost of new technology to address departure resistance have matured 
such that the FAA believes it is time to introduce this requirement to 
reduce loss of control accidents. Aerodynamics and systems combined can 
address departure resistance without compromising performance and 
handling. The FAA will not accept a means of compliance that has a 
detrimental effect on safety.
    Transport Canada questioned whether proposed Sec.  23.215(b) would 
result in designs that have a significant effect on the loss of control 
accident rate and asked what the flight test requirements would be for 
demonstrating compliance with paragraph (b). American Champion Aircraft 
Corporation (American Champion) stated the regulation should provide a 
means to determine acceptable departure resistance, or a description of 
an acceptable means of compliance.
    The FAA recognizes that the means of compliance will be very 
important in the success of this requirement to improve safety. The FAA 
adopts a general performance-based requirement in Sec.  23.2150(b) to 
enable numerous alternative approaches to meet the requirement. For 
this reason, it is impossible to specify a single set of flight test 
requirements. The flight test requirements will depend on the 
applicant's approach to complying with this rule and the means of 
compliance it uses. It would have been impossible to adopt requirements 
for all combinations of safety features and characteristics that reduce 
the tendency to inadvertently depart controlled flight in the 
requirements themselves. However, applicants can still use the spin 
resistance requirements from former Sec.  23.221 for spins, and a stick 
pusher compliant with former Sec.  23.691 for artificial stall barrier 
systems. Additionally, ASTM is developing an expandable matrix concept 
that will allow credit for combinations of stall warning, stall/
envelope protection, and flight characteristics. This matrix should 
result in not only encouraging manufacturers to install more safety 
enhancing equipment, but more importantly, it will also encourage the 
development of innovative approaches to preventing inadvertent 
departure because of the speed at which new technology can be 
incorporated into the certification process. To address the wide range 
of airplane characteristics and solutions, the FAA is adopting a 
standard that the airplane may not have tendency to inadvertently 
depart controlled flight.
    American Champion noted inconsistencies with the required degree of 
departure resistance throughout the NPRM. For example, the commenter 
noted proposed Sec.  23.215(b) stated ``must not have a tendency to 
inadvertently depart controlled flight.'' Section V of the NPRM 
referred to departure resistant as ``stall characteristics that make it 
very difficult for the airplane to depart controlled flight,'' and 
section VI states certification levels would have required 
``substantial departure resistance.'' American Champion recommended the 
FAA clarify the degree of departure resistance intended by proposed 
Sec.  23.215(b).
    The FAA notes Sec.  23.2150(b) states that single-engine airplanes, 
not certified for aerobatics, ``must not have a tendency'' to 
inadvertently depart controlled flight. Therefore, ``must not have a 
tendency'' is the standard. The FAA acknowledges, however, that the 
NPRM discussions should have been more consistent when discussing the 
proposed rule language.

[[Page 96605]]

    Optimal expressed concern about removing the requirement for 
single-engine airplanes not certified for aerobatics to recover from a 
one-turn/three-second spin at this time because pilots have been adept 
at finding unanticipated ways to get spin resistant airplanes to depart 
from controlled flight and because airplanes that are the most 
reluctant to spin tend to be the most reluctant to recover. Optimal 
recommended the FAA retain the requirement to recover from an incipient 
spin until sufficient certification and operational experience has been 
acquired with departure resistant airplanes.
    The FAA removes the requirement for the one-turn/three-second spin 
for normal category single-engine airplanes. Historically, airplanes 
that were reluctant to spin tended to be reluctant to recover. This 
history is based on airplanes with inherent stability and reversible 
controls, which to date are all small airplanes. The FAA intentionally 
focused on the prevention of the conditions that lead to an inadvertent 
spin (departing controlled flight) versus the historical focus on spin 
recovery. For decades, the FAA has focused on spin recovery in 
certification programs only to have those same certified airplanes 
depart controlled flight at altitudes so low that even experienced 
pilots could not recover. For decades, this scenario has accounted for 
a large percentage of fatal accidents. The FAA has to change the 
approach to certification in order to reduce the number of departure 
from controlled flight fatal accidents.
    Kestrel expressed concern that demonstrating compliance to proposed 
Sec.  23.215(d) would be prohibitively expensive and potentially 
impossible. Kestrel suggested the FAA modify the proposed rule language 
to read ``with any typical use of the flight or engine power 
controls.''
    The FAA agrees that proposed Sec.  23.215(d)(1) (now Sec.  
23.2150(e)(1)) could have been interpreted as imposing an unbounded 
requirement, which was not the FAA's intent. The FAA revises the 
proposed rule language as Kestrel suggested.
    EASA commented that proposed Sec.  23.215(d)(2) (now Sec.  
23.2150(e)(2)) would have contained a flightcrew interface requirement 
that does not belong in the airworthiness (design) requirements. EASA 
recommended the FAA move this requirement to subpart G, which addresses 
flightcrew interface requirements.
    The FAA is retaining the requirement in subpart B because it 
originated from former subpart B, Sec.  23.221(c). The FAA finds that 
keeping it in the same subpart, in this instance, will avoid confusion.
    American Champion commented that it is unnecessary to restrict 
certification of dual-purpose airplanes by requiring a mechanical or 
electronic change, as described in the NPRM, because airplanes can both 
meet the enhanced stall characteristics and also be suitable for some 
aerobatic maneuvers. The commenter noted that departure resistance, 
proposed Sec.  23.215(b), does not preclude an airplane from aerobatic 
maneuvering, although it may affect the ability of the airplane to 
enter a spin.
    The FAA proposed to restrict certification of new airplanes for 
dual use to prevent inadvertent stalls, which was one of the proposal's 
objectives. If an airplane can spin for spin training, then the 
airplane can inadvertently stall and depart into a spin during normal 
operations. In light of American Champion's comment, however, the FAA 
acknowledges there may be airplanes in the future that are approved for 
limited aerobatics that do not include spins. This would be similar to 
military fighter airplane. The military approach has historically been 
to explore thoroughly the post stall regime including spins and 
departures from controlled flight that do not result in traditional 
spins. This is done in the military and for civilian aerobatic 
airplanes to address the situation where a mistake during a planned 
maneuver results in departing controlled flight. The FAA can envision a 
flight control system that could prevent departures from all approved 
maneuvers. To the FAA's knowledge, the F-16 flight control system has 
been very successful in preventing inadvertent departures from 
controlled flight even though these airplane are frequently flown 
``acrobatically.'' For these reasons, the FAA may allow certification 
of a new airplane for dual use even if the airplane is not approved for 
spins. However, an applicant proposing a system, such as a flight 
control system that could prevent departure from controlled flight 
during normal operations, should expect to work with the FAA to 
thoroughly address FAA concerns for safe margins from inadvertent 
departure from controlled flight.
    Proposed Sec.  23.215(d) would have precluded airplanes certified 
for aerobatics from having spin characteristics that would result in 
unrecoverable spins due to pilot disorientation or incapacitation or 
any use of the flight or engine power controls. Upon further 
reflection, the FAA revises the proposed rule language to require spin 
characteristics in airplanes certified for aerobatics to recover 
``without exceeding limitations.'' The FAA inadvertently omitted this 
clause from proposed Sec.  23.215(d) (nowSec.  23.2150(e)), which was 
intended to capture the safety intent of former Sec.  23.221(c). Former 
Sec.  23.221(c) required the applicable airspeed limits and limit 
maneuvering load factors not to be exceeded. Additionally, including 
this clause in the requirement will better align the FAA language with 
EASA's NPA language.
    The NTSB commented that while it supports reducing the rate of loss 
of control accidents in general aviation, it is unclear how proposed 
Sec. Sec.  23.200 and 23.215 would have accomplished this. The NTSB 
explained that the only link it sees to reducing loss of control 
accidents is the change to VMC and asked the FAA to clarify 
exactly how the revisions will reduce loss of control accidents.
    The FAA notes that the NPRM included a substantial discussion 
explaining how the FAA envisions the rule reducing loss of control 
accidents. The new rules allow alternative approaches that an applicant 
may use, ranging from a stick pusher to full spin resistance. Adding 
flexibility to the rule will allow alternate approaches to address 
inadvertent departure by using combinations of new technology not 
addressed in the former requirements. These alternatives will be 
addressed in means of compliance. There is no ``exact'' approach to 
meet the new rule because the objective is to encourage new approaches 
to loss of control that are more effective than the ones that are 
failing us today.
    Additionally, the NTSB submitted detailed comments on the stall 
departure characteristic exception in the ASTM standard. The FAA will 
address these comments in the AC because these comments are on the 
acceptability of an ASTM standard as a means of compliance rather than 
on the proposed rule.
l. Ground and Watering Handling Characteristics (Proposed Sec.  23.220/
Now Sec.  23.2155)
    In the NPRM, proposed Sec.  23.220 (now Sec.  23.2155) would have 
required airplanes intended for operation on land or water to have 
controllable longitudinal, and directional handling characteristics 
during taxi, takeoff, and landing operations. Proposed Sec.  23.220 
would have also required an applicant to establish a maximum wave 
height shown to provide for controllable longitudinal, and directional 
handling characteristics and any necessary water

[[Page 96606]]

handling procedures for those airplanes intended for operation on 
water.
    Textron and the Associations noted that the FAA proposed to remove 
the prescriptive requirements related to establishing demonstrated 
crosswind capability from former Sec.  23.233, but proposed to retain 
similar requirements for water operations to establish wave height 
criteria. These commenters stated that operational specificity related 
to water landings should be addressed in means of compliance standards 
and recommended that the FAA not adopt proposed Sec.  23.220(b).
    The FAA agrees with the commenters that proposed Sec.  23.220(b) 
would have been overly prescriptive for water operations and that it 
would be more appropriate as a means of compliance. While proposed 
Sec.  23.220(a) would have included the top-level safety requirements 
for both land and water operations, proposed Sec.  23.220(b) would have 
been inconsistent with the approach taken for land airplanes as it 
would have contained prescriptive requirements only for airplanes 
intended for operation on water. Accordingly, the FAA is not adopting 
proposed Sec.  23.220(b). The information necessary to comply with 
proposed Sec.  23.220(a) (now Sec.  23.2155 in its entirety) and the 
method to communicate that information to the pilot will be addressed 
in means of compliance with this section.
    EASA also recommended that the FAA not adopt proposed Sec.  
23.220(b). EASA explained that the AFM requirements in subpart G should 
cover ``how-to'' information and how that information is provided to 
the pilot, as proposed in the NPRM. Therefore, proposed Sec.  23.220(b) 
should not require what must be included in the AFM.
    The FAA agrees with EASA that the information is more appropriately 
addressed in the AFM means of compliance. The AFM requirements are 
located in subpart G.
m. Vibration, Buffeting, and High-Speed Characteristics (Proposed Sec.  
23.225/Now Sec.  23.2160)
    In the NPRM, proposed Sec.  23.225 (now Sec.  23.2160) would have--
     Precluded vibration and buffeting from interfering with 
the control of the airplane or causing fatigue to the flightcrew, for 
operations up to VD/MD;
     Allowed stall warning buffet within these limits;
     Precluded perceptible buffeting in cruise configuration at 
1g and at any speed up to VMO/MMO, except stall 
buffeting for high-speed airplanes and all airplanes with a maximum 
operating altitude greater than 25,000 feet (7,620 meters) pressure 
altitude;
     Required an applicant seeking certification of a high-
speed airplane to determine the positive maneuvering load factors at 
which the onset of perceptible buffet occurs in the cruise 
configuration within the operational envelope and preclude likely 
inadvertent excursions beyond this boundary from resulting in 
structural damage; and
     Required high-speed airplanes to have recovery 
characteristics that do not result in structural damage or loss of 
control, beginning at any likely speed up to VMO/
MMO, following an inadvertent speed increase and a high-
speed trim upset.
    Textron and the Associations noted that the language from which 
proposed Sec.  23.220(a) originated (former Sec.  23.251) included the 
term ``excessive fatigue,'' rather than ``fatigue.'' These commenters 
recommended that the FAA use the term ``excessive fatigue'' in proposed 
Sec.  23.220(a). Textron explained that by omitting the term 
``excessive,'' any perceptible level of fatigue could be considered 
unacceptable and the proposal would result in an unwarranted change in 
standards for vibration.
    The FAA agrees with the commenters and is adding the term 
``excessive'' to Sec.  23.2160(a).
    ICON contended that proposed Sec.  23.225(b) would have been fine 
for landplanes, but not for seaplanes because seaplanes, with their 
hull step, will always have some buffet in cruise. Additionally, ICON 
noted that airplane with windows removed will have perceptible 
buffeting at all speeds.
    The FAA agrees with ICON that seaplanes and floatplanes routinely 
operate with a limited amount of buffet during normal operation. The 
FAA did not intend for proposed Sec.  23.225(b) to increase the level 
of safety over former Sec.  23.251, which allowed for the limited 
buffeting normal to seaplanes and floatplanes. Historically, this level 
of buffeting has not interfered with the control of the airplane or 
caused excessive fatigue to the pilot. Because the proposed rule 
language originated from former Sec.  23.251, the FAA finds that it 
does not create a new certification burden on applicants with seaplanes 
or floatplanes. Accordingly, the FAA adopts the language as proposed. 
Furthermore, airplanes approved for operations without doors or 
windows, or those that allow the windows to open in flight, were not 
intended to be addressed under this rule.
    Textron and the Associations noted that the former requirement for 
a high-speed trim upset (former Sec.  23.255) applied to designs with 
adjustable horizontal stabilizers. However, the FAA did not specify 
whether proposed Sec.  23.220(d)(2) would have been limited to 
airplanes with adjustable horizontal stabilizers. Textron explained 
that, as proposed, Sec.  23.220(d)(2) would have contained an 
additional requirement for high-speed airplanes that did not have 
trimmable horizontal stabilizers. The commenters recommended the FAA 
limit the application of proposed Sec.  23.220(d)(2) to airplanes that 
incorporate a flight adjustable horizontal stabilizer.
    The FAA intended to keep this requirement as general as possible, 
not to propose a new requirement on high-speed airplanes that lacked 
trimmable horizontal stabilizer. As stated in the NPRM, the FAA 
intended proposed Sec.  23.220(d)(2) (now Sec.  23.2160(d)(2)) to 
address the current safety intent of former Sec.  23.255, which applied 
only to airplanes that included trimmable horizontal stabilizers. The 
FAA adopts language in Sec.  23.2160(d)(2) to clarify that the 
requirement applies only to airplanes that incorporate trimmable 
horizontal stabilizers.
n. Performance and Flight Characteristics Requirements for Flight in 
Icing Conditions (Proposed Sec.  23.230/Now Sec.  23.2165)
    In the NPRM, proposed Sec.  23.230 (now Sec.  23.2165) would have 
required--
     An applicant requesting certification for flight in icing 
conditions to demonstrate compliance with each requirement of this 
subpart. Exceptions to this rule would have been requirements 
applicable to spins and any requirement that would have to be 
demonstrated at speeds in excess of 250 KCAS, VMO or 
MMO, or a speed at which an applicant demonstrates the 
airframe would be free of ice accretion;
     The stall warning for flight in icing conditions and non-
icing conditions to be the same.
     An applicant requesting certification for flight in icing 
conditions to provide a means to detect any icing conditions for which 
certification is not requested and demonstrate the airplane's ability 
to avoid or exit those conditions; and
     An applicant to develop an operating limitation to 
prohibit intentional flight, including takeoff and landing, into icing 
conditions for which the airplane is not certified to operate.
    Proposed Sec.  23.230 would have also added optional icing 
conditions where a manufacturer may demonstrate its airplane can either 
safely operate in, detect and safely exit, or avoid. Finally,

[[Page 96607]]

proposed Sec.  23.230 would have only applied to applicants seeking 
certification for flight in icing.
    NJASAP stated it viewed proposed Sec.  23.230 as a safety 
enhancement and noted that several accidents have demonstrated a 
benefit to having one stall standard--meaning the airplane should be 
able to remain largely free of ice in conditions within which it is 
certified to operate. The NTSB stated that adopting proposed Sec. Sec.  
23.230 and 23.1405 will likely result in Safety Recommendation A-96-54 
being classified as ``Closed--Acceptable Action.''
    Textron and the Associations asked the FAA to clarify that proposed 
Sec.  23.230(a) applies to the airplane's ice protection system when it 
is operating normally, not when it is in a failed or degraded mode. 
Therefore, rather than requiring the applicant to demonstrate the 
requirements of proposed paragraphs (a)(1) and (a)(2), the Associations 
recommended that the FAA require the normally-operating airplane ice 
protection systems to include the requirements of proposed paragraphs 
(a)(1) and (a)(2).
    The FAA agrees with the comments made by the Associations and 
Textron, and the FAA adopts language to clarify that Sec.  23.2165(a) 
applies to the normal operation of an ice protection system. 
Accordingly, Sec.  23.2165(a) now requires the applicant to demonstrate 
the requirements of paragraphs (a)(1) and (a)(2) under the normal 
operation of the ice protection system.
    The FAA is also changing the language in Sec.  23.2165(a) to 
clarify that Sec.  23.2165 applies to an applicant who requests 
certification for flight in icing conditions defined in part 1 of 
appendix C to part 25, or to an applicant who requests certification 
for flight in these icing conditions and any additional atmospheric 
icing conditions. This change better reflects the FAA's intent.\27\
---------------------------------------------------------------------------

    \27\ 81 FR 13452, 13462
---------------------------------------------------------------------------

    Additionally, the FAA is using the phrase ``must show'' rather than 
``must demonstrate'' in Sec.  23.2165(a), because ``must demonstrate'' 
may be interpreted as requiring a flight test, as Textron suggested in 
its comment on proposed Sec.  23.230(b) (discussed later). This change 
is consistent with the NPRM, which explained that demonstration, as a 
means of compliance, may include design review and/or analysis and does 
not mean flight tests are required.\28\
---------------------------------------------------------------------------

    \28\ 81 FR 13452, 13493
---------------------------------------------------------------------------

    The FAA is also adding the never-exceed speed (VNE) to 
the exception in Sec.  23.2165(a), under paragraph (a)(1)(ii), to 
correct an inadvertent omission in the proposal. Because proposed Sec.  
23.230(a)(1)(ii) was intended to apply to both piston and turbine 
airplanes, the addition of VNE is necessary as the proposed 
VMO/MMO would only have applied to turbine 
airplanes. This change from what was proposed is consistent with the 
current guidance in AC 23.1419-2D.
    BendixKing, Daher,\29\ the Associations, Kestrel, and Textron all 
requested clarification of the wording of proposed Sec.  23.230(a)(2), 
which proposed that the applicant must demonstrate that the stall 
warning for flight in the icing conditions and non-icing conditions is 
``the same.'' Several of the commenters explained that the stall 
warning in icing conditions needs to provide a similar notification as 
the stall warning in non-icing conditions, but it does not need to 
occur in the same way.
---------------------------------------------------------------------------

    \29\ In its comment, Daher quoted 23.230(a)(2) but attributed 
that quote to 23.300
---------------------------------------------------------------------------

    Textron similarly stated that proposed Sec.  23.230(a)(2) could be 
interpreted as indicating that the stall warning must be the same in 
all of its aspects, which should not be the intent. Textron explained 
that the stall warning system in icing conditions cannot be the same as 
in non-icing conditions because some designs require a different angle 
of attack schedule in icing to obtain the same airspeed margin between 
stall warning and stall. Textron recommended requiring ``the means by 
which stall warning is provided to the pilot'' to be the same in icing 
and non-icing conditions.
    In response to the comments on proposed Sec.  23.230(a)(2), the FAA 
did not intend to require the stall warning to be the same in all 
material aspects for flight in icing conditions and non-icing 
conditions. Rather, the FAA intended proposed Sec.  23.230(a)(2) to 
require the same type of stall warning, such as an artificial stall 
warning system or an aerodynamic buffet. Therefore, the FAA adopts 
Textron's recommendation. Accordingly, Sec.  23.2165(a)(2) now requires 
the means by which the stall warning is provided to the pilot to be the 
same in both icing and non-icing conditions. This change from the 
proposal addresses the other commenters' concerns by clarifying that 
the type of stall warning provided to the pilot, rather than the design 
of the stall warning system, must be the same.
    Textron recommended replacing the words ``must demonstrate'' with 
the words ``must show'' in proposed Sec.  23.230(b), because the former 
typically implies compliance by flight testing, whereas the latter 
allows more than one means of compliance. Similarly, the Associations 
commented that proposed Sec.  23.230(b) should ensure the design 
includes a means to safely avoid and exit icing conditions. However, 
the FAA should not require the applicant to ``demonstrate the 
airplane's ability'' to avoid or exit icing conditions because the 
means by which the airplane safely avoids or exits icing conditions may 
not have to be demonstrated under part 21. The commenters noted that 
amended designs, for example, may use similarity to a previously 
approved design to show compliance.
    The FAA agrees that ``must demonstrate'' in proposed Sec.  
23.230(b) may be interpreted as requiring a flight test. Because the 
FAA did not intend to preclude other means of compliance, the FAA 
adopts the phrase ``must show,'' as recommended by Textron. 
Accordingly, Sec.  23.2165(b) now requires an applicant requesting 
certification for flight in icing conditions to show the airplane's 
capability to avoid or exit icing conditions for which certification is 
not requested.
    Kestrel supports categorizing SLD as an icing condition, but noted 
that guidance in AC 23.1419-2D is currently used on part 23 icing 
certification programs to establish SLD detection cues and exit 
procedures. Kestrel asked the FAA to clarify whether this guidance will 
continue to be an acceptable means of compliance for the ice detection 
requirement.
    The NPRM stated ``many manufacturers already have equipped recent 
airplanes with technology to meet the standards for detecting and 
exiting SLD conditions in accordance with current FAA guidance.'' 
Although systems to detect SLD are being developed, none have been 
certified. Inclusion of the pilot cues as listed in AC 23.1419-2D into 
the AFM have been an acceptable means to detect SLD, and will continue 
to be an acceptable means of compliance to Sec.  23.2165(b).
    ANAC questioned whether proposed Sec.  23.230(c) was intended to 
prohibit flight into known icing conditions or forecast icing 
conditions. ANAC recommended including the term ``known'' before 
``icing conditions.''
    The FAA agrees with ANAC's position that only ``known'' icing 
conditions should be prohibited. However, Sec.  23.2165(c) prohibits 
intentional flight into icing conditions. Because the term 
``intentional'' implies that the icing conditions are known, the FAA 
finds it unnecessary to include the term ``known'' before ``icing 
conditions.'' Accordingly, the FAA

[[Page 96608]]

adopts the language in Sec.  23.2165(c) as proposed.
    An individual commenter appeared to criticize the FAA for not 
requiring de-icing to work and suggested that ``[a] wind tunnel at the 
far North or South may be enough for a conclusive test.'' In response 
to the individual commenter, an icing tunnel is a standard means of 
compliance to test ice protection systems on new airplane designs. Any 
resulting intercycle, residual, or runback ice has to be accounted for 
when showing compliance with the subpart B regulations in icing. No 
changes are made as a result of this comment.
4. Subpart C--Structures
a. Structural Design Envelope (Proposed Sec.  23.300/Now Sec.  23.2200)
    In the NPRM, proposed Sec.  23.300 (now Sec.  23.2200) would have 
required the applicant to determine the structural design envelope, 
which describes the range and limits of airplane design and operational 
parameters for which the applicant would show compliance with the 
requirements of subpart C. Proposed Sec.  23.300 would have required 
the applicant to account for all airplane design and operational 
parameters that affect structural loads, strength, durability, and 
aeroelasticity, including structural design airspeeds and Mach numbers.
    Several commenters identified concerns with the detailed 
definitions of airspeeds for which applicants would be required to 
account. They pointed out that, for some types of airplanes, these 
airspeeds may not be appropriate in particular circumstances. EASA 
recommended removal of the speed definitions for a more generic 
proposal in its proposed CS 23.320.
    The FAA recognizes the commenters' concerns on the various issues 
in proposed Sec.  23.300(a). The FAA believes the best way to address 
these comments is to adopt regulatory text similar to the text in 
EASA's section CS 23.320, which removes the need to define individual 
design airspeeds in the regulation. Some comments on proposed Sec.  
23.300(a) recommended retaining certain methods of compliance language, 
such as defining VC in terms of VH, which is in 
former part 23. In keeping with the intent of this rulemaking, however, 
the FAA believes these types of prescriptive standards are best moved 
to means of compliance.
    Air Tractor commented on proposed Sec.  23.300(b), which addressed 
design maneuvering load factors for the structural design envelope. Air 
Tractor raised concerns that obtaining consensus compliance from the 
FAA without the prescriptive formula established by former Sec.  
23.337(a) would be a protracted battle--worse than the existing issue 
paper process for non-standard design.
    Regarding Air Tractor's concerns, the FAA has decided to move the 
prescriptive formula for determining the design maneuvering load 
factors to means of compliance. The FAA also reiterates that the phrase 
``service history'' is intended to mean the design maneuvering load 
factors should be based on those load factors used for airplanes with 
successful service histories that have similar design, operational 
capabilities, and intended use. If there are no existing similar 
designs, the FAA will work with the applicant to identify the most 
appropriate means of compliance. In general, the FAA does not expect 
applicants to measure and record maneuvering load factors on new 
designs.
    EASA asserted that the language in proposed Sec.  23.300(c) was too 
design specific and could be replaced with the text from its proposed 
CS 23.305.
    The FAA finds that proposed Sec.  23.300(c) is not overly design 
specific, because each of the enumerated items must be taken into 
account, regardless of the applicant's design. The FAA therefore adopts 
paragraph (c) as proposed.
    Air Tractor recommended the FAA change ``empty weight to the 
maximum weight'' to ``minimum flying weight to maximum weight,'' in 
proposed Sec.  23.300(c)(1). Air Tractor stated this language applies 
to all airplanes and is appropriate for certification; while ``empty 
weight'' applies only to certain airplanes' operational requirements.
    The FAA notes Air Tractor's recommendation that ``empty weight'' in 
Sec.  23.2200(c)(1) should be replaced with ``minimum flying weight.'' 
However, the FAA believes that establishing a design empty weight is 
necessary so that variations in the mass of properties such as fuel, 
payloads, and occupants, when added to the airplane, can be accounted 
for.
    The Associations recommended deleting the term ``All'' from the 
beginning of proposed Sec.  23.300(c)(1) and (e) for simplification. 
Textron recommended changing ``All'' in proposed Sec.  23.300(c)(1) to 
``Each.'' Textron stated the change would be consistent with former 
part 23, which uses ``each weight'' throughout the subparts, whereas 
``all'' implies an applicant would have to evaluate an infinite number 
of weights rather than those that are relevant. Textron also 
recommended replacing ``All'' in proposed Sec.  23.300(e) with ``Each 
critical altitude,'' because ``all'' is too encompassing.
    The FAA agrees with the recommendation to replace ``All'' with 
``Each'' in proposed Sec.  23.300(c) and (e) and revises the language 
in both paragraphs accordingly. The FAA also adds the word ``critical'' 
so the subsection text reads ``Each critical. . .''. In this context, 
``critical'' refers to a weight or altitude that results in a maximum 
or minimum structural loading condition. A ``critical weight'' will, 
for example, be the weight of the airplane at its highest possible 
value with no fuel in the wing. This condition will reduce the effects 
of inertia in the wing and result in maximum structural loads. A 
``critical altitude'' will be the altitude where the maximum pressure 
differential occurs in a pressurized cabin, or an altitude where the 
effects of atmospheric compressibility cause changes to the airplane 
aerodynamic coefficients, resulting in maximum structural loads.
    EASA commented that proposed Sec.  23.300(d) was too design 
specific and should cover loads resulting from controls.
    The FAA interprets EASA's comment to mean the FAA should consider 
non-traditional methods of control, such as vectored thrust. The FAA 
agrees and revises paragraph (d) to include non-traditional control 
systems.
    EASA also commented on proposed Sec.  23.300(e), stating it would 
create a requirement that is not applicable to very-light aircraft 
(VLA) today. EASA asserted that the intent can be covered by the new 
proposal for flight loads in proposed Sec.  23.310 (now Sec.  23.2210).
    While the FAA notes EASA's concern with proposed Sec.  23.300(e), 
the FAA finds that paragraph (e), as proposed, would place only an 
insignificant burden on an applicant using the VLA standard. The FAA 
finds a simple method of compliance, such as for a maximum altitude of 
14,000 feet, could be incorporated into an industry consensus standard 
to meet this requirement.
b. Interaction of Systems and Structures (Proposed Sec.  23.305/Now 
Sec.  23.2205)
    In the NPRM, proposed Sec.  23.305 (now Sec.  23.2205) would have 
provided a regulatory framework for the evaluation of systems intended 
to modify an airplane's structural design envelope or structural 
performance, and other systems whose normal operating state or failed 
states may affect structural performance. Compliance with proposed 
Sec.  23.305 would have provided acceptable mitigation of structural

[[Page 96609]]

hazards identified in the functional hazard assessments required by 
proposed Sec.  23.1315.
    Textron recommended removing proposed Sec.  23.305 because the NPRM 
makes clear that, with or without proposed Sec.  23.305, the safety 
intent of proposed Sec.  23.1315 covers the interaction of systems and 
structures. Textron also objected to the use of, or reference to, non-
part 23 data. As an example, Textron cited the reference in the 
preamble to FAA special condition number 25-390-SC,\30\ which the FAA 
said would be an acceptable means of compliance with proposed Sec.  
23.305. Textron questioned whether there was justification for this 
requirement if part 23 data was not available.
---------------------------------------------------------------------------

    \30\ http://rgl.faa.gov/Regulatory_and_Guidance_Library/rgSC.nsf/MainFrame?OpenFrameset.
---------------------------------------------------------------------------

    In response to Textron's comment regarding the necessity of 
proposed Sec.  23.305, the FAA notes the intent stated in the NPRM was 
erroneous in its description of the relationship between proposed Sec.  
23.305 and proposed Sec.  23.1315 (now Sec.  23.2510). The correct 
intent of proposed Sec.  23.305 is to provide a requirement for those 
systems intended to directly affect structural performance. An example 
of this type of system is a structural load alleviation system. Former 
Sec.  23.1309 and Sec.  23.2510 do not envision these types of systems 
and the FAA has previously issued special conditions to address these 
unique and novel systems. Therefore, the FAA retains proposed Sec.  
23.305 as Sec.  23.2205 in this final rule because it provides a way 
for applicants to address failures in systems intended to directly 
affect structural performance by accounting for the probability of such 
failures and the likely pilot reactions to them.
    Also, regarding Textron's comment that the NPRM preamble referenced 
a part 25 special condition that did not contain part 23 data, the FAA 
notes the reference was used as an example because the wording of the 
special condition was typical of others relating to Interaction of 
Systems and Structure, which establish an acceptable method of 
compliance with this section. The FAA has issued a part 23 special 
condition (23-258A-SC).\31\ However, the FAA did not use the part 23 
special condition as an example because, while it is an acceptable 
method of compliance with this section, the approach used in it is not 
typical of other special conditions addressing these issues.
---------------------------------------------------------------------------

    \31\ 78 FR 10055, February 13, 2013.
---------------------------------------------------------------------------

    Textron also stated the phrase ``affect structural performance'' 
was too vague and should be better defined for clarity. Textron noted 
every trim system, flight control system, and high lift system affects 
structural performance at some level. Textron recommended either 
eliminating this phrase or using the preamble to define ``structural 
performance.'' Textron recommended proposed Sec.  23.305 be revised to 
provide that, for airplanes equipped with systems intended to alleviate 
the impact of the requirements of this subpart and affect the 
structural design envelope, either directly or as a result of failure 
or malfunction, the applicant must account for the influence and 
failure conditions of these systems when showing compliance with the 
requirements of this subpart.
    The Associations commented that proposed Sec.  23.305 was intended 
to address systems, which may use aerodynamic or other means to 
alleviate loads in certain conditions and to ensure structural 
integrity remains in the event these systems were to fail. The 
commenters requested the FAA change the language to ensure the intent 
of this section is clear and there are no unintended consequences, such 
as creating a requirement to perform systems safety assessments on all 
systems and structure interactions. The commenters asserted that this 
would create a tremendous burden with no measurable benefit. The 
commenters proposed Sec.  23.305 be revised to provide that, for 
airplanes equipped with systems that are intended to alleviate 
structural loads, the applicant must account for the influence and 
failure conditions of these systems when showing compliance with the 
requirements of this subpart.
    The FAA agrees with Textron and the Associations that Sec.  23.2205 
should address only those systems intended to affect structural 
performance. In the NPRM, the FAA referred to these types of systems as 
``structural systems''. The FAA referred to other types of systems as 
``non-structural systems''. The FAA agrees that these non-structural 
systems are adequately addressed by Sec.  23.2510. The FAA is using the 
NPRM description of structural systems in rewording Sec.  23.2205 to 
ensure that any airplane equipped with a system intended to affect 
structural performance would be provided the same level of safety as an 
airplane not equipped with such a system.
c. Structural Design Loads (Proposed Sec.  23.310/Now Sec.  23.2210)
    In the NPRM, proposed Sec.  23.310 (now Sec.  23.2210) would have 
required--
     An applicant to determine structural design loads 
resulting from an externally or internally applied pressure, force, or 
moment that may occur in flight, ground and water operations, ground 
and water handling, and while the airplane is parked or moored.
     An applicant to determine structural design loads at all 
combinations of parameters on and within the boundaries of the 
structural design envelope that would result in the most severe loading 
conditions; and
     The magnitude and distribution of these loads be based on 
physical principles and be no less than service history has shown can 
occur within the structural design envelope.
    The Associations recommended adding the phrase ``as applicable'' to 
proposed Sec.  23.310(a) to address the varying bases to determine load 
calculations. These commenters also recommended replacing the term 
``any'' with the word ``likely,'' because the calculation of any 
externally or internally applied pressure, force, or moment would 
result in boundless design and calculation. Textron recommended the 
same revisions. Textron noted that the rule implies that all airplanes 
will be required to determine both ground and water loads, but not all 
airplanes are amphibious.
    The FAA agrees with Textron and the Associations concerning the 
comments on adding the phrase ``as applicable'' and removing the word 
``any'' in proposed Sec.  23.310(a). The FAA also agrees with limiting 
the scope of proposed Sec.  23.310(a) by adding the word ``likely'' to 
the description of the loading conditions the applicant must consider. 
As explained in the discussion of proposed Sec.  23.205, ``likely'' 
means reasonably expected based on the conditions that may exist. 
Accordingly, the FAA revises Sec.  23.2210(a) to capture these changes.
    Air Tractor recommended the FAA delete the ``service history'' 
clause from proposed Sec.  23.310(c) because there is no ``service 
history'' for most new airplanes and there is danger that the FAA will 
require that service history be collected before certification is 
granted for a new design. EASA also noted that a ``service history'' 
will not always be available for innovative designs.
    The FAA partially agrees with Air Tractor regarding the meaning of 
``service history'' in proposed Sec.  23.310(c). Service history, in 
this sense, refers to the service history and experience gained 
throughout aviation history. In Air Tractor's case, service history 
would be the service history of other restricted category agricultural 
airplanes of similar design. The FAA finds Sec.  23.2200(b) adequately 
covers the intent of the ``service history''

[[Page 96610]]

requirement and therefore removes it from Sec.  23.2210(c).
d. Flight Load Conditions (Proposed Sec.  23.315/Now Sec.  23.2215)
    In the NPRM, proposed Sec.  23.315 (now Sec.  23.2215) would have 
required an applicant to determine the loads resulting from vertical 
and horizontal atmospheric gusts, symmetric and asymmetric maneuvers, 
and, for multiengine airplanes, failure of the powerplant unit which 
results in the most severe structural loads.
    EASA noted the proposed rule did not cover the objective that loads 
should be considered for the operational envelope, but instead based 
the requirement on measured gust statistics. EASA proposed using its CS 
23.315 language because it is more objective and does not include 
design details.
    The FAA finds the requirement to consider loads throughout the 
operational envelope is addressed by proposed Sec.  23.310(b) (now 
Sec.  23.2210(a)(2)). However, the FAA agrees with EASA's comment that 
the proposed rule language is too design specific. Therefore, FAA 
revises the rule language to remove design specifics. In particular, 
the FAA removes proposed Sec.  23.215(c), which addressed canted 
lifting surfaces. The FAA finds Sec.  23.2210(c) adequately addresses 
this requirement. The FAA also changes the wording of proposed Sec.  
23.215(d) (now 23.2215(c)) to account for the possibility that a single 
powerplant, operating two separate propellers, could develop asymmetric 
thrust if one propeller system experienced a failure. This would result 
in a condition similar to an engine failure in a multiengine airplane, 
described in the former regulations. Although no applicant has 
submitted such a design for approval to date, given the increased 
flexibility this rule provides, future applicants may propose such a 
design. In that case, this design will be subject to the same safety 
concern and the same need to address it, as applicants for approval of 
multiengine airplanes.
    Air Tractor commented on proposed Sec.  23.315(a) and questioned 
whether the gust velocities in former part 23 or CAR 3 were based on 
``measured gust statistics.'' Air Tractor noted it has never seen a 
technical report to that effect. Air Tractor also questioned whether 
the FAA would deem the CAR 3 and current part 23 values sufficient, and 
raised concerns that making up its own requirements to meet FAA 
approval would be difficult.
    The FAA changed the gust load formula in former Sec.  23.341, 
amendment 23-7 \32\ to incorporate the mass parameter approach to 
calculating gust loads. The mass parameter approach was developed and 
calibrated against measured gust data on transport category airplanes. 
The FAA does not intend for applicants for a new TC to measure gust 
loadings. The former gust formula remains an acceptable method of 
compliance with this regulation. The FAA developed this regulation so 
certain airplanes could take advantage of alternate analysis methods, 
including the power spectral density approach. Examples of these types 
of airplanes include high altitude and endurance airplanes, where 
dynamic response of the airplane structure must be considered in the 
gust load analysis.
---------------------------------------------------------------------------

    \32\ 34 FR 13078, August 13, 1969.
---------------------------------------------------------------------------

e. Ground and Water Load Conditions (Proposed Sec.  23.320/Now Sec.  
23.2220)
    In the NPRM, proposed Sec.  23.320 (now Sec.  23.2220) would have 
required an applicant to determine the loads resulting from taxi, take-
off, landing, and ground handling conditions occurring in normal and 
adverse attitudes and configurations.
    EASA proposed using its A-NPA CS 23.325 language because it is more 
objective and covers more situations, such as landing on snow or other 
surfaces not covered in proposed Sec.  23.320. BendixKing asked that 
the FAA delete ``sea,'' stating the word is neither required nor 
accurate.
    The FAA agrees with EASA's comments and revises the text in Sec.  
23.2220 to include all operating surfaces, which includes, at a 
minimum, snow or ice covered land and water. EASA referred to snow and 
other surfaces not covered in the proposed text, presumably meaning 
EASA does not consider operations on ``snow or other surfaces'' to be 
operations on the ground. While the FAA is using EASA's CS A-NPA 23.325 
language, the FAA finds EASA's language citing weight and velocity to 
be unnecessary. These parameters are addressed in Sec.  23.2200.
    Air Tractor asked whether the ``ground handling conditions'' in 
proposed Sec.  23.320(a) would be different from the ``jacking and 
towing conditions'' in proposed Sec.  23.320(c). If so, the commenter 
asked what ``ground handling conditions'' meant. Air Tractor also asked 
whether this dealt with protection from ``hangar rash.'' Finally, Air 
Tractor sought clarification on whether it would now need to define the 
structural loads associated with docking an airplane, or from wave 
motion causing scuffing when a seaplane is moored against a dock.
    The FAA notes the ``ground handling conditions'' referenced in 
proposed Sec.  23.320(a) (now Sec.  23.2220) are different than the 
``jacking and towing conditions'' referenced in Sec.  23.320(c) (now 
Sec.  23.2220). The reference to ``handling conditions'' is intended to 
cover both ground handling conditions and jacking and towing 
conditions. The FAA revises Sec.  23.2220 to cover ``taxi, takeoff, 
landing, and handling conditions.''
f. Component Loading Conditions (Proposed Sec.  23.325/Now Sec.  
23.2225)
    In the NPRM, proposed Sec.  23.325 (now Sec.  23.2225) would have 
required an applicant to determine the loads acting on each engine 
mount, flight control, high lift surface, and the loads acting on 
pressurized cabins.
    EASA commented that proposed Sec.  23.325(b) covered the loads on 
components subject to earlier defined loads in proposed Sec. Sec.  
23.305 through 23.320. EASA recommended the FAA simplify the 
requirement to avoid different interpretations by reflecting the 
relation to the previous requirements as follows:

 Interaction of systems and structures
 Structural design loads
 Flight Load Conditions
 Ground and water load conditions

    The FAA finds that a separate rule for component loading conditions 
is necessary to address structural loading conditions that do not fall 
under the requirements for flight and ground loads. Examples of these 
loading conditions include control surface jamming and pressurized 
cabin loads. The FAA revises Sec.  23.2225 to clarify the types of 
loads applicants must account for.
    Textron and the Associations asked the FAA to revise the ``relief 
valve'' language in proposed Sec.  23.325(c), which was a design-
specific solution, in favor of more performance-based language. Textron 
suggested language such as ``from zero to the maximum relief pressure 
combined with gust and maneuver loads.'' The Associations recommended 
replacing ``valve'' with ``pressure.''
    The FAA agrees with Textron and the Associations on the use of the 
term ``relief valve.'' The FAA revises Sec.  23.2225(c)(1), (2), and 
(3) by replacing the term ``relief valve'' with ``relief pressure.''
    The FAA agrees with a comment made at the public meeting by the 
Associations that proposed Sec.  23.325 should cover sudden engine 
stoppage loads for turbine engines, as did former part 23. A 
requirement for the design of

[[Page 96611]]

engine mounts for turbine engines to be able to withstand a sudden 
engine stoppage has been in former part 23 since 1980.\33\ Former Sec.  
23.361(b)(1) required, in pertinent part, that for turbine engine 
installations, the engine mounts and supporting structure be designed 
to withstand an engine torque load imposed by a sudden engine stoppage. 
The requirement applied only to turbine engines because reciprocating 
engines typically do not have significant rotational moments of 
inertia. As in former part 23, reciprocating powerplants, with their 
lower moments of inertia, are not included in this section of the rule. 
The requirement applies only to turbines and other types of powerplants 
that have significant rotational moments of inertia created by rotating 
powerplant components (e.g., electric motor powerplants). Therefore, 
the FAA adds protection of powerplant mounts and supporting structure 
from sudden powerplant stoppage for all non-reciprocating powerplants 
to Sec.  23.2225(a)(2). This change is consistent with the goal of 
capturing the safety intent of former part 23, including Sec.  23.361, 
as stated in the NPRM preamble, and with the performance-based nature 
of this rule and its goal of more easily accommodating future designs 
and technologies.
---------------------------------------------------------------------------

    \33\ 45 FR 60171, September 11, 1980.
---------------------------------------------------------------------------

    Finally, the FAA revises Sec.  23.2225(b) to clarify the gust loads 
that must be accounted for and the meaning of ``ground operations,'' 
making this section consistent with the changes discussed previously 
for Sec.  23.2220.
g. Limit and Ultimate Loads (Proposed Sec.  23.330/Now Sec.  23.2230)
    In the NPRM, proposed Sec.  23.330 (now Sec.  23.2230) would have 
described how the applicant must determine the limit and ultimate loads 
associated with the structural design loads. Proposed Sec.  23.330 
retained the current 1.5 safety factor for ultimate loads.
    The Associations recommended the FAA revise proposed Sec.  23.330 
by deleting the phrase ``special or other factors of safety are 
necessary to meet the requirements of'' and replacing it with 
``ultimate loads are specified in.'' These commenters noted the 
section, as written, would not require the establishment of limit loads 
if a special factor of safety is used to meet the requirement. Textron 
recommended the same revision, explaining that proposed Sec.  23.330 
need not address ``special or other factors of safety,'' other than in 
some cases when an ultimate load is specified, because proposed Sec.  
23.515(c) specified that limit and ultimate loads are multiplied by 
special factors of safety.
    The FAA agrees with the comments regarding cases where loads are 
expressed only as ultimate loads. The FAA deletes the introductory 
phrase ``unless special or other factors of safety are necessary to 
meet the requirements of this subpart,'' in proposed Sec.  23.330. The 
FAA notes Sec.  23.2265(c) specifies that limit and ultimate loads are 
multiplied by special factors of safety. Furthermore, the FAA revises 
Sec.  23.2230 by inserting the phrase ``unless otherwise specified 
elsewhere in this part,'' which captures the intent of former Sec.  
23.303.
    EASA recommended the FAA should also address the former requirement 
for redistribution of loads due to deflections under loads. EASA also 
recommended the regulation cover the specific case where strength 
specifications are expressed only in ultimate loads and permanent 
deformation is accepted.
    The FAA notes Sec.  23.2210(b) addresses the issue of 
redistribution of loads. Specifically, 23.2210(b) requires the 
distribution of loads be based on physical principles. The FAA finds 
redistribution of load due to deflection is an expression of physical 
principles and is retaining this requirement in Sec.  23.2210(b) of 
this rule.
    An individual commenter asked the FAA to remove the ``arbitrarily 
prescriptive'' 1.5 factor of safety and substitute a more performance-
based approach. The commenter explained that advances in probabilistic 
analysis have increased understanding of actual variables like load 
predictions, material properties, and airplane operations. The 
commenter proposed defining the value for structural failure more 
explicitly and allowing the applicant to account for the variations to 
achieve the value, allowing for more efficient designs. The commenter 
suggested retaining the 1.5 factor of safety as a possible approval 
approach to establish the means of compliance.
    The FAA notes the 1.5 factor of safety has been used for many years 
and has provided an acceptable level of safety. Probabilistic analysis 
methods and the data necessary to support them are not sufficiently 
mature to provide the same level of assurance of safety. As 
probabilistic methods mature, the FAA will consider their use if 
applicants can show they provide an equivalent level of safety.
h. Structural Strength (Proposed Sec.  23.400/Now Sec.  23.2235)
    In the NPRM, proposed Sec.  23.400 (now Sec.  23.2235) would have 
required an applicant to demonstrate the structure will support limit 
and ultimate loads. The NPRM explained that in this context, 
``demonstrate'' means the applicant must conduct structural tests to 
show compliance with the structural performance requirements unless the 
applicant shows that a structural analysis is reliable and applicable 
to the structure.
    The Associations recommended adding ``unsafe'' at the beginning of 
proposed Sec.  23.400(a)(1) to clarify the intent of the requirement 
and ensure it is not viewed as including expected or non-critical types 
of interference, such as thrust reverser buckets making normal contact 
with each other. Similarly, Textron recommended inserting the word 
``safe'' before ``operation'' in proposed paragraph (a)(1) to ensure 
that ``interference'' in the regulation will always be interpreted to 
mean interference that would cause an unsafe condition.
    The FAA agrees that inserting the word ``safe'' in the text of 
proposed Sec.  23.400(a)(1) will clarify that the structure must 
support limit loads without interference with the ``safe'' operation of 
the airplane. This suggested change is consistent with the 
corresponding requirements in former part 23, and will resolve the 
Associations' concern as well. Accordingly, the FAA revises Sec.  
23.2235(a)(1) to capture this change.
    NJASAP asked why the FAA proposed removing time requirements (the 
capability of the airplane structure to support ultimate loads without 
failure for at least three seconds) in proposed Sec.  23.400.
    As discussed in the NPRM preamble, the FAA considers the ``3-
second'' rule a statement of physical principles and sound testing 
practices that does not need to be stated in the requirements for 
structural strength. It is more appropriate for inclusion in a means of 
compliance. The FAA makes no change to the regulatory text based on 
NJASAP's comment.
i. Structural Durability (Proposed Sec.  23.405/Now Sec.  23.2240)
    In the NPRM, proposed Sec.  23.405 (now Sec.  23.2240) would have 
required an applicant to develop and implement procedures to prevent 
structural failures due to foreseeable causes of strength degradation, 
and to prevent rapid decompression in airplanes with a maximum 
operating altitude greater than 41,000 feet. Proposed Sec.  23.405 
would have also required an airplane to be capable of continued safe 
flight and landing with foreseeable structural damage caused by high-
energy

[[Page 96612]]

fragments from an uncontained engine or rotating machinery failure.
    The Associations said proposed Sec.  23.405 remains ``far too 
prescriptive and design oriented.'' The commenters recommended language 
that they believed addresses the objectives of the rule without being 
so design focused. Specifically the Associations suggested the phrase 
``serious or fatal injuries, loss of the airplane, or extended periods 
of operation with reduced safety margins'' in Sec.  23.2240(a) be 
replaced with ``unsafe conditions.''
    Textron suggested that the proposed rule is too prescriptive 
regarding the number of compartments for compartment floor 
depressurization, as well as in prescribing the ``design'' structure 
rather than specifying the required capability of the structure. 
Textron suggested revising proposed Sec.  23.405 similar to that 
suggested by the Associations.
    An individual commenter recommended the FAA delete the phrase 
``loss of the airplane'' from proposed Sec.  23.405(a). The commenter 
stated this would address the long-understood interpretation that part 
23 does not include certain structures for required evaluation on the 
effects of fatigue failure, such as landing gear and engine support (or 
hull loss, as discussed in the NPRM preamble). Without this revision, 
the commenter noted the intent of the rule not to increase the burden 
on certification would be nullified. In effect, the commenter found the 
proposed rule would require the same structure as is currently 
evaluated in part 25, which is inconsistent with former part 23. The 
commenter favored incorporating a comprehensive fatigue evaluation of 
structure as is currently in part 25.
    The FAA agrees with the suggestion to delete the phrase ``loss of 
the airplane'' in paragraph (a). The FAA finds the prevention of 
serious or fatal injuries and the prevention of extended periods of 
operation with reduced safety margins is the objective of Sec.  
23.2240. The FAA will not adopt the Associations' recommended change to 
replace the phrase ``serious or fatal injuries, loss of the airplane, 
or extended periods of operation with reduced safety margins'' with 
``unsafe conditions.'' The term ``unsafe condition'' is the threshold 
for the FAA issuing airworthiness directives under 14 CFR part 39, and 
is not an accurate term to be used in this section.
    The FAA also revises paragraph (a) to reflect more completely the 
requirements of the former part 23 regulations this section is 
replacing.\34\ Because proposed Sec.  23.405(a) did not refer 
specifically to the Airworthiness Limitations section (ALS) of the 
Instructions for Continued Airworthiness (ICA) (as did former Sec.  
23.575), it could be interpreted as allowing the procedures to be 
placed in another part of the ICA. Therefore, the FAA revises the text 
in paragraph (a) to clarify that these procedures must be in the ALS. 
The FAA also clarifies that ``inspections'' developed under this 
section must be included in the ALS in addition to the ``procedures'' 
developed under the section, because former Sec.  23.575 required both 
to be in the ALS. Appendix G to former part 23, now appendix A to this 
final rule, requires the FAA to approve the ALS. Finally, the FAA notes 
that compliance with the ALS is mandatory under Sec. Sec.  43.16 and 
91.403(c).
---------------------------------------------------------------------------

    \34\ Sec. Sec.  23.365(e), Pressurized cabin loads; 23.571, 
Metallic pressurized cabin structures; 23.572, Metallic wing, 
empennage, and associated structures; 23.573, Damage tolerance and 
fatigue evaluation of structure; 23.574, Metallic damage tolerance 
and fatigue evaluation of commuter category airplanes; 23.575, 
Inspections and other procedures; and 23.627, Fatigue strength. (81 
FR 13476, March 14, 2016).
---------------------------------------------------------------------------

    EASA suggested replacing the design-specific requirements in 
proposed Sec.  23.405(b) with more objective requirements from EASA's 
CS 23.340(b) to allow proportionality for different airplane levels. In 
particular, EASA said more objective requirements should replace the 
proposed requirements related to pressurized airplanes and uncontained 
engine failure.
    The FAA notes the language in EASA's proposed CS 23.340 could be 
interpreted as expanding the scope of the former regulations by 
requiring evaluation of discrete source damage for all airplanes 
certificated under part 23. As stated in the NPRM, the FAA intended 
proposed Sec.  23.405(b) and (c) to capture the intent of former 
Sec. Sec.  23.365(e) and 23.571(d), which only addressed airplanes with 
pressurized compartments. Sudden release of pressure and operating 
above 41,000 feet altitude present the same hazards to the airplane 
occupants regardless of airplane category or size.
    The FAA moves the content of proposed Sec.  23.405(b) and (c) to 
Sec.  23.2240(c)(1) and (c)(2) in the final rule. The final rule also 
adds new Sec.  23.2240(b), which addresses the requirement for level 4 
airplanes. This requirement is similar to the former Sec.  23.574 
requirement for damage tolerance evaluations of commuter category 
airplanes. The FAA inadvertently left this requirement out of the NPRM.
    The FAA agrees with the comments that proposed Sec.  23.405(b) was 
overly prescriptive. The FAA deletes the detailed description of the 
pressurized compartment and emphasizes the sudden release of pressure 
in Sec.  23.2240(c)(1) and (c)(2). The FAA retains reference to door 
and window failures as examples of the types of failures that could 
result in sudden release of pressure.
    EASA stated that proposed Sec.  23.405(d) is too specific to engine 
rotorburst; however, other risks could be expected from new 
technologies that should also be considered.
    The FAA agrees with EASA's comment that paragraph (d) should 
address all high-energy fragments, not just fragments from an engine 
rotorburst. The FAA revises Sec.  23.2240(d) to include all high-energy 
fragments. The FAA also includes turbine engines and rotating machinery 
as sources of high-energy fragments.
    Several other commenters also commented on proposed Sec.  
23.405(d), noting that former part 23 required ``minimizing'' hazards 
associated with damage from uncontained engine or rotating machinery 
failures, but the NPRM would require the airplane be able to ``continue 
safe flight and landing'' following such damage. The commenters 
asserted that there is no way to eliminate all the risks that will 
prevent the ``continued safe flight and landing,'' and asked the FAA 
maintain the requirement to ``minimize'' these hazards as in former 
Sec.  23.903(b)(1).
    The FAA agrees that proposed Sec.  23.405(d) is inconsistent with 
the description in the NPRM preamble. Therefore, the FAA agrees with 
the commenters' recommendation to adopt the term ``minimize'' in Sec.  
23.2240(d). The FAA does not intend for applicants to incorporate all 
possible design precautions against rotorburst hazards, especially 
those that are resource prohibitive or have a negligible impact on 
safety. The FAA expects an applicant's compliance with Sec.  23.2240(d) 
to incorporate all practical design precautions to minimize the hazards 
due to high-energy fragments.
j. Aeroelasticity (Proposed Sec.  23.410/Now Sec.  23.2245)
    In the NPRM, proposed Sec.  23.410 (now Sec.  23.2245) would have 
required an airplane to be free from flutter, control reversal, and 
divergence at all speeds within and sufficiently beyond the structural 
design envelope, for any configuration and condition of operation, 
accounting for critical

[[Page 96613]]

degrees of freedom, and any critical failures or malfunctions. Proposed 
Sec.  23.410 would have also required an applicant to establish 
tolerances for all quantities that affect flutter.
    Air Tractor and Transport Canada raised concerns about the phrase 
``sufficiently beyond the structural design envelope'' in proposed 
Sec.  23.410(a)(1). Transport Canada said the wording is subjective and 
does not convey a performance requirement and suggested complementing 
the phrase ``sufficiently beyond'' with safety objective requirements. 
Air Tractor noted the existing regulations do not extend beyond the 
design envelope. Air Tractor asked for clarification on what is 
considered ``sufficiently beyond.''
    Regarding Air Tractor's assertion that the former regulations did 
not extend beyond the design envelope, the FAA intended proposed Sec.  
23.410 to capture the safety intent of former Sec. Sec.  23.629, 
23.677, and 23.687 without introducing the inflexibility created by the 
former regulations. Former Sec.  23.629(c) required that flutter 
analysis show freedom from flutter, control reversal, and divergence up 
to 20 percent above dive speed. Existing part 25 rule language requires 
flutter analysis to show this up to 15 percent above dive speed. This 
is to account for uncertainties inherent in analytical techniques. Part 
25 requires a smaller margin above dive speed due to its more rigorous 
analytical requirements. Additionally, former Sec.  23.629(b)(4) 
precluded any large or rapid reduction in damping as dive speed is 
approached in flight tests.
    As for Air Tractor's comment requesting clarification on what is 
considered ``sufficiently beyond'' in proposed Sec.  23.410(a)(1), the 
former part 23 requirements for margins on analyses and flight tests 
worked together to ensure a momentary inadvertent excursion above dive 
speed in operation, or combined variations in quantities that may 
affect flutter, did not result in a catastrophic flutter event. Thus, 
the FAA required a sufficient margin above dive speed in former part 23 
for many years. The phrase ``sufficiently beyond the structural design 
envelope'' is intended to require a sufficient margin consistent with 
the requirements of former part 23. However, as technology and 
analytical techniques evolve and improve, the new language will allow 
room for the methods of compliance to adapt and possibly change the 
appropriate margin needed for safe operations. This language is also 
harmonized with EASA's proposed rule language.
    Several commenters raised concerns about the use of the term 
``any'' in proposed Sec.  23.410(a). The Associations asked the FAA to 
revise proposed Sec.  23.410(a)(2) to require the airplane to be free 
from flutter, control reversal, and divergence for ``approved'' 
configurations and conditions of operation, rather than for ``any'' 
configuration and condition of operation. Textron recommended the FAA 
require the airplane to be free from flutter, control reversal, and 
divergence for ``any likely'' configuration and condition of operation. 
Similarly, the Associations suggested removing the term ``any'' from 
proposed Sec.  23.410(a)(4).
    The FAA notes the commenters concerns about the term ``any'' in 
Sec.  23.2245(a)(2) and (a)(4). In the NPRM, the FAA explained that 
Sec.  23.2245 would capture the safety intent of former Sec.  23.629. 
Former Sec.  23.629(a) has required the airplane to be free from 
flutter, control reversal, and divergence for ``any condition of 
operation'' since 1978. This terminology originated from CAR 3.311, the 
predecessor to former Sec.  23.629, was adopted in 1947 and required 
the wings, tail, and control surfaces to be free from flutter, 
divergence, and control reversal for ``all conditions of operation.'' 
The FAA recognizes it is impossible to evaluate an infinite number of 
data points, but that is not the intent of Sec.  23.2245 nor was it the 
intent of its predecessor regulations. Rather, the FAA interprets the 
term ``any'' in Sec.  23.2245(a)(2) as requiring the applicant to 
exercise due diligence by accounting for a sufficient number of data 
points that would enable the applicant to state the entire envelope has 
been evaluated and is safe. This interpretation is consistent with the 
way the FAA has interpreted CAR 3.311 and former Sec.  23.629. Because 
the FAA has used the terms ``any'' and ``all'' in its flutter 
requirements for decades, the FAA is retaining the term ``any'' in 
Sec.  23.2245(a)(2) and (a)(4). This maintains harmonization with 
EASA's proposed rule language.
    Several commenters raised concerns with terminology in proposed 
Sec.  23.410(b). Textron and the Associations suggested the FAA require 
the applicant to establish and account for ``sensitivities'' rather 
than ``tolerances'' because the term ``tolerances'' has a very specific 
meaning and a proper flutter analysis is a collection of flutter 
sensitivity analyses.\35\ The Astronautics Corporation of America 
(Astronautics) sought clarification of the term ``quantities'' in 
proposed Sec.  23.410(b) and offered alternative regulatory language in 
an attempt to clarify its meaning. Textron proposed replacing 
``quantities'' with ``parameters.''
---------------------------------------------------------------------------

    \35\ Textron specifically noted that proposed Sec.  23.2245(b) 
``would require the applicant to specify a +/-X% tolerance on things 
such as cross sectional properties (torsional GJ), cross sectional 
moments of inertia, or other qualities that affect flutter but 
aren't intended to have a +/-X% tolerance.''
---------------------------------------------------------------------------

    Regarding Textron, the Associations and Astronautics' comments on 
the use of ``tolerances'' and ``quantities'' in proposed Sec.  
23.410(b), the FAA is retaining the terms ``tolerances'' and 
``quantities'' in Sec.  23.2245(b). The FAA intends Sec.  23.2245 to 
capture the safety intent of former Sec.  23.629, which has contained 
the terms ``tolerances'' and ``quantities'' since 1978.\36\ The FAA has 
interpreted them consistently from that time, and will continue to do 
so in Sec.  23.2245. This language is also harmonized with EASA's 
proposed rule language.
---------------------------------------------------------------------------

    \36\ See 43 FR 50592, October 30, 1978.
---------------------------------------------------------------------------

    Textron recommended removing the word ``establish'' from the 
proposed language. The commenter noted that you cannot account for 
something without establishing it first.
    The FAA agrees with Textron that it would be redundant to require 
an applicant to establish and account for tolerances. For that reason, 
the FAA retains the word ``establish'' and deletes the words ``and 
account for'' from Sec.  23.2245(b) in the final rule. This change 
emphasizes the necessity of fully analyzing these tolerances and 
harmonizes with EASA's proposed rule language.
k. Design and Construction Principles (Proposed Sec.  23.500/Now Sec.  
23.2250)
    In the NPRM, proposed Sec.  23.500 (now Sec.  23.2250) would have 
required--
     An applicant to design each part, article, and assembly 
for the expected operating conditions of the airplane;
     The design data to adequately define the part, article, or 
assembly configuration, its design features, and any materials and 
processes used;
     An applicant to determine the suitability of each design 
detail and part having an important bearing on safety in operations; 
and
     The control system to be free from jamming, excessive 
friction, and excessive deflection when the control system and its 
supporting structure are subjected to loads corresponding to the limit 
airloads when the primary controls are subjected to the lesser of the 
limit airloads or limit pilot forces, and when the secondary controls 
are subjected to loads not less than those corresponding to maximum 
pilot effort.

[[Page 96614]]

    The Associations recommended the FAA change the title of proposed 
Sec.  23.500 from ``Structural design'' to ``Design and construction 
principles.''
    The FAA concurs with the recommendation by the Associations to 
change the title of Sec.  23.2250 to ``Design and construction 
principles.'' The FAA agrees the suggested title is a better descriptor 
and will harmonize with EASA's proposed title for this section, and 
adopts it for this rule.
    Several comments addressed proposed Sec.  23.500(d). Air Tractor 
recommended that the FAA revise the wording of proposed Sec.  23.500(d) 
to specify that it applies to flight controls. Air Tractor further 
noted that it appears that the definition of ``maximum pilot effort'' 
has been untethered from former Sec. Sec.  23.397(b) and 23.143(c), 
making it necessary for every applicant ``to re-invent the wheel.''
    Regarding Air Tractor's comment proposing to add the term 
``flight'' to further define ``control system'', the term ``control 
system'' has been used consistently for many years in this context in 
the former regulations, and is understood to refer to ``flight'' 
controls. This text also harmonizes with EASA's proposed rule language. 
Therefore, the FAA adopts the language as proposed in the NPRM.
    As for Air Tractor's concern that maximum pilot effort has been 
untethered from former Sec. Sec.  23.397(b) and 23.143(c), the FAA 
notes that under the new performance-based regulations, applicants will 
be free to use former part 23 or other accepted means, such as industry 
consensus standards, as a means of compliance. These accepted means of 
compliance will detail how the airplane will meet the performance-based 
requirements.
    The Associations stated that it is appropriate for means of 
compliance to specify how airframe and control system interactions will 
be tested up to limit loads and that, depending on the nature of the 
control system, it may be more or less appropriate to perform such a 
test. These tests ensure the appropriate level of testing is always 
applied to traditional flight controls and also to future systems, 
which may include fans or thrusters. The commenters suggested the level 
of detail be contained in accepted standards. Additionally, the 
commenters recommended the FAA consider revising proposed Sec.  
23.500(d) by deleting paragraphs (1), (2), and (3) and adding the 
phrase ``the airplane is subjected to expected limit airloads'' to the 
end of paragraph (d). EASA also recommended the FAA remove details in 
proposed Sec.  23.500(d) that describe what parts of the system should 
be subject to which loads because this is design specific and should be 
covered in the means of compliance.
    The FAA agrees with EASA and the Associations to revise proposed 
Sec.  23.500(d)(1), (d)(2), and (d)(3) and adds the phrase ``the 
airplane is subjected to expected limit airloads'' to the end of Sec.  
23.2250(d). This change aligns with EASA's recommendation and assists 
in harmonization with EASA's proposed rule. The FAA considers these 
suggestions to be more in line with the original intent of the 
performance standards. Therefore, the FAA adopts the changes proposed 
by the commenters.
    Textron suggested the FAA remove the Sec.  23.500(d)(1) requirement 
that the supporting structure is loaded with limit airloads while the 
control system is loaded, which the commenter noted has historically 
never been a part 23 requirement. Textron further suggested the FAA 
change the phrase ``controls are'' in both subparagraphs (2) and (3) to 
``control system is'' to further specify that this is a control system 
test. Textron commented that the word ``controls'' could imply 
something other than the entire system is the intent.
    As noted above in this section, the FAA removes paragraphs 
paragraph (d)(1), (d)(2) and (d)(3). The FAA adopts the terminology 
``control system'' in the revised proposed Sec.  23.500(d).
    EASA also suggested the FAA consider moving the general principle 
for doors, canopies, hatches, and access panels from proposed Sec.  
23.750(f) to a new Sec.  23.2250(e).
    The FAA concurs with EASA's recommendation to move the general 
principle for doors, canopies, hatches, and access panels from proposed 
Sec.  23.750(f) to a new Sec.  23.2250(e). The requirement is more 
appropriate in this section because it states a general design 
principle rather than a requirement relating to emergency evacuation. 
The FAA also notes that making this change further helps to harmonize 
FAA and EASA regulations.
l. Protection of Structure (Proposed Sec.  23.505/Now Sec.  23.2255)
    In the NPRM, proposed Sec.  23.505 (now Sec.  23.2255) would have 
required an applicant to protect each part of the airplane, including 
small parts such as fasteners, against deterioration or loss of 
strength due to any cause likely to occur in the expected operational 
environment. Proposed Sec.  23.505 would have also required each part 
of the airplane to have adequate provisions for ventilation and 
drainage and would require an applicant to incorporate a means into the 
airplane design to allow for required maintenance, preventive 
maintenance, and servicing.
    Textron recommended clarifying the intent of proposed Sec.  
23.505(a) by including a reference to specific sources of damage 
because it is unclear whether the proposed rule would be an increase 
from what was previously required.
    The FAA considered Textron's comment. However, as far back as 1949 
(Sec.  3.295, ``Protection''), the regulations required all members of 
the structure to be ``suitably protected against deterioration or loss 
of strength in service due to weathering, corrosion, abrasion, or other 
causes. . . .'' The CAR 3 requirement was included in the 1965 
recodification as former Sec.  23.609, which included a non-exhaustive 
list of possible causes of deterioration. In the NPRM, the FAA removed 
the listed examples, but maintained the requirement to account for 
deterioration or loss of strength due to ``any cause likely to occur.''
    Textron further stated that it is unclear whether the phrase 
``expected operational environment'' is intended to include any 
environment that might occur during failure conditions, or just the 
environment during normal operating conditions. Textron recommended 
replacing the phrase ``expected operational environment'' with 
``intended operational environment'' or ``normal operational 
environment.''
    The FAA considered Textron's recommendation to change ``expected 
operational environment'' to ``intended operational environment'' or 
``normal operational environment.'' The FAA did not intend to limit 
this requirement only to the normal operational environment because, if 
the failure conditions are an expected environment, then an applicant 
should consider those conditions and protect the structure. 
Deterioration or loss of strength due to corrosion, weathering, and 
abrasion are all examples of failure conditions because capability has 
been degraded. For many years, the rule has expressly required 
consideration of these causes. It was an expected environment for items 
to be corroded, weathered, and abraded, but applicants had to consider 
any other causes too.
m. Materials and Processes (Proposed Sec.  23.510/Now Sec.  23.2260)
    In the NPRM, proposed Sec.  23.510 (now Sec.  23.2260) would have 
required--
     An applicant to determine the suitability and durability 
of materials used for parts, articles, and assemblies, the failure of 
which could prevent continued safe flight and landing, while accounting 
for the effects of likely

[[Page 96615]]

environmental conditions expected in service; and
     The methods and processes of fabrication and assembly used 
to produce consistently sound structures and, if a fabrication process 
requires close control to reach this objective, an applicant would have 
to perform the process under an approved process specification.
    Additionally, proposed Sec.  23.510 would have required an 
applicant to justify the selected design values to ensure material 
strength with probabilities, accounting for--
     The criticality of the structural element; and
     The structural failure due to material variability, unless 
each individual item is tested before use to determine that the actual 
strength properties of that particular item would equal or exceed those 
used in the design, or the design values are accepted by the 
Administrator.
    Proposed Sec.  23.510 would have required a determination of 
required material strength properties to be based on sufficient tests 
of material meeting specifications to establish design values on a 
statistical basis. Proposed Sec.  23.510 would have also required an 
applicant to determine the effects on allowable stresses used for 
design if thermal effects were significant on an essential component or 
structure under normal operating conditions.
    Textron commented that, as proposed, the regulatory text in 
paragraph (a) was unclear as to whether an applicant must account for 
the effects of likely environmental conditions expected in service on 
parts, articles, and assemblies. Textron proposed combining the two 
sentences in paragraph (a) to clarify the FAA's intent for the effect 
of specific environmental conditions on parts, articles, and assemblies 
to be considered in determining the suitability and durability of 
materials.
    The FAA concurs with Textron's comment regarding the lack of 
clarity in paragraph (a), and revises the regulation accordingly. 
Although the revision creates a slight disharmony with EASA's proposed 
rule language, the intent of the two regulations remains the same, and 
the change helps to clarify the FAA's intent.
    Textron also requested the FAA to replace the word ``essential'' 
with the word ``critical''. The commenter stated the word ``essential'' 
has not been used or defined historically in part 23 structural 
compliance, whereas the word ``critical'' is used more frequently and 
is better defined.
    Based on Textron's comment for clarity, the FAA revises Sec.  
23.2260(e) to replace the word ``essential'' with the word 
``critical'', since ``critical'' is a more common and widely used term 
of art amongst structural engineers than ``essential.'' Specifically, 
the failure of a critical component or structure is potentially 
catastrophic.
    In the public meeting, Aspen Avionics asked the FAA to clarify 
whether the requirement in proposed paragraph (b) to perform the 
process under an ``approved process specification'' refers to an FAA-
approved process specification or an accepted industry standard or some 
other approved process specification. Aspen Avionics also commented on 
proposed paragraph (d), which stipulates that if material strength 
properties are required, a determination of those properties must be 
based on sufficient tests of material meeting the specifications. Aspen 
Avionics questioned whether this requirement applies to the applicant 
or whether the applicant can rely on statements from a manufacturer--
i.e., Aspen asked the FAA to clarify who has to do what testing for the 
materials. Aspen also asked whether the testing requirement applies to 
primary, secondary, or tertiary structure.
    Regarding Aspen Avionics' request for clarification of what 
constitutes an approved process specification for paragraph (b), the 
FAA does not intend any change from current practices under former 
regulation Sec.  23.605(a), where nearly identical language was used. 
The process specification is ``approved'' by the FAA, and the FAA 
expects to have access to the specification in order to review and 
determine whether it contains sufficient control to substantiate 
compliance with the regulation. The specification may be proprietary to 
the OEM or sub-contractor, but should have formal document approval and 
control procedures like other engineering reports, documents and 
drawings necessary for the type design.
    As for Aspen Avionics' question regarding the test requirements and 
whether the requirement is for primary, secondary, or tertiary 
structure, the FAA does not intend any change from current practices 
under former regulation Sec.  23.613(a), where nearly identical 
language was used. The TC holder is responsible for data used to 
substantiate its type design. Whether the required testing is performed 
by the OEM or a sub-contractor does not matter as the FAA holds the OEM 
responsible, and expects the data to be available for FAA review to 
ensure compliance with the regulation. This requirement for 
statistically based material properties applies to any airplane primary 
structure. Existing published FAA guidance and widely used industry 
practices should be consulted for the finer divisions of structure, 
such as secondary and tertiary, and the material properties typically 
used.
n. Special Factors of Safety (Proposed Sec.  23.515/now Sec.  23.2265)
    In the NPRM, proposed Sec.  23.515 (now Sec.  23.2265) would have 
required an applicant--
     To determine a special factor of safety for any critical 
design value that was uncertain, used for a part, article, or assembly 
likely to deteriorate in service before normal replacement, or subject 
to appreciable variability because of uncertainties in manufacturing 
processes or inspection methods;
     To determine a special factor of safety using quality 
controls and specifications that accounted for each structural 
application, inspection method, structural test requirement, sampling 
percentage, and process and material control; and
     To apply any special factor of safety in the design for 
each part of the structure by multiplying each limit load and ultimate 
load by the special factor of safety.
    The Associations recommended changing Sec.  23.515(a) by requiring 
special factors of safety be ``established and applied'', rather than 
determined, by the applicant. Additionally, they suggested the language 
of the regulation focus on critical design values ``affecting 
strength.''
    The FAA has used ``determine'' in numerous other places in the 
NPRM. The commenters' suggested change would not imply a different 
meaning. As for the commenters' suggestion that the term ``critical 
design value'' should be limited to those values ``affecting 
strength,'' there may be other critical design values aside from 
strength that warrant the use of special factors of safety. For 
example, former part 23 specified bearing factors for certain 
applications. These were intended to account for not only strength, but 
also for durability and consideration of possible dynamic loading. In a 
performance-based standard where these factors are not specified, it is 
necessary to make sure that future designs, materials, and 
applications, not yet envisioned, account for any critical ``design 
values,'' in the same way the former regulations account for known 
critical values in those applications today. The FAA adopts Sec.  
23.2265(a) with minor modifications.

[[Page 96616]]

    Air Tractor commented that proposed Sec.  23.515(b) added 
unwarranted specificity and is worded such that the special factor must 
account for each inspection method, whether or not it is critical. Air 
Tractor further commented that certain conditions, such as structural 
test requirements, sampling percentages, and process and material 
controls, would be defined in a quality system approved under a 
production certificate (PC), not as part of a type design. Air Tractor 
contended that a type design should be approved independently of any 
quality system or production system requirements.
    The FAA agrees with Air Tractor that conditions, such as structural 
test requirements, sampling percentages, and process and material 
controls, would be defined in a quality system that is approved under a 
PC. However, there are instances where those items are defined by type 
design or inspection methods in an approved type design. As with the 
former Sec.  23.621, ``Casting factors,'' special casting factors of 
safety are to be applied to any structural casting, not just critical 
ones. The specific casting factor used in all those cases is 
inseparably tied to the applicable tests and inspections, both of which 
include sampling percentages specified for the part being produced. 
Former Sec.  23.621(a) required these factors to be defined in the type 
design, and they are in addition to whatever tests and inspections are 
required for foundry quality control. Therefore, proposed Sec.  
23.515(b) is not substantively different from the former regulations.
    The FAA generally agrees with Air Tractor's comment that approval 
of a type design is independent of any quality system or production 
system requirements. However, as explained previously in this section, 
the special factor of safety used to substantiate the type design is 
approved for use based completely on the part criticality, inspections, 
tests, and sampling percentages specified for a particular part.
    Additionally, the Associations recommended changing proposed Sec.  
23.515(b)(1) by replacing ``structural'' application with ``kind of'' 
application. The commenters contended it would ensure that special 
factors of safety continue to be applied in the same manner as they are 
applied in the former rule, while also providing for more flexibility 
for new materials and construction techniques.
    The FAA agrees with the Associations that the term ``structural'' 
in proposed Sec.  23.515(b)(1) should be revised. However, the FAA 
believes the words ``type of'' is more accurate than ``kind of'' in 
this application, and revises the text of Sec.  23.2265(b) accordingly.
    The Associations recommended changing proposed Sec.  23.515(c) to 
require a factor of safety established under proposed Sec.  23.330(b) 
to be multiplied by the highest pertinent factor of safety established 
under proposed Sec.  23.515(b). The commenters explained that this 
change would ensure special factors of safety are applied in the same 
manner as they are applied in the former rule, while also providing for 
more flexibility for new materials and construction techniques.
    The FAA disagrees with the Associations as such a change has led to 
convoluted regulations in the past. Further, the limit and ultimate 
loads are clearly defined in this subpart, so this cross-reference is 
unnecessary.
    Additionally, EASA noted that although the strict wording in former 
part 23 and CS 23 did not require special factors to be applied to 
ultimate loads that do not have corresponding limit loads (e.g., 
emergency landing conditions), this is not reflected in the NPRM. 
Referring to proposed Sec.  23.515(c), EASA noted that former part 23 
and CS 23 use the highest pertinent special factor, instead of any 
special factor as proposed in the NPRM. EASA suggested that 
coordination is necessary for harmonization.
    The FAA does not agree with EASA's assertion that a narrow 
interpretation of former part 23 would not require special factors of 
safety to be applied to ultimate loads that do not have corresponding 
limit loads. Former Sec.  23.625(d) required the attachments of seats, 
berths, and safety belts and harnesses to multiply the inertia loads in 
the emergency landing conditions in former Sec.  23.561 by a special 
factor of safety (i.e., fitting factor) of 1.33. However, the FAA 
concurs with EASA that new part 23 should require the use of the 
``highest pertinent'' special factor of safety, and not ``any'' special 
factor of safety. Therefore, the FAA revises Sec.  23.2265(c) 
accordingly.
    Additionally, upon further review, the FAA finds that the proposed 
wording in Sec.  23.515(c) appears to require an applicant to multiply 
not only each ultimate load by the special factor of safety, but also 
each limit load by the same factor even though sometimes there is no 
corresponding limit load. Therefore, the FAA also revises Sec.  
23.2265(c) to state that the special factor of safety is applied 
regardless of whether there is a limit load condition corresponding to 
the ultimate load condition. Although the FAA's language may not be 
harmonized with EASA's NPA, the intent is the same.
o. Emergency Conditions (Proposed Sec.  23.600/Now Sec.  23.2270)
    In the NPRM, proposed Sec.  23.600 (now Sec.  23.2270) would have 
required--
     The airplane, even if damaged in emergency landing 
conditions, to provide protection to each occupant against injury that 
would preclude egress;
     The airplane to have seating and restraints for all 
occupants, consisting of a seat, a method to restrain the occupant's 
pelvis and torso, and a single action restraint release, which meets 
its intended function and does not create a hazard that could cause a 
secondary injury to an occupant;
     The airplane seating, restraints, and cabin interior to 
accommodate likely flight and emergency landing conditions and should 
not prevent occupant egress or interfere with the operation of the 
airplane when not in use;
     Each baggage and cargo compartment be designed for its 
maximum weight of contents and for the critical load distributions at 
the maximum load factors corresponding to the determined flight and 
ground load conditions; and
     Each baggage and cargo compartment to have a means to 
prevent the contents of the compartment from becoming a hazard by 
impacting occupants or shifting, and to protect any controls, wiring, 
lines, equipment, or accessories whose damage or failure would affect 
operations.
    Air Tractor, commenting on proposed Sec.  23.600(a), said the NPRM 
preamble suggested that future certification endeavors will require 
more effort (e.g., possibly full-scale crash testing of the fuselage) 
to meet necessary requirements. Air Tractor also noted that inertial 
loads likely to occur in an emergency landing were not defined. 
Additionally, Air Tractor presumed the conditions defined in former 
Sec.  23.561 would be accepted, but doing so would not make things 
under the proposed rule any easier, faster, or less expensive. Air 
Tractor also claimed that should some other inertial loads likely to 
occur in an emergency landing be proposed, the applicant should expect 
a protracted discussion with the FAA to defend any differences.
    The FAA disagrees that future certification endeavors will require 
more effort and possibly full-scale crash testing of the fuselage to 
meet the requirements. Existing conditions of current static and 
dynamic testing would remain as a means of compliance. Proposed Sec.  
23.600(a) would

[[Page 96617]]

not have required full-scale crash testing of the fuselage. The FAA's 
intent was to allow for an evaluation of a ``crash landing'' 
considering the performance of the entire airframe, safety equipment, 
and occupant. The former requirements only required evaluation of the 
seat from the floor up, and the restraints, using generic floor 
impulses independent of airframe reaction. Additionally, the FAA did 
not define inertial loads because one of the goals of creating 
performance-based standards was to move away from mandated prescriptive 
standards, which inhibit innovation and safety enhancing technology 
adoption. The inertial loads likely to be encountered will be contained 
in the means of compliance. An applicant may propose inertial loads 
other than those contained in industry standards already accepted by 
the Administrator, and substantiate why they are adequate, 
representative, and equally safe as accepted loads. This rule will 
allow applicants to evaluate crash landing conditions considering the 
entire airplane and its performance, instead of limiting applicants to 
just these tests.
    The NTSB noted the NPRM stated that proposed Sec.  23.600 would 
capture the safety intent of former Sec. Sec.  23.561 and 23.562, which 
the FAA described as containing prescriptive design standards. The NTSB 
disagreed that former Sec. Sec.  23.561 and 23.562 are prescriptive 
design standards, and stated former Sec. Sec.  23.561 and 23.562 were 
performance-based standards that do not specify any elements of the 
design, but instead prescribed a test and measureable levels of 
performance needed to ensure safety.
    The NTSB shared the FAA's concern regarding consideration of 
occupiable space in a post-crash situation, and agreed former standards 
do not address these issues. However, the NTSB disagreed with the FAA's 
suggestion that analysis techniques available in the automotive 
industry are transferable to new airplane designs. The NTSB said it is 
likely that differences between airframe and automotive structures will 
require a significant number of full-scale aircraft crash tests before 
analytical techniques have been validated to the point they can be used 
as means of compliance. Pointing to NTSB Safety Recommendation A-11-3, 
which it issued in 2011 after conducting a study of the performance of 
airbags in general aviation airplane, the NTSB recommended the FAA 
consider the variation in the sizes and anthropometry of airplane 
occupants when evaluating a proposed means of compliance.
    The FAA understands the NTSB's comments, but does not agree. Former 
Sec. Sec.  23.561 and 23.562 assessed only the seat, attachment, 
restraints, and head strike. The generic floor impulse used did not 
take into account the variables inherent to the airplane, such as the 
ability to protect the survivable volume, crushable airplane structure, 
or features that absorb impact energy or offer the ability to evaluate 
how all of these variables can work together to enhance 
crashworthiness. This rule will allow a more holistic approach to 
crashworthiness. Not prescribing a specific seat test opens the door 
for future technology and advances in analytical techniques to 
demonstrate equivalent and even enhanced safety, utilizing all advances 
available to the engineer. At the same time, until these enhanced 
techniques become available and proven, the existing seat test methods 
are still acceptable for showing compliance with this rule and will be 
contained in a means of compliance.
    Additionally, the FAA will accept the former regulations as an 
acceptable method of compliance, despite their limitations. Testing in 
accordance with the former regulations has provided a certain level of 
safety for many years; therefore, continuing to accept them for future 
designs will maintain that level of safety. However, the FAA contends 
that having a prescriptive set of tests in the rule has prevented the 
industry from moving beyond this one standard of protecting occupants. 
This is because the former regulations required a very specific seat 
sled test; detailing seat mounting misalignment, impulse force peak and 
rise times, and maximum forces allowed to be experienced by the 
restraint system, and the occupant's lumbar spine among other things. 
Due to the rule specifying all these details, it is nearly impossible 
for the FAA to find equivalency in applicants proposed alternatives. By 
changing the requirement from a prescriptive test to the safety intent 
behind the test, the FAA will only need to evaluate whether new methods 
meet the safety intent, and not have to evaluate their relative safety 
against the former requirements. The determination that likely crash 
scenarios do not generate loads on the occupants that exceed the limits 
of human injury was the basis of the former rule language, and how the 
test and crash impulse was derived. It was a combination of various 
scenarios, represented by one specific set of tests. The new rule will 
allow a holistic approach to enable designs to achieve occupant 
protection more effectively.
    While the automotive industry generally has a more-developed 
crashworthiness analysis capability than that used in the aviation 
industry, the FAA wants to allow for incorporation of holistic 
crashworthiness in addition to conventional compliance. The FAA notes 
the NTSB's concern that automotive technology will not directly 
transfer to aerospace applications because it requires significant 
numbers of full-scale aircraft crash tests for validation to yield the 
confidence in the analytical techniques. However, the FAA disagrees. 
The FAA has not yet determined how much and what type of validation 
will be required for a given crash scenario. This determination will 
depend on the particular design and what the validation is attempting 
to demonstrate. The automotive and other industries have gained a lot 
of knowledge on what is needed to demonstrate valid models using 
dynamic transient analysis. The FAA believes that the knowledge from 
these industries can be leveraged to reduce or eliminate the need for 
full-scale aircraft crashes for validation. For example, there may be 
scenarios where only a small part needs validation for demonstration of 
its energy absorption. This rule will provide an applicant with the 
option to examine the performance of more than just the seat and 
restraints, and avoids defining methods of restraint. This will allow 
consideration of a myriad of ways to protect an occupant in an 
emergency landing, such as using airbags.
    Also, the FAA notes the NTSB's recommendation that the FAA consider 
the variation in the sizes and anthropometry of airplane occupants when 
evaluating a proposed means of compliance. This would be an increase in 
the burden to the manufacturers, and this burden has not been 
justified.
    Several organizations commented on proposed Sec.  23.600(b). 
Kestrel noted that proposed Sec.  23.600(b)(1) referred to impact at 
stall speed, but did not specify the configuration and atmospheric 
conditions associated with this stall speed. Kestrel also requested 
clarification on whether applicants must design for stall speed in 
icing conditions.
    The FAA revises the proposed rule language. The configuration and 
atmospheric conditions will be located in the means of compliance based 
on a determination of the conditions that are likely to occur.
    In discussing proposed Sec.  23.600(b)(1), ICON questioned whether 
industry can deliver on this ``new requirement.'' Textron noted that 
proposed Sec.  23.600(b) referred to the emergency landing conditions 
specified in paragraph (a), which would mean the items of mass

[[Page 96618]]

specified in paragraph (a) must meet the dynamic conditions specified 
in paragraph (b). Textron noted this is a significant departure from 
the former rule and assumed it was not the FAA's intent to require 
dynamic conditions for items of mass. Similarly, the Associations 
commented that Sec.  23.600(b) would be a new requirement without 
foundation. They believed the FAA intended to apply the requirement 
only to occupant restraint systems.
    The FAA agrees with Textron and others that an unintentional new 
requirement would have been imposed by the proposed wording of 
paragraph (b)(1). The FAA did not intend to apply dynamic loading 
requirements to items of mass that previously required accounting only 
for static loads. The FAA modifies the text of paragraph (b) to refer 
only to subparagraphs (a)(1) and (a)(2) instead of all of paragraph 
(a), thereby eliminating reference to items of mass.
    EASA said the ``dynamic'' condition specified in paragraph (b)(1) 
should be in the means of compliance, not in the rule. ICON noted that 
proposed Sec.  23.600(b)(1) would require a very long list of variables 
be considered in an impact, which seems prohibitively difficult to 
achieve with any degree of confidence.
    The FAA agrees with ICON and EASA. The long list of variables is 
reduced to simply ``emergency landing'' conditions, which can then be 
further detailed as part of the means of compliance.
    Transport Canada said the requirement in proposed Sec.  
23.600(b)(2) appeared inaccurate. It noted that what must not exceed 
established injury criteria for human tolerance are the loads 
experienced by the occupant, not the emergency landing conditions. 
Transport Canada recommended a rewrite of paragraph (b)(2) that would 
state that the occupants would not experience loads which exceed 
established injury criteria for human tolerance due to restraint or 
contact with objects in the airplane.
    The FAA agrees with Transport Canada. The FAA adopts the 
recommended language and revises the rule to clarify it is the loads 
experienced by the occupant, not the emergency landing conditions that 
should not exceed the established injury criteria for human tolerance.
    BendixKing suggested replacing the word ``restraints'' with 
``protection'' in the two instances the word occurs in proposed Sec.  
23.600(c). BendixKing suggested this change is appropriate because the 
intent of the rule is to ensure crash protection for the occupant, 
which may or may not be what is understood to be restraint. BendixKing 
also stated it is important not to assume a particular solution, but to 
focus on the safety intent or occupant protection from harmful motion 
during an impact. Therefore, it suggested words used in proposed Sec.  
23.600(d) like ``restraint,'' ``pelvis,'' ``torso,'' be replaced with 
language like ``protection'' or ``securing the occupant from harm.'' 
EASA commented that proposed Sec. Sec.  23.600(c) and (d) should be an 
accepted means of compliance, not regulatory requirements. The 
Associations commented that the language in proposed Sec.  23.600(d) 
should be aligned with current DOT practices related to automobile 
safety. The commenters noted the proposed language may preclude some 
better methods of safety in crashworthiness and might unnecessarily 
restrict design capabilities.
    The FAA agrees with BendixKing that using design-specific solution 
terminology such as ``restraints'' is not appropriate for a 
performance-based regulation. While the occupant needs to be 
restrained, restraints should be considered on a broader basis. The FAA 
also agrees with EASA that the portions of Sec. Sec.  23.600(c) and (d) 
that use design-specific terminology should be in the means of 
compliance. As such, the FAA will use more generic terms like 
``protection'' or ``occupant protection system'' in lieu of the design-
specific terms proposed in paragraphs (c) and (d), to allow for other 
methods of compliance to meet the safety intent of the rule. Finally, 
due to these word changes, the FAA moved the consideration of ``ground 
loads'' from paragraph (d) to paragraph (c).
    Transport Canada noted the reference to water loads is missing in 
paragraphs (d) and (e)(1). Transport Canada recommended those 
paragraphs be modified by adding the word ``water'' in the phrase ``For 
all flights and ground loads.''
    The FAA considered Transport Canada's comment, but one of the goals 
of adopting performance-based regulations is to remove some of the 
specificity, to enable the flexibility to adapt to changing 
technologies and environments. Specifying every possible landing 
surface would not align with this goal. Therefore, the FAA is not 
incorporating Transport Canada's changes into the final rule.
    Transport Canada also commented that proposed Sec.  23.600(e) 
should provide a performance-based standard for the requirements in 
former Sec.  23.787(b) for baggage or cargo sharing the same 
compartment as passengers.
    The FAA agrees baggage and cargo sharing the same compartment with 
passengers should be restrained. However, a change to the proposed rule 
is not necessary to address this. Section 23.2270(a) of this rule 
requires restraint of items of mass within the cabin utilizing static 
inertial loads, including baggage or cargo that is in the cabin.
    The Associations and Textron addressed the requirement in proposed 
Sec.  23.600(e)(3) that baggage and cargo compartments must protect 
controls, wiring, lines, equipment, or accessories whose damage or 
failure would ``affect operations.'' Textron noted that any kind of 
damage or failure would arguably ``affect operations,'' making it 
difficult to comply with the rule. Textron recommended the FAA qualify 
the requirement by adding the word ``safe'' in front of ``operations.'' 
The Associations recommended the FAA delete the word ``any'' in front 
of ``controls,'' delete the word ``affect,'' and add the words ``limit 
safe'' in front of ``operations.''
    The FAA agrees with the comments from Textron and the Associations 
and is adding ``safe'' to modify ``operations.'' Adopting this change 
will harmonize the text with EASA's proposed rule language. The FAA 
will not adopt the other recommended changes as they would not have a 
substantive effect on the rule.
    Daher commented generally on Sec.  23.600, indicating the phrase 
``rolling and pitching'' would be more appropriate than ``pitching and 
yawing.'' Daher did not indicate where these phrases were, but the FAA 
believes it is referring to a statement made in the NPRM preamble 
discussion of proposed Sec.  23.600 that stated dynamic seat testing 
requirements address the ability of seat assemblies to remain attached 
to the floor, even when the floor shifts during impact. Pitching and 
yawing of the seat tracks during dynamic seat tests demonstrates the 
gimbaling and flexibility of the seat.
    Furthermore, the FAA believes Daher was specifically inferring that 
``rolling and pitching'' would be more appropriate in Sec.  
23.2270(b)(1) because the rule language in former Sec.  23.562 required 
the seat rails to be misaligned by 10 degrees in the ``pitch'' and 
``roll'' axis, not the ``pitch'' and ``yaw'' axis. The FAA's intent was 
not simply to mimic the original Sec.  23.562 misalignment 
requirements, but to identify static airplane orientation at impact in 
order to assess the level of airframe crushing and energy absorption. 
However, based on other comments on proposed Sec.  23.600, the FAA has 
removed specific references to

[[Page 96619]]

the terms ``flight path angle,'' ``flight pitch angle,'' ``yaw,'' and 
``airplane configuration.'' These parameters will be included in the 
means of compliance.
    An individual commenter in the seatbelt manufacturing industry 
suggested putting a life limit of 10 years on seatbelts, because the 
webbing loses its strength due to exposure to UV lights and heat. The 
FAA notes that a seat belt life limit is not within the scope of this 
rulemaking. The details of seat belts and seat belt webbing materials 
are controlled by industry standards and Technical Standard Orders 
(TSOs). Additionally, specifying those types of design-specific 
solutions is counter to performance-based regulations.
5. Subpart D--Design and Construction
a. Flight Control Systems (Proposed Sec.  23.700/Now Sec.  23.2300)
    In the NPRM, proposed Sec.  23.700 (now Sec.  23.2300) would have 
required an applicant to design airplane flight control systems to 
prevent major, hazardous, and catastrophic hazards. Proposed Sec.  
23.700 would have required an applicant to design trim systems to 
prevent inadvertent, incorrect, or abrupt trim operation. In addition, 
proposed Sec.  23.700 would have required an applicant to design trim 
systems to provide a means to indicate--
     The direction of trim control movement relative to 
airplane motion;
     The trim position with respect to the trim range;
     The neutral position for lateral and directional trim; and
     For all airplanes except simple airplanes, the range for 
takeoff for all applicant requested center of gravity ranges and 
configurations.
    Proposed Sec.  23.700 would have also required an applicant to 
design trim systems to provide control for continued safe flight and 
landing when any one connecting or transmitting element in the primary 
flight control system failed, except for simple airplanes. 
Additionally, proposed Sec.  23.700 would have required an applicant to 
design trim systems to limit the range of travel to allow safe flight 
and landing, if an adjustable stabilizer is used.
    Furthermore, proposed Sec.  23.700 would have required the system 
for an airplane equipped with an artificial stall barrier system to 
prevent uncommanded control or thrust action and provide for a 
preflight check. The FAA also proposed requiring an applicant seeking 
certification of a level 3 high-speed or level 4 airplane to install a 
takeoff warning system on the airplane, unless the applicant 
demonstrates that the airplane, for each configuration, could takeoff 
at the limits of its trim and flap ranges.
    In light of comments received, the FAA revises proposed Sec.  
23.700 to withdraw paragraphs (a)(1) and all its subparagraphs, rename 
proposed paragraph (a)(2) as (a)(1), add new paragraph (a)(2), withdraw 
proposed paragraphs (b)(3), (b)(4), and paragraphs (c) and (d) and all 
their subparagraphs. This section discusses these changes in more 
detail.
    Textron and Kestrel questioned how the term ``prevent'' was 
intended to be used with the system safety analysis terms ``major,'' 
``hazardous,'' and ``catastrophic.''
    The FAA acknowledges the term ``prevent'' caused confusion in 
proposed Sec.  23.700(a)(1), and replaces ``prevent'' with ``protect 
against'' in Sec.  23.2300(a)(2). The FAA did not intend to require 
additional safety analysis in this section, as suggested by these 
comments.
    The Associations, Kestrel, Air Tractor, and Textron expressed 
concern that proposed Sec.  23.700 appears to require that applicants 
perform System Safety Assessments (SSAs) for traditional mechanical 
flight control systems that have never been subject to this requirement 
in the past. They note this would impose substantial new costs on 
applicants. The commenters acknowledge that SSAs would be appropriate 
for unconventional designs, such as fly-by-wire systems.
    The FAA did not intend to imply that a safety analysis would be 
required for all flight control systems, including simple mechanical 
flight control systems in proposed Sec.  23.700(a). The FAA deletes the 
terms that could have been associated with safety analysis and revises 
Sec.  23.2300(a)(2) to require the applicant to design airplane flight 
control systems to protect against likely hazards. The FAA intends 
``protect against likely hazards'' to be a high-level requirement to 
consider potential hazards to the flight control system, and 
incorporate features in the design to protect against these hazards. 
One way for a traditional flight control system to satisfy this would 
be to use the former part 23 regulations, which addressed hazards such 
as jamming, chafing, interference, incorrect assembly, asymmetric 
flaps, control system lock inadvertent engagement in flight, etc.
    The FAA agrees with the comments stating that safety analysis is 
necessary, as required by Sec.  23.2510 (proposed as Sec.  23.1315), 
for fly-by-wire flight control systems, powered flight control systems, 
and automatic flight control systems. The FAA withdraws the safety 
analysis requirement in Sec.  23.2300 because Sec.  23.2510 adequately 
addresses the requirement for safety analysis. The FAA notes the 
applicability of the Sec.  23.2510 safety analysis requirements will be 
addressed as a means of compliance, similar to the current practice in 
AC 23.1309-1E.
    The Associations and Textron recommended the FAA eliminate proposed 
paragraph Sec.  23.700(a)(1)(iii), which lists ``flutter'' as one of 
the possible major, hazardous or catastrophic hazards, because it is 
redundant and unnecessary as the safety intent of flutter is covered in 
the aeroelastic section, proposed Sec.  23.410 (now Sec.  23.2245). The 
FAA agrees because Sec.  23.2245 ``Aeroelasticity'' adequately 
addresses flutter for normal operation, exceedances and failure 
conditions. The FAA also withdrew the other examples of hazards in 
proposed Sec.  23.700(a)(1) so that they can be addressed more 
completely in means of compliance.
    The Associations and Textron also questioned the use of the term 
``misconfiguration'' in proposed Sec.  23.700(a)(1)(v). Textron asked 
the FAA to clarify whether the term refers to items like rigging and 
installation or items like wing configurations (e.g., flaps, speed 
brakes) and trim. The Associations recommended ``misconfiguration'' be 
replaced with ``misrigging'' for clarity and anticipated the 
traditional misrigging practices would continue to apply. Proposed 
Sec.  23.700(a)(1)(v) was intended to address the requirement from 
former Sec.  23.685(d) that each element of the flight control system 
must have design features, or must be distinctively and permanently 
marked, to minimize the possibility of incorrect assembly that could 
result in malfunctioning of the control system. The FAA agrees that 
``misrigging'' incorporates the intent of this requirement more clearly 
than ``misconfiguration.'' However, the FAA has decided to remove 
proposed Sec.  23.700(a)(1)(v) from the final rule as discussed.
    With the withdrawal of the list in proposed Sec.  23.700(a)(1), the 
FAA renumbers proposed Sec.  23.700(a)(2) as Sec.  23.2300(a)(1) and 
adds a new paragraph (a)(2).
    Textron commented that proposed Sec.  23.700(a)(2) could seem 
reasonable for all systems and recommended moving the paragraph to 
proposed Sec.  23.1305 (now Sec.  23.2505).
    The FAA disagrees with applying proposed Sec.  23.700(a)(2) to all 
systems and equipment because the requirement to ``operate easily, 
smoothly and positively enough to allow normal operation'' does not 
apply to all

[[Page 96620]]

systems. For example, evaluating a flight data recorder for 
``smoothness'' would not make sense. The FAA revises Sec.  
23.2300(a)(1) to be consistent with former Sec.  23.671(a) because it 
states the intent of the requirement more clearly.
    The Associations proposed revising Sec.  23.700(b) to state ``the 
trim systems must . . .'' instead of ``[t]he applicant must design trim 
systems to.'' They made a similar comment on proposed Sec.  23.700(a).
    The FAA used ``the applicant must design . . .'' throughout the 
NPRM. The FAA retains this wording because it's consistent with part 21 
to impose the obligation on the applicant.
    Textron noted that proposed Sec.  23.700(b)(1) was a general 
concept that should actually apply to all systems, and therefore 
recommended changing the word ``trim'' to ``system,'' and moving 
proposed Sec.  23.700(b)(1) to proposed Sec.  23.1305. Textron also 
questioned whether the term ``prevent'' in proposed Sec.  23.700(b)(1) 
meant ``meet the associated requirements of a system safety 
assessment.'' Textron recommended rewriting proposed paragraph (b)(1) 
to provide that the applicant must design trim systems to meet system 
safety requirements, according to the assessment mandated by proposed 
Sec.  23.1310, and that the evaluation of the system shall include 
hazards caused by inadvertent (uncommanded) trim operation and 
incorrect (motion in the opposite direction than commanded) trim 
operations.
    The FAA notes the requirement to ``prevent inadvertent, incorrect, 
or abrupt system operation'' would not be appropriate for some systems. 
For example, evaluating a flight data recorder for ``abrupt system 
operation'' would not make sense. Therefore, the FAA did not 
incorporate Textron's recommendation in this rule. The FAA also 
declines to move the regulation to proposed Sec.  23.1305 (now Sec.  
23.2505) because that section applies to all systems, while this 
requirement is only intended for flight control trim systems. In light 
of Textron's comment, the FAA has changed ``prevent'' to ``protect 
against'' for consistency with Sec.  23.2300(a)(2). However, the FAA 
did not incorporate Textron's recommendation to change proposed Sec.  
23.700(b)(1) because this section does not require safety analysis. 
This section applies to all trim systems while Sec.  23.2510 does not 
apply to trim systems that are considered ``flight control surfaces and 
their simple systems'' as discussed in AC 23.1309-1E.
    Several organizations commented on proposed Sec.  23.700(b)(3). The 
Associations recommended deleting proposed paragraph (b)(3). They 
stated that addressing the loss of any single flight control link with 
traditional mechanical flight controls has provided a substantial level 
of safety and as new stability and fly-by-wire systems are discussed, 
it will be increasingly important to develop adequate means of 
compliance in acceptable documents.
    EASA asserted the proposed requirement to have a trim system as a 
means of control in case of failure of a connecting or transmitting 
element was too prescriptive and should be captured by the intent that 
a flight control system must prevent major, hazardous, and catastrophic 
hazards for likely failure conditions.
    The FAA agrees that proposed Sec.  23.700(b)(3) was too 
prescriptive because means other than trim could be used to safely 
control the airplane when any one connecting or transmitting element in 
the primary flight control system fails. The requirement to protect the 
airplane from loss of control when any one connecting or transmitting 
element in the primary flight control system fails is captured in Sec.  
23.2300(a)(2) at a high level. Therefore, the FAA withdraws proposed 
Sec.  23.700(b)(3). In addition, the FAA adds ``if installed'' to Sec.  
23.2300(b) in light of the comments that future designs may not use 
trim systems.
    Transport Canada observed that VLA rules permit trim systems that 
do not provide safe flight and landing following failure of the primary 
control system. Transport Canada said it did not believe this 
alleviation should be carried into the part 23 revisions, even for 
small airplanes. Transport Canada recommended the level of safety for 
trim system failures be raised for simple airplanes.
    As discussed elsewhere, the FAA has decided to withdraw the simple 
category, proposed in Sec.  23.5(d), and also to withdraw proposed 
Sec.  23.700(b)(3) because Sec.  23.2300(a)(2) captures the 
requirement. The FAA has determined that the level of safety for trim 
system failures should not be raised for entry-level airplanes. One of 
the goals of the NPRM was to provide appropriate standards for ``entry-
level airplanes'', and the FAA finds Sec.  23.2300(a)(2) meets that 
goal. As discussed in this section, Sec.  23.2300(a)(2) requires the 
applicant to design airplane flight control systems to protect against 
likely hazards. While the FAA's intent is that flight control systems 
that meet the former part 23 requirements adequately protect against 
the likely hazard of failures in any one connecting or transmitting 
element in the primary flight control system, those airplanes certified 
under EASA's Certification Specification--Very Light Aeroplanes (CS-
VLA), were not certified under part 23. Rather, they were imported to 
the U.S. and certificated as special class airplanes in accordance with 
Sec.  21.17(b). Under Sec.  23.2300(a)(2), these airplanes could be 
certified under part 23, using the CS-VLA to meet the requirements.
    Upon further consideration of proposed Sec.  23.700(b)(4), the FAA 
decided the safety intent of the requirement to limit the range of 
travel to allow safe flight and landing, if an adjustable stabilizer is 
used, is already incorporated in the regulations through the 
requirement for the applicant to design airplane flight control systems 
to protect against likely hazards. The proposed requirement was 
prescriptive and may not be appropriate for non-traditional airplane 
designs. Therefore, the FAA withdraws proposed Sec.  23.700(b)(4).
    The Associations asserted including specific information for the 
verification of stall barrier systems in proposed Sec.  23.700(c) is 
not beneficial because the issue being addressed is already covered by 
``flight control reliability aspects.'' The commenters also noted the 
simple checks being specified may not be appropriate for all stall 
barrier systems and that addressing stall barrier flight controls would 
be better detailed in means of compliance. The commenters recommended 
deleting proposed Sec.  23.700(c).
    The FAA agrees that there is no benefit to including Sec.  
23.700(c) because Sec.  23.2510 adequately addresses stall barrier 
system failure conditions and checks for latent failures. Therefore, 
the FAA withdraws Sec.  23.700(c).
    Textron, ANAC, and Air Tractor commented that proposed Sec.  
23.700(d) would require a takeoff warning system without explanation of 
what it would be, and this could increase complexity.
    The FAA withdraws proposed Sec.  23.700(d) because the safety 
requirement of warning a pilot who is attempting to takeoff with the 
trim or flaps in an unsafe configuration is adequately addressed in 
Sec.  23.2605(c).
b. Landing Gear Systems (Proposed Sec.  23.705/Now Sec.  23.2305)
    In the NPRM, proposed Sec.  23.705 (now Sec.  23.2305) would have 
required--
     The landing gear and retracting mechanism be able to 
withstand operational and flight loads;
     An airplane with retractable landing gear to have a 
positive means to keep the landing gear extended and a secondary means 
for extending the

[[Page 96621]]

landing gear that could not be extended using the primary means;
     A means to inform the pilot that each landing gear is 
secured in the extended and retracted positions; and
     Airplanes, with retractable landing gear, except for 
airplanes intended for operation on water, to also have a warning to 
the pilot if the thrust and configuration is selected for landing and 
yet the landing gear is not fully extended and locked.
    Furthermore, if the landing gear bay is used as the location for 
equipment other than the landing gear, proposed Sec.  23.705 would have 
required that equipment be designed and installed to avoid damage from 
tire burst and from items that may enter the landing gear bay. Proposed 
Sec.  23.705 would have also required the design of each landing gear 
wheel, tire, and ski account for critical loads and would require a 
reliable means of stopping the airplane with kinetic energy absorption 
within the airplane's design specifications for landing. For level 3 
high-speed multiengine and level 4 multiengine airplanes, proposed 
Sec.  23.705 would have required the braking system to provide kinetic 
energy absorption within the design of the airplane specifications for 
rejected takeoff as the current rules do for multiengine jets over 
6,000 pounds and commuter category airplanes.
    Several commenters argued that proposed Sec.  23.705 was too design 
specific and recommended the FAA replace specific design elements such 
as brakes, wheels, and tires with objectives that would work for a wide 
array of technologies.
    In light of comments received, the FAA revises proposed Sec.  
23.705 to withdraw proposed paragraphs (a)(1) through (d), to be 
replaced with new paragraphs (a)(1), (a)(2), (b), (c)(1) and (c)(2). 
This section discusses these changes in more detail.
    The FAA reassessed the need for the language of proposed Sec.  
23.705(a)(1) and (b) and decided not to adopt the proposed paragraphs. 
The FAA has determined these requirements are adequately addressed by 
proposed Sec. Sec.  23.310 (now Sec.  23.2210), 23.320 (now Sec.  
23.2220), and 23.400 (now Sec.  23.2235). Section 23.2210 requires 
structural design loads to be determined that result from likely 
externally or internally applied pressures, forces or moments, that may 
occur in flight, ground and water operations, ground and water 
handling, and while the airplane is parked or moored. This includes 
operational and flight loads on the landing gear and retracting 
mechanism, including the wheel well doors specified in the FAA's 
proposed Sec.  23.705(a)(1). Section 23.2235 requires the structure to 
support these loads. Section 23.2220 requires the applicant to 
determine the structural design loads resulting from taxi, takeoff, 
landing, and ground handling conditions occurring in normal and adverse 
attitudes and configurations. This includes the critical loads on 
wheels, tires, and skis specified in proposed Sec.  23.705(b). Section 
23.2235 requires the structure to support these loads.
    Commenters noted proposed Sec.  23.705 diverged from EASA's 
proposed CS 23.425, and recommended the FAA work with EASA to achieve 
harmonization. Several commenters recommended the FAA reject the 
language originally proposed for Sec.  23.705 and replace it with the 
language from EASA's proposed CS 23.2325.
    The FAA agrees that it should harmonize Sec.  23.2305 as much as 
possible with CS 23.2325, and has done so where appropriate.
    The Associations recommended the FAA revise proposed paragraph (a), 
which would define landing gear. Textron recommended the FAA add a 
requirement to provide stable support and control to the airplane 
during ground operation. The commenters noted the change to paragraph 
(a) would harmonize with EASA.
    The FAA finds the recommended language for paragraph (a) 
unnecessary. The FAA also finds the accepted means of compliance will 
describe what is considered landing gear for a particular airplane 
design. The FAA notes the recommended language is overly broad and can 
be read to encompass rudder systems and other systems that do not 
directly interact with the ground, but are necessary to control the 
airplane during surface operation. The FAA notes rudder systems and 
other systems are adequately addressed elsewhere.
    The FAA revises Sec.  23.2305(a)(1) to adopt CS 23.2325(b)(1) by 
requiring the landing gear to be designed to provide stable support and 
control during surface operation. Although the NPRM did not 
specifically address this requirement, the FAA intended for the revised 
regulations to capture the safety intent of the former part 23 
regulations. This also harmonizes with EASA.
    The FAA will not adopt the landing gear loads and energy absorption 
requirements in CS 23.2325(b)(2) and (b)(3) because these requirements 
are adequately addressed in Sec. Sec.  23.2210, 23.2220, and 23.2235. 
The FAA notes the airplane has to be designed for the anticipated 
loads, and energy absorbed by the landing gear affects the airframe 
loads, which are addressed in these sections. Additionally, proper 
function of any systems related to absorption of energy in the landing 
gear is addressed in Sec.  23.2505.
    The FAA adopts CS 23.2325(b)(4) as Sec.  23.2305(a)(2), requiring 
the landing gear to be designed to account for likely system failures 
and likely operation environment, including anticipated limitation 
exceedances and emergency procedures. As a result of this revision, the 
FAA withdraws proposed Sec.  23.705(a)(3).
    Although the NTSB supported proposed Sec.  23.705(a)(3), the FAA 
notes proposed Sec.  23.705(a)(3) only addressed tire failures on 
airplanes with retractable landing gear based on the assumption that 
tire burst and foreign object risk is greater on airplanes with 
retractable landing gear. This is generally true for traditional 
airplane designs. The risk is generally more severe on airplanes with 
large numbers of passengers, flight critical systems near the landing 
gear, complex systems, and high-speed operation on the ground. These 
factors generally exist on airplanes with retractable landing gear, but 
they could exist on airplanes with fixed landing gear. Conversely, the 
risk is generally less severe on airplanes with no passengers, no 
flight critical systems near the landing gear, simple systems and low-
speed operation on the ground. These factors generally exist on 
airplanes with fixed landing gear, but they could exist on airplanes 
with retractable landing gear (e.g., powered gliders). Therefore, the 
proposed Sec.  23.705(a)(3) assumption that airplanes with retractable 
landing gear should be protected from the risks of tire failures and 
foreign objects, but airplanes with fixed landing gear should not be 
protected, may not be correct for future designs.
    Section 23.2305(a)(2) applies to all landing gear and requires 
landing gear failures to be considered more generally. The FAA finds 
Sec.  23.2305(a)(2) will allow traditional designs to comply using 
current practices as means of compliance, with the flexibility to 
develop new means of compliance more appropriate for potential future 
designs. This furthers the goal of moving to performance-based 
requirements.
    The FAA notes Sec.  23.2305(a)(2) captures the intent of former 
Sec. Sec.  23.721, 23.729, 23.735, and 23.1309, which required that 
applicants account for likely landing gear failures. It also captures 
the intent of former Sec. Sec.  23.603, 23.721, 23.729, 23.735, 
23.1301, and 23.1309, which required that applicants account for likely 
operation environments, and/or anticipated

[[Page 96622]]

limitation exceedances and emergency procedures.
    The commenters recommended that the FAA move the substance of 
proposed Sec.  23.705(a) for airplanes with retractable landing gear to 
proposed Sec.  23.705(c) and replace the proposed language with CS 
23.2325(d), which deals with airplanes that have a system that actuates 
the landing gear.
    The FAA has considered the comments and has decided to adopt CS 
23.2325(d)(1) and (4) as Sec.  23.2305(c)(1) and (2). CS 23.2325(d)(1) 
and (4) require a positive means to keep the landing gear in the 
landing position and an alternative means available to bring the 
landing gear in the landing position when a non[hyphen]deployed system 
position would be hazardous. The FAA adopts Sec.  23.2305(c)(1) because 
it is less prescriptive than proposed Sec.  23.705(a)(2)(i). The FAA 
notes the recommended phrase ``in the landing position'' is less 
prescriptive than ``extended'' and better expresses the intent of the 
requirement. Moreover, Sec.  23.2305(c)(1) does not increase the burden 
on traditional designs; provides flexibility to allow new designs to be 
certified because it applies to all landing gear actuated by a system, 
not just retractable landing gear; and assists in harmonization.
    The FAA adopts the language of CS 23.2325(d)(4) as Sec.  
23.2305(c)(2), with one minor change. The FAA is using the phrase ``a 
hazard'' instead of ``hazardous'' to avoid confusion with former Sec.  
23.1309's use of the phrase ``hazardous failure condition.'' The 
language of CS 23.2325(d)(4) better captures the safety intent of 
former Sec.  23.729(c), which did not require a secondary means for 
landing gear that could be extended manually, and is less prescriptive 
because it only requires an alternative means to bring the landing gear 
to the landing position if a non-deployed position would be a hazard. 
Additionally, moving the location of this requirement has no technical 
impact and harmonizes with CS 23.2325.
    The FAA does not adopt proposed Sec.  23.705(a)(2)(iii) or the 
language from CS 23.2325(d)(2) and (d)(3) because the FAA considers 
both proposals to be adequately addressed by proposed Sec.  23.1500(b) 
(now Sec.  23.2600(b)). Section 23.2600(b) requires the applicant to 
install flight, navigation, surveillance, and powerplant controls and 
displays so qualified flightcrew can monitor and perform defined tasks 
associated with the intended functions of systems and equipment. The 
systems and equipment design must minimize flightcrew errors which 
could create additional hazards. Section 23.2600(b) incorporates the 
safety intent of previous requirements for landing gear indications and 
effectively requires the pilot to be informed of the landing gear 
position (secured in extended or retracted position) should the pilot 
need that information.
    Textron recommended the FAA remove the requirement for a secondary 
means of extending the landing gear in proposed Sec.  23.705 and rely 
instead on the requirements of proposed Sec.  23.1315.
    The FAA disagrees as Textron's recommendation does not capture the 
intent of the former regulation, which was a specific requirement for a 
secondary means of deploying landing gear. Furthermore, this 
requirement in proposed Sec.  23.705 was not covered by the general 
systems failure requirements of proposed Sec.  23.1315.
    Several commenters recommended deleting proposed Sec.  
23.705(a)(2)(iv), in part, because it was too prescriptive. One 
commenter recommended rewriting the rule as a performance[hyphen]based 
regulation to encourage alternate--and perhaps better--means of 
detecting wrong configurations for landing.
    The FAA agrees that proposed Sec.  23.705(a)(2)(iv) is too 
prescriptive, and finds it is adequately addressed by the requirements 
of new Sec.  23.2605(c), which requires information concerning an 
unsafe system operating condition must be provided in a timely manner 
to the crewmember responsible for taking corrective action. 
Accordingly, the FAA withdraws proposed Sec.  23.705(a)(2)(iv).
    Textron recommended the FAA add the word ``essential'' before 
``equipment'' in proposed Sec.  23.705(a)(3),\37\ asserting that non-
essential equipment is not important to protect in the landing gear 
bay.
---------------------------------------------------------------------------

    \37\ Textron referenced ``the 2nd line of the 2nd paragraph,'' 
but the FAA infers they intended to reference proposed Sec.  
23.705(a)(3) because this is the provision that would require 
protection of equipment.
---------------------------------------------------------------------------

    The FAA disagrees with Textron's recommendation as it is possible 
that failures of non-essential equipment like a fuel line for a 
combustion heater may result in hazards more severe than the loss of 
the non-essential function. Therefore, the FAA is not adopting this 
change in the final rule.
    Textron recommended rewording proposed Sec. Sec.  23.705(c) and (d) 
to limit their applicability to airplanes with wheels, asserting these 
paragraphs required airplanes without wheels to have brakes. 
Alternatively, Textron suggested moving the requirement to proposed 
Sec.  23.1300(a) (now Sec.  23.2500(a)) because an airplane with wheels 
will need a braking system to meet proposed Sec.  23.1300(a), making 
Sec.  23.705(c) redundant. Other commenters recommended the FAA replace 
proposed Sec.  23.705(c) and (d) with the CS 23.2325(c), which 
addresses kinetic energy absorption.
    The FAA concurs with the recommendation to replace proposed Sec.  
23.705(c) and (d) with CS 23.2325(c). The FAA notes CS 23.2325(c) has 
the same meaning as proposed Sec.  23.705(c) and (d), but harmonizes 
with EASA's NPA 2016-05. The FAA has determined the removal of the 
phrase ``within the airplane's design specifications for landing'' and 
replacement with ``sufficient . . . to account for landing'' has no 
technical impact. The FAA adopts the change as Sec.  23.2305(b).
    The FAA disagrees with Textron's recommendation to reword Sec.  
23.705(c) and (d) to limit their applicability to airplanes with 
wheels. The FAA notes proposed paragraphs (c) and (d) would not require 
brakes. While the FAA has considered Textron's alternative 
recommendation, the specific energy absorption requirement of proposed 
Sec.  23.705(c) is not adequately addressed by the general system 
performance requirements of proposed Sec.  23.1300(a). Therefore, the 
FAA is not adopting this change in the final rule.
    Textron suggested the FAA should harmonize its proposed regulations 
on this topic with CS 23.600 by removing language related to brakes as 
a subset of meeting the requirements of proposed Sec.  23.1300(a).
    The FAA agrees with harmonizing with EASA wherever possible. 
However, specifically requiring a reliable means of stopping the 
airplane is not excessively prescriptive and provides clarity to the 
regulation. Furthermore, Textron's suggested text would not harmonize 
with CS 23.2325.
    EASA recommended eliminating the reference to level 3 and 4 
airplanes in proposed Sec.  23.705(d), and replacing it with a 
reference to airplanes ``required to demonstrate aborted take-off 
capacity,'' which links the requirement to takeoff performance. 
Similarly, all of the comments on this section recommended making 
proposed Sec.  23.705(d) applicable to the same airplanes covered by 
proposed Sec.  23.115(c)(1) (now Sec.  23.2115(c)(1)).\38\ Textron also 
suggested directly referencing proposed Sec.  23.115 to prevent the 
link between the two

[[Page 96623]]

requirements from being inadvertently broken.
---------------------------------------------------------------------------

    \38\ Proposed Sec.  23.115(c)(1) would have applied to ``levels 
1, 2, and 3 high-speed multiengine airplanes, multiengine airplanes 
with a maximum takeoff weight greater than 12,500 pounds and level 4 
multiengine airplanes.''
---------------------------------------------------------------------------

    The FAA agrees with the recommendation to make Sec.  23.2305(b) 
applicable to the same airplanes as Sec.  23.2115(c)(1) for several 
reasons. First, in order to comply with Sec.  23.2115(c)(1), applicants 
must design airplanes with a means to decelerate the airplane after a 
rejected takeoff, regardless of the requirements in Sec.  23.2305(b), 
so adopting the recommended change would not increase the burden on 
applicants. Second, making the applicability of Sec.  23.2305(b) 
different from Sec.  23.2115(c)(1) could cause confusion, especially 
because the proposed applicability would have included airplanes 
excluded from Sec.  23.2115(c)(1). In former Sec. Sec.  23.55 and 
23.735(e), the FAA applied the requirement to determine the distance 
for an aborted takeoff at critical speed to the same airplanes required 
to provide kinetic energy absorption in the brakes for a rejected 
takeoff, and there is no reason to discontinue this practice. 
Additionally, adopting this recommendation harmonizes the FAA 
requirement with CS 23.2325(c).
c. Buoyancy for Seaplanes and Amphibians (Proposed Sec.  23.710/Now 
Sec.  23.2310)
    In the NPRM, proposed Sec.  23.710 (now Sec.  23.2310) would have 
required airplanes intended for operations on water to provide buoyancy 
of 80 percent in excess of the buoyancy required to support the maximum 
weight of the airplane in fresh water. Proposed Sec.  23.710 would have 
also required airplanes intended for operations on water to have 
sufficient watertight compartments so the airplane will stay afloat at 
rest in calm water without capsizing if any two compartments of any 
main float or hull are flooded.
    The FAA noted in the NPRM that it was proposing to remove the 
requirement that each main float must contain at least four watertight 
compartments of approximately equal volume because it was a specific 
design requirement that would be addressed by the proposed performance-
based standard.
    All of the comments on this section noted a problem with the 
prescriptive design specificity of proposed Sec.  23.710(b); in 
particular, the requirement to have watertight compartments. The 
commenters noted an erroneous assumption that all airplanes intended 
for operations on water would have watertight compartments. The 
commenters noted that manufacturers could employ a different solution--
such as foam-filled floats--eliminating the need for compartments, and 
still meet the buoyancy intent. BendixKing commented that the buoyancy 
requirement needs to be ``more generic to address the core safety 
intent, which is adequate floatation in the event of a failure.'' The 
Associations and Textron offered alternative regulatory language that 
would remove the requirement to have watertight compartments and 
provide a general performance-based standard for demonstrating 
buoyancy.
    The FAA agrees that proposed Sec.  23.710(b) is excessively 
prescriptive. The FAA recognizes there are other ways to meet the 
safety goal of protecting the airplane from capsizing. Therefore, the 
FAA revises proposed Sec.  23.710(b) to establish a more performance-
based standard for demonstrating buoyancy.
    ICON noted that hull type and float seaplanes were treated 
differently in former part 23, and recommended that they be treated 
differently in the new part 23 as well, because they deal with a loss 
of buoyancy in different ways. In particular, ICON noted differences in 
the rate of capsizing, the ability to detect an intrusion of water, and 
the pilot's ability to remove the water while operating the airplane. 
ICON asked the FAA to eliminate the separate compartment requirements 
for hull[hyphen]type seaplanes.
    The FAA agrees that, as proposed, the combination of hulls and 
floats into one regulation would have imposed a requirement on hulls 
that is more stringent than the requirements in former part 23. The FAA 
revises the proposed language to remove the prescriptive requirement 
for watertight compartments. As such, Sec.  23.2310 contains a more 
general standard for buoyancy that is appropriate for both floats and 
hulls.
d. Means of Egress and Emergency Exits (Proposed Sec.  23.750/Now Sec.  
23.2315)
    In the NPRM, proposed Sec.  23.750 (now Sec.  23.2315) would have 
required--
     The airplane cabin exit be designed to provide for 
evacuation of the airplane within 90 seconds in conditions likely to 
occur, excluding ditching, following an emergency landing. For 
ditching, proposed Sec.  23.750 would have required the cabin exit for 
all certification levels 3 and 4 multiengine airplanes be designed to 
allow evacuation in 90 seconds;
     Each exit to have a simple and obvious means, marked 
inside and outside the airplane, to be opened from both inside and 
outside the airplane, when the internal locking mechanism is in the 
locked position; and
     Airplane evacuation paths to protect occupants from 
serious injury from the propulsion system, and require that doors, 
canopies, and exits be protected from opening inadvertently in flight.
    Proposed Sec.  23.750 would have precluded each exit from being 
obstructed by a seat or seat back, unless the seat or seat back could 
be easily moved in one action to clear the exit. Proposed Sec.  23.750 
would have also required airplanes certified for aerobatics to have a 
means to exit the airplane in flight.
    The Associations, BendixKing, Textron, and EASA recommended the FAA 
remove the 90-second evacuation requirement in proposed Sec.  23.750(a) 
and replace it with less prescriptive language. EASA stated that the 
90-second evacuation time was not contained in the former part 23 
regulations and would not be reasonable for all airplanes. EASA stated 
that leaving the acceptable design solutions to an acceptable means of 
compliance would be better. As alternatives to the proposed language, 
BendixKing suggested a requirement for ``adequate and timely'' 
evacuation, Textron suggested a requirement for ``rapid'' evacuation, 
and the Associations suggested a requirement for ``rapid and safe'' 
evacuation.
    The FAA agrees and removes the airplane 90-second evacuation 
requirement because specifying the time limit in the regulation is 
unnecessarily prescriptive. The FAA replaces the evacuation requirement 
with the requirement to ``facilitate rapid and safe evacuation of the 
airplane in conditions likely to occur following an emergency landing, 
excluding ditching for level 1, level 2, and single-engine level 3 
airplanes.'' This harmonizes more closely with EASA's proposed CS 
23.2335.
    The Associations specifically proposed revisions to the regulatory 
text, which appeared to align with EASA's proposed regulation. In 
accordance with their recommendation, the FAA revises the beginning of 
proposed Sec.  23.750(a) to move a portion of its content into Sec.  
23.2315(a)(1). Section 23.2315(a) is revised to read: ``With the cabin 
configured for take-off or landing, the airplane is designed to,'' 
followed by more detailed requirements in the subparagraphs. The FAA 
believes this change more clearly preserves the intent of former 
regulations. It also harmonizes with EASA's proposed regulation.
    Textron also commented that the FAA should either replace the word 
``likely'' in proposed Sec.  23.750(a) or ensure the

[[Page 96624]]

``likely conditions'' referred to in paragraph (a) are clearly defined 
in the ASTM standards. The FAA intends the term ``likely'' to be 
nonprecise or within a mathematical certainty. As explained in the 
discussion of proposed Sec.  23.205, the FAA finds the most appropriate 
location for defining ``likely conditions'' is in a means of 
compliance, because these conditions may vary for different airplanes; 
therefore, the FAA retains the word ``likely'' in paragraph (a).
    Textron also noted that proposed Sec.  23.750(a) specifies ``likely 
conditions,'' but excludes ditching for all but levels 3 and 4 
multiengine airplanes. However, Textron stated that ditching as a 
likely condition associated with emergency evacuation had not been 
required previously. It recommended the FAA add a requirement to 
proposed Sec.  23.750, to require a means on levels 3 and 4 multiengine 
airplanes to evacuate the airplane safely following a ditching event.
    The FAA notes the requirement to safely evacuate the airplane 
during ditching is already addressed generally in Sec.  23.2315(a)(1). 
The methods for meeting this requirement will be in a means of 
compliance.
    Textron further commented on using former Sec.  23.807(e) as a 
means of compliance to show that occupants have a means available to 
safely evacuate the airplane. Textron stated that former Sec.  
23.807(e) only prescribes one exit on each side of the airplane to be 
above the waterline or alternative methods must be employed.
    The FAA agrees that providing one exit on each side of the airplane 
above the waterline is an acceptable means of compliance. While this 
may be one means of compliance that is acceptable for traditional 
designs, the FAA's goal in this rule is to use means of compliance, 
developed by industry or individuals, to allow for non-traditional 
designs.
    Transport Canada commented on proposed Sec.  23.750(a), noting that 
cabin exit design is just one of several elements that affect 
evacuation performance. Transport Canada also noted that the 
expectation to meet the evacuation performance with the airplane's 
maximum certified occupancy should be made explicit. Transport Canada 
suggested a revision to proposed paragraph (a) stating that the 
airplane design, including the cabin exit design, must provide for 
evacuation of the airplane of the maximum number of occupants within 90 
seconds in conditions likely to occur following an emergency landing.
    The FAA agrees that cabin exit design is just one of several 
elements that affect evacuation performance and that rapid evacuation 
with the airplane's maximum certified occupancy is required, but the 
regulation does not have to explicitly include this requirement. 
Section 23.2315 addresses generally all the likely conditions that 
affect emergency evacuation, which would include an airplane with 
maximum certificated occupancy. Therefore, the FAA is not adopting the 
language proposed by Transport Canada.
    The Associations recommended the following revisions to proposed 
Sec.  23.750(a), which deleted or combined portions of proposed 
paragraphs (a), (b), (c), (d) and (f) into a new paragraph (a), and 
renumbered paragraph (e) as paragraph (b). Their proposed paragraph 
(a)(1) appears to correlate with proposed Sec.  23.750(a). They 
proposed a revision to proposed paragraph (a)(1) stating that, with the 
cabin configured for take-off or landing, the airplane is designed to 
facilitate rapid and safe evacuation of the ``aeroplane'' in conditions 
likely to occur following an emergency landing, excluding ditching for 
level 1, level 2, and single-engine level 3 airplanes.
    The FAA adopts this language as Sec.  23.2315(a)(1), except for 
spelling ``aeroplane'' as ``airplane.'' This is better organized and 
more understandable than the proposed language, while still retaining 
the intent of former regulations and harmonizes the regulations between 
FAA and EASA.
    Textron commented that the phrase ``when the internal locking 
mechanism is in the locked and unlocked position'' in proposed Sec.  
23.750(b) is not necessary and should be deleted. The FAA agrees and 
removes the phrase because this is a detailed design consideration, 
which is more appropriately addressed in means of compliance.
    Textron also recommended the FAA add a requirement similar to the 
requirement for auxiliary locking devices in former Sec.  23.783(c)(6), 
which would provide, in pertinent part, that auxiliary locking devices 
that are actuated externally to the airplane may be used but such 
devices must be overridden by the normal internal opening means. 
Textron's view was that auxiliary locking devices used to secure the 
airplane would likely be needed to prevent unauthorized entry into the 
airplane when it is left unattended.
    The FAA disagrees with Textron's recommendation as the suggested 
text because it is more appropriate for a means of compliance.
    The Associations proposed revisions to proposed Sec.  23.750(a)(2) 
that coincidently address Textron's comment on internal locking 
mechanisms. They suggested adding language stating that, with the cabin 
configured for take-off or landing, the airplane is designed to have 
means of egress (openings, exits or emergency exits), that can be 
readily located and opened from the inside and outside. The means of 
opening must be simple and obvious.
    The FAA adopts this language as Sec.  23.2315(a)(2), except the 
proposed marking requirement is retained. This revision captures the 
safety intent of the former regulations more clearly and harmonizes 
regulations between the FAA and EASA.
    The Associations recommended deleting proposed Sec.  23.750(c). The 
FAA agrees because paragraph (a)(1), as revised, already addresses 
similar requirements, rendering paragraph (c) redundant.
    Textron commented on proposed Sec.  23.750(d) by recommending the 
FAA address obstructions more generally (i.e., not just seat backs), 
and offered the language stating that each exit must not be obstructed 
unless the obstruction can be easily moved in one action to clear the 
exit.
    Transport Canada similarly suggested the requirement should more 
generally address that any component of the interior should be 
considered as a potential obstruction, and also address temporary 
obstructions during flight. Transport Canada proposed a revision to 
proposed paragraph (d) stating that each exit must not be obstructed by 
any interior component during taxi, take-off or landing. In addition, a 
seat or seat back may obstruct an exit if the seat or seat back can 
[be] easily moved in one action to clear the exit.
    The FAA considered Transport Canada's proposed wording, but moving 
a seat back easily in one motion to reach an emergency exit is more 
appropriate as a means of compliance. The FAA agrees with Textron's and 
Transport Canada's comments on proposed Sec.  23.750(d) that 
obstructions that could potentially block exits should be addressed 
more generally and not limited to seat backs, because other items could 
block exits and impair evacuation. The FAA revises the regulation 
accordingly as Sec.  23.2315(a)(3).
    The Associations proposed a revision to proposed Sec.  23.750(a)(3) 
stating that, with the cabin configured for take-off or landing, the 
airplane is designed to have easy access to emergency exits when 
present.
    The FAA is incorporating this suggestion in Sec.  23.2315(a)(3). 
The new language captures the safety intent of the former regulations 
more generally

[[Page 96625]]

and harmonizes the FAA language with the EASA NPA language.
    The Associations recommended to renumber proposed Sec.  23.750(e) 
as proposed Sec.  23.750(b) (now Sec.  23.2315(b)). The FAA agrees and 
adopts the proposed renumbering. This relocation will not change the 
substantive content of the paragraph, but matches with EASA's numbering 
and will lessen confusion.
    The Associations recommended deleting proposed Sec.  23.750(f). 
EASA commented that the requirement in proposed Sec.  23.750(f) for 
doors, etc. is too design-specific and can be covered by generic 
principles covered in Sec.  23.2250 (proposed as Sec.  23.500).
    The FAA understands EASA's comment, but requiring doors, canopies, 
and exits to be protected from opening inadvertently in flight is a 
general requirement that does not limit possible design solutions. 
However, the FAA moves this requirement to Sec.  23.2250(e) to 
harmonize the location of the requirement with EASA's rule.
    Upon further review, the FAA is replacing the word ``approved'' in 
proposed Sec.  23.750(e) (now Sec.  23.2315(b)) with the word 
``certified''. This change does not affect the original intent of 
paragraph (e), but harmonizes the language with EASA.
e. Occupant Physical Environment (Proposed Sec.  23.755/Now Sec.  
23.2320)
    In the NPRM, proposed Sec.  23.755 (now Sec.  23.2320) would have 
required an applicant to design the airplane to allow clear 
communication between the flightcrew and passengers and provide a 
clear, sufficiently undistorted external view to enable the flightcrew 
to perform any maneuvers within the operating limitations of the 
airplane. Proposed Sec.  23.755 would have also required an applicant 
to design the airplane to protect the pilot from serious injury due to 
high-energy rotating failures in systems and equipment, and protect the 
occupants from serious injury due to damage to windshields, windows, 
and canopies.
    Additionally, proposed Sec.  23.755 would have required, for level 
4 airplanes, each windshield and its supporting structure directly in 
front of the pilot to withstand the impact equivalent of a two-pound 
bird at maximum approach flap airspeed and allow for continued safe 
flight and landing after the loss of vision through any one panel.
    Furthermore, proposed Sec.  23.755 would have required any 
installed oxygen system to include a means to determine whether oxygen 
is being delivered and a means for the flightcrew to turn on and shut 
off the oxygen supply, and the ability for the flightcrew to determine 
the quantity of oxygen available. Proposed Sec.  23.755 would have also 
required any installed pressurization system to include a 
pressurization system test and a warning if an unsafe condition exists.
    EASA commented the requirement in proposed Sec.  23.755(a)(2) for 
the airplane design to provide a clear, sufficiently undistorted 
external view should be covered in the ``crew interface'' paragraph.
    The FAA agrees with EASA that the Sec.  23.755(a)(2) flightcrew 
visibility requirement is more directly related to flightcrew interface 
than occupant environment. The FAA is including the words ``including 
pilot view'' in Sec.  23.2600(a). This change harmonizes Sec.  
23.2600(a) more closely with proposed CS 23.2600(a).
    Similarly, the FAA relocates the proposed Sec.  23.755(b)(2) 
requirement to Sec.  23.2600(c), because this change harmonizes Sec.  
23.2600(c) more closely with EASA's proposed CS 23.2600(d). 
Additionally, the FAA adopts the language in EASA's proposed CS 
23.2600(d), except for the spelling of ``aeroplanes'' versus 
``airplanes'' for improved clarity and harmonization.
    The Associations suggested the FAA delete the word ``any'' from the 
phrase ``any maneuvers within the operating limitations of the 
airplane,'' in proposed Sec.  23.755(a)(2). The commenters did not 
provide a rationale for this suggestion.
    The FAA disagrees as removing the word ``any'' could unduly 
restrict the scope of the rule. The FAA's intent is that adequate 
visibility must be provided to perform any maneuvers within the 
operating limitations of the airplane. Therefore, the FAA adopts Sec.  
23.2600(a) as proposed in the NPRM.
    The Associations, Transport Canada, EASA, and ANAC questioned 
proposed Sec.  23.755(a)(3), which would require the airplane design to 
protect the pilot from serious injury due to high-energy rotating 
failures. The Associations stated there may be new systems which may 
include high amounts of energy that is not the result of rotating 
equipment. The commenters suggested proposed Sec.  23.755(a)(3) be 
broadened to include the new systems, such as high voltage systems. 
EASA similarly suggested amending the protection of pilots against 
serious injury due to high-energy rotating failures to include any 
high-energy risks.
    The FAA has considered the commenters' suggestion to change 
proposed Sec.  23.755(a)(3) as recommended. However, the FAA has 
concluded that the safety requirements contained in Sec.  23.2510, 
``Equipment, systems and installations,'' (proposed as Sec.  23.1315) 
of this rule adequately address hazards from high-energy sources. 
Therefore, no change is being made to the final rule based on the 
commenters' suggestion.
    ANAC referenced former Sec.  23.1461(d) and asked the FAA to 
explain why proposed Sec.  23.755(a)(3) excluded protection for 
airplane occupants other than the pilot from certain hazards. 
Additionally, Transport Canada commented the proposed language requires 
protecting the pilot from high-energy rotating failures, which suggests 
a lower level of safety for the other airplane occupants. It 
recommended replacing the word ``pilot'' with ``occupants''.
    The FAA agrees with ANAC and Transport Canada that proposed Sec.  
23.755(a)(3) would effectively lower the level of safety because it did 
not protect all occupants from high-energy rotor failures. It also did 
not protect the airplane from high-energy rotor failures, and allowed 
the pilot and pilot controls to be in the inboard propellers' plane of 
rotation. The FAA intended to incorporate the safety intent of former 
Sec. Sec.  23.771(c) and 23.1461.
    Therefore, the FAA adopts Sec.  23.2550 to better capture the 
safety intent of former Sec.  23.1461. Section 23.2550 requires 
equipment containing high-energy rotors to be designed or installed to 
protect the occupants and airplane from uncontained fragments. The FAA 
also revises Sec.  23.2320(a)(2) (proposed as Sec.  23.755(a)(3)) to 
capture the safety intent of former Sec.  23.771(c). Section 
23.2320(a)(2) will require the pilot and flight controls be protected 
from propellers.
    Textron and NJASAP commented on the requirement in proposed Sec.  
23.755(b)(1) for level 4 airplanes to ensure that the windshield and 
its supporting structure directly in front of the pilot can withstand 
the impact equivalent of a two-pound bird. Textron noted the 14 CFR 
part 33 engine requirement for medium bird ingestion is based on a 2.5-
pound bird and questioned why the FAA did not use 2.5-pounds in 
proposed Sec.  23.755(b)(1). Textron also recommended the FAA consider 
language from CS 23.440(a) with weight/type specifics being defined in 
the industry standards.
    The FAA notes NJASAP's and Textron's comment on the weight of the 
bird in proposed Sec.  23.755(b)(1). Former Sec.  23.775(h)(1) required 
windshield panes directly in front of pilots in the normal conduct of 
their duties, and the supporting structure for these panes, to 
withstand, without penetration, the

[[Page 96626]]

impact of a two-pound bird when the velocity of the airplane (relative 
to the bird along the airplane's flight path) is equal to the 
airplane's maximum approach flap speed for commuter category airplanes. 
The FAA codified this requirement in part 23, amendment 23-49.\39\ The 
preamble of the NPRM \40\ for amendment 23-49 explains that the two-
pound bird requirement was based on ICAO bird strike data that occurred 
on airplanes of 19,000 pounds or less from 1981 through 1989. Also, 
this requirement is well established in the former regulations and has 
provided an acceptable level of safety. Therefore, the FAA retains the 
two-pound bird requirement.
---------------------------------------------------------------------------

    \39\ Final Rule, Airworthiness Standards; Systems and Equipment 
Rules based on European Joint Aviation Requirements, 61 FR 5151, 
5166 (Feb. 9, 1996).
    \40\ NPRM, Airworthiness Standards; Systems and Equipment Rules 
based on European Joint Aviation Requirements (59 FR 37620, July 22, 
1994).
---------------------------------------------------------------------------

    NJASAP commented the methodology used to discriminate between level 
3 and 4 airplanes will motivate OEMs to certify more airplanes within 
level 3. The commenter also noted that airplanes in this category have 
experienced fatal accidents due to bird strikes. NJASAP recommended the 
FAA apply the requirements of proposed Sec.  23.755(b)(1) to level 3 
high-speed airplanes.
    The FAA acknowledges the requirement in former Sec.  23.775(h)(1) 
applied to commuter category airplanes, while the proposed requirement 
would have applied only to level 4 airplanes. Under the former 
regulations, a commuter category airplane was limited to multiengine 
airplanes with a seating configuration, excluding pilot seats, of 19 or 
less and a maximum certificated weight of 19,000 pounds or less.\41\ 
Additionally, a normal category airplane was limited to those airplanes 
that had a seating configuration, excluding pilot seats, of nine or 
less, a maximum certificated takeoff weight of 12,500 pounds or less, 
and intended for nonacrobatic operation.\42\ Under the proposal, level 
4 airplanes would be airplanes with a maximum seating configuration of 
10 to 19 passengers. Thus, the proposal would have the effect of 
providing relief to a percentage of part 23 airplanes with a maximum 
certified takeoff weight more than 12,500 pounds, but have fewer than 
10 passengers seating configuration.
---------------------------------------------------------------------------

    \41\ See Sec.  23.3(d), amendment 23-62.
    \42\ See Sec.  23.3(a), amendment 23-62.
---------------------------------------------------------------------------

    Under NJASAP's proposal, this requirement would apply to airplanes 
with 7 to 9 passengers and a maximum certified takeoff weight of 12,500 
pounds or less, which would increase the certification requirements of 
former Sec.  23.775(h)(1). This regulation has proven to be an 
acceptable level of safety. Additionally, adding level 3 airplanes 
would increase the cost for a number of these airplanes that weigh less 
than 12,500 pounds.
    Transport Canada and ANAC noted that former Sec.  23.831 addresses 
smoke, which was not included in proposed Sec.  23.755(c). Transport 
Canada recommended the FAA add the phrase ``and solid or liquid 
particulates'' after the word ``vapors'' in proposed paragraph Sec.  
23.755(c) because smoke is a collection of airborne solid and liquid 
particulates and gases.
    The FAA agrees with Transport Canada and ANAC and revises Sec.  
23.2320(c) to require the air provided to each occupant be free of 
hazardous concentrations of smoke during normal operations and likely 
failures. The FAA intended proposed Sec.  23.755(c) to incorporate the 
safety intent of former Sec.  23.831(b), which requires the ventilating 
air in the flightcrew and passenger compartments to be free of harmful 
or hazardous concentrations of gases and vapors in normal operations 
and in the event of reasonably probable failures or malfunctioning of 
the ventilating, heating, pressurization, or other systems and 
equipment. It also requires smoke evacuation be accomplished quickly if 
accumulation of hazardous quantities of smoke in the cockpit area is 
reasonably probable.
    The FAA chose the term ``smoke'' instead of ``solid or liquid 
particulates'' because it is a more common term. Section 23.2320(c) 
requires air at a breathable pressure, free of hazardous concentrations 
of gases, vapors, and smoke, to be provided to each occupant during 
normal operations and likely failures.
    ANAC questioned whether general rules (like proposed Sec.  23.1315) 
would address the concern of smoke evacuation capability and requested 
the FAA clarify how airplane manufacturers would be driven to develop a 
smoke evacuation system in case there is no explicit requirement, just 
general ones.
    The FAA considers Sec.  23.2320(c) to be an explicit requirement 
for cockpit smoke evacuation but general regulations may also require 
smoke evacuation to be considered. A pressurized airplane design that 
cannot evacuate smoke from the cockpit sufficiently to allow the 
flightcrew to safely perform their duties, does not provide each 
occupant with air at a breathable pressure, free of hazardous 
concentrations of gases, vapors and smoke, during normal operations and 
probable failures. Therefore, an effective smoke evacuation system is 
necessary to comply with Sec.  23.2320(c) of this rule.
    The Associations recommended reordering proposed Sec.  23.755(d) 
and (e) to place the oxygen requirements after the pressurization 
requirements. The FAA agrees with the recommendation and notes this 
change harmonizes with EASA's regulation. In EASA's regulation, 
pressurization system requirements precede the oxygen systems 
requirements.
    Textron commented that the FAA should remove proposed Sec.  
23.755(e)(1), as it covers the same subject area as proposed Sec.  
23.1305(c). Proposed Sec.  23.1305(c) would have required information 
concerning an unsafe system operating condition to be provided in a 
timely manner to the crewmember responsible for taking corrective 
action. Presentation of this information must be clear enough to avoid 
likely crewmember errors.
    The FAA agrees with Textron's comment, as both sections would 
require the crewmembers to be made aware of unsafe conditions. 
Therefore, the FAA adopts Sec.  23.2605(c) as proposed and withdraws 
proposed Sec.  23.755(e)(1).
    Proposed Sec.  23.755(e)(2) would have required pressurization 
systems, if installed, to include a pressurization system test. The FAA 
intended to capture the safety intent of former Sec.  23.843, 
``Pressurization system tests,'' which required specific tests for 
demonstrating compliance with safety requirements. Upon further review, 
the FAA finds that proposed Sec.  23.755(e)(2) contains prescriptive 
requirements, which is inconsistent with the FAA's goal of establishing 
performance-based requirements as was set forth in the NPRM. Therefore, 
the FAA withdraws proposed Sec.  23.755(e)(2).
    The FAA reviewed the former regulations related to proposed Sec.  
23.755 to determine if it inadvertently omitted any safety requirements 
for pressurization systems. As a result of this review, the FAA has 
identified the following omissions, which are addressed in this rule.
    This final rule now requires pressurization systems, if installed, 
to be designed to protect against decompression to an unsafe level, 
which captures the safety intent of former Sec. Sec.  23.841(c), (d)(2) 
and (d)(3). This final rule also requires pressurization systems, if 
installed, to be designed to protect against excessive differential 
pressure, which captures the safety intent of Sec. Sec.  23.841(b)(1), 
(b)(2), (b)(3) and (b)(8).

[[Page 96627]]

    Section 23.2320(e)(1) specifically requires that if an oxygen 
system is installed in the airplane, it must effectively provide oxygen 
to each user to prevent the effects of hypoxia and be free from hazards 
in itself, in its method of operation, and its effect upon other 
components. This requirement captures the safety intent of former 
Sec. Sec.  23.1441(a) and (d); 23.1443, and 23.1447(a), (b), (c), (d), 
(e), and (g). These provisions require pressure/demand oxygen equipment 
for the crew on high altitude airplanes; minimum oxygen flowrates and 
pressures at specified conditions; standards for oxygen mask and 
cannula effectiveness; ease of donning, retention, and accessibility; 
and standards for crew communication while using oxygen equipment.\43\ 
The FAA revises 23.2320(e)(1) to capture the safety intent of these 
former regulations, but without their prescriptive requirements, by 
requiring that if an oxygen system is installed in the airplane, it 
must effectively provide oxygen to each user to prevent the effects of 
hypoxia.
---------------------------------------------------------------------------

    \43\ These specifications were intended to protect against 
hypoxia.
---------------------------------------------------------------------------

    The FAA has also decided to add the specific language from former 
Sec.  23.1441(b) into Sec.  23.2320. Requiring an oxygen system, if 
installed, to be free from hazards in itself, in its method of 
operation, and its effect upon other components restates former Sec.  
23.1441(b) verbatim and captures the safety intent of former Sec. Sec.  
23.1441(b) and (e), 23.1445, 23.1447(f), 23.1449, 23.1450(b), 23.1451, 
and 23.1453. These provisions required--
     A means for the crew to turn on and shut off oxygen supply 
at the high-pressure source in flight;
     Materials that could be used for oxygen tubing to be 
considered;
     A means to reserve oxygen for the flightcrew if a source 
is shared with passengers;
     A manual means to deploy passenger oxygen masks (or other 
units) for high-altitude airplanes;
     A means to allow the crew to determine whether oxygen is 
being delivered;
     Hazards from chemical oxygen generator temperature and 
pressure to be addressed;
     Protection of oxygen equipment and lines from fire 
hazards; and
     Protection against overload, unsafe temperatures, and 
hazards in a crash landing.
    The FAA withdraws proposed Sec.  23.755(d)(1) as it is rendered 
redundant by adopted Sec.  23.2600(b).\44\ Furthermore, by making the 
revisions described previously, the FAA is able to eliminate proposed 
Sec.  23.755(d)(2) and (3) as redundant. Proposed Sec.  23.755(d)(2) 
and (3) would have required oxygen systems to include a means to 
determine if oxygen is being delivered and a means to permit the 
flightcrew to turn on and shut off the oxygen supply at any high-
pressure source in flight. The FAA considers these requirements 
redundant because failure to deliver oxygen to a user who needs oxygen 
for protection against hypoxia with no way to determine that oxygen is 
not flowing is a hazard in the oxygen system; and an oxygen leak that 
cannot be shutoff at the high pressure source is a hazard in the oxygen 
system. If oxygen is needed for the survival of the pilots or 
passengers and it is turned off at the high-pressure source 
(intentionally or inadvertently), the inability to turn it on would be 
a hazard in the oxygen system.
---------------------------------------------------------------------------

    \44\ Proposed Sec.  23.755(d)(1) would have required oxygen 
systems to include a means to allow the flightcrew to determine the 
quantity of oxygen available in each source of supply on the ground 
and in flight. Adopted Sec.  23.2600(b) requires the applicant to 
install displays so qualified flightcrew can monitor and perform 
defined tasks associated with the intended functions of systems and 
equipment.
---------------------------------------------------------------------------

f. Fire Protection (Proposed Sec.  23.800/Now Sec.  23.2325)
    In the NPRM, proposed Sec.  23.800 (now Sec.  23.2325) would have 
required the--
     Insulation on electrical wire and electrical cable outside 
designated fire zones be self-extinguishing;
     Airplane cockpit and cabin materials in certification 
levels 1, 2, and 3 be flame-resistant;
     Airplane cockpit and cabin materials in level 4 airplanes 
be self-extinguishing;
     Airplane materials in the baggage and cargo compartments, 
which are inaccessible in flight and outside designated fire zones, be 
self-extinguishing; and
     Electrical cable installation that would overheat in the 
event of circuit overload or fault be flame resistant.
    Additionally, proposed Sec.  23.800 would have precluded thermal 
acoustic materials outside designated fire zones from being a flame 
propagation hazard. Proposed Sec.  23.800 would have also required 
sources of heat that are capable of igniting adjacent objects outside 
designated fire zones to be shielded and insulated to prevent such 
ignition.
    Proposed Sec.  23.800 would have required airplane baggage and 
cargo compartments, outside designated fire zones, to be located where 
a fire would be visible to the pilots, or equipped with a fire 
detection system and warning system, and--
     Be accessible for the manual extinguishing of a fire;
     Have a built-in fire extinguishing system, or
     Be constructed and sealed to contain any fire within the 
compartment.
    Proposed Sec.  23.800 would have required a means to extinguish any 
fire in the cabin, outside designated fire zones, such that the pilot, 
while seated, could easily access the fire extinguishing means, and for 
levels 3 and 4 airplanes, passengers would have a fire extinguishing 
means available within the passenger compartment. Where flammable 
fluids or vapors might escape by leakage of a fluid system, proposed 
Sec.  23.800 would have required each area, outside designated fire 
zones, be defined and have a means to make fluid and vapor ignition, 
and the resultant hazard, if ignition occurs, improbable. Additionally, 
proposed Sec.  23.800 would have also required combustion heater 
installations outside designated fire zones be protected from 
uncontained fire.
    EASA commented that the fire protection outside designated fire 
zones requirements proposed in Sec.  23.800 were design solutions 
instead of objectives. EASA contended these proposed provisions would 
hamper the development of different, but acceptable future designs. 
EASA recommended the FAA follow the A-NPA text from CS 23.445.
    The FAA does not share EASA's view that the proposed Sec.  23.800 
requirements were design specific solutions. For the foreseeable 
future, there will be wiring, cabling, insulating, and covering 
materials used in airplane cabins, cockpits, and baggage and cargo 
compartments. The performance standard requires certain materials be 
self-extinguishing, flame resistant, etc., in order to prevent the 
initiation or propagation of a fire. The way to demonstrate compliance 
with the performance standard is now moved to accepted methods of 
compliance instead of being specified in rule language or appendices. 
Additionally, the former part 23 regulations for commuter category 
airplanes, and the proposed regulations for level 4 airplanes, intended 
for personnel to be alerted to the presence of a fire and a way to 
extinguish it. Based on the FAA's understanding of the current 
technology available, for the foreseeable future, fire detection 
systems and extinguishers are the methods to achieve this. The FAA is 
not prescribing the technology and design of those systems.

[[Page 96628]]

    Additionally, the FAA finds that following the A-NPA text from CS 
23.445 would be a new approach to achieving the safety intent of 
preventing the initiation or propagation of a fire, which was not set 
forth for notice and comment. Further, the FAA has concerns whether 
EASA's proposed rule language would meet the same level of safety as 
provided for in the former part 23 regulations, as EASA's proposed text 
would require minimization of the risk of ``fire initiation'' and 
``fire propagation''. The word ``minimize'' has not historically been 
used in this safety standard where specific tests were used with 
specific pass/fail criteria. The FAA also finds using the word 
``minimize'' may introduce ambiguity in the rule. While the FAA is not 
adopting EASA's recommendation, the FAA contends the requirement in 
Sec.  23.2325 harmonizes with EASA's requirements because the effect is 
the same.
    Embraer recommended modifying the title of proposed Sec.  23.800 to 
remove the word ``designated,'' as well as removing the phrase 
``Outside designated fire zones'' from the lead sentence of the 
proposed rule.
    The FAA agrees with Embraer's comment that it is unnecessary to 
state ``designated'' in the title. The FAA eliminates the phrase ``fire 
zones'' as well because the term may lead to confusion. This revision 
aligns the final rule with the safety intent of former regulations and 
has the benefit of aligning the title with EASA's proposed title. 
Furthermore, the FAA changes the title of Sec.  23.2325 to ``Fire 
protection'' and deletes the lead-in sentence ``Outside designated fire 
zones:''. Finally, the FAA adds ``. . . in the fuselage . . .'' to 
subparagraph (c) so as not to expand the applicable area of the rule.
    Transport Canada recommended the FAA define several terms used in 
this section, specifically, ``self-extinguishing,'' ``flame 
resistant,'' and ``flame propagation hazard'', because this section 
would otherwise be subject to a wide range of interpretation. Transport 
Canada stated the performance statement, as expressed, may not ensure 
the level of safety of former Sec.  23.853.
    The FAA finds that defining these terms is not necessary, nor that 
this rule will be subject to a wide range of interpretation. Putting 
the parameters necessary to precisely define these terms would mean 
specifying test standards, which is contrary to the rule's intent to 
move away from prescriptive standards. The specifications for meeting 
these requirements will be contained in an accepted means of 
compliance. One means of compliance accepted by the FAA is to use the 
former prescriptive means of compliance contained in former part 23, 
together with a policy statement issued by the FAA identifying means by 
which the FAA has addressed errors, ELOS findings to various provisions 
of former part 23, and special conditions (i.e., ``prescriptive 
means''). The performance standard, plus this accepted means of 
compliance, will ensure the same level of safety as former Sec.  
23.853. The FAA notes that to be acceptable, any future proposed means 
of compliance would have to provide at least an equivalent level of 
safety.
    Transport Canada questioned whether proposed Sec.  23.800(a) would 
cover components located in between the fuselage skin and the 
compartment liners that were explicitly covered under former Sec.  
23.853. The commenter recommended the FAA consider these components.
    The FAA finds it unnecessary to list these specific parts in the 
rule since all materials in those compartments must meet the standards 
specified for that compartment. The FAA notes, just as under former 
Sec.  23.853(d)(3)(ii), items behind compartment liners are considered 
materials that exist in those compartments.
    In level 4 airplanes, proposed Sec.  23.800(a)(3) would have 
required materials in the cockpit, cabin, and baggage and cargo 
compartments be self-extinguishing. NJASAP stated level 3 high-speed 
airplanes should also be required to have self-extinguishing cockpit 
and cabin materials. NJASAP noted many business jets that fly at high 
altitude will fall into the level 3 high-speed category in the future. 
NJASAP indicated if a fire were to break out in this airplane type, it 
could take several minutes to detect it and to make an emergency 
landing.
    The FAA notes under the former Sec.  23.853(d), only commuter 
category airplanes needed to meet the self-extinguishing requirement 
for these specified items. In the NPRM, the FAA correlated level 4 
airplanes to the commuter category. Therefore, adding the requirement 
to make cockpit and cabin materials self-extinguishing for level 3 
airplanes would impose requirements beyond those imposed under former 
Sec.  23.853 and would be beyond the scope of the notice. Furthermore, 
the FAA is unaware of service experience with level 3 airplanes that 
would justify the increased cost associated with the NJASAP's comment.
    Textron and the Associations requested clarification regarding the 
use of ``or'' in proposed Sec.  23.800(b)(2) with respect to circuit 
overload or fault. The Associations asked whether the FAA intends to 
allow some electrical systems, such as high-reliability primary power 
wires in electrically-powered airplanes, to use reliable design 
practices in place of circuit protection for some wires. Textron 
thought the use of ``or'' meant both overload and failure of the 
protective device do not need to be considered and asked whether the 
intent is to allow some circuits without overload protection, such as 
main start cables.
    The FAA notes the focus of this rule is fire protection rather than 
circuit design. The FAA's intent is to make certain electrical cable 
installations that could overheat are flame resistant, regardless of 
whether this is due to a circuit overload or fault. Proposed Sec.  
23.800 nearly mirrors former Sec.  23.1365(b), which used the same 
phrase ``. . . circuit overload or fault . . . .'' \45\ The FAA did not 
intend to change the meaning of former Sec.  23.1365(b). To address the 
commenters' concerns, the FAA revises Sec.  23.2325 to reflect the 
language as stated in former Sec.  23.1365(b).
---------------------------------------------------------------------------

    \45\  See 61 FR 5151, February 9, 1996.
---------------------------------------------------------------------------

    Also, the FAA noted a typographical error in proposed paragraph 
(c). A slash (``/'') between ``thermal'' and ``acoustic'' was missing. 
The absence of the ``/'' indicate only insulation that was both thermal 
and acoustic must comply. The FAA's intention was either thermal or 
acoustic, as required under the former Sec.  23.856. The FAA has 
corrected this inadvertent omission in this rule.
    Textron and the Associations submitted comments on proposed Sec.  
23.800(d), which would have required sources of heat that are capable 
of igniting adjacent objects, to be shielded and insulated to prevent 
such ignition. Textron noted the proposed rule broadened the scope of 
the former requirement from ``cargo and baggage compartments'' to 
anything that is not a designated fire zone. Textron recommended the 
FAA modify proposed Sec.  23.800(d) to include the phrase ``located in 
the cargo and baggage compartments'' after ``Sources of heat.'' Textron 
also commented that preventing hot equipment from starting fires in 
normal operation is needed, but in the case where materials and 
proximities are controlled by type design (i.e., other than the cargo 
and baggage compartments), this is sufficiently addressed by proposed 
Sec.  23.1300 (now Sec.  23.2500). The Associations recommended 
modifying proposed Sec.  23.800(d) by adding the

[[Page 96629]]

phrase ``located in the cargo compartment.''
    The FAA agrees the proposed rule would have unintentionally 
broadened the prior requirements. The FAA revises the rule language to 
add ``within each cargo and baggage compartment''. The FAA also agrees 
with Textron that other regulations in subpart F sufficiently address 
the issue of preventing hot equipment from starting fires in normal 
operation where materials are located in places other than the cargo 
and baggage compartments.
    The Associations proposed removing the word ``any'' in front of 
``fire'' from proposed Sec.  23.800(e)(2) and (f). The commenters did 
not provide a reason for the proposal. Although ``any'' is implied, the 
FAA prefers to leave the word in the rule language to be explicit.
    Regarding proposed Sec.  23.800(g)(2),\46\ Textron asked whether 
the probability of the leak is considered (i.e., the ``improbable'' 
requirement is for ignition and hazard after a leak). Textron 
recommended the FAA clarify whether the requirement presumes a leak. 
Transport Canada commented that the language of proposed Sec.  
23.800(g)(2) was not consistent with AC 23.1309-1E. An individual 
commenter submitted a similar comment. Transport Canada recommended the 
FAA revise this provision to be consistent with AC 23.1309-1E, thereby 
changing the qualitative probability to be remote, extremely remote, or 
extremely improbable.
---------------------------------------------------------------------------

    \46\ Textron cited proposed ``Sec.  23.2325(a)(2)'', but it 
appears the commenter intended to refer to Sec.  23.2325(g)(2).
---------------------------------------------------------------------------

    The FAA agrees the wording of proposed Sec.  23.800(g)(2) was 
problematic because the term ``improbable'' was associated with 
quantitative failure rates in former Sec.  23.1309. The FAA did not 
intend to require an assessment of the probability of a flammable fluid 
leak or ignition of a flammable fluid leak. The FAA's intent is that 
reasonable design precautions are used to reduce (i) the likelihood of 
flammable fluid leaks, (ii) the likelihood of flammable fluid ignition, 
and (iii) the severity of flammable fluid ignition. The FAA agrees that 
since the proposed rule would have required ignition to be assumed, it 
does not make sense to make the hazard improbable ``if'' ignition 
occurs.
    The FAA intended to capture the safety intent of the requirement in 
former Sec.  23.863. The FAA considered the suggestions for revising 
proposed Sec.  23.800(g), and is using the text of former Sec.  
23.863(a). Former Sec.  23.863(a) was a performance-based requirement 
and former Sec.  23.863(b) and (c) provided details on how former Sec.  
23.863(a) must be addressed. New Sec.  23.2325(g)(2) requires a means 
to minimize the probability of ignition of the fluids and vapors and 
the resultant hazard if ignition does occur in each area where 
flammable fluids or vapors might escape by leakage of a fluid system. 
``Minimize'' means to reduce the probability and consequences of 
occurrence to the extent practical. It does not establish a 
probabilistic requirement, but rather requires application of sound 
engineering judgment to use effective means to achieve the safety 
objective.
g. Fire Protection in Designated Fire Zones and Adjacent Areas 
(Proposed Sec.  23.805/Now Sec.  23.2330)
    In the NPRM, proposed Sec.  23.805 (now Sec.  23.2330) would have 
required--
     Flight controls, engine mounts, and other flight 
structures within or adjacent to designated fire zones be capable of 
withstanding the effects of a fire;
     Engines inside designated fire zones to remain attached to 
the airplane in the event of a fire or electrical arcing; and
     Terminals, equipment, and electrical cables, inside 
designated fire zones, used during emergency procedures, be fire-
resistant.
    Embraer recommended modifying proposed Sec.  23.805 to change the 
title from ``Fire protection in designated fire zones'' to ``Fire 
protection in fire zones and adjacent areas.''
    The FAA agrees with the recommendation to add ``and adjacent 
areas'' to the title for clarification. The FAA notes that Sec.  
23.805(a) references flight controls, engine mounts, and other flight 
structures adjacent to a designated fire zone.
    However, ``designated fire zone'' has a particular meaning. Embraer 
viewed this proposed definition as prescriptive and recommended the FAA 
use the definition of ``fire zone'' contained in the draft of AC 
25.863-1. That definition stated a fire zone means a ``zone that 
contains a nominal ignition source and may be exposed to a flammable 
fluid/material as a result of a failure.'' The FAA reviewed the 
definition of ``fire zone'' in AC 25.863-1 and determined this 
definition would impose requirements beyond those in the former part 23 
regulations.
    Embraer also recommended removing the modifying phrase ``inside 
designated fire zones'' contained in the proposed regulation. Embraer 
stated that ``former Sec.  23.1181 defined the `hot' parts of an engine 
installation is an ignition source and considering that there are fuel, 
oil, and hydraulic fluids being carried around such areas, they shall 
be considered a fire zone, and then the term `designated' would apply, 
which means that it is not necessary [for] further analysis to define 
if it is a flammable fluids zone or a fire zone.''
    The FAA agrees with Embraer's recommendation and removes the 
modifying phrase from the first line of the proposed text for Sec.  
23.805(b). The FAA will clarify within each requirement if it applies 
in designated fire zones, or designated fire zones and adjacent areas.
    EASA stated that proposed Sec.  23.805(b) reflects current design-
specific requirements that should be amended to cover other ``new'' 
designated fire zones, such as for batteries. Proposed Sec.  23.805(b) 
would have required engines inside designated fire zones to remain 
attached to the airplane in the event of a fire or electrical arcing. 
EASA recommended revising proposed Sec.  23.805(b) to read: ``A fire in 
a designated fire zone must not preclude continued safe flight and 
landing''.
    The FAA finds EASA's proposal is beyond the scope of the NPRM. The 
FAA intended proposed Sec.  23.805 to capture the safety intent of 
former Sec. Sec.  23.865 and 23.1359(b). Former Sec.  23.865, in part, 
required engine vibration isolators to incorporate suitable features to 
ensure the engine is retained if the non-fireproof portions of the 
vibration isolators deteriorate from the effects of a fire. The FAA 
finds this requirement is still applicable to engines that use 
flammable fuels and should be retained. However, the FAA agrees 
proposed Sec.  23.805(b) reflected current design-specific requirements 
that would not be applicable to other potential designs that do not use 
flammable fuels for propulsion. Therefore, the FAA is making this 
requirement only applicable to engines in designated fire zones. The 
FAA also withdraws the proposed requirement for engines to remain 
attached to the airplane in the event of electrical arcing, because the 
FAA finds that the threat of electrical arcing causing structural 
failure is addressed adequately in the electrical systems requirements 
in subpart F.
    Embraer commented that the word ``engine'' should be replaced with 
the phrase ``power unit'' in proposed Sec.  23.805(b). The FAA 
understands Embraer's rationale, but the FAA's authority to issue TCs 
refers to ``aircraft engines,'' not power units (49 U.S.C. 44704(a)(1)) 
so the term ``aircraft engines'' needs to be retained. Therefore, the 
FAA is not adopting EASA's recommendation in the final rule.

[[Page 96630]]

    Textron recommended the FAA replaces ``terminals, equipment, and 
electrical cables'' with the word ``equipment'' in proposed Sec.  
23.805(c). Paragraph (c) would have required terminals, equipment, and 
electrical cables inside designated fire zones, that are used during 
emergency procedures, be fire resistant. Textron stated that if this 
provision is supposed to apply to anything in a fire zone that gets 
used in an emergency, it is potentially misleading.
    The FAA disagrees with Textron's comment. The FAA intended proposed 
Sec.  23.805(c) to capture the safety intent of former Sec.  
23.1359(b), which stated ``Electrical cables, terminals, and equipment 
in designated fire zones that are used during emergency procedures must 
be fire-resistant.'' Accordingly, the FAA is not making any change to 
the language proposed in Sec.  23.805(c) (now Sec.  23.2330(c)).
h. Lightning Protection (Proposed Sec.  23.810/Now Sec.  23.2335)
    In the NPRM, proposed Sec.  23.810 (now Sec.  23.2335) would have 
precluded primary structure failure caused by exposure to the direct 
effects of lightning, that could prevent continued safe flight and 
landing for airplanes approved for IFR. Proposed Sec.  23.810 would 
have required airplanes approved only for VFR to achieve lightning 
protection by following FAA-accepted design practices found in FAA-
issued ACs and in FAA-accepted consensus standards.
    Air Tractor and Transport Canada commented that ``FAA-accepted 
design practices'' does not establish a performance standard in 
proposed Sec.  23.810(b). Air Tractor also noted this proposed 
regulation would make the ACs required and regulatory. Transport Canada 
further stated that specifying ``FAA'' in the rule is not conducive to 
harmonization between authorities and recommended replacing ``FAA-
accepted design practices'' with a performance-based requirement in the 
form of a safety objective.
    The FAA agrees that proposed Sec.  23.810(b) is not consistent with 
the goal to develop performance-based standards and to spur innovation. 
The FAA recognizes new methods of protecting the airplane from 
catastrophic effects from lightning may be developed that are not 
currently FAA-accepted design practices and these methods should be 
permitted if found acceptable to the FAA.
    In light of the comments received for this section, the FAA 
revisited the goal of proposed Sec.  23.810. The FAA intended to 
capture the safety intent of the former lightning regulations in former 
Sec.  23.867. Former Sec.  23.867(a) was a high-level performance-based 
requirement requiring the airplane to be protected against catastrophic 
effects from lightning. Former Sec.  23.867(b) and (c) were means of 
compliance with Sec.  23.867(a). Former Sec.  23.867(b) specified how 
metallic components must be designed to protect the airplane against 
catastrophic effects from lightning, while former Sec.  23.867(c) 
specified how non-metallic components must be designed to protect the 
airplane from catastrophic effects from lightning. The FAA also 
intended to establish safety requirements for direct and indirect 
effects of lightning on all systems and structure in proposed 
Sec. Sec.  23.810, 23.930, and 23.1320. Proposed Sec.  23.810 would 
have addressed protection of structure, proposed Sec.  23.930 would 
have addressed protection of fuel systems, and proposed Sec.  23.1320 
would have addressed protection of electrical and electronic systems. 
However, upon review, proposed Sec.  23.810 did not address all 
structure and proposed Sec.  23.1320 did not address all systems and 
equipment.
    The FAA has determined that retaining the language of former Sec.  
23.867(a) would more appropriately capture the FAA's intent for Sec.  
23.2335 because it applies to the entire airplane including all 
systems, equipment and structure. Therefore, the FAA revises Sec.  
23.2335 to require the airplane to be protected against catastrophic 
effects from lightning, which is a performance standard. The FAA finds 
this revision addresses Air Tractor's and Transport Canada's remaining 
concerns.
    The FAA also identified an error in the proposed correlation table 
in the NPRM. Former Sec.  23.867(b) was correlated with proposed Sec.  
23.1320, ``Electrical and electronic system lightning protection'', and 
not proposed Sec.  23.810, ``Lightning protection of structure''. This 
reference was incorrect because proposed Sec.  23.1320 did not address 
all aspects of protecting the airplane against catastrophic effects 
from lightning for metallic components. The FAA corrected the 
correlation in the table provided in this final rule.
    EASA commented that the requirement of lightning protection of the 
structure should relate to the type of environment that causes the 
risk, instead of the type of operation. EASA recommended replacing IFR 
with instrument meteorological conditions (IMC), and replacing VFR with 
visual meteorological conditions (VMC).
    The FAA agrees with EASA's comment that the requirements for 
lightning protection should be related to the risk of lightning. Rather 
than drawing a distinction between IFR and VFR, or IMC and VMC, the 
language provided in this final rule now reflects a performance-based 
standard. The standard will be met by an accepted means of compliance. 
The FAA finds this approach provides greater flexibility to allow 
development of means of compliance that are appropriate for different 
types of airplanes and different types of operation depending on the 
risk of lightning.
6. Subpart E--Powerplant
a. General Discussion
    In the NPRM, the FAA proposed substantial changes to former subpart 
E based on two considerations. First, the FAA stated many of the former 
regulations could be combined to provide fewer regulations that 
accomplish the same safety intent. Second, the FAA also stated part 23 
overlaps with the requirements in parts 33 and 35.
    Textron noted that subpart E appeared to be missing performance 
requirements for key propulsion aspects. Textron recommended the FAA 
include rules that address engine controls, powerplant accessories and 
components, and powerplant instruments and indicators as set forth in 
former Sec. Sec.  23.1141, 23.1163, and 23.1225 of appendix E of the 
Part 23 ARC Report.
    The FAA reviewed each requirement mentioned by the commenter and 
finds those requirements have been addressed in the final rule using 
less prescriptive language. In most cases several regulations, rather 
than any single rule, capture the intent of the former regulations 
referenced by the commenter. Requirements contained in regulations for 
powerplant installation, airplane level systems, and flightcrew 
interface combined with more specific requirements found in regulations 
for powerplant fire protection, instrument markings, control markings, 
and placards, address the specific requirements noted by the commenter.
    An individual commenter stated the FAA's removal of all references 
to part 33 and part 35 from proposed part 23 was inappropriate. The 
commenter contended the FAA's conclusion that those references are 
redundant because the requirements are already addressed during the 
certification of the engine or propeller is incorrect. The commenter 
noted that compliance with specific performance standards for engines 
and propellers is only ensured by requiring a product to be approved to 
a specific

[[Page 96631]]

amendment level of part 33 or 35, before it is eligible for 
installation on a particular airplane. The commenter also noted that 
engines and propellers approved prior to a specific part 23 amendment 
level may not have met a specific installation level requirement 
specified by that amendment. For example, the commenter noted that 
former Sec.  23.903 required minimum engine ingestion performance by 
the installation of an engine certified to a specific amendment level 
of part 33, thereby ensuring that any installed turbine engine had met 
a minimum performance level mandated by the FAA through that amendment 
level.
    The individual commenter also stated engine and propeller 
limitations are established during the type certification of the engine 
or propeller, and that these limitations are required to be included in 
the TCDS and associated installation manuals. The installer must comply 
with these limitations. The commenter further implied that, if the 
installed engine or propeller limitations cannot be complied with, safe 
operation of the product cannot be ensured. For example, the commenter 
stated that former Sec. Sec.  23.1041 through 23.1047 required the 
engine installation to be designed such that the temperature 
limitations--established under part 33 for the engine--are maintained 
in the installed configuration.
    The individual commenter also noted that some components of an 
engine or propeller are approved at both the engine or propeller level 
and at the airplane level, but that all components require approval at 
the airplane level. According to the commenter, the approval of the 
engine or propeller TC can include items such as a propeller reversing 
system or a turbocharger, and this data can be used for approval of 
these systems at the airplane level. If an applicant prefers approval 
at the airplane level only, this commenter noted, the former rule 
provided a reference to the requirements contained in part 33 or 35, as 
appropriate. Without the inclusion of these references in proposed part 
23, certification may require special conditions.
    The commenter recommended the FAA include--
     References to parts 33 and 35 for type certificated 
engines and propellers being installed and consider the inclusion of 
similar standards when the installation of non-type certificated 
engines or propellers are permitted;
     A specific rule stating the powerplant installation design 
must be such that all installed type certificated engines and 
propellers remain within their respective approved limitations and 
installation manual requirements and that a similar provision be 
included when the installation of non-type certificated engines and 
propellers is permitted; and
     Reference in the proposal to the applicable provisions of 
parts 33 and 35 for engines, propellers, and any related components of 
those products being installed only at the airplane level.
    The FAA agrees with the general intent of the commenter. The FAA 
notes that while some requirements in the former part 23 indeed overlap 
with those of parts 33 and 35, the FAA did not intend to imply that 
compliance with those requirements necessary for type certification of 
an engine or propeller were no longer applicable to the certification 
of the installed configuration of a type certificated engine or 
propeller. Historically, TCs have been required for engines and 
propellers installed in airplanes certificated under part 23 and this 
rule retains this requirement for all airplanes certificated under part 
23, with the exception of level 1 low-speed airplanes.\47\ Essentially, 
this requirement makes the requirements in parts 33 and 35 for type 
certificated engines and propellers applicable to the certification of 
airplanes under part 23, because the part 33 and 35 requirements must 
be met in order to install these engines and propellers on part 23 
airplanes. As a result, data used to show compliance for an engine or 
propeller TC is considered FAA approved, and can be used to show 
compliance with any applicable part 23 requirement. In many cases, this 
permits a single showing of compliance such that a re-showing of 
compliance at the airplane installation level may not be required. 
Approval of some components, such as propeller controls or 
turbocharges, have been permitted at the airplane level by referencing 
the applicable part 33 or 35 requirements and using those requirements 
as an acceptable means of compliance. This certification approach will 
continue to remain acceptable.
---------------------------------------------------------------------------

    \47\ Discussed in the preamble discussion for Sec.  23.2400.
---------------------------------------------------------------------------

    The FAA does not intend to accept a means of compliance for an 
engine or propeller installation that would result in a level of safety 
lower than that set forth in a part 33 or 35 amendment level 
specifically referenced in former part 23.
    Limitations set forth in the approval of an engine or propeller 
must be maintained in the installation on the part 23 airplane. These 
operating limitations are established in accordance with Sec. Sec.  
33.7 and 35.5. Installation instructions are provided to the installer 
in accordance with Sec. Sec.  33.5 and 35.3. This regulation does not 
change this approach.
    Additionally, the FAA is adding a requirement from existing Sec.  
23.901(e) to Sec.  23.2400, requiring installed powerplant components--
which include engines and propellers--to meet the FAA-approved 
component limitations and installation instructions, or be shown not to 
create a hazard. This requirement will ensure that any operating 
limitations and installation instructions applicable to the engine or 
propeller remain applicable to the certification of the airplane.
    In the NPRM, an exception permitting the installation of non-type 
certificated engines and propellers as part of the airplane was 
proposed for simple airplanes. The proposal mirrors the precedent 
established for the certification of airplanes under EASA CS-VLA. The 
rule slightly expands the relief provided by the proposal, and permits 
the certification of engines as part of the airplane for level 1 low-
speed airplanes. This change encompasses the same class of airplanes as 
originally proposed while removing the restriction that these airplanes 
be limited to VFR-only operations.\48\
---------------------------------------------------------------------------

    \48\ Discussed in the preamble discussion for Sec.  23.2400.
---------------------------------------------------------------------------

    In response to the individual commenter's concerns that the 
proposal does not require certain engines to meet a specific amendment 
level of part 33, as set forth in former regulations, and the 
commenter's specific concern that engine ingestion performance was not 
specifically addressed, the FAA notes those sections of former subpart 
E that required compliance with a specific amendment level for an 
engine installation are addressed in this performance-based rule. The 
engine ingestion requirements of former Sec.  23.903(a)(2), for 
example, are addressed by the performance-based requirements of Sec.  
23.2400(c). The former rule specified that an applicant must construct 
and arrange each powerplant installation to account for likely 
operating conditions including foreign object threats and likely 
hazards in operation. Although Sec.  23.2400(c) does not refer to a 
specific requirement or amendment level of part 33, the FAA expects the 
means of compliance with this regulation will include provisions for 
certificating engines with acceptable foreign object ingestion 
performance as required by former Sec.  23.903(a)(2), which may include 
references to different amendment levels of part 33 where appropriate. 
Additionally, the FAA

[[Page 96632]]

intends to accept part 23 through amendment 23-62, which contained 
references to specific requirements in part 33, as a means of 
compliance to the performance-based requirements of this rule. The FAA 
will only accept a means of compliance for a performance-based 
regulation that encompasses the safety intent of a former regulation 
requiring compliance with a particular amendment level of part 33 or 
35, if that means of compliance provides a level of safety equivalent 
to the level of safety found in former part 23.
b. Powerplant Installation and Propeller Installation (Proposed 
Sec. Sec.  23.900 and 23.905/Now Sec.  23.2400)
    In the NPRM, proposed Sec. Sec.  23.900 and 23.905 (now Sec.  
23.2400) would have clarified, for the purpose of this subpart, that 
the airplane powerplant installation must include each component 
necessary for propulsion, affects propulsion safety, or provides 
auxiliary power to the airplane. Proposed Sec.  23.900 would have 
required the applicant to construct and arrange each powerplant 
installation to account for likely hazards in operation and 
maintenance, and, except for simple airplanes, each aircraft engine 
would have to be type certificated. Proposed Sec.  23.905 would have 
retained the requirement that each propeller be type certificated, 
except for propellers installed on simple airplanes. Proposed Sec.  
23.905 would have retained the requirement that each pusher propeller 
be marked so it is conspicuous under daylight conditions.
    EASA commented that design-specific requirements for propeller 
installations should be covered by proposed Sec.  23.900, not proposed 
Sec.  23.905.
    The FAA adopts the regulatory approach taken by EASA for propeller 
installation. Under this approach, the FAA includes the requirements 
for propeller installation within Sec.  23.2400. Specifically, the 
requirements of proposed Sec.  23.905(a) are addressed by Sec.  
23.2400(b), proposed Sec.  23.905(b) are addressed by Sec.  
23.2400(c)(3), and proposed Sec.  23.905(c) are addressed by Sec.  
23.2400(c)(4). These revisions also clarify that a propeller 
installation must not deviate from any limitations or installation 
instructions as required by Sec.  23.2400(e). Addressing propeller 
installation requirements in the section of the rule that establishes 
powerplant installation requirements also results in closer 
harmonization of the rule with EASA's proposed requirements in NPA 
2016-05.
    The FAA received numerous comments regarding the issue of whether 
``power units'' should be certified under part 23 as part of the 
airplane type certification. The Associations noted the proposed 
language would allow engine and propellers that meet required standards 
to be certified as part of the airframe, provided the airplane is 
certificated as a simple airplane. The commenters contended the ability 
to certificate these components as part of an airframe should be based 
on the complexity of the components rather than on the certification or 
performance levels of the airplane in which they are installed. The 
commenters supported permitting the certification of engine and 
propellers that comply with traditional engine and propeller type 
certification requirements either through the issuance of a standalone 
TC or through the certification process for the airframe. The 
commenters also noted since electric propulsion is ``on the threshold 
of becoming mainstream'', the ability to certify engines and propellers 
as part of the airframe is critical to the successful and safe 
integration of that technology.
    EASA asserted the need to type certify an engine should be 
addressed by part 21; therefore, the powerplant either could be type 
certificated or certified as part of the airplane. EASA noted the type 
certificate-related design and production controls that are part of the 
current type certification process are also expected to be applicable 
for other components such as batteries and converters. EASA stated 
certification of the engine should not be related to the size or speed 
of the airplane; therefore, EASA did not support limiting the 
installation of propulsion systems that are not individually type 
certificated to airplanes classified as simple airplanes.
    Textron noted the purpose of the proposed rule is to enhance the 
ability to introduce new technology efficiently, and contended that 
treating each powerplant installation (e.g., electric propulsion) using 
a unique ELOS finding would not be an effective way to address the 
issue. Textron recommended either adding the requirements for 
certifying the power unit as part of the airplane, or changing and 
including the specific requirements in the industry standard to avoid 
the need for unique ELOS findings. Additionally, Textron recommended 
adopting proposed CS 23.500(b), which would not restrict the 
installation of non-type certificated engines that meet an industry 
standard to simple level 1 airplanes.
    An individual commenter expressed support for the proposal to not 
require certified engines for ``simple'' airplanes, but suggested 
expanding the definition of ``simple'' to at least four-seat airplanes 
with VS0Now 
Sec.  23.2410)
    In the NPRM, proposed Sec.  23.910 (now Sec.  23.2410) would have 
required an applicant to assess each powerplant separately and in 
relation to other airplane systems and installations to show that a 
failure of any powerplant system component or accessory will not--
     Prevent continued safe flight and landing;
     Cause serious injury that may be avoided; and
     Require immediate action by crewmembers for continued 
operation of any remaining powerplant system.
    Several commenters expressed concern that proposed Sec.  23.910 
would have been impossible to meet for certain existing airplane 
designs. The FAA response to these comments is below.
    The Associations stated that proposed Sec.  23.910 should apply to 
the ``likely'' failure of powerplant systems. The commenters asserted 
that applying the proposed requirements to any failure would require 
complete redundancy, which cannot be achieved in traditional single-
engine airplanes and smaller twin-engine airplanes. The commenters 
contended the slower stall speeds and higher levels of crashworthiness 
in the designs of these airplanes mitigate all but ``unlikely'' 
powerplant failures. These commenters recommended the FAA require the 
applicant to assess each powerplant separately and in relation to other 
airplane systems and installations to show that ``hazards resulting 
from a likely failure of any powerplant system component or accessory 
are minimized.''
    Textron stated proposed Sec.  23.910 was ``too high level'' and 
would not have established adequate performance-based requirements for 
an applicant to demonstrate compliance. As an example, Textron 
contended that proposed Sec.  23.910(a) would have been an impossible 
requirement to meet, especially for a single-engine airplane. Textron 
recommended replacing the language of proposed Sec.  23.910 with 
language from EASA CS 23.510, ``Powerplant Hazard Mitigation''
    EASA, Garmin, and Air Tractor stated the requirements of proposed 
Sec.  23.910(a) would have been applicable to single-engine airplane 
certification. Garmin stated, however, that a single-engine airplane 
cannot meet proposed Sec.  23.910(a) unless the FAA clarifies the loss 
of the thrust from the propulsion unit will not necessarily prevent 
continued safe flight and landing. Garmin recommended the FAA either 
revise proposed Sec.  23.910 or revise the definition of ``continued 
safe flight and landing'' to allow for failure of the engine or 
propeller in a single-engine airplane.
    Air Tractor stated proposed Sec.  23.910(a) would have ruled out 
the certification of single-engine airplanes. Air Tractor observed, for 
example, that under the proposed rule, if a fuel line or hose were 
considered a ``system component,'' then the failure of one fuel line 
that feeds the engine would certainly result in an engine failure. Air 
Tractor noted that there may be similarly insurmountable scenarios 
involving the controls for an engine. Air Tractor stressed the need for 
clearly-written rules to prevent unforeseen interpretations of 
provisions that have the potential to make the design and certification 
of light airplanes much more difficult than previously, or even 
impossible.
    An individual commenter stated that proposed Sec.  23.910(a) 
appears to be a derivation of former Sec.  23.903(c)(1), which only 
applied to multiengine installations and only required continued safe 
operation of the remaining engines. The commenter asserted the proposed 
rule would have increased the requirement from ``ensuring continued 
safe operation of the remaining engines'' to ``ensuring continued safe 
flight and landing of the airplane.'' The commenter further noted 
proposed Sec.  23.910 would have applied to single-engine airplanes 
with no justification and could have resulted in elimination of some 
airplanes from certification, such as large single-engine or 
multiengine airplanes where rotor non-containment effects on the 
remaining engine cannot be eliminated. The commenter also stated the 
proposed rule would have made ``continued safe flight and landing'' a 
part of the regulation, where previously it only existed in guidance 
material. The commenter indicated this may make it difficult to provide 
a conditional definition of the term. To ensure safe design of 
multiengine airplanes, the commenter recommended using the wording of 
former Sec.  23.903(c)(1) rather than requiring a system safety 
approach to powerplant installation that does not permit single 
failures. The commenter also recommended using the term ``minimize'' 
when specifying the evaluation criteria for powerplant installations. 
The commenter noted that term has been used for many years, is well 
understood, and best describes the regulatory intent for those 
powerplant unique systems where a single failure cannot be reasonably 
eliminated from the design.
    Another individual commenter said compliance with proposed Sec.  
23.290 would neither be practical nor possible in all situations that 
may result in a forced landing; therefore, the proposed rule should not 
include a requirement for completely eliminating hazards, which the 
commenter asserted is not achievable. The commenter asserted that 
replacing a standard based on minimization with an absolute standard is 
not an acceptable alternative. Ultimately, the commenter recommended 
revising the definition of ``continued safe flight and landing'' to 
allow for catastrophic outcomes of forced landings, and to either 
maintain the minimization standard, or withdraw the requirement. The 
commenter further noted that compliance with the proposed requirement 
of absolute prevention of hazards would be impractical or impossible 
for many conventional multiengine airplane configurations regarding 
rotor non-containment. This is also true for all single-engine and many 
multiengine airplanes regarding a propeller blade loss--especially 
since the proposed rule applies to uncontained engine failure and 
engine case burn-through failures for which former Sec.  23.903(b)(1) 
only required the design to minimize the hazard.
    Embraer observed that for turbine or reciprocating engine rotor 
failure and/or

[[Page 96636]]

burn-through events, there is no way to eliminate all the risks that 
will prevent continued safe flight and landing. Embraer recommended 
revising the language to clarify certain proposed provisions and to add 
additional provisions that would require applicants to show operating 
limitations, which may adversely affect rotating component structural 
integrity that would not be exceeded in service. Embraer's revisions 
would require design precautions to minimize hazards to the airplane in 
the event of an uncontained engine rotor or rotating component failure 
or a fire originating within the engine, which burns through the engine 
case.
    The FAA concurs with the commenters' recommendations to revise 
proposed Sec.  23.910 to make its requirements only applicable to 
likely failures and to permit minimization of certain hazards, which 
could prevent continued safe flight and landing. The FAA notes the 
inclusion of the term ``likely'' in the requirement for the applicant 
to address hazards resulting from failures is intended to place 
reasonable and prudent bounds on the scope of analysis necessary to 
meet the requirement and not to require consideration of all possible 
failures, however remote. The scope of this analysis will be set forth 
in accepted means of compliance for this regulation.
    In response to commenters' concerns that the term ``minimize'', or 
the philosophy encompassed by the use of the term, will be included in 
the rule, the FAA notes that the term ``minimize'' has been included in 
Sec.  23.2410(a) to permit the applicant to address those hazards, 
which may prevent continued safe flight and landing of an airplane, 
that cannot reasonably be eliminated. The FAA will consider 
incorporation by an applicant of all practical design precautions, 
which minimize hazards to the airplane, associated with a particular 
failure acceptable in complying with this regulation. The FAA has 
historically accepted this compliance approach when a minimization of 
hazards has been required. This approach provides a simple means to 
continuously improve airplane safety as new technologies and design 
approaches evolve. It also permits acceptance of existing designs that 
cannot reasonably eliminate hazards resulting from certain failures, 
even if accepted design precautions have been incorporated into the 
airplane's design. Such failures could include rotor non-containment, 
engine case burn-through, and engine failures on single-engine 
airplane. This change specifically addresses a concern expressed by all 
commenters that the proposed regulation would make it impossible for an 
applicant to show compliance with the regulation for many existing 
airplane designs. Additionally, the rule will continue to permit the 
use of simple parts, such as fuel lines and control cables, in airplane 
designs. The FAA has traditionally considered their use acceptable 
without requiring redundancy where it is neither practical nor likely 
that a failure of the component would occur. The FAA's revisions to the 
proposed regulation account for the normal use of these types of simple 
components.
    In response to the commenter who noted the term ``continued safe 
flight and landing'' in proposed Sec.  23.910(a) appears to be based on 
former Sec.  23.903(c), which only applied to multi-engine airplanes, 
the FAA agrees that proposed Sec.  23.910(a) does not properly address 
certain failures on single-engine airplanes. The FAA believes the 
revisions discussed above addresses the individual's concerns.
    Textron also recommended the FAA withdraw proposed Sec.  23.910, as 
its subject area overlaps with proposed Sec.  23.1315 (now Sec.  
23.2510).
    The FAA revises proposed Sec.  23.910 to clarify that any failure 
resulting in the loss of a single powerplant on an airplane with 
multiple powerplants cannot result in the failure of other powerplants 
unless those failures cannot be reasonably eliminated, in which case 
the hazards must be minimized. So, while Sec.  23.2510 does apply to 
all powerplant systems, the FAA notes Sec.  23.2410 includes an 
exception to the general requirement of Sec.  23.2510 to account for 
certain powerplant failures that may prevent continued safe flight and 
landing or for which use of a traditional system safety compliance 
approach may not be appropriate. Examples of such failures include 
engine rotor non-containment and fire. Therefore, the FAA does not 
adopt Textron's recommendation to withdraw proposed Sec.  23.910.
    Garmin commented that proposed Sec.  23.910(b) seemed highly 
subjective and recommended eliminating paragraph (b).
    The FAA notes Sec.  23.2410(b) requires consideration of failures 
affecting passenger safety such as a fan disconnect on fuselage 
embedded engines or exhaust heat exchanger failures that may allow 
hazardous fumes to enter the occupant compartment. The FAA finds 
withdrawing paragraph (b) would eliminate the requirement for an 
applicant to assess potential causes of serious injury to airplane 
occupants. Additionally, it serves as the underlying requirement for 
the development of a more-detailed means of compliance. Therefore, the 
FAA adopts the language in Sec.  23.2410(b) as proposed.
    ANAC observed that there is no requirement in proposed Sec.  23.910 
to ensure powerplant-driven components, necessary for airplane 
operation, are suitable for installation in airplanes certificated 
under part 23, and the powerplant installation requirement in proposed 
Sec.  23.900 (now Sec.  23.2400) is related only to components that 
affect propulsion safety. ANAC noted the rule does not capture the 
design precautions established in the former Sec. Sec.  23.933 and 
23.1155. The commenter also asserted that while proposed Sec.  23.910 
addresses hazard mitigation in the event of powerplant systems failure, 
compliance with proposed Sec.  23.910 for turbine engines would be 
directly related to protection against inadvertent thrust reverser 
deployment.
    The FAA notes ANAC's concerns; however, as discussed in the 
preamble for Sec.  23.2400, the FAA has added paragraph (e) to Sec.  
23.2400 to address powerplant component installation. Additionally, the 
FAA addresses the design precautions of former Sec. Sec.  23.933 and 
23.1155, which provided reversing system requirements for turbojets, 
turbofans, and propellers, in the performance-based requirements 
contained in Sec.  23.2420, ``Reversing systems'' (proposed as Sec.  
23.920).
d. Automatic Power or Thrust Control Systems (Proposed Sec.  23.915/Now 
Sec.  23.2405
    In the NPRM, proposed Sec.  23.915 (now Sec.  23.2405) would have 
required a power or thrust augmentation system that automatically 
controls the power or thrust on the operating powerplant to provide an 
indication to the flightcrew when the system is operating, provide a 
means for the pilot to deactivate the automatic functions, and prevent 
inadvertent deactivation.
    Textron commented the requirements of proposed Sec.  23.915 could 
easily be addressed by revising proposed Sec.  23.900 to state that 
state an automatic power reserve (APR) system that automatically 
advances the power or thrust on the operating engine(s), when any 
engine fails during takeoff, must comply with the applicable 
requirements of the subpart. Textron noted that this language is 
included in Appendix E of the Part 23 ARC Report. Also, Textron 
recommended deleting the prescriptive requirement in proposed Sec.  
23.915(a) for the system to provide an indication that it is operating, 
stating that such a requirement and other high level requirements are 
redundant.

[[Page 96637]]

    The FAA finds the adoption of the proposed Part 23 ARC language, as 
recommended by Textron, would limit the scope of this rule to existing 
APR type systems. The FAA also finds the intent of the ARC language is 
better captured in this rule, which can apply to a wider range of 
potential future automatic power or thrust control systems. The FAA 
partially agrees with the commenter's request to remove the requirement 
for annunciation from proposed Sec.  23.915(a). Although the proposal 
did not specifically state there must be an annunciation of the 
system's status, it did require the system to provide an indication of 
the status. The proposal has been revised to require a means to 
indicate the system is in an operating condition. The FAA finds this 
revision will provide applicants with more flexibility in designing a 
system to provide the flightcrew with information regarding the 
operational status of this critical safety system.
    ANAC stated the proposed requirements of this section are too 
prescriptive and the requirements of proposed Sec. Sec.  23.1310, 
23.1500, and 23.910, which address system reliability, status 
monitoring, flightcrew interface, and warning indications, provide 
equivalent requirements that eliminate the need for a specific 
regulation to address APR systems.
    The FAA does not find the provisions of proposed Sec.  23.915 are 
adequately addressed by the requirements in proposed Sec.  23.900. The 
requirements in Sec.  23.2405 (proposed Sec.  23.915) provide 
additional specific requirements the FAA considers necessary for the 
certification of APR systems in airplanes. The FAA does not find the 
requirements of Sec.  23.2400 (proposed Sec.  23.900) alone would 
adequately address the requirements necessary for approval of an 
automatic power control system. The specific requirements in the rule 
for the system to provide indication to the flightcrew that it is 
operating are necessary given the critical nature of both existing and 
future APR systems that may vary thrust or power to provide airplane 
control during the failure of an engine. In response to ANAC's comment 
that Sec.  23.915 could be replaced with a more general rule covering 
system reliability, crew interface, monitoring, and warning, the FAA 
finds attempting to address too many systems under a general system 
safety requirement may result in the excessive application of non-
standard performance requirements across the industry. Accordingly, for 
systems where basic performance requirements can be established, 
without requiring specific knowledge of the system's design, those 
requirements will be contained in a specific rule. This concept is 
further discussed under Sec.  23.2420.
    EASA suggested the FAA address auto power control systems and 
reverser systems (proposed Sec. Sec.  23.915 and 23.920) in a single 
requirement that would address other systems such as those that use 
asymmetric thrust to provide directional control. EASA recommended 
changing the title of the proposed section to ``Propulsion Augmentation 
Systems'' to ensure systems that augment propulsion in any direction 
(drag, thrust, direction, lift) are addressed.
    The FAA notes the basic performance requirements for automatic 
power control systems are different from those required for reverser 
systems. Additionally, the FAA also notes adopting the term 
``augmentation'' implies that only a system's use of additional thrust 
or power would be addressed, whereas systems are envisioned that may 
also reduce power on an operating propulsion system or use aerodynamic 
means to respond to power or thrust abnormalities. The FAA considers an 
automatic power or thrust control system to be a system that 
automatically intervenes and provides direct or modified control to 
each engine, leaving the pilot indirectly in control or possibly not in 
control for an automatic recovery type function. Reversing systems 
simply change the direction of thrust or power at the direct control of 
the pilot. As these systems are significantly different, the FAA has 
determined it is necessary to retain a specific section for both 
automatic power or thrust control systems and reversing systems.
    The FAA reviewed the draft language of CS 23.2405, Propulsion 
augmentation systems, and found it directly applicable to automatic 
power or thrust control systems. Its provisions also address many of 
the commenters' concerns, especially with respect to the certification 
of airplanes with advanced automatic control systems. This language is 
consistent with, but less prescriptive than, the requirements of former 
appendix H to part 23. Accordingly, the FAA revises proposed Sec.  
23.915 by adopting the language from CS 23.2405(b) through (e) in Sec.  
23.2405(a) through (d).
    Textron noted it was unclear if the proposed rule was attempting to 
address ``auto throttle'' applications exclusively.
    The FAA did not intend proposed Sec.  23.915 to address 
autothrottle or autothrust systems unless the system has the capability 
to command a change to power or thrust that is not directly commanded 
by movement of the primary power setting control. Such a system might 
vary power on multiple powerplants to maintain level flight or add 
thrust beyond that commanded by the throttle when an engine failure is 
detected.
    Garmin and the Associations suggested eliminating proposed Sec.  
23.915(b). Garmin stated that emerging technology may include systems 
that have sufficient design integrity and provide enough safety benefit 
that permitting deactivation as required by proposed Sec.  23.915(b) 
could have the unintended effect of reducing safety. The Associations 
noted in the event the automatic power control systems of less 
reliability are used, compliance with proposed Sec.  23.910 should 
result in designs that achieve the risk mitigations intended by the 
requirements of proposed Sec.  23.915(b).
    The FAA agrees that requiring a means for a pilot to deactivate the 
automatic function may have an adverse effect on safety. The FAA also 
agrees emerging technology may result in the development of a system 
with sufficient integrity the flightcrew does not directly control the 
thrust of each engine, but rather the power control system takes 
commands from the flightcrew and automatically controls each engine to 
execute that command, in both normal conditions and in the event of a 
failure of an engine. Accordingly, the FAA revises the rule to account 
for the possibility of a broader range of automatic power or thrust 
control systems and has removed the requirement for pilot deactivation 
of the automatic function of these systems where a system failure is 
shown to be extremely remote. The type of system that would have this 
level of authority is envisioned to be similar to an automated flight 
control or fly-by-wire system, and an applicant would be expected to 
show the system has sufficient design integrity to meet this standard. 
To provide applicants with greater design flexibility, the FAA also 
revises the proposal to require the flightcrew to be able to override, 
rather than deactivate systems with lower design integrity. It is 
intended this requirement will apply to those systems whose failure can 
be reasonably detected by the flightcrew and for which overriding the 
automatic function would not have an adverse effect on safety. Such a 
situation typically exists with traditional automatic power reserve 
systems.
    ANAC suggested the requirement to maintain the maximum thrust/power 
increment limit be specifically retained in the regulation and not 
serve as a possible means of compliance. ANAC

[[Page 96638]]

believes that although it is arbitrary, the 10 percent limit for the 
APR is considered in the current regulation to be a straightforward and 
acceptable decrement from a safety standpoint in limiting both runway 
critical takeoffs and degradation of all-engine climb performance 
factors that are not addressed by former part 23 Appendix H, paragraphs 
H23.4(b) and (c).
    The FAA notes any automatic power or thrust control system will be 
required to meet all applicable regulations including Sec.  23.2415, 
which requires that failures that would prevent continued safe flight 
not result from a single failure or from a likely combination of 
failures. In addition, the FAA notes that takeoff performance is 
determined considering a critical loss of thrust. Although the 10 
percent value referred to by ANAC may be considered an arbitrary limit 
on the additional thrust that can be provided by an APR system, the FAA 
considers it unlikely an APR design would be proposed that reserves a 
significant amount of thrust for use only in the event of an engine 
failure during takeoff. Yet given the broader scope of this rule, 
limiting automatic power control thrust to 10 percent may not 
realistically permit system designs intended to augment lift, control, 
or stability through the propulsion system. Therefore, the FAA has 
decided not to include the 10 percent limit in the rule.
    Kestrel questioned whether the proposed section would permit 
alternate automatic power control systems (such as those without thrust 
lever drivers) that could meet the intent of proposed Sec.  23.1500 
(now Sec.  23.2600) without an ELOS finding or an issue paper. Kestrel 
noted former Sec.  23.779 requires commanded engine thrust and actual 
engine thrust agree, which the commenter said has historically been 
accomplished by the thrust levers being mechanically driven to the 
actual engine thrust position.
    The FAA notes that Sec.  23.2600 does not specifically require a 
throttle lever, only powerplant controls. Therefore, if a design were 
proposed that allowed a qualified flightcrew member to perform all 
tasks associated with the intended powerplant control functions, an 
ELOS finding would not likely be required to obtain approval of that 
automatic power control system.
    NJASAP supported the language of proposed Sec.  23.915 and noted 
automatic power control system technology will be available to more 
airplanes in lower certification categories in the not-too-distant 
future.
e. Reversing Systems (Proposed Sec.  23.920/Now Sec.  23.2420)
    In the NPRM, proposed Sec.  23.920 (now Sec.  23.2420) would have 
required an airplane to be capable of continued safe flight and landing 
under any available reversing system setting.
    Textron stated the proposed language is too ``high-level'' and does 
not provide adequate performance-based requirements for an applicant to 
show compliance with the rule. Textron also stated the rule was ``a bit 
severe'' and noted the rule could be interpreted to mean that a single- 
or multiengine turboprop may now need a reverser lock out system for 
flight. Textron also claimed the flight testing required to demonstrate 
compliance with the proposed requirement may be complicated and 
dangerous. To address its concerns, Textron recommended using the 
language from CS 23.505.
    Air Tractor commented that it seems impossible to expect an 
airplane to be capable of safe flight and landing with application of 
full reverse thrust. Air Tractor suggested the proposed language 
expected the airplane to ``know'' the difference between a pilot 
command for reverse thrust when the airplane is on the ground versus 
when it is in air, and to overrule the pilot command if the airplane is 
still flying. Air Tractor observed that while this might be an easy 
control issue when combined with a squat switch, many airplanes with 
spring steel fixed landing gear do not have squat switches. Air Tractor 
also noted that it has not been a safety issue to have reverse thrust 
capability on certain types of single-engine turboprop airplanes, all 
of which employ multiple means to prevent inadvertent selection of the 
reverse range and warn when that range is selected.
    The Associations noted the proposed rule could be misconstrued to 
indicate the FAA will no longer permit throttle gates, which are 
traditionally used on turboprop designs. The commenters contended this 
would necessitate the development of weight on wheels lockouts and 
other complex designs that were not required by the former rule, and 
for which there is no measurable safety data to indicate this was an 
area of safety concern. The commenters recommended revising the rule to 
state the airplane must be capable of safe flight and landing under any 
``easily selectable'' reversing system setting, rather than ``any 
available'' reversing system setting.
    ICON asked for clarification as to whether proposed Sec.  23.920 
was intended to mean that if a reversible pitch setting exists on a 
propeller, an airplane must be able to continue flight even with 
selection of full reverse pitch. ICON also believed the proposed rule 
could be interpreted to require a demonstration of safe flight and 
landing at full reverse power.
    The FAA notes that numerous commenters expressed concern with the 
proposed requirement that the airplane must be capable of continued 
safe flight and landing under any available reversing system setting. 
The FAA recognizes this language did not account for many airplane 
designs that do not incorporate a system that detects when the airplane 
is on the ground, which can be used to lockout or prevent manual 
inflight reversal. Additionally, the FAA recognizes the proposed rule 
did not provide a basic performance requirement to ensure safe 
operation of the reverser system under normal operating conditions, and 
the airplane is capable of continued safe flight and landing after 
failures of the reversing system.
    As explained in the NPRM, proposed Sec.  23.920 (now Sec.  23.2420) 
was intended to capture the safety intent of former Sec.  23.933(a) and 
(b). Therefore, given the variety of the commenters' concerns, the FAA 
revises proposed Sec.  23.920 based on former Sec.  23.933 to address 
the comments. The FAA intends Sec.  23.2420 to address the requirements 
for propeller, turbojet, and turbofan reversing systems specified in 
former Sec.  23.933. Section 23.2420 now requires each reversing system 
to be designed so that the airplane is capable of continued safe flight 
and landing after any single failure, likely combination of failures, 
or malfunction of the reversing system. This rule accounts for existing 
reversing system designs that use a mechanical throttle gate to prevent 
inadvertent in-flight reversing system operation that could result in 
an unsafe condition. For turbofan or turbojet engine reversing systems 
intended for ground use only, the FAA notes that a reverser lock out 
system for flight is not specifically required by the rule. However, 
the FAA expects that in the event of an inflight reverser deployment, 
the engine will revert to idle thrust, and the reverser can be restowed 
as required by former Sec.  23.933(a)(1). The FAA also notes that Sec.  
23.2420 should result in the inclusion of these features in airplane 
designs, as the FAA finds they are currently the only likely means to 
prevent the occurrence of an unsafe condition and permit continued safe 
flight and landing after a failure resulting in a reverser deployment 
in flight. In addition to basing the revisions to the proposed rule on 
former Sec.  23.933(a)(1) and (b) for ground use only reversing 
systems, the

[[Page 96639]]

FAA has included in Sec.  23.2420(a) the requirement from former Sec.  
23.933(a)(2) for reversing systems intended for use in-flight that no 
unsafe condition result during normal operation. The FAA finds this 
action responds to commenters' concerns and will readily permit future 
approval of systems intended for use in-flight, which incorporate new 
technology.
    Regarding Textron's recommendation that the FAA adopt requirements 
for reversing systems proposed by EASA in CS 23.505, proposed CS 23.505 
combines requirements for reverser systems, thrust augmentation 
systems, and automatic power controls in a single regulation. For the 
reasons discussed in responding to this comment in the context of Sec.  
23.2405, the FAA determines the requirements for a reversing system 
should remain separate from those for thrust augmentation or automatic 
power or thrust control systems (referred to as automatic power reserve 
systems in former regulations), and that the basic performance 
requirements for these systems are significantly different.
    Additionally, Sec.  23.2405, ``Automatic power or thrust control 
systems,'' applies to future systems that may automatically adjust 
thrust to manage airplane control and stability. Such a system might 
operate upon a single command from the flightcrew and automatically 
manage multiple powerplants to perform a requested action. For this 
type of system, in-flight reversing of a particular propulsion unit may 
occur (as commanded by a flight management system) even though the 
flightcrew may not have specifically requested application of reverse 
thrust. For certification of this type of system as part of an 
airplane's design, the FAA envisions the requirements of both 
Sec. Sec.  23.2420 and 23.2405 will apply.
    Both Embraer and Garmin expressed concern the proposed requirement 
would not permit the use of a system safety approach for a reverser 
system under certain conditions that may prevent continued safe flight 
and landing, as long as those conditions are shown to be extremely 
improbable. Embraer recommended replacing the phrase ``under any 
available reversing system setting'' in proposed Sec.  23.920 with the 
phrase ``at normal operating conditions and the failures not shown to 
be extremely improbable.'' Garmin recommended revising the proposed 
rule to permit the use of a safety analysis to demonstrate that certain 
conditions, which would potentially prevent safe flight and landing, 
are extremely improbable.
    In response to Garmin's and Embraer's concern, the FAA notes that 
Sec.  23.2420, as revised, permits the use of a system safety approach 
for certification of an airplane with a reverser system.
    NJASAP believed a thrust reverser must have an override or the 
ability to emergency stow in the unlikely event of inflight deployment.
    The FAA notes NJASAP's recommendation to reintroduce the 
requirement to stow reversers after inadvertent deployment; however, 
specifically requiring a system to have the capability to restow a 
reverser in-flight may limit or prevent the certification of certain 
acceptable reversing system designs. As noted in Garmin's comment, for 
a reverser system that cannot be shown to result in safe flight and 
landing of the airplane after an in-flight deployment, an applicant may 
include a robust control and monitoring system in its design that could 
be shown to make an in-flight deployment extremely improbable and not 
resulting from any single failures. Including this capability could 
prevent the system from complying with the requirement that no single 
failure prevent continued safe flight and landing.
f. Powerplant Operational Characteristics (Proposed Sec.  23.925/Now 
Sec.  23.2425)
    In the NPRM, proposed Sec.  23.925 (now Sec.  23.2425) would have 
required the powerplant to operate at any negative acceleration that 
may occur during normal and emergency operation within the airplane 
operating limitations. Proposed Sec.  23.925 would have required the 
pilot to have the capability to stop and restart the powerplant in 
flight. Proposed Sec.  23.925 would have also required the airplane to 
have an independent power source for restarting each powerplant 
following an in-flight shutdown.
    Embraer commented that although the preamble indicated that 
proposed Sec.  23.925 intended to address the requirements of former 
Sec.  23.939(a) and (b), proposed Sec.  23.925 did not appear to 
require evaluation of traditional operational characteristics and did 
not address the adverse effects evaluation of air inlet distortion, 
powerplant handling, operating characteristics, and other adverse 
effects of an installed engine or power unit. Textron and ANAC had 
similar concerns. Embraer recommended the FAA revise proposed Sec.  
23.925(a) to require the powerplant handling and operating 
characteristics to be investigated in flight to determine that no 
adverse characteristics are present, to a hazardous degree, during 
normal and emergency operation within the range of operating 
limitations of the airplane and of the aircraft power unit. Textron 
also noted the intent of former Sec.  23.939 was to require 
demonstration of proper operation of the powerplant, as installed. 
Textron stated it was inappropriate to claim that the tests necessary 
to meet part 33 requirements will demonstrate proper operation of the 
powerplant as installed, which the NPRM preamble seemed to imply. 
Textron also suggested engine vibration requirements be incorporated 
into Sec.  23.2425.
    Additionally, ANAC stated that proposed Sec.  23.910 addressed 
hazard mitigation in powerplant failure conditions and proposed Sec.  
23.900 addressed ``likely hazards in operation.'' ANAC noted the term 
``hazards in operation'' might be construed to mean external threats to 
the engine from foreign object ingestion or a crosswind, causing 
confusion for applicants seeking to meet the proposed requirements and 
making it difficult to accurately interpret proposed Sec.  23.925. To 
remedy this concern, ANAC recommended that proposed Sec.  23.925 
include a requirement for an applicant to demonstrate the proper 
functioning of the powerplant in normal operation within the range of 
operating limits of the power unit.
    In light of these comments, the FAA revises proposed Sec.  
23.925(a) (now Sec.  23.2425(a)) to require the installed powerplant to 
operate without any hazardous characteristics during normal and 
emergency operation within the range of operating limitations for the 
airplane and the engine. The FAA finds this change from what was 
proposed indicates that evaluation of all traditional operational 
characteristics required by former regulations is also required by 
Sec.  23.2425(a). The FAA has added the term ``installed'' before 
``powerplant,'' in response to Textron, to clarify that Sec.  
23.2425(a) applies to the operation of the powerplant, as installed. 
The FAA notes if the installation of powerplant components do not 
remain within established limits, Sec.  23.2400 requires any deviation 
from the component limitations or installation instructions must be 
shown to not create a hazard. Additionally, the requirement to evaluate 
the powerplant installation for vibration and fatigue characteristics 
is contained in Sec.  23.2400.
    Textron also recommended the FAA revise proposed Sec.  23.925(a) to 
require the powerplant to operate at any condition, including negative 
acceleration. The Associations suggested the FAA remove the term

[[Page 96640]]

``negative acceleration'' from paragraph (a) and replace it with 
``acceleration or deceleration.''
    In response to Textron and the Associations, the FAA has removed 
the term ``negative acceleration'' from the regulation because the more 
general reference to ``normal and emergency operation'' in the revised 
language includes ``negative acceleration.'' Additionally, the FAA 
notes that Sec.  23.2400(c) requires an applicant to construct and 
arrange each powerplant installation to account for likely operating 
conditions and likely hazards in operation. This requirement addresses 
all components and systems that comprise the powerplant installation, 
such as the oil and fuel systems, and establishes a requirement for the 
applicant to address all likely conditions and hazards, which may not 
be specifically encountered in the approved operating envelope. The 
original intent of former Sec.  23.943 was to ensure no hazardous 
condition resulted when a powerplant or APU is exposed to negative 
accelerations expected in flight. The FAA finds that Sec.  23.2425(a), 
together with Sec.  23.2400(c), adequately address this need.
    The Associations also submitted comments regarding proposed Sec.  
23.925(c), which would have required an airplane have an independent 
power source for restarting the engine after an in-flight shutdown. 
These commenters contended the FAA's intent in drafting Sec.  23.925(c) 
was to ensure that engines can be reliably restarted in flight 
following an in-flight shutdown. However, these commenters noted while 
an independent power source may be an adequate solution for some 
designs, there are many designs for which an independent power source 
would be inappropriate. For example, the Associations stated that 
electric propulsion systems may include a single power source that 
manages many cells, which start and stop in flight, but will not have 
independent sources of power to restart them. As written, the 
commenters suggested proposed Sec.  23.925(c) could be interpreted to 
require that a two[hyphen]engine airplane needs three batteries for 
restarting (one main and an independent source for each powerplant). To 
address these concerns, the commenters recommended the FAA require the 
airplane to have a ``reliable'' power source, rather than an 
``independent'' power source.
    Textron, Garmin, and an individual commenter had similar concerns 
regarding proposed Sec.  23.925(c). Garmin recommended either 
withdrawing proposed Sec.  23.925(c) or clarifying its intent. Textron 
commented that proposedSec.  23.925(c) was ``too high level'' and did 
not provide adequate performance-based requirements for an applicant to 
demonstrate compliance. Textron recommended the FAA revise proposed 
Sec.  23.925(c) based upon language contained in appendix E of the 
ARC's final report.'' The individual commenter noted that proposed 
Sec.  23.925(c) would appear to require multiengine airplanes to have 
multiple and possibly duplicate electronic distribution systems for in-
flight restarts by battery power. The commenter suspected this was an 
unintended expansion of the requirements of former Sec. Sec.  23.903(g) 
and (or alternatively) Sec.  23.1165. The commenter stated this 
unintended consequence would impose cost and weight penalties beyond 
former part 23 requirements, which the commenter maintained were not 
addressed in the regulatory analysis or the preamble to proposed Sec.  
23.925(c), or otherwise justified by service experience. The individual 
commenter recommended the FAA either withdraw proposed Sec.  23.925(c) 
or clarify its intent.
    In response to the significant number of comments the FAA received 
regarding the proposed requirement that each airplane have an 
independent power source for restarting the engine after an in-flight 
shutdown, the FAA withdraws Sec.  23.925(c). The FAA's intent in 
drafting proposed Sec.  23.925(c) was to ensure a power source, 
independent from any power generated by a particular engine shutdown in 
flight, be available for restarting the powerplant. This requirement 
was originally adopted as former Sec.  23.903 to address ignition 
systems on turbine engines and to ensure a source of ignition energy 
for in-flight engine restarting exists in the event of a loss of 
combustion in all engines during flight. The requirement in Sec.  
23.2425(b), which requires the pilot have the capability to stop the 
powerplant in flight and restart the powerplant within an established 
operational envelope, establishes the performance-based requirement the 
prescriptive requirements of proposed Sec.  23.925(c) were intended to 
address. The FAA's intent was not to require redundant electrical 
power; rather, the intent was to require power independent from that of 
the engine-driven electrical power generating system to be available if 
insufficient power was available at the minimum windmilling restart 
speed. If an engine power generating system is capable of providing 
sufficient power to operate all required systems at the minimum 
windmilling restart speed, or in a normal shutdown state, an 
independent power source would not be required.
    In recognition that an aircraft engine may not be able to be 
restarted within an airplane's entire flight envelope, the FAA revises 
proposed Sec.  23.925(b) (now Sec.  23.2425(b)) to require restart 
capability within an established operational envelope, which in 
accordance with Sec.  23.2620 (proposed as Sec.  23.1510), must be 
documented in the AFM.
g. Fuel Systems (Proposed Sec.  23.930/Now Sec.  23.2430)
    In the NPRM, proposed Sec.  23.930 (now Sec.  23.2430) would have 
required that each fuel system provide an independent fuel supply to 
each powerplant in at least one configuration and avoid ignition from 
unplanned sources. It would have required that each fuel system provide 
the fuel required to achieve maximum power or thrust plus a margin for 
likely variables in all temperature conditions within the operating 
envelope of the airplane and provide a means to remove the fuel from 
the airplane. Finally, proposed Sec.  23.930 would have required each 
fuel system to be capable of retaining fuel when subject to inertia 
loads under expected operating conditions and prevent hazardous 
contamination of the fuel supply.
    The Associations asserted that proposed Sec.  23.930 does not 
permit the certification of electric propulsion systems. These 
commenters recommended the FAA delete the word ``fuel'' from the title 
of proposed Sec.  23.930 and adopt the provisions of proposed CS 
23.530. Additionally, the commenters suggested replacing ``fuel'' with 
``energy'' to clarify the requirements of this regulation are 
applicable to all energy sources and not just traditional petroleum-
based fuels.
    EASA, while recognizing that the term ``fuel'' covered other energy 
sources, stated it believed a more independent set of design 
requirements would be needed to address all energy systems, rather than 
those that are more appropriate for propulsion systems and APUs. 
Additionally, EASA specifically recommended adoption of its set of 
requirements for energy supply systems, set forth in A-NPA 2015-06, 
which provided useful requirements for a variety of systems, including 
fuel, electric, and hybrid systems. EASA also noted that its A-NPA 
2015-06 created several new subparagraphs to address particular 
functions of an energy system.
    The FAA did not intend to preclude the certification of electric 
propulsion systems or other non-fossil-fuel-based propulsion systems in 
part 23. The FAA

[[Page 96641]]

agrees the use of the term ``fuel'' rather than the term ``energy'' 
could lead individuals to reach this conclusion. However, the FAA is 
concerned that adoption of the term ``energy'' in this rule, and 
throughout this subpart, could lead to confusion, because the term 
``energy'' is used in numerous regulations and in guidance material to 
address requirements for other systems and components (i.e., braking 
systems and rotating machinery) and also to describe environmental 
conditions (i.e., those involving lightning). Therefore, the FAA 
retains the term ``fuel'' in the regulation, but notes the term 
``fuel'' in this subpart includes any form of energy used by an engine 
or powerplant installation, such as provided by carbon-based fuels or 
electrical potential. Fuel systems will also include the means of 
energy storage for the power provided (i.e., batteries that provide 
power to an electric motor) or devices that generate power for 
propulsion (i.e., solar panels or fuel cells). Furthermore, while the 
FAA agrees with many of the provisions proposed by EASA, the FAA is 
electing to retain the requirements for energy systems under a single 
section, titled ``Fuel system.'' While Sec.  23.2430 and EASA's 
proposed language may not be identical, the FAA finds Sec.  23.2430 
harmonizes with the intent of EASA's requirements.
    The FAA notes EASA's recommendation to adopt EASA's proposed 
language to address powerplant support systems to replace its current 
regulatory requirements for induction and exhaust section systems. The 
FAA has decided to retain a specific section to address powerplant 
induction and exhaust systems. The FAA will address future energy 
systems that incorporate systems such as converters or battery cooling 
as part of the powerplant installation. The FAA notes the requirements 
for those future systems will be adequately addressed in Sec. Sec.  
23.2400, 23.2410, and 23.2430.
    ANAC stated that proposed Sec.  23.930 does not address the 
requirements of former Sec.  23.951(d), which required fuel systems for 
turbine engine airplanes to meet the fuel venting requirements of part 
34. ANAC stated the former requirement applied to airplanes and not 
engines, and should therefore be specifically included in the rule. 
ANAC also recommended the reference in the former rule to part 34, 
which prevents intentional fuel venting, be included in the new rule.
    The FAA notes part 23 historically provided only a reference to 
part 34, and those requirements continue to remain applicable to the 
certification of any airplane. Sections 21.17 and 21.101 require part 
34 to be always included in the certification basis of airplanes. 
Requirements such as fuel venting will therefore continue to apply to 
the certification of these airplanes.
    Textron suggested deleting the term ``avoid'' and inserting the 
phrase ``prevent hazardous'' in proposed Sec.  23.930(a)(2), which 
addressed the avoidance of ignition from unplanned sources. Textron 
noted that using the term ``prevent'' would be consistent with the use 
of the term in other sections of part 23.
    An individual commenter also raised concerns about the undefined 
term ``avoid'', and questioned whether the term was an absolute, 
probability, or minimize requirement, or whether it covers single or 
multiple failures. Presuming the proposed requirement covered fuel 
ignition by lightning strikes addressed in former Sec.  23.954, the 
commenter requested the proposed rule not be more stringent than the 
former rule, which imposes an absolute requirement to prevent ignition 
hazards but only for certain types of strikes and strike locations. The 
commenter noted the FAA did not discuss the rationale, interpretation, 
or intent of this requirement in the NPRM preamble. The commenter also 
noted that the draft ASTM standard was identical to former Sec.  
23.954, and remarked that it was unclear why proposed Sec.  23.910 did 
not address this requirement. The commenter agreed with Textron and 
recommended inserting the term ``hazardous'' before ``ignition'' in 
paragraph (a)(2) to better clarify the proposed requirement.
    Embraer and other commenters raised concerns about use of the term 
``unplanned sources'' in proposed Sec.  23.930(a)(2). Embraer noted 
there are no ``planned'' ignition sources, making compliance with the 
rule impossible. Embraer proposed revising the requirement to account 
for ignition sources not shown to be extremely improbable, and proposed 
the rule require that each fuel system be demonstrated that it is 
designed and arranged to prevent catastrophic ignition from sources not 
shown to be extremely improbable; taking into account flammability, 
critical lightning strikes, and failures within the fuel system. 
Textron noted the NPRM preamble discussion for ``unplanned sources'' or 
``unknown sources'' was impossible to design for because it was too 
vague.
    The FAA agrees the proposed requirement for unplanned sources was 
vague and could result in numerous interpretations. Section 
23.2430(a)(2) is intended to prevent catastrophic effects resulting 
from ignition of an airplane's fuel source due to lightning, or from 
corona or streamering at fuel vent outlets, as former Sec.  23.954 
required. It is not intended to impose additional requirements to 
protect the fuel system from other ignition sources. The FAA revises 
Sec.  23.2430(a)(2) based upon former Sec.  23.954 to more accurately 
convey this requirement and to ensure its application to any fuel used 
to power an airplane. This revision also addresses the commenters' 
concerns regarding the meaning of ``avoid'' and ``unplanned sources'' 
by using the phrase ``prevent ignition'' and by enumerating the 
specific ignition sources that must be addressed.
    Embraer also stated the phrase ``margin for likely variables'' in 
proposed Sec.  23.930(a)(3) could generate confusion as to what margins 
must be observed when providing the fuel required to provide maximum 
power or thrust. The commenter explained that ``margin'' is usually 
used to define a rate higher than what is required for an engine's 
proper operation in the expected envelope and for the expected life of 
operation, but stated the meaning of the term ``likely variables'' is 
not clear. The commenter noted that the former rule considered a 
determination of the worst fuel rate for proper operation. Embraer 
suggested using text similar to that found in former Sec.  23.951(a).
    The FAA agrees with Embraer's comment that proposed Sec.  
23.930(a)(3) could generate confusion as to what margins must be 
observed when providing the fuel required to provide maximum power or 
thrust. Therefore, the FAA revises paragraph (a)(3) to require the fuel 
system provide fuel necessary to ensure proper operation of each 
powerplant and APU, in all likely operating conditions. This 
requirement ensures adequate fuel can be provided for proper operation 
of any powerplant or APU. The FAA notes an applicant's means of 
compliance with this requirement should consider the worst case 
conditions for fuel flow, including any additional demand due to 
expected efficiency losses, consumption by other systems, or secondary 
requirements such as engine cooling.
    Embraer stated that it understood proposed Sec.  23.930(a)(4) 
required a means to remove fuel and referred to fuel storage. 
Therefore, Embraer suggested the FAA move the requirement in proposed 
paragraph (a)(4) to Sec.  23.930(b), which addressed fuel storage 
systems. Embraer suggested that the cross-reference table be updated

[[Page 96642]]

accordingly for former Sec.  23.971 and Sec.  23.999.
    An individual commenter requested the proposed regulations include 
a requirement for determining or indicating usable or unusable fuel or 
energy quantities, as was formerly required. This commenter noted that 
because fuel starvation is ``always'' cited as one of the top reasons 
for off-field landings in general aviation accidents, it should be 
adequately addressed by a specific performance requirement in part 23.
    The FAA agrees with the recommendation to add a requirement to the 
final rule to ensure the flightcrew is provided with information on the 
total useable fuel available. The FAA adds this requirement as Sec.  
23.2430(a)(4), corresponding to the requirement in former Sec.  
23.1337(b), which required a means to indicate to the flightcrew 
members the quantity of usable fuel in each tank. The intent of this 
revision is to require applicants to both determine the usable quantity 
of fuel that can be stored and provide information to the flightcrew 
regarding the remaining useable fuel in the airplane.
    The FAA has decided not to move proposed paragraph (a)(4) as 
Embraer suggested. Since different types of fuel systems could be 
certificated under the rule, the FAA has added the term ``isolate'' in 
Sec.  23.2430(a)(5). The FAA recognizes that certain fuel sources may 
not be removable from the system, and that isolating the fuel from the 
system will provide the appropriate minimum level of safety.
    Additionally, the FAA clarifies Sec.  23.2430(a)(5) to require the 
fuel system be designed to retain fuel under all likely operating 
conditions and minimize hazards to the occupants during any survivable 
emergency landing. The FAA also includes a requirement in Sec.  
23.2430(a)(6) that these failures be taken into account, consistent 
with former Sec.  23.967. For the certification of level 4 airplanes, 
the paragraph also provides that any failure due to an overload of the 
landing system is taken into account in airplanes equivalent to those 
currently certificated in the commuter category, consistent with former 
Sec.  23.721.
    An individual commenter asked the FAA to revise proposed Sec.  
23.930(a)(6), which would require the fuel system prevent hazardous 
contamination of the fuel supply, to specify that the requirement was 
intended to prevent hazardous contamination of fuel delivered to 
engines. The commenter noted this revision was necessary if, as the 
preamble indicated, this requirement replaces former Sec.  23.997. The 
proposed requirement could be interpreted to require prevention of 
contamination of fuel within the fuel tank, which would be more 
stringent than the former rule and of questionable practicality. The 
former rules only required removal of contamination from the fuel being 
provided to the engine, and not necessarily from the fuel in the tank.
    The FAA agrees with the commenter and revises Sec.  23.2430 to 
require removal of hazardous contamination from the fuel supplied to 
each powerplant and APU. This requirement is now in new Sec.  
23.2430(a)(7).
    Embraer recommended the FAA revise proposed Sec.  23.930(b)(1) to 
require fuel storage systems to also withstand without failure, the 
vibration, inertial loads, and pressures under expected operating 
conditions.
    The FAA agrees with Embraer that fuel storage systems must be able 
to withstand loads and pressures under expected operating conditions 
without failure and has added the term ``without failure'' to paragraph 
(b)(1). However, the FAA does not add specific references to vibration, 
inertia, fluid, and structural loads as the FAA believes the use of 
``loads under likely operating conditions'' addresses all applicable 
loads, including those resulting from vibration and other sources.
    The FAA revises Sec.  23.2430(b)(2) to require the fuel storage 
system be isolated from personnel compartments and protected from 
hazards due to unintended temperature influences. The FAA recognizes 
that it did not adequately address these requirements in the NPRM. This 
revision addresses the requirements of former Sec.  23.967(c) and (d), 
which restricted installation of fuel tanks around engine compartments 
and firewalls, and required fuel systems to be isolated from personnel 
compartments. It is also consistent with the provisions of CS 
23.2465(b)(2), which requires each energy storage and supply system to 
be installed in such a way to be protected against hazards due to 
unintended temperature influence.
    Air Tractor requested adding the term ``significant'' after 
``prevent'' in proposed Sec.  23.930(b)(2). Embraer concurred with this 
revision because it would allow for small amounts of fuel loss through 
vent lines, such as when the tanks are full and there is normal 
``sloshing'' during taxi or takeoff, or when fuel expands as it warms. 
An individual commenter also requested revising proposed Sec.  
23.930(b)(2) to specify the fuel storage system must prevent hazardous 
fuel loss during maneuvers. The commenter believed the proposal would 
require the prevention of even minor fuel loss from vents, which is 
more stringent than the former standard. The commenter believed the 
more stringent standard was of questionable utility and practicality, 
and noted it was not justified in the preamble.
    An individual commenter requested the FAA delete proposed Sec.  
23.930(b)(3), which would require each fuel storage system to prevent 
discharge when transferring fuel, because other proposed regulations 
would address any potential hazards associated with fuel transfer. The 
commenter further stated it was unclear if the proposed requirement 
would apply to fuel returned from the engine to other than the 
specified tank. This commenter explained that some multiengine 
airplanes feature fuel-transfer cross feeding, which can result in a 
fuel discharge if the receiving tank is full. This approach has both 
advantages and disadvantages, but should not be prohibited by 
regulation. The commenter also noted this proposal was not justified in 
the preamble or addressed in the Regulatory Analysis, was more 
stringent than the former rule, and would require additional hardware 
or revised architecture for some designs.
    The FAA agrees with the recommendation to delete the requirement in 
proposed paragraph (b)(3) that each fuel storage system prevent 
discharge when transferring fuel. The FAA recognizes it has approved 
the design of certain fuel systems under former regulations that may 
result in a non-hazardous discharge of small amounts fuel when fuel is 
transferred between fuel tanks or fed from a specific fuel tank and 
returned to another tank under certain conditions. To ensure the 
continued acceptability of these systems under the new rule, the FAA 
has combined proposed paragraph (b)(2) and (b)(3) into paragraph (b)(3) 
in this final rule. Paragraph (b)(3) now requires the fuel system to be 
designed to prevent significant loss of stored fuel from any vent 
system due to fuel transfer between storage or supply systems under 
likely operating conditions.
    One commenter stated the proposed rule did not specifically address 
the potential of water in the airplane's fuel system, and the commenter 
proposed it should contain a requirement to include fuel tank water 
sensors. The commenter noted that water accumulates in fuel tanks in a 
number of ways, such as when temperature changes or when air enters a 
tank from which fuel has been consumed.
    The FAA notes the specific hazard associated with water in 
petroleum-based fuels is addressed generally in

[[Page 96643]]

Sec.  23.2430(a)(7), which requires the prevention of hazardous 
contamination of the fuel supplied to the powerplant. Additionally, the 
FAA notes that a compound such as water may not necessarily be 
considered a contaminant or hazard in certain future fuel systems. The 
commenter's proposal would introduce specific language that may not be 
appropriate for future fuel systems and has therefore not been adopted.
    Finally, the FAA revises Sec.  23.2430(c) to remove the restrictive 
language applicable only to pressure refueling systems. The rule now 
applies to fuel storage refilling and recharging systems. This revision 
will establish more appropriate requirements to accommodate the 
introduction of new propulsion systems such as electric motors. 
Accordingly, the FAA adopts performance-based requirements that will 
require prevention of improper refilling or recharging, prevention of 
stored fuel contamination during likely operating conditions, and the 
prevention of the occurrence of any hazard to the airplane or to 
persons during refilling or recharging.
h. Powerplant Induction and Exhaust Systems (Proposed Sec.  23.935/Now 
Sec.  23.2435)
    In the NPRM, proposed Sec.  23.935 (now Sec.  23.2435) would have 
required the air induction system to supply air needed for each power 
unit and its accessories under expected operating conditions, and 
provide a means to discharge potential harmful material.
    EASA recommended removal of the design-specific requirements in 
proposed Sec.  23.935 because those requirements should be addressed as 
a means of compliance. Textron requested a complete rewrite of proposed 
Sec.  23.935, stating the section was ``too high level'' and did not 
provide adequate performance-based requirements for an applicant to be 
able to demonstrate compliance. Textron asked the FAA to derive the 
language for proposed Sec.  23.935 from appendix E of the final Part 23 
ARC Report.
    The FAA notes EASA's recommendation to remove Sec.  23.935 based on 
its contention the section appears to be a means of compliance instead 
of a performance-based requirement. However, the FAA finds the 
provisions of the rule set forth performance-based requirements for 
induction and exhaust systems that are appropriate for inclusion in 
this rule. Rather than stipulating a specific means of compliance, 
these requirements serve as high-level performance-based requirements 
for which a number of alternative means of compliance could be 
developed by applicants.
    The FAA partially agrees with Textron's comment that the rule is 
``too high level.'' Accordingly, the FAA revises Sec.  23.2435 based on 
the requirements for powerplant induction and exhaust systems contained 
in former Sec. Sec.  23.1091, 23.1121, 23.1123, 23.1125, and the final 
Part 23 ARC Report. Section 23.2435 now sets forth performance-based 
requirements that encompass these prescriptive regulations and the Part 
23 ARC's proposed requirements. The FAA notes while it is adding all of 
the ARC's proposed requirements for exhaust and induction systems in 
this rule, not all of its recommendations for revisions to this section 
were appropriate. Some of the ARC's recommendations are more 
appropriately addressed by other sections of this rule. For example, 
the ARC's proposed requirement for the system that supplies air to the 
cabin to prevent hazardous quantities of toxic gas from entering the 
cabin is addressed by Sec.  23.2400(d) while the engine accessory 
component cooling requirements are addressed by Sec.  23.2400(e), which 
requires powerplant components to comply with their limitations and 
installation instructions, or be shown not to create a hazard.
    Embraer requested the FAA revise proposed Sec.  23.935 to clarify 
the design and induction system must prevent distortion as described in 
former Sec.  23.939(c). Embraer also recommended the FAA revise the 
proposal to include a requirement that the air induction system for 
each power unit and its accessories must not, as a result of airflow 
distortion during normal operation, cause vibration harmful to the 
power unit.
    The FAA notes that former Sec.  23.939(c) addressed distortion as a 
cause of vibration and required the air inlet not, as a result of 
distortion during normal operation, cause vibration harmful to the 
engine. Embraer's general concerns are addressed by Sec.  
23.2435(a)(1), which requires the air induction system for each 
powerplant or auxiliary power unit and its accessories to supply the 
air required under likely operating conditions. Embraer's specific 
concern that the air induction system not cause ``vibration harmful to 
the power unit'' is addressed by the powerplant installation 
requirements contained in Sec.  23.2400(c)(4), which requires the 
applicant to ``construct and arrange each powerplant installation to 
account for . . . vibration and fatigue,'' which occur as a result of 
distortion.
    Air Tractor and ANAC raised concerns about whether proposed Sec.  
23.935(b) was intended to address exhaust systems or air induction 
systems. Air Tractor stated it did not believe the FAA intended 
proposed Sec.  23.935(b) to mandate the use of an inertial bypass 
particle separator (as proposed Sec.  23.935(b) could have been 
interpreted to require), and recommended the FAA clarify proposed Sec.  
23.935(b) to indicate the requirement applies only to exhaust systems. 
ANAC commented that proposed Sec.  23.935(b) should require the exhaust 
system to ensure safe disposal of exhaust gases, as the former rule 
required.
    The FAA agrees with Air Tractor and ANAC's concern that proposed 
Sec.  23.935(b) is unclear because it only appears to discuss induction 
systems (whereas the title of proposed Sec.  23.935 includes exhaust 
systems). Accordingly, the FAA has modified Sec.  23.2435 to clearly 
indicate the requirements of paragraph (a) apply to induction systems 
and the requirements of paragraph (b) apply to exhaust systems. This 
makes it clear the rule does not require use of an inertial bypass 
particle separator as a means for the induction system to discharge 
potential harmful material.
    If a complete rewrite of proposed Sec.  23.935 is not adopted, 
Textron requested clarification as to whether the proposed requirements 
were intended to address the cooling air requirements for powerplant 
accessories in former Sec. Sec.  23.1041 through 23.1047, and the 
intent of former Sec.  23.1091. If proposed Sec.  23.935 was intended 
to match the provisions of former Sec.  23.1091, Textron commented that 
the proposed section was adequate. However, if proposed Sec.  23.2435 
was intended to address Sec. Sec.  23.1091 and 23.1041 through 23.1047, 
Textron asked for clarification of the proposed section's requirements. 
Textron also specifically recommended revising the regulatory text to 
clarify the intent of the proposed requirements were ``to ensure proper 
operation within established limitations'' of the air induction system 
for each power unit and its accessories.
    The FAA notes the engine cooling requirements are not specifically 
addressed in Sec.  23.2435, other than in a requirement that the 
induction system be designed to supply the air required by each 
powerplant or auxiliary power unit and its accessories under likely 
operating conditions. However, the powerplant cooling requirements are 
addressed more directly by Sec.  23.2400(e), which requires powerplant 
components to comply with their limitations and installation 
instructions, or be shown not to create a hazard. This requirement

[[Page 96644]]

ensures an applicant addresses engine cooling.
    Additionally, the FAA revises proposed Sec.  23.2435(b) to 
specifically indicate exhaust systems include exhaust heat exchangers 
for each powerplant or APU. Specifically referencing these systems as 
part of the airplane exhaust system continues the FAA's practice of 
applying exhaust system requirements to exhaust heat exchangers. The 
FAA also revises requirements for exhaust systems by adding paragraph 
(b)(2) to ensure these systems are designed to prevent likely hazards 
from heat, corrosion, or blockage. These requirements address the 
specific requirements of former Sec.  23.1121(a) and (h) and Sec.  
23.1123(a).
i. Powerplant Ice Protection (Proposed Sec.  23.940/Now Sec.  23.2415)
    In the NPRM, proposed Sec.  23.940 (now Sec.  23.2415) would have 
required the airplane design to prevent foreseeable accumulation of ice 
or snow that would adversely affect powerplant operation. Proposed 
Sec.  23.940 would have also required the powerplant design to prevent 
any accumulation of ice or snow that would adversely affect powerplant 
operation, in those icing conditions for which certification is 
requested.
    Textron recommended withdrawing proposed Sec.  23. 940, as it 
believed the requirement to protect engines could be adequately 
addressed in proposed Sec.  23.910 by including language that would 
ensure safe powerplant operation under all likely operating conditions 
or enable satisfactory powerplant functioning in icing conditions. 
Alternatively, Textron proposed consolidating the requirements of 
proposed Sec.  23.940 by removing paragraph (b) and revising paragraph 
(a) to require the airplane design prevent ``any accumulation''--rather 
than ``foreseeable accumulation''--of ice or snow that adversely 
affects powerplant operation in those icing conditions for which 
certification is requested.
    The FAA does not agrees that eliminating proposed Sec.  23.940 (now 
Sec.  23.2415) and adding a requirement to proposed Sec.  23.910 (now 
Sec.  23.2410) would result in designs that would prevent the 
accumulation of ice or snow that could adversely affect powerplant 
operations. Including Textron's proposed regulatory language in Sec.  
23.2410 as part of the powerplant installation hazard assessment could 
permit designs that only address ice accretion as part of a powerplant 
installation assessment, and not airframe ice accretion that may pose 
an ice shed hazard. Additionally, Textron's proposal could be 
interpreted to only require the powerplant's performance be evaluated 
for the environmental icing conditions for which certification is 
requested, and not for other conditions that may be conducive to ice 
accretion in reciprocating engine induction systems. In contrast, the 
FAA finds Sec.  23.2415 establishes specific requirements that will 
apply to all airplane designs, to include those for which certification 
in icing conditions was not requested, and adds requirements that will 
apply to powerplant designs for airplanes intended for certification 
for flight in icing conditions.
    The FAA also finds Textron's recommendation to revise proposed 
Sec.  23.940(a) and withdraw paragraph (b) would specifically eliminate 
the applicability of the requirement to the powerplant design. By only 
setting forth a requirement for the airplane design and not the 
powerplant design, Textron's proposed revision would neither ensure an 
independent assessment of the adequacy of the engine design for icing 
conditions, nor require an evaluation of the engine's tolerance for ice 
ingestion. Additionally, it would not apply to propellers, which are 
considered powerplant components. The FAA's intent in paragraph (b) is 
to require an applicant to assess the adequacy of the engine's 
certification basis for installation in an airplane, the engine's 
service history of ice ingestion, and propeller design.
    The FAA expects that an acceptable means of compliance would 
specify an evaluation of the engine's tolerance for ice ingestion that 
would not be limited to the conditions specified in part 25, appendix 
C, and that such an evaluation would show that it meets, or exceeds, 
those standards prescribed in former Sec.  23.903(a)(2).
    Textron also commented that proposed Sec.  23.940 does not address 
ice accretion that could affect the performance of cooling air inlets 
for the engine and its accessories.
    In light of Textron's comment, the FAA is adding the term 
``installation'' to proposed Sec.  23.940(b) to clarify the regulation, 
like former Sec.  23.929, applies to ``other components of complete 
engine installations,'' which include cooling air inlets. Accordingly, 
Sec.  23.2415(b) now requires the ``powerplant installation design'' to 
prevent any accumulation of ice or snow that adversely affects 
powerplant operation, in those icing conditions for which certification 
is requested. This change from what was proposed is consistent with the 
NPRM, which explained that powerplant design in proposed Sec.  
23.940(b) refers to the engine, propeller, and other powerplant 
components such as cooling inlets.
    Additionally, the FAA is inserting the phrase ``including the 
induction and inlet system'' after ``airplane design'' to clarify that 
Sec.  23.2415(a) is intended to address the engine induction ice 
protection requirements found in former part 23. This change from what 
was proposed is consistent with the NPRM, which explained that the 
airplane design in proposed Sec.  23.940(a) refers to the engine 
induction system and airframe components on which accumulated ice may 
shed into the powerplant. The FAA also reiterates that paragraph (a) 
applies to all airplanes regardless of whether certification for flight 
in icing conditions is sought, and requires applicants to address ice 
accretion anywhere on the airplane that may pose a threat to the 
powerplant if that ice is shed. ``Foreseeable'' accumulation of ice and 
snow, rather than ``any'' accumulation as recommended by Textron, is 
used in paragraph (a). The icing and snow conditions to be evaluated 
are not simply the icing conditions for which the airplane is to be 
certified, as in paragraph (b). For example, on non-icing certified 
airplanes, conditions to be evaluated range from carburetor icing on 
reciprocating powered airplanes to part 25, Appendix C icing on turbine 
powered airplanes.
j. Powerplant Fire Protection (Proposed Sec.  23.1000/Now Sec.  
23.2440)
    In the NPRM, proposed Sec.  23.1000 (now Sec.  23.2440) would have 
required a powerplant be installed in a designated fire zone and would 
have required an applicant to install a fire detection system in each 
designated fire zone for levels 3 and 4 airplanes. Proposed Sec.  
23.1000 would have also required an applicant to install a fire 
extinguishing system for levels 2, 3, and 4 airplanes with a powerplant 
located outside the pilot's view that uses combustible fuel.
    Additionally, proposed Sec.  23.1000 would have required each 
component, line, and fitting carrying flammable fluids, gases, or air 
subject to fire conditions to be fire resistant, except components 
storing concentrated flammable material would have to be fireproof or 
enclosed by a fireproof shield. Proposed Sec.  23.1000 would have also 
required an applicant to provide a means to shut off fuel or flammable 
material for each powerplant, while not restricting fuel to remaining 
units, and prevent inadvertent operation.
    EASA noted the proposed regulation contained too many design 
details,

[[Page 96645]]

which are better addressed as means of compliance. EASA contended that 
the sole objective of proposed Sec.  23.1000 should be to require a 
means to isolate and mitigate hazards to the airplane in the event of a 
powerplant system fire or overheat in operation.
    Although the FAA concedes that some of the proposed requirements 
are prescriptive in nature, the FAA has determined that inclusion of 
these requirements for fire protection are critical to safety and 
should be retained to prevent any potential degradation of safety. 
Fire, while not a common occurrence, greatly reduces the likelihood of 
survival when occurring in flight. Detection, isolation, and 
extinguishing have historically provided an acceptable means for 
mitigating hazards from powerplant-related fires. Accordingly, the 
final rule retains what the FAA considers to be sufficient prescriptive 
requirements to ensure the existing level of fire protection. In 
response to EASA's comment, as discussed in more detail later, the FAA 
has added a requirement in Sec.  23.2440(b), requiring each designated 
fire zone provide a means to isolate and mitigate hazards to the 
airplane in the event of a powerplant system fire or overheat.
    Zee questioned whether the requirement in proposed Sec.  23.1000(a) 
for all powerplants to be installed in a designated fire zone is 
appropriate. The commenter noted electric propulsion systems can be 
designed and installed with no flammable liquids or materials, thus 
eliminating the need for fire protection. Zee requested the FAA revise 
proposed paragraph (a) to indicate installation in a fire zone is not 
required if not applicable. The Associations also recognized the same 
issue and proposed revising the requirement to only apply to flammable 
powerplant components. Embraer recommended the FAA delete proposed 
Sec.  23.1000(a).
    ANAC observed that the intent to define ``designated fire zones'' 
in the proposal is to identify areas of the airplane in which a high 
degree of safety precautions must be taken, recognizing that fire will 
occur in these regions because of the presence of both ignition sources 
and flammable fluid. ANAC contended proposed Sec.  23.1000 could be 
interpreted as the region where a powerplant is to be installed must 
first be evaluated for ignition sources and flammable fluids. ANAC 
noted the proposed requirement could also be interpreted as the 
powerplant can only be installed in regions that already contain 
ignition sources and flammable fluids. Embraer contended that former 
Sec.  23.1181 defined the ``hot'' parts of an engine installation as 
ignition sources, and considering that there are fuel, oil, and 
hydraulic fluids being carried around such areas, they should be 
considered fire zones. Thus the term ``designated'' would apply, 
obviating further analysis.
    The FAA has considered the comments regarding the requirement to 
install all powerplants in proposed Sec.  23.1000(a) (now Sec.  
23.2440(a)) in a designated fire zone. The FAA notes that while 
virtually every kind of powerplant (to include electric motors) may 
present a potential fire hazard, some types of powerplants may not 
present a likely fire hazard or require installation in a designated 
fire zone. Accordingly, the FAA revises Sec.  23.2440(a) to require a 
powerplant be installed in a designated fire zone only if it includes a 
flammable fluid and an ignition source for that fluid. The term 
``flammable fluid'' includes any flammable substance such as liquids, 
gases, or gels that are capable of flowing. This change is intended to 
alleviate the need to install powerplants that do not present a likely 
fire hazard in a designated fire zone. The FAA also adds the term 
``combustion heater'' to Sec.  23.2440(a), which are required to be 
located in designated fire zones under former Sec.  23.1181. The 
devices were inadvertently omitted from consideration under the fire 
and high-energy protection requirements of proposed subpart D.
    ANAC noted the NPRM preamble discussion indicated that fire must be 
evaluated in the powerplant installation hazard assessment required 
under proposed Sec.  23.910. ANAC expressed concern the dedicated 
requirement for powerplant fire protection in proposed Sec.  23.1000 
could be interpreted to require evaluation of fire hazards beyond the 
scope of proposed Sec.  23.910. ANAC recommended the FAA include a 
requirement for a firewall that ensures a fire originating in any fire 
zone will not be a hazard to the airplane.
    The FAA did not intend to require the use of a hazard assessment 
process in proposed Sec.  23.1000 (now Sec.  23.2440). The FAA notes 
the purpose of the firewall discussion in proposed Sec.  23.1000 is to 
determine if a particular component or system would need to be placed 
in a designated fire zone. If a component is required to be located in 
a fire zone by a rule other than Sec.  23.2410, such as Sec.  
23.2440(a), that requirement must be complied with regardless of the 
results of any hazard assessment. The FAA revises Sec.  23.2440(a) to 
require that a powerplant, APU or combustion heater, that includes a 
flammable fluid and an ignition source for that fluid, be installed in 
a designated fire zone. In response to ANAC's recommendation to add a 
requirement for a firewall that ensures a fire originating in any fire 
zone will not be a hazard to the airplane, the FAA notes Sec.  
23.2440(b) requires each designated fire zone provide a means to 
isolate and mitigate hazards to the airplane in the event of a 
powerplant system fire or overheat. Isolation of a designated fire zone 
is typically accomplished by use of a firewall or other equivalent 
means.
    An individual commenter raised concerns that proposed Sec.  
23.1000(b) fails to address critical fire protection requirements and 
only requires components carrying flammable liquid to be fire 
resistant. Specifically, the commenter noted that former Sec.  
23.1141(f) required powerplant controls required to operate in the 
event of a fire to be fire resistant, former Sec.  23.1189 required 
shutoff valves to be outside the fire zone, former Sec.  23.1203 
required certain fire detector components to be fire resistant, and 
former Sec.  23.1201 required fire extinguisher components in the fire 
zone to be fireproof. To resolve this, the commenter recommended 
implementation of basic system performance requirements for fire 
protection, preserving the former fire protection standards, but not 
compromising future designs. Another commenter noted the proposed rule 
did not capture some of the specific fire protection requirements for 
items such as powerplant controls, shutoff valves, fire detectors and 
extinguishers.
    The FAA agrees the proposed language was not sufficiently 
comprehensive to establish clear requirements necessary for the 
prevention of hazards resulting from fire. The FAA revises proposed 
Sec.  23.1000(b) and renumbers it as Sec.  23.2440(c) to ensure 
adequate fire protection is maintained for those noted components, 
along with any other components determined critical to safety. The FAA 
adds paragraph (c)(1) to ensure the design of components and the 
placement within the airplane not only prevent fire hazards but also 
account for the effects of fire in adjacent fire zones. This 
requirement addresses the requirements in former Sec.  23.1183(a) to 
ensure flammable fluid-carrying components be shielded, or located to 
safeguard against the ignition of flammable fluid. These requirements 
are also consistent with the provisions of former Sec.  23.1182.
    Embraer recommended the FAA revise proposed Sec.  23.1000(c) to 
allow for the flow of quantities of fuel that are

[[Page 96646]]

small enough not to be hazardous to enter into the powerplant. Textron 
similarly asserted proposed Sec.  23.1000(c) was unnecessary and could 
be addressed by proposed Sec.  23.910. Textron recommended the FAA 
revise its proposal to conform with CS 23.510(e), or Sec.  23.906(i) in 
appendix E of the Part 23 ARC Report.\49\ Alternatively, Textron 
recommended revisions to proposed Sec.  23.1000(c), (d), and (e).
---------------------------------------------------------------------------

    \49\ In each area or component where flammable fluids or vapors 
might escape by leakage of a fluid system, there must be means to 
minimize the probability of ignition of the fluids and vapors, and 
the resultant hazard if ignition does occur and prevent the 
introduction of hazardous toxic gases into the cabin.
---------------------------------------------------------------------------

    The FAA agrees with Embraer's comment that small amounts of fuel 
may still enter a powerplant after a shutoff means has been activated. 
The FAA revises paragraph (c) and paragraph (d) to require that the 
applicant provide a means to prevent hazardous quantities of flammable 
fluid from flowing into the designated fire zone. Accordingly, this 
revision will permit the flow of small amounts of residual flammable 
fluid if it is shown not to present a hazard, after activation of any 
shutoff means.
    With respect to Textron's comment, the FAA finds the requirements 
for a means to shut off fuel or flammable material for each powerplant 
necessary. The FAA has determined Sec.  23.2410 does not adequately 
address this requirement because Sec.  23.2410 sets forth the 
requirements for a powerplant hazard assessment in which an applicant 
could feasibly conclude that a means to shut off fuel flow for each 
powerplant would not be necessary to comply with the stated 
requirement. At this time, the FAA does not intend to permit the 
certification of airplanes without a means to shut off fuel to their 
powerplants.
    The FAA also considered Textron's recommendation to revise proposed 
Sec.  23.1000 to conform to CS 23.510(e) or the Part 23 ARC's proposed 
Sec.  23.906(i). The FAA finds the hazard minimization requirements 
contained in these provisions do not specifically preclude the 
certification of an airplane without a means to shut off fuel flow to 
each powerplant, a requirement the FAA considers essential for hazard 
mitigation. Accordingly the FAA does not adopt that recommendation, and 
considers such action to be outside the scope of this rulemaking 
effort.
    Textron recommended the FAA revise the introductory text of 
proposed paragraph (c) to require the applicant to provide a means to 
shut off both fuel and flammable material for each powerplant. Textron 
recommended changing ``or'' to ``and''; otherwise, the language would 
suggest there is no requirement to shut off other flammable fluid flow. 
Textron also requested the FAA to clarify that the applicant must only 
demonstrate that the means of shut off, and not each powerplant, meets 
the requirements of proposed paragraphs (c)(1) and (c)(2).
    The FAA agrees with Textron's concern that proposed Sec.  23.1000 
could be interpreted to require shutoff of either fuel or flammable 
material, which could permit a design that does not shutoff all 
flammable materials to the fire zone. Therefore, the FAA removes the 
term ``fuel'' from the requirement. Section 23.2440(d) now requires 
prevention of all hazardous quantities of flammable fluid from entering 
a fire zone. This is consistent with former Sec.  23.1189(a)(1). During 
review of the existing shutoff requirements, the FAA also determined a 
critical flammable fluid shutoff valve fire performance requirement was 
not included in the proposed rule. Therefore, the requirement of former 
Sec.  23.1189(a)(4) is included in the final rule as Sec.  
23.2440(d)(3).
    The FAA notes that proposed Sec.  23.1000(d) included a qualifier 
that required only powerplants that use a combustible fuel to have a 
fire extinguishing system. Based on the commenter's concerns, the FAA 
removes this specific requirement and revises Sec.  23.2440(a) to 
require any powerplant or APU that includes a flammable fluid source 
and an ignition source for that fluid be located in a fire zone. This 
regulatory approach is consistent with former requirements for 
designated fire zones that contain a flammable fuel and an ignition 
source where any leakage of flammable fluid would likely result in a 
fire. Concerns relating to possible electrical engine fires are noted, 
but not considered likely such that they would require installation in 
a designated fire zone. Electric motors are commonly used on airplanes, 
although not for propulsion, and have not required the protection of a 
designated fire zone.
    Additionally, the FAA adds paragraph (d)(3) to the final rule. The 
revision requires the applicant to provide a means to prevent hazardous 
quantities of flammable fluids from flowing into, within, or through 
each designated fire zone located outside the fire zone unless an equal 
degree of safety is provided with a means inside the fire zone. This 
revision is based on the provisions of former Sec.  23.1189(a)(4) and 
intends to ensure the specific requirements of that section are met by 
an applicant.
    Textron also reiterated the concept that fire protection actually 
applied to all systems and recommended removing proposed Sec.  
23.1000(c)(2) and broadening its applicability to all systems by 
placing the requirement in proposed Sec.  23.1305.
    While the FAA understands Textron's comment that fire protection 
applies to all systems, the FAA notes the fire protection for areas 
outside of fire zones are addressed by Sec.  23.2325 of the final rule. 
The requirements for fire protection in fire zones are more extensive 
than those for other areas of the airplane. The FAA requires designated 
fire zones, and their corresponding extensive fire protection 
requirements, for those areas where both nominal ignition sources and 
flammable fluids must be co-located such that a single failure is 
likely to result in a fire. Zones of the airplane that are outside a 
fire zone should not contain both nominal ignition sources and 
flammable fluids. Because there is a lower likelihood of fire in these 
areas, they have correspondingly less extensive requirements.
    Textron also recommended revising proposed Sec.  23.1000(d) because 
it believed the proposal would limit the applicability of the 
requirement for a fire extinguishing system to those powerplants 
``outside the pilot's view'' and those powerplants that use 
``combustible fuels.'' The commenter believed the intent of the 
proposal was not clear, and recommended the FAA consider the need for 
extinguishing systems in hybrid electric configurations where fire 
extinguishing systems may be needed to address an electrical fire. 
Textron also did not believe the rule's requirement should be limited 
to level 3 and 4 airplanes. Textron recommended the FAA retain the 
provisions of former Sec.  23.1195, which required extinguishing 
systems for ``all airplanes with engine(s) embedded in the fuselage or 
in pylons on the aft fuselage.'' Textron also recommended the FAA 
incorporate additional provisions from the Part 23 ARC Report, which 
recommended requiring that fire extinguishing systems be installed in 
all airplanes with engines embedded in the aft fuselage or in pylons on 
the aft fuselage, and for an APU, if installed. The systems must not 
cause a hazard to the rest of the airplane.
    Textron asserted that fire detection systems should not be 
mandatory for all level 3 and 4 airplanes as proposed in Sec.  
23.1000(e), but rather should be required based upon the type and 
location of engines used in the airplane. The commenter recommended 
using the

[[Page 96647]]

proposed requirements from the Part 23 ARC Report, which describes the 
top level safety requirements and then would allow the industry 
standard to provide more specifics as to what engine types and 
configurations would require a fire detection system. Textron further 
commented that proposed Sec.  23.1000(e) should be revised to only 
require fire detection systems for those airplanes that have the 
characteristics specified in former Sec.  23.1203(a).
    An individual commenter also noted that proposed Sec.  23.1000(d) 
and (e) were inconsistent with the requirements of the former rule and, 
in some cases, would impose more stringent requirements without 
providing justification. Specifically, the commenter stated that, as 
proposed, a level 1 or 2 airplane with the engine located outside the 
view of the pilot could be required to have a fire extinguisher, but 
not a fire detector. The commenter also noted a single-engine level 3 
or level 4 airplane, such as a Cessna 208 or Pilatus PC-12, was not 
required to have a fire detection system under the former rule, but 
would be required to have such a system under the proposed rule. The 
commenter further noted that the requirements of former Sec.  23.1203 
were based on designs determined to be at greater risk for fire (e.g., 
multiengine turbines and reciprocating engines with turbochargers), 
which justified inclusion of a fire detection system. The commenter 
also noted the former rule addressed other designs and required fire 
extinguishing systems for all commuter category airplanes, whereas the 
proposed rule lacks these specific requirements. The commenter 
recommended the FAA revise proposed Sec.  23.1000(d) and (e) to ensure 
no additional burden would be placed on future designs unless justified 
and to ensure the former level of fire protection would be retained.
    The FAA agrees with the commenters that proposed Sec.  23.1000(d) 
and (e) were confusing and inconsistent with former fire extinguishing 
and detection requirements. The FAA revises those paragraphs, now 
located in Sec.  23.2440(e) and (f), to be consistent with former 
requirements by removing the language limiting the applicability of the 
requirements to only level 3 and level 4 airplanes, and basing the need 
for a fire extinguishing system on the location of a fire zone instead 
of on the location of the powerplant. However, the FAA retains the 
specific requirement for a means to extinguish fires within fire zones 
on level 4 airplanes, because these airplanes are functionally 
equivalent to airplanes currently certificated in the commuter 
category. These changes make Sec.  23.2440(e) and (d) consistent with 
the requirements of former Sec. Sec.  23.1195, ``Fire extinguishing 
systems,'' and 23.1203, ``Fire detector system.''
    Finally, Air Tractor also recommended adding ``if installed'' after 
``fire detection system'' in proposed Sec.  23.1000(f) and (g) to avoid 
the perception a fire detection system is a requirement.
    The FAA notes that, if a particular system is not required and not 
installed on the airplane, any specific requirements related to that 
system will not be applicable. Therefore, the FAA does not add the text 
proposed by Air Tractor to the final rule.
7. Subpart F--Equipment
a. General Discussion
    The FAA proposed substantial changes to former subpart F. The 
thirty-seven former system sections were consolidated into eight 
sections. An effort was made to maintain the safety intent of the rules 
while removing the prescriptive nature of these rules which were based 
on technology available at the time the rule was introduced. This was 
intended to increase future flexibility to facilitate the installation 
of systems that enhance safety as new technology becomes available.
    EASA recommended the FAA add an additional requirement to proposed 
subpart F that describes what system and equipment information should 
be determined. EASA further suggested subpart G cover how this 
information is displayed.
    The FAA finds EASA's recommendation to add a new requirement for 
system and equipment information unnecessary because this information 
is already addressed in several requirements, including proposed Sec.  
23.1305 (now Sec.  23.2505), Function and installation; proposed Sec.  
23.1400 (now Sec.  23.2540), Safety Equipment; proposed Sec.  23.1505 
(now Sec.  23.2605), Installation and operation; proposed Sec.  23.1310 
(now Sec.  23.2615), Flight, navigation and powerplant instruments; and 
proposed Sec.  23.1515 (now Sec.  23.1529), Instructions for continued 
airworthiness. The FAA agrees, however, that subpart G should address 
how the information is presented.
b. Airplane Level Systems Requirements (Proposed Sec.  23.1300/Now 
Sec.  23.2500)
    In the NPRM, proposed Sec.  23.1300 (now Sec.  23.2500) would have 
required equipment and systems required for an airplane to operate--
     Safely in the kinds of operations for which certification 
is requested;
     Be designed and installed to meet the level of safety 
applicable to the certification and performance levels of the airplane; 
and
     Perform their intended function throughout the operating 
and environmental limits specified by an applicant.
    Proposed Sec.  23.1300 would have also mandated that 
non[hyphen]required airplane equipment and systems, considered 
separately and in relation to other systems, be designed and installed 
so their operation or failure would not have an adverse effect on the 
airplane or its occupants.
    NATCA observed the requirements of proposed Sec.  23.1300 and Sec.  
23.1305 (now Sec.  23.2505) appeared similar and requested the FAA 
combine the two sections.
    While the FAA agrees there is some similarity between Sec.  23.2500 
and Sec.  23.2505, the requirements of Sec.  23.2500 are at the 
airplane level and create a distinction between ``required'' and ``non-
required'' equipment and systems. In contrast, the requirements of 
Sec.  23.2505 are at the system level and apply to all installed 
equipment, regardless of whether it is required.
    Garmin asked the FAA to clarify whether proposed Sec. Sec.  23.1300 
and 23.1305 are of general applicability and do not supersede other 
specific part 23 requirements. Garmin noted that CS 23.600(a) includes 
such clarifying language concerning CS 23.600 and CS 23.605, and that 
the FAA's decision to omit similar wording from proposed Sec.  23.1300 
makes it unclear whether the FAA agrees with EASA in this respect or 
not.
    In light of Garmin's comment, the FAA revises proposed Sec. Sec.  
23.1300 and 23.1305 to clarify the requirements of these sections apply 
generally to installed equipment and systems. However, the requirements 
do not apply if another section of part 23 imposes specific 
requirements on a particular piece of installed equipment or systems. 
The FAA finds this revision is consistent with the NPRM. The FAA 
intended proposed Sec. Sec.  23.1300 and 23.1305 to capture the safety 
intent of former Sec.  23.1309. Former Sec.  23.1309 was a regulation 
of general requirements that did not supersede any requirements 
contained in other part 23 sections. Sections 23.2500 and 23.2505 are 
harmonized with CS 23.600 and CS 23.605.
    Air Tractor stated proposed Sec.  23.1300(a)(l) failed to define a 
standard for the required level of safety for systems.

[[Page 96648]]

    The FAA is construing Air Tractor's comment as referring to the 
qualitative levels of safety for systems, which were previously 
contained in former Sec.  23.1309(c). These qualitative levels of 
safety are now contained in Sec.  23.2510 (proposed as Sec.  23.1315), 
which provides system-level requirements. The FAA notes Sec.  
23.2500(a)(1) provides airplane-level requirements, and does not 
specify the level of safety because the acceptable level of safety 
varies depending on the certification level of the airplane. Former 
part 23 is one acceptable means of compliance for the new part 23. 
Therefore, applicants may use as a means of compliance the levels of 
safety defined in figure 2 of AC 23.1309-1E, ``System Safety Analysis 
and Assessments for Part 23 Airplanes'', which were a means of 
compliance to former Sec.  23.1309 and varied depending on the 
certification class of airplane. Alternatively, applicants--individuals 
or organizations--may assist in the development of industry-consensus 
standards, or propose their own means of compliance to Sec.  
23.2500(a)(1).
    ANAC commented the phrase ``operating and environmental conditions 
specified by the applicant'' in proposed Sec.  23.1300(a)(2) could lead 
to misinterpretation. ANAC asserted these conditions may not be 
adequate or achieve the minimum requirements for certification. ANAC 
suggested using the phrase ``conditions for which the airplane is 
certified.''
    The FAA agrees with ANAC and revises the proposed rule language for 
clarity. Accordingly, Sec.  23.2500(a)(2) now requires the equipment 
and systems required for an airplane to operate safely, in the kinds of 
operations for which certification is requested, to be designed and 
installed to perform their intended function throughout the operating 
and environmental limits ``for which the airplane is certificated.''
    Several commenters commented on the use of the phrase ``non-
required'' in proposed Sec.  23.1300(b). EASA stated that the proposed 
provisions of Sec.  23.1300(a) and (b) raised ambiguity regarding what 
systems and equipment are ``required.'' EASA recommended clarifying the 
distinction between ``required'' and ``non-required'' in paragraphs (a) 
and (b), respectively, by revising the proposed rule language in 
paragraph (b) to make clear ``non-required'' systems and equipment are 
those not covered by paragraph (a). The Associations recommended the 
FAA clarify what non-required systems and equipment include and offered 
rule language similar to that proposed by EASA. Lastly, ANAC 
recommended replacing ``non-required'' with ``each'' in proposed Sec.  
23.1300(b) because the requirements should apply to all systems and 
equipment.
    The FAA agrees the distinction between proposed Sec.  23.1300(a) 
and proposed Sec.  23.1300(b), which would have applied to ``non-
required'' equipment, was unclear. The FAA adopting EASA's recommended 
rule language, which clarifies the distinction between the two 
requirements by linking them together. Accordingly, Sec.  23.2500(b) 
(proposed as Sec.  23.1300(b)), now requires the systems and equipment 
not covered by Sec.  23.2500 (a) to be designed and installed so their 
operation does not have an adverse effect on the airplane or its 
occupants.
    While the FAA agrees with ANAC that both ``required'' and ``non-
required'' equipment and systems must be designed and installed so 
their operation does not have an adverse effect on the airplane or its 
occupants, the FAA finds it unnecessary to apply new Sec.  23.2500(b) 
to ``required'' equipment, because Sec.  23.2500(a) (proposed as Sec.  
23.1300(a)) already covers this requirement. Required equipment and 
systems that are designed and installed to meet the level of safety 
applicable to the certification and performance level of the airplane, 
in accordance with Sec.  23.2500(a)(1), and that perform their intended 
function, in accordance with Sec.  23.2500(a)(2), will not have an 
adverse effect on the airplane or its occupants. Furthermore, the FAA 
is intentionally making a distinction between ``required'' and ``non-
required'' equipment in Sec.  23.2500(a) and (b) because ``non-
required'' equipment and systems should not always be required to 
perform their intended function throughout the entire operating and 
environmental limits of the airplane.
    Air Tractor suggested the FAA compare former Sec.  23.1309 and 
proposed Sec.  23.1300(b). They noted the proposed rule may make it 
easier to certify non-required equipment; however, the proposed rule 
still seemed to require a Functional Hazard Assessment (FHA) and System 
Safety Assessment (SSA). Air Tractor suggested the FAA relieve the 
undue burden associated with the required system safety analysis for 
non-required equipment and systems.
    The FAA has determined some method of assessment is necessary to 
ensure that equipment and systems installed on an airplane meet an 
acceptable safety level. The safety assessment must show that a logical 
and acceptable inverse relationship exists between the average 
probability per flight hour and the severity of failure conditions 
effects. The depth and scope of the safety assessment will depend on 
the types of functions performed by the systems, the severity of 
failure conditions, and whether the system is complex. For simple and 
conventional systems with well-established designs, the safety 
assessment may be satisfied by a qualitative assessment such as the 
single-failure concept and experience based on service-proven designs 
and engineering judgment. Former guidance for complex systems relied on 
industry standards such as ARP 4761, ``Guidelines and Methods for 
conducting the Safety Assessment Process on Civil Airborne Systems and 
Equipment,'' and ARP 4754A, ``Guidelines for Development of Civil 
Aircraft and Systems,'' as well as AC 23.1309-1E, to define an 
acceptable means of compliance. As explained in the NPRM, former part 
23 and associated guidance may be used as one means of compliance with 
the new part 23. Alternatively, applicants may rely on industry 
consensus standards, or develop their own methods of compliance 
appropriate to the various airworthiness certification levels.
    Garmin stated it was unclear what the phrase ``or failure does not 
have an adverse affect'' in proposed Sec.  23.1300(b) means and that 
failures would be covered under proposed Sec.  23.1315. Garmin implied 
that proposed Sec.  23.1300(b) was redundant with proposed Sec.  
23.1315, which already addressed the failure of a non-required system 
as it would have provided the basis for assessing the implications of 
any failure for installed equipment. The commenter requested that the 
FAA delete ``or failure'' from the proposed rule.
    The FAA agrees with Garmin and deletes the words ``or failure'' 
from the proposed rule language. Section 23.2510 (proposed as Sec.  
23.1315) addresses failure conditions of all equipment. Therefore, 
proposed Sec. Sec.  23.1300 and 23.1315 would have been redundant by 
requiring the same showing of compliance. Additionally, the phrase 
``failure does not have an adverse effect on the airplane or its 
occupants'' could have been misinterpreted as requiring the failure to 
have no effect on the airplane. For example, if the equipment was 
installed to provide a benefit, although not required, it could have 
been wrongly interpreted that the failure of that benefit would have an 
``adverse effect'' on the airplane.
c. Function and Installation (Proposed Sec.  23.1305/Now Sec.  23.2505)
    In the NPRM, proposed Sec.  23.1305 (now Sec.  23.2505) would have 
required each item of installed equipment to

[[Page 96649]]

perform its intended function, be installed according to limitations 
specified for that equipment, and the equipment be labeled, if 
applicable, as to its identification, function, or operation 
limitations, or any combination of these factors. Proposed Sec.  
23.1305 would have required a discernable means of providing system 
operating parameters required to operate the airplane, including 
warnings, cautions, and normal indications to the responsible flight 
crewmember. Proposed Sec.  23.1305 would have also required information 
concerning an unsafe operating condition be provided in a clear and 
timely manner to the crewmember responsible for taking corrective 
action.
    In light of comments received, the FAA revises proposed Sec.  
23.1305 to withdraw paragraph (a)(2), merge paragraph (a) and (a)(1) 
into new paragraph (a), and relocate paragraphs (a)(3) through (c) to 
new Sec.  23.2605 in subpart G. This section discusses these changes in 
more detail.
    The Associations, Textron, and ANAC commented on proposed Sec.  
23.1305(a)(1). Textron commented that proposed Sec.  23.1305(a) appears 
to be redundant with proposed Sec.  23.1300(a) and asked the FAA to 
clarify whether proposed Sec.  23.1305(a)(1) would apply to the non-
required equipment addressed in proposed Sec.  23.1300(b).
    ANAC recommended that the FAA remove proposed Sec.  23.1305(a)(1) 
because the requirement is adequately addressed in Sec.  23.1300(a)(2) 
for required equipment. ANAC explained that proposed Sec.  
23.1305(a)(1) would contradict the requirement for non-required 
equipment in proposed Sec.  23.1300(b). The Associations, noted that 
one of the reasons for distinguishing ``required'' and ``non-required'' 
equipment in proposed Sec.  23.1300 was to alleviate the issues with 
requiring non-required equipment to prove their intended function. The 
commenters contended the rule should only require non-required 
equipment and systems (which are not required for safe flight) to 
verify their operation or failure does not interfere with required 
equipment. The commenters recommended confining the proposed 
requirement of Sec.  23.1305(a) to ``required'' systems and equipment.
    The FAA considered the comments to proposed Sec.  23.1305(a)(1) and 
recognizes the confusion between Sec. Sec.  23.1300 (now Sec.  25.2500) 
and 23.1305. The FAA notes Sec.  23.2505 applies to both required and 
non-required equipment. All equipment, when installed, should function 
as intended to maintain a minimum level of safety. The requirement of 
Sec.  23.2505 is not addressed by Sec.  23.2500(a)(2) as Sec.  23.2505 
applies to both required and non-required equipment when the equipment 
is installed on the airplane. Section 23.2500(a)(2) applies only to 
required equipment in operation. The FAA finds Sec.  23.2505(a) does 
not contradict the requirement of Sec.  23.2500(b), which applies to 
non-required equipment during airplane operations once in service. As 
explained in the NPRM, Sec.  23.2500(b) would not require non-required 
equipment and systems to function properly during all airplane 
operations once in service, provided all potential failure conditions 
do not affect safe operation of the airplane. However, the non-required 
equipment or system would have to function in the manner expected by 
the manufacturer's operating manual for the equipment or system when 
installed. To clarify the FAA's intent and better harmonize with EASA, 
the FAA is merging proposed paragraph (a) with (a)(1) to revise Sec.  
23.2505 to require each item of equipment, when installed, to function 
as intended.
    The Associations also maintained that proposed Sec.  23.1305(a)(2) 
and (3) were unnecessary because installed equipment needs to operate 
safely despite any markings.\50\ The commenters recommended the FAA not 
adopt paragraphs (a)(2) and (a)(3). Alternatively, EASA recommended 
moving the pilot interface issues of proposed Sec.  23.1305(a)(3) 
through (c) to subpart G, which covers flightcrew interface. Textron 
recommended the FAA move the labeling requirement to proposed Sec.  
23.1300(a)(3). Transport Canada recommended clarifying proposed Sec.  
23.1305(a)(3) to provide the criteria to determine the applicability of 
the labeling requirement.
---------------------------------------------------------------------------

    \50\ The commenters actually stated they believe proposed Sec.  
23.1305(a)(1) and (2) were unnecessary. However, based on the rest 
of their comments and the recommendation to delete paragraphs (a)(2) 
and(a)(3) (and retain (a)(1)), the FAA assumes the commenters meant 
to state that Sec.  23.1305(a)(2) and (3) are unnecessary.
---------------------------------------------------------------------------

    The FAA withdraws proposed Sec.  23.1305(a)(2) as it is redundant 
of paragraph (a)(1). In order to function as intended, the equipment 
would have to meet its limitations. As previously noted, the FAA has 
revised proposed Sec.  23.1305 by merging paragraph (a) with (a)(1). 
The FAA agrees with EASA's recommendation to move certain flightcrew 
interface requirements to subpart G and is relocating the requirement 
of proposed Sec.  23.1305(a)(3) to subpart G, Sec.  23.2605(a) in this 
rule. The commenters are correct that while a system needs to operate 
safely despite any markings, markings related to identification, 
function, and limitations are necessary to aid the aircrew and other 
personnel to safely operate the systems. The requirement for equipment 
to be labeled, if applicable, dates back to CAR 3.652 effective 
December 7, 1949. If further criteria to determine the applicability of 
the labeling requirement are found to be necessary, additional guidance 
will be developed either by the FAA or in an industry consensus 
standard.
    After further analysis, the FAA finds the proposed requirements to 
provide system operating parameters, including warnings and cautions, 
were not adequately covered in proposed subpart G. Based on this and 
EASA's comments, the FAA relocates the pilot interface requirements of 
proposed Sec.  23.1305(b) and (c) to new Sec.  23.2605 in subpart G to 
adequately address these issues.
    Garmin, Textron, and ANAC commented on the second sentence of 
proposed Sec.  23.1305(c). Garmin recommended the FAA delete the phrase 
``presentation of'', as it could be interpreted as requiring a light or 
other visual alert. Textron recommended the FAA replace the phrase 
``clear enough to avoid likely crewmember errors'' with the phrase 
``designed to minimize crewmember errors.'' ANAC contended the term 
``likely'' is ambiguous and recommended the FAA replace the phrase ``to 
avoid likely crewmember errors'' with the phrase ``to minimize 
crewmember errors, which could create additional hazards.''
    The FAA agrees with the commenters as the FAA did not intend to 
limit the presentation to visual displays only. Warning information can 
include visual, aural, tactile, or any combination. The FAA deletes 
``presentation of'' in the proposed Sec.  23.1305(c). Although both 
``minimize'' and ``likely'' may be ambiguous, as was the concern from 
ANAC, the term ``minimize''--associated with the mitigation of hazards 
in the rule language--can be traced back to CAR 3, effective December 
7, 1949. Although using a new term such as ``likely'' may be 
interpreted as a new requirement or standard for the minimization of 
errors, this was not the FAA's intent. Therefore, the FAA replaces the 
term ``minimize flightcrew errors'' in place of ``avoid likely 
crewmember errors'' in Sec.  23.2600(b).
    Embraer noted that the cross-reference table in the proposal stated 
that the intent of former Sec.  23.1023 is addressed in proposed Sec.  
23.935(b)(1); however, there is no Sec.  23.935(b)(1) in the proposed 
rule. To address this mistake, Embraer suggested including a similar

[[Page 96650]]

requirement from former Sec.  23.1023 in proposed Sec.  23.1305, which 
would apply to any equipment. Specifically, Embraer recommended an 
addition to proposed Sec.  23.1305(a)(4) stating equipment be able to 
withstand without failure, the vibration, inertia and loads (including 
fluid pressure loads) to which it would be subjected in operation.
    Embraer stated that it understood that part 33 would not address 
all the concerns if the radiator is installed by the airframer, and 
noted that its same comment applies to former Sec. Sec.  23.1013 and 
23.1015.
    The FAA has corrected and updated the table to accurately reference 
the relationship between the former rule and the final rule. Also, the 
FAA does not adopt Embraer's recommendation to add a requirement to 
Sec.  23.2505 to address specific environmental conditions equipment 
must be able to withstand. The FAA notes Embraer was describing a 
specific failure mode, which is covered by Sec. Sec.  23.2500(a)(2) and 
23.2510.
d. Flight, Navigation, and Powerplant Instruments (Proposed Sec.  
23.1310/Now Sec.  23.2615)
    In the NPRM, proposed Sec.  23.1310 (now Sec.  23.2615) would have 
required installed systems to provide the flightcrew member who sets or 
monitors flight parameters for the flight, navigation, and powerplant 
information necessary to do so during each phase of flight. Proposed 
Sec.  23.1310 would have required this information include parameters 
and trends, as needed for normal, abnormal, and emergency operation, 
and limitations, unless an applicant showed the limitation would not be 
exceeded in all intended operations. Proposed Sec.  23.1310 would have 
prohibited indication systems that integrate the display of flight or 
powerplant parameters to operate the airplane or are required by the 
operating rules of this chapter, from inhibiting the primary display of 
flight or powerplant parameters needed by any flightcrew member in any 
normal mode of operation. Proposed Sec.  23.1310 would have required 
these indication systems be designed and installed so information 
essential for continued safe flight and landing would be available to 
the flightcrew in a timely manner after any single failure or probable 
combination of failures.
    In light of comments received, the FAA renumbers Sec.  23.1310 to 
Sec.  23.2615, and moves this section to Subpart G. The section for 
Sec.  23.2615 in Subpart G discusses these changes in more detail.
e. Equipment, Systems, and Installation (Proposed Sec.  23.1315/Now 
Sec.  23.2510)
    In the NPRM, proposed Sec.  23.1315 (now Sec.  23.2510) would have 
required an applicant--
     To examine the design and installation of airplane systems 
and equipment, separately and in relation to other airplane systems and 
equipment, for any airplane system or equipment whose failure or 
abnormal operation was not specifically addressed by another 
requirement in this part;
     To determine if a failure of these systems and equipment 
would prevent continued safe flight and landing, and if any other 
failure would significantly reduce the capability of the airplane or 
the ability of the flightcrew to cope with adverse operating 
conditions; and
     To design and install these systems and equipment, 
examined separately and in relation to other airplane systems and 
equipment, such that each catastrophic failure condition is extremely 
improbable, each hazardous failure condition is extremely remote, and 
each major failure condition was remote.
    In light of comments received, the FAA revises proposed Sec.  
23.1315 (now Sec.  23.2510) by withdrawing paragraph (a), merging 
paragraph (b) into the introductory sentence, and renaming paragraphs 
(b)(1), (b)(2) and (b)(3) as Sec.  23.2510(a), (b) and (c), 
respectively. This section discusses these changes in more detail.
    Garmin commented that proposed Sec.  23.1315 should be located with 
the other general rules applicable to all systems and equipment.
    The FAA agrees with Garmin's comment and is placing the regulation 
with the other general rules at the beginning of subpart F.
    Textron commented the intent of proposed Sec.  23.1315 is not as 
clearly written as CS 23.600 and 23.605 and an AC will be needed to 
determine the meaning of the proposed rule. The commenter recommended 
using the wording of CS 23.600 and 23.605. In contrast, The 
Associations preferred the FAA's proposed Sec.  23.1315 to the EASA's 
A-NPA language, which they stated may unduly tie means of compliance to 
an objective-based rule. EASA suggested that proposed Sec.  23.1315 
show the inverse relationship between probability and severity in an 
illustration.
    To clarify the intent of the rule, the FAA revises the proposed 
rule language to require each system and equipment to be designed and 
installed such that ``there is a logical and acceptable inverse 
relationship between the average probability and the severity of 
failure condition.'' This change is consistent with the NPRM, which 
explained that proposed Sec.  23.1315 (now Sec.  23.2510) would require 
an engineering safety analysis to identify possible failures, 
interactions, and consequences, and require an inverse relationship 
between the probability of failures and the severity of consequences. 
The logical inverse relationship should be proportionate and flexible 
with respect to risk levels. The FAA notes that if the FAA provided 
more detail and graphics in the rule, future interpretation of the rule 
may be more restrictive than intended. The FAA finds the additional 
information provided in EASA's A-NPA is more suitable for guidance 
similar to AC 23.1309-1E and is not adding this to the rule.
    The Associations recommended the FAA add a new paragraph to 
proposed Sec.  23.1315 that would allow the FAA to accept a higher 
failure probability for functionality that enhances the safety of the 
airplane beyond the required minimum functionality. The commenters 
noted such a provision would allow for safety-enhanced equipment to be 
treated in a less stringent manner that accounts for the significant 
benefits it could have. The commenters explained this would ensure the 
lowest cost of this equipment without sacrificing the safety-enhancing 
benefits. Garmin similarly noted that system safety analysis and design 
assurance are focused on system and equipment failures rather than the 
safety benefit such systems and equipment can provide. For example, 
TSO-C151, ``Terrain Awareness and Warning System (TAWS),'' equipment 
specifies a major failure classification, but no credit is given for 
the offsetting safety benefit provided for installation of TAWS with 
its corresponding reduction in Controlled Flight into Terrain (CFIT) 
accidents. Garmin asked the FAA to consider adopting a requirement that 
allows for design assurance certitude for systems that provide an 
increased safety benefit.
    The FAA has determined adding a new requirement to proposed Sec.  
23.1315 (now Sec.  23.2510) would create a special class of equipment 
in the rule, which is contrary to the FAA's intent. The objective of 
this rulemaking is to provide clear safety objectives without 
prescribing design solutions. The objective of proposed Sec.  23.1315 
is to require each system and equipment to be designed and installed 
such that there is a logical and acceptable inverse relationship 
between the average probability and the severity of failure conditions. 
This applies to all

[[Page 96651]]

equipment whether required or non-required, safety-enhancing or not. 
The rule does not specify a required numeric probability of failure. 
The rule is written to allow a proportionate and flexible numerical 
value to the probabilities regarding risk levels of the equipment and 
airplane. System safety assessment standards will be relied on to 
provide a suitable approach for the different risk levels, similar to 
what is currently found in AC 23.1309-1E for the various classes of 
airplanes. Section 23.2510 provides a proportionate and flexible 
structure for future technology implementation.
    Garmin and the Associations recommended the FAA use the term 
``failure condition'' rather than ``failure'' to ensure the rule 
addresses the broader impacts of failures, rather than just those that 
occur within the equipment that may have failed. Garmin explained that 
by using ``failure condition,'' the rule would address combinations of 
failures in the system and equipment and other systems and equipment. 
ANAC stated the use of ``failure'' in paragraph (a) and use of 
``failure condition'' in paragraph (b) may add confusion.
    The FAA agrees with the commenters and revises proposed Sec.  
23.1315 (now Sec.  23.2510) to use ``failure condition'' throughout the 
section.
    Textron noted some simple systems were exempt from former Sec.  
23.1309. Textron asked if there was a list of systems exempt from 
proposed Sec.  23.1315 (now Sec.  23.2510), or if the FAA intended to 
apply the regulation to all systems. Textron specifically asked for 
confirmation that propulsion, fuel systems, fire protection systems, 
exits, landing gear, flight navigation, powerplant instruments, system 
power generation, storage, and distribution and flight controls were 
exempt from proposed Sec.  23.1315 (now Sec.  23.2510), since they each 
have their own rules dealing with failures.
    This final rule does not contain a list of systems exempt from 
proposed Sec.  23.2510 (proposed as Sec.  23.1315). Consistent with 
former Sec.  23.1309, proposed Sec.  23.1315 (now Sec.  23.2510) 
applies generally to installed equipment and systems, except that Sec.  
23.2510 does not apply if another section of part 23 imposes 
requirements for specific equipment or systems. The FAA is not 
providing a list of systems exempt from the rule, as Textron requested, 
because such a list would be based on today's technology and would be 
overly prescriptive and inflexible over time. This would conflict with 
the goal of allowing coverage for future unforeseen technological 
advancements.
    Textron asked the FAA to clarify the intent of the safety 
requirements in proposed Sec.  23.1315. In particular, Textron noted 
that paragraph (a) simply stated ``determine'', while paragraph (b) 
stated ``design and install'' to achieve safety goals that have no 
connection with those stated in paragraph (a). Textron asked for 
clarification of the relationship between the two paragraphs, as well 
as the overall intent of the rule. Textron recommended using the 
language in CS 23.605(a), which would have required each equipment and 
system to be designed and installed so there is a logical and 
acceptable inverse relationship between the average probability and the 
severity of failure condition effects. ANAC similarly noted that no 
clear safety objective was stated in proposed Sec.  23.1315(a); rather, 
an applicant needed only determine if conditions (1) and (2) were 
examined. Embraer suggested the FAA remove proposed Sec.  23.1315(a), 
asserting that the intent of proposed Sec.  23.1315(b) would be 
sufficient to meet compliance.
    EASA asserted the terminology in proposed Sec.  23.1315(a) may be 
confusing. Phrases such as ``continued safe flight and landing'' and 
``significantly reduce the capacity of the airplane'' or ``the ability 
of the flightcrew to cope with adverse operating conditions,'' are not 
as clear as terms ``catastrophic,'' ``hazardous,'' and ``major'' in 
describing the failure condition.
    In light of these comments, the FAA withdraws proposed paragraph 
(a). Proposed Sec.  23.1315(a) could have been interpreted as an 
element of the means of compliance to paragraph (b) in that the 
determinations of the potential consequences of failures is necessary 
to establish whether the probability of their occurrence is acceptable. 
Additionally, the FAA adopts Textron's recommendation and revises the 
proposed rule language to require each system and equipment to be 
designed and installed so there is a logical and acceptable inverse 
relationship between the average probability and the severity of 
failure condition effects. To comply with Sec.  23.2510(a), applicants 
must account for airplane systems and equipment, separately and in 
relation to other airplane systems and equipment.
    Textron indicated that the terms used in proposed Sec.  23.1315(b) 
were not defined in the regulations.
    The FAA did not define the terms ``catastrophic failure 
condition,'' ``hazardous failure condition,'' and ``major failure 
condition'' in the regulations because the terms are better addressed 
in guidance. These terms are currently defined in AC 23.1309-1E. 
Furthermore, the rule language is consistent with the historical rule 
language of former Sec.  23.1309.\51\
---------------------------------------------------------------------------

    \51\ See 55 FR 43306, October 26, 1990.
---------------------------------------------------------------------------

    ANAC commented that proposed Sec.  23.1315(b) implied specific 
classification and probability terms that may be considered 
prescriptive. The commenter noted that, as written, this may prevent an 
applicant from using a means of compliance that employs different 
hazard categories or terminology.
    The FAA notes the terms used in proposed Sec.  23.1315 (now Sec.  
23.2510) are already defined in guidance (i.e., AC 23.1309-1E) and 
originated from former Sec.  23.1309, and should not prevent an 
applicant from using a means of compliance that employs different 
hazard categories or terminology. The FAA may accept a means of 
compliance standard that uses different hazard categories or 
terminology, if they align with the failure condition effects in 
paragraphs (a) through (c) so the requirements of proposed Sec.  
23.1315 (now Sec.  23.2510) are met.
    Rockwell Collins noted that former Sec.  23.1309(c)(1) required 
each catastrophic failure condition to be extremely improbable and not 
result from a single failure. However, proposed Sec.  23.1315(b)(1), 
which was intended to capture the safety intent of former Sec.  
23.1309, would have required only that each catastrophic failure 
condition be extremely improbable. It would not have prohibited single-
point catastrophic failures. Rockwell Collins asked the FAA to retain 
the phrase ``and not result from a single failure'' in the regulation, 
because the commenter believed the FAA's intent was not to propose 
changes with regard to single-point catastrophic failures.
    The FAA notes the ARC recommended the FAA require systems and 
equipment to be designed and installed so there is a logical acceptable 
inverse relationship between the average probability and the severity 
of failure condition effects whether the result of a single failure or 
multiple failures. With the advancement of technology and increased 
integration of systems, it is virtually impossible to eliminate all 
theoretical potential single-points of failure. The rule will allow in 
some cases, as is true today with some portions of the airplane, to 
have the potential of single-point failures if the risk and probability 
of such failure is acceptable. The FAA adopts the rule language as 
proposed in Sec.  23.1315(b)(1).
    Noting that key pieces of FAA guidance are critical to design and 
certification, Kestrel asked whether AC

[[Page 96652]]

23.1309 would remain the primary guidance for SSA. If not, Kestrel 
asked what the recommended guidance would be.
    Guidance for proposed Sec.  23.1315 may consist of existing FAA 
guidance, such as AC 23.1309, future FAA-generated guidance, and FAA-
accepted industry standards.
    Textron noted the NPRM stated applicants who use the means of 
compliance described in the existing special conditions would be able 
to use data developed for compliance with proposed Sec.  23.1315. 
Textron recommended the FAA revise the statement to clarify the FAA was 
referring to special conditions for part 25 airplanes.
    The statement in the NPRM is correct. Applicants who use the means 
of compliance described in the existing special conditions for parts 
23, 25, 27, or 29 may use data developed for compliance with Sec.  
23.2510.
f. Electrical and Electronic System Lightning Protection (Proposed 
Sec.  23.1320/Now Sec.  23.2515)
    In the NPRM, proposed Sec.  23.1320(a) would have required, for an 
airplane approved for IFR operations, that each electrical or 
electronic system that performs a function, the failure of which would 
prevent the continued safe flight and landing of the airplane, be 
designed and installed such that--
     The airplane system level function continues to perform 
during and after the time the airplane is exposed to lightning; and
     The system automatically recovers normal operation of that 
function in a timely manner after the airplane is exposed to lightning, 
unless the system's recovery conflicts with other operational or 
functional requirements of the system.
    Proposed Sec.  23.1320(b) would have required each electrical and 
electronic system that performed a function, the failure of which would 
reduce the capability of the airplane or the ability of the flightcrew 
to respond to an adverse operation condition, to be designed and 
installed such that the function recovers normal operation in a timely 
manner after the airplane is exposed to lightning.
    Several commenters raised concerns with the term ``system'' in 
proposed Sec.  23.1320(a)(1). BendixKing explained that the proposed 
phrase ``airplane system level function'' may lead to multiple 
interpretations of the regulation. BendixKing asked the FAA to delete 
``system'' from the proposed rule language because the rule addresses 
failure at the airplane level. The Associations recommended the FAA 
require the function, rather than the airplane system level function, 
to comply with the requirement in paragraph (a)(1).
    Garmin stated that there has been much discussion in the GAMA HIRF 
(High-Intensity Radiated Fields) ad-hoc meetings regarding the 
interpretation of the term ``system.'' Garmin explained the rule 
language could be interpreted as requiring all redundant systems, which 
perform the same function, to meet the lightning requirements. Garmin 
explained that not all redundant systems should be required to meet the 
catastrophic requirements to prevent potentially catastrophic failure; 
proposed Sec.  23.1320(a) should apply to the function level only. 
Garmin recommended alternative regulatory language would prevent 
catastrophic, major, or hazardous failure conditions at the airplane 
level.
    The FAA agrees proposed Sec.  23.1320(a)(1) (now Sec.  
23.2515(a)(1)) could have been misinterpreted due to the confusion 
surrounding the phrase ``airplane system level function.'' The FAA 
intended to require the function at the airplane level to meet the 
requirements of paragraph (a)(1), consistent with proposed Sec.  
23.1325(a)(1) (now Sec.  23.2520). Thus, the FAA intended proposed 
Sec.  23.1320(a)(1) to require the function at the airplane level not 
to be adversely affected during and after the time the airplane is 
exposed to lightning. This means if multiple systems perform the same 
function, only one of those systems is required to provide the function 
under Sec.  23.2515(a)(1). Therefore, not all redundant systems are 
required to meet the requirements of Sec.  23.2515(a)(1). The FAA 
deletes the term ``system'' from the phrase ``airplane system level 
function,'' as several commenters recommended to ensure the FAA's 
intent is clear. The FAA revises the rule language to make clear that 
the requirements of proposed Sec.  23.1320(a)(1) (now Sec.  
23.2515(a)(1)) apply to the function at the airplane level.
    Garmin noted that the proposed Sec.  23.1320 rule language was 
essentially the same as former Sec.  23.1306, which was overly 
burdensome for low-end part 23 airplanes. Garmin stated that proposed 
Sec.  23.1320 is contrary to the goal of the part 23 reorganization and 
explained the objective should be to prevent catastrophic, hazardous, 
and major failure conditions for the airplane. Garmin suggested 
revising proposed Sec.  23.1320 to be more general and to allow the 
ASTM standards to provide the necessary means of compliance, which 
should consist of a tiered compliance approach for different airplane 
certification levels.
    The FAA does not agree to make Sec.  23.2515 more general. Section 
23.2515 is intended to address catastrophic, hazardous, and major 
failure condition at the airplane level due to the effects of lightning 
on systems. Critical functions that would prevent continued safe flight 
and landing (catastrophic) should remain available to the crew 
throughout a lightning exposure. How to maintain the function, whether 
with redundant systems or non-susceptible systems, is a means of 
compliance and is not specified. Likewise, systems that perform a 
function, the failure of which would significantly reduce the 
capability of the airplane (hazardous), must recover normal operation 
of that function. A means of compliance is not specified and could 
include redundancy. The FAA has revised the rule to state more clearly 
that the concern for catastrophic failure conditions is at the airplane 
level. Furthermore, the rule already allows a tiered compliance 
approach based on the environment the airplane is likely to see.
    Several commenters raised concerns with applying proposed Sec.  
23.1320 to airplanes approved for IFR operations. The Associations 
noted the FAA has recently approved required equipment for use in IFR 
airplanes, without the need for lightning testing based on the history 
of lightning strikes in the general aviation fleet. However, these 
commenters indicated the proposed rule would have prohibited airplanes 
with a low probability of lightning strikes from benefiting from such 
an approach. These commenters asked the FAA to revise the proposed rule 
language to ensure the rule does not apply to airplanes with a low 
probability of lightning strike.
    Garmin noted that former Sec.  23.1306 required both VFR and IFR 
airplanes to meet lightning requirements for systems with catastrophic 
failure conditions. However, while proposed Sec.  23.1320 would have 
removed the requirement for VFR airplanes, the burden for industry is 
primarily IFR airplanes as there are very few VFR airplanes, if any, 
that have systems with catastrophic failure conditions. Garmin 
recommended revising the proposed rule language by removing the 
language that would have made proposed Sec.  23.1320 applicable to 
airplanes approved for IFR operations.
    EASA also asked the FAA to remove the language that would have made 
proposed Sec.  23.1320 applicable to airplanes approved for IFR 
operations. EASA explained that this revision

[[Page 96653]]

would permit credit for reliable systems that allow for avoidance of 
thunderstorms, as these systems would make exposure to lightning 
unlikely.
    In light of these comments, the FAA recognizes the proposed rule 
language would not have adequately relieved the burden of former Sec.  
23.1306, which required all airplanes regardless of their design or 
operational limitations meet the same requirements for lightning 
regardless of the potential threat. As explained in the NPRM, the FAA 
intended to relieve this burden by applying the lightning requirements 
to airplanes with the greatest threat of lightning. The FAA proposed to 
meet this objective by making the rule applicable to airplanes approved 
for IFR operations. Because airplanes approved for IFR operations may 
also have a low probability of lightning exposure, the proposed rule 
language did not meet the FAA's objective. Accordingly, the FAA adds an 
exception to the rule language for applicants who can show that 
exposure to lightning is unlikely. This change from what was proposed 
is more consistent with the FAA's intent as it relieves an airplane 
approved for IFR operations from complying with Sec.  23.2515 if it is 
shown the airplane has a low probability of lighting exposure. The 
method of compliance is not specified in the rule and could be system, 
operational, or environment based.
    Garmin and the Associations recommended the FAA revise proposed 
Sec.  23.1320(b) to make the requirement only applicable to levels 3 
and 4 airplanes approved for IFR operations.
    The FAA disagrees. Section 23.2520(b) is a general safety objective 
with compliance tailored to the specific design intent. Exposure to 
lightning is an environmental threat not directly associated with 
airplane certification levels and therefore could apply to all 
airplanes. The intent is to set requirements appropriately to the 
design. Therefore, the FAA adds an exception to the rule language for 
applicants who can show that exposure to lightning is unlikely.
    Daher, Textron, and the Associations suggested the FAA, in proposed 
Sec.  23.1320(a)(1) (now Sec.  23.2515(a)(1)), require the function to 
not be ``adversely affected'' during and after the time the airplane is 
exposed to lightning, but require the function to ``continue to 
perform.'' Daher and Textron explained that requiring the function to 
not be ``adversely affected'' would be more consistent with the 
language of proposed Sec.  23.1325 (now Sec.  23.2520). The 
Associations asserted that this revision would permit equipment 
installations that may be affected by lightning, provided the loss of 
equipment does not result in catastrophic events. Textron further noted 
this revision would ensure harmony with EASA's proposed CS 23.620.
    In response to these comments, the FAA revises the proposed rule 
language to require the function at the airplane level to not be 
``adversely affected'' during and after the time the airplane is 
exposed to lighting. As explained in the NPRM, the FAA intended 
proposed Sec.  23.1320(a)(1) (now Sec.  23.2515(a)(1)) to capture the 
safety intent of former Sec.  23.1306. Former Sec.  23.1306(a)(1) 
required the function to not be ``adversely affected'' during and after 
the time the airplane is exposed to lightning. Because the proposed 
language could be interpreted as an increase in burden, which would not 
meet the intent of former Sec.  23.1306, the FAA is reverting back to 
the former rule language. It should be noted that ``adversely 
affected'' was not previously limited to catastrophic events as 
suggested by the commenters, but included hazardous and major failure 
conditions as well.
    Textron questioned if crew action could be involved in the recovery 
of the function or must recovery be automatic. Textron asked the FAA to 
clarify whether proposed Sec.  23.1320(a)(2) would permit crew action 
in recovery of the function. Garmin recommended the FAA not adopt 
proposed Sec.  23.1320(a)(2).
    Based on Textron's comment, the FAA clarifies paragraph (a)(2) by 
removing the term ``automatic'' from the proposed rule to allow either 
flightcrew action or automatic recovery. One of the goals of the 
proposal was to remove prescriptive design solution for the 
airworthiness standards and replace them with performance-based rules. 
Automatic reset of a system is a design solution, while the safety 
objective is the function be usable to the flightcrew in a timely 
manner such that the intermittent loss or malfunction does not have an 
adverse effect on the safety of the flight. Therefore, the recovery of 
the function may be automatic or manual. While Garmin recommended that 
the FAA not adopt proposed Sec.  23.1320(b) (now Sec.  23.2515(b)), the 
FAA believes the safety intent of former Sec.  23.1306, which addressed 
catastrophic and hazardous failure condition due to the effects of 
lightning on systems, must be retained.
    Transport Canada noted that proposed Sec.  23.1320(a)(2) would 
benefit from inclusion of a specific safety objective. The commenter 
suggested revising the proposed rule language to require the system to 
automatically recover normal operation of the function in such time as 
to allow a safety objective to be achieved.
    The FAA notes the safety objective of paragraph (a)(2) is ``the 
timely recovery of the system's function.'' Additionally, the rule 
language existed in former Sec.  23.1306(a)(2). Based on this, the FAA 
does not adopt the change proposed by Transport Canada in the final 
rule.
    Textron requested the FAA insert ``significantly'' before 
``reduce'' in proposed Sec.  23.1320(b), because any reduction in 
capacity would trigger this rule.
    The FAA agrees with Textron and revises the language in proposed 
Sec.  23.1320(b) (now Sec.  23.2515(b)) accordingly. This change is 
consistent with former Sec.  23.1306, which used the phrase 
``significantly reduce.'' Also, this change is necessary because 
without the term ``significantly'', the language could be interpreted 
as imposing requirements on each electrical and electronic system that 
performs a function, the failure of which would reduce--no matter how 
minimal--the capability of the airplane or the ability of the 
flightcrew to respond to an adverse operating condition. This would 
increase the burden from former part 23, which was not the FAA's 
intent.
g. High-Intensity Radiated Fields (HIRF) Protection (Proposed Sec.  
23.1325/Now Sec.  23.2520)
    In the NPRM, proposed Sec.  23.1325 (now Sec.  23.2520) would have 
required electrical and electronic systems that perform a function 
whose failure would prevent the continued safe flight and landing of 
the airplane, to be designed and installed such that--the airplane 
system level function is not adversely affected during and after the 
time the airplane is exposed to the HIRF environment. Proposed Sec.  
23.1325 would have also required these systems automatically recover 
normal operation of that function in a timely manner after the airplane 
is exposed to the HIRF environment, unless the system's recovery 
conflicts with other operational or functional requirements of the 
system.
    For airplanes approved for IFR operations, proposed Sec.  
23.1325(b) would have required the applicant to design and install each 
electrical and electronic system that performs a function--the failure 
of which would reduce the capability of the airplane or the ability to 
the flightcrew to respond to an adverse operating condition--so the 
function recovers normal operation in a timely manner after the 
airplane is exposed to the HIRF environment.

[[Page 96654]]

    Several commenters raised concerns about the term ``system'' in 
proposed Sec.  23.1325(a)(1). Textron stated the phrase ``airplane 
system level'' \52\ could be interpreted to mean that if multiple 
systems provide a redundant function, each system needs to work through 
the threat although only one is required. Textron asked the FAA to 
clarify if proposed Sec.  23.1325(a)(1) was intended to require a means 
to provide the airplane level function for continued safe flight and 
landing. BendixKing similarly commented that the failure being 
addressed in proposed Sec.  23.1325(a)(1) is at the airplane level, but 
the proposed phrase ``airplane system level function'' would lead to 
multiple interpretations of the regulation. Textron and BendixKing 
suggested deleting the term ``system'' from proposed Sec.  
23.1325(a)(1) to clarify the requirement applies to the airplane level.
---------------------------------------------------------------------------

    \52\ Safety requirements exist at the airplane, system, and item 
level. SAE International, ARP 475A Guidelines for Development of 
Civil Aircraft Systems, 4.1.3 Introduction to Hierarchical Safety 
Requirements Generated from Safety Analyses (2010).
---------------------------------------------------------------------------

    Garmin noted there has been much discussion in the GAMA HIRF ad-hoc 
meetings regarding the definition of a ``system.'' Garmin asked the FAA 
whether ``system'' means each individual redundant system or all 
redundant systems. Garmin explained that proposed Sec.  23.1325(a)(2) 
could be interpreted to impose additional requirements to the extent 
that all redundant systems must meet the catastrophic failure 
requirements of paragraph (a). Garmin suggested that not all redundant 
systems should be required to meet the catastrophic requirements and 
proposed Sec.  23.1325(a) should apply only to the function level. 
Garmin recommended alternative regulatory language that reflected its 
comments.
    The FAA agrees that proposed Sec.  23.1325(a)(1) (now Sec.  
23.2520(a)(1)) could be misinterpreted due to the confusion surrounding 
the phrase ``airplane system level function.'' As explained in the 
NPRM, the FAA intended the proposed rule language to clarify the 
failure consequence of interest is at the airplane level. Thus, the FAA 
intended paragraph (a)(1) to require the function at the airplane level 
not to be adversely affected during and after the time the airplane is 
exposed to the HIRF environment. This means if multiple systems perform 
the same function, only one of those systems is required to provide the 
function under paragraph (a)(1). Therefore, in response to Garmin's 
comment, the FAA notes not all redundant systems are required to meet 
the requirements of paragraph (a)(1). To clearly reflect the intent of 
proposed Sec.  23.1325(a)(1) (now Sec.  23.2520(a)(1)), the FAA deletes 
the term ``system'' from the phrase ``airplane system level function,'' 
as recommended by Textron and BendixKing, and revises the proposed rule 
language to clarify that the requirements of paragraph (a)(1) apply to 
the function at the airplane level.
    Furthermore, in light of Garmin's comment, the FAA revises the 
proposed rule language in Sec.  23.1325(a) (now Sec.  23.2520(a)) to 
clarify that ``each'' electric and electronic system that performs a 
function--the failure of which would prevent the continued safe flight 
and landing of the airplane--must be designed and installed such that 
the requirements of Sec.  23.2520(a)(1) and Sec.  23.2520(a)(2) of this 
section are met.
    Garmin recommended the FAA delete proposed Sec.  23.1325(a)(2) and 
explained that proposed Sec.  23.1325(a)(2) is unnecessary because 
proposed Sec.  23.1325(a)(1) already prohibits systems from preventing 
safe flight and landing after a HIRF event. The commenter maintained 
paragraph (a)(1) would be sufficient to ensure a tiered means of 
compliance could be developed based on the criticality of the HIRF 
event. Garmin stated that proposed Sec.  23.1325(a)(2) contains design 
information, which is contrary to the goal of the part 23 
reorganization, and explained the objective should be to prevent 
catastrophic, hazardous, and major failure conditions for the airplane. 
Garmin suggested revising proposed Sec.  23.1325 to be more general and 
allow the ASTM standards to provide the necessary means of compliance.
    The FAA disagrees with the commenter's recommendation to delete 
proposed Sec.  23.1325(a)(2) and to make paragraph (a) more general. 
The FAA agrees with a tiered means of compliance approach for hazardous 
and major failure conditions, which are addressed in Sec.  23.2520(b). 
However, for catastrophic failure conditions addressed in Sec.  
23.2520(a), the FAA finds it necessary to require each system that 
performs a function, the failure of which would prevent the continued 
safe flight and landing of the airplane, to be able to recover normal 
operation of the function. Paragraph Sec.  23.2520(a)(2) is not design 
specific; it captures the safety intent of former Sec.  23.1308(a) at a 
high level, allowing for means of compliance other than appendix J to 
part 23--``HIRF Environments and Equipment HIRF Test Levels''.
    Textron asked the FAA to clarify whether proposed Sec.  
23.1325(a)(2) would permit flightcrew action in recovery of the 
function.
    The FAA is removing the term ``automatically'' from the proposed 
rule language to clarify that flightcrew action is permitted in 
recovering the normal operation of the system's function. The FAA 
intended proposed Sec.  23.1325 to capture the safety intent of former 
Sec.  23.1308, which required the system to ``automatically'' recover 
normal operation of the function in a timely manner. Automatic reset of 
a system is a design solution. The safety objective of former Sec.  
23.1308(a) is that the function be usable to the flightcrew in a timely 
manner such that the intermittent loss or malfunction does not have an 
adverse effect on the safety of the flight. The FAA finds that 
permitting the flightcrew to manually recover normal operation of the 
system's function in a timely manner would maintain the level of safety 
found in former Sec.  23.1308(a). Therefore, the recovery of the 
function may be automatic or manual under Sec.  23.2520(a)(2).
    The Associations commented that current policy and guidance may 
apply HIRF requirements differently to part 23 products than in other 
areas and suggested that the IFR discriminator in paragraph (b) may not 
be as valid as using airworthiness level. The commenters recommended 
the FAA restrict paragraph (b) to level 3 and 4 airplanes that are 
approved for IFR operations.
    Mooney International (Mooney) questioned the intent of including 
IFR-related HIRF requirements in paragraph (b). Mooney contended that 
HIRF is related to environments from ground-based transmission of RF 
energy from radars, radios, etc., which is unrelated to IFR 
environmental operations.
    The FAA has considered the comments on inconsistent application of 
HIRF requirements, but notes the hazardous and major failure conditions 
of paragraph (b) should apply to airplanes certificated for IFR 
operations regardless of airworthiness level. The different types of 
operations an airplane may be certificated for are Day VFR, Night VFR, 
and IFR. Airplanes certified for only VFR operations are restricted 
from operating under IFR, which includes flight into IMC. IFR-certified 
airplanes, however, are not prohibited from flight into IMC. The 
severity of a HIRF event is greater in IMC. Therefore, the FAA finds it 
necessary to apply the hazardous and major failure conditions to all 
airplanes certified for IFR operations. Furthermore, while the FAA is 
not restricting the application of paragraph (b) to only level 3 and 4 
airplanes, paragraph (b) allows for a

[[Page 96655]]

tiered means of compliance approach based on airworthiness level and 
the associated risk. The FAA replaced the prescriptive requirements, 
which were further defined in former appendix J to part 23, with the 
wording ``exposed to the HIRF environment.'' The intent is to allow for 
the exposure environment to match the risk associated with each 
airplane level. Therefore, the threat will be appropriately scaled to 
the airworthiness level as the data and risk supports.
    Garmin suggested revising the proposed rule language of paragraph 
(b) to require each electrical and electronic system to be designed and 
installed, rather than requiring the applicant to design and install 
each system.
    The FAA adopts Garmin's recommendation, which makes the language of 
paragraph (b) parallel the language of paragraph (a).
    Embraer suggested the FAA adopt the same HIRF environments and test 
levels that are described in former appendix J to part 23, which were 
associated with former Sec.  23.1308.
    The FAA finds the prescriptive environments and test levels found 
in former appendix J to part 23 are more appropriately addressed as a 
means of compliance to proposed Sec.  23.1325 (now Sec.  23.2520). This 
allows the test levels to change as the environment changes without new 
regulatory action. Additionally, one prescriptive level for all 
airplanes does not allow for a tiered compliance approach, which was an 
objective of this rule.
h. System Power Generation, Storage, and Distribution (Proposed Sec.  
23.1330/Now Sec.  23.2525)
    In the NPRM, proposed Sec.  23.1330 (now Sec.  23.2525) would have 
required the power generation, storage, and distribution for any system 
be designed and installed to supply the power required for operation of 
connected loads during all likely operating conditions. Proposed Sec.  
23.1330 would have required the design installation ensure no single 
failure or malfunction would prevent the system from supplying the 
essential loads required for continued safe flight and landing. 
Finally, proposed Sec.  23.1330 would have required the design and 
installation have enough capacity to supply essential loads, should the 
primary power source fail, (for at least 30 minutes for airplanes 
certificated with a maximum altitude of 25,000 feet or less and at 
least 60 minutes for airplanes certificated with a maximum altitude 
over 25,000 feet.
    Textron requested the FAA make slight revisions to proposed Sec.  
23.1330(a) to harmonize the wording with CS 23.630. Specifically, 
Textron recommended requiring the power generation, storage, and 
distribution for any system be designed and installed to supply the 
power required for operation of connected loads during all intended 
operating conditions rather than ``all likely operating conditions'' 
because it would provide a clear boundary for demonstration of 
compliance. In the alternative, Textron suggested removing proposed 
paragraph (a) because the requirement is already covered more broadly 
in proposed Sec.  23.1300(a)(2).
    The FAA agrees with Textron's recommendation to replace ``likely'' 
with ``intended'' to harmonize with EASA and make clear the boundary 
for demonstration of compliance. Therefore, the FAA did not consider 
Textron's alternative recommendation to remove paragraph (a). The FAA 
notes that proposed Sec.  23.1330(a) (now Sec.  23.2525) is not 
redundant with proposed Sec.  23.1300(a)(2) (now Sec.  23.2500). 
Section 23.2500 is a rule of general applicability and does not 
supersede more specific rules. It is appropriate for system power 
generation, storage, and distribution to be addressed by a specific 
rule.
    Air Tractor noted that proposed Sec.  23.1330(b) appears more 
restrictive than former Sec.  23.1310 in regards to single-point 
failures. The commenter further noted this may require there be no 
single failure points between the power supply and the essential load 
bus.
    The FAA did not intend for proposed Sec.  23.1330(b) (now Sec.  
23.2525(b)) to be more restrictive than the requirements under former 
part 23. The FAA revises proposed Sec.  23.1330(b) for clarity by 
adding ``of any one power supply, distribution system, or other 
utilization system.'' This sets limits as to what needs to be 
considered when examining single-point failures.
    Several commenters, including EASA, Kestrel, Daher, and the 
Associations raised concerns about the minimum flight times (i.e., 30 
minutes and 60 minutes) set forth in proposed Sec.  23.1330(c). The 
commenters generally focused on allowing the means of compliance to 
define the appropriate minimum flight times and basing the minimum 
flight times on airplane performance. Daher suggested that ASTM 
standards should provide minimum flight times for battery systems. The 
Associations raised concerns the requirement in proposed Sec.  
23.1330(c)(1) may be excessive for airplanes with a maximum ceiling 
much lower than 25,000 feet. The Associations requested the FAA provide 
a reasonable window of essential power required for these lower flying 
airplanes for which electrical power will be controlled in a very 
reliable but efficient manner due to the nature of their design. 
Similarly, BendixKing noted that 25,000 feet and 30 minutes capacity 
requirement to supply essential loads may be restrictive to newer 
``simple'' airplanes, which operate only at 10,000 feet and require 
only 10-15 minutes. Garmin noted the wording of the proposed rule would 
require some new electrical-powered airplanes, which may have flight 
durations of less than 30 or 60 minutes, to carry the power supply 
regardless.
    In response to numerous comments opposing the specific flights 
times outlined in proposed Sec.  23.1330(c)(1) and (c)(2) (now Sec.  
23.2525(c)), the FAA agrees the language would have been overly 
prescriptive and incompatible with new technologies. The FAA revises 
proposed Sec.  23.1330(c) to remove the specific time requirements and 
add the safety intent requiring enough capacity for the time needed to 
complete the functions required for continued safe flight and landing.
    Kestrel questioned whether the language ``design and installation 
have enough capacity to supply essential loads'' permitted use of both 
the engine start battery and the emergency battery in combination to 
supply essential loads in the event of loss of the primary electrical 
power generating systems, without the need for an alternate means of 
compliance. The commenter noted this is typically addressed using an 
ELOS finding to former Sec.  23.1353(h).
    Kestrel also raised concerns about the possible misinterpretation 
of the phrase ``if the primary source fails'' in proposed Sec.  
23.1330(c). Kestrel said it was aware of at least one such instance, 
resulting in the issuance of an STC based on the understanding this 
meant failure of the primary generator and proper operation of the 
backup alternator. Kestrel asked FAA to revise the wording to prevent 
this possible misinterpretation.
    Both of Kestrel's comments relate to a specific design solution and 
method of compliance that should be addressed with the use of industry 
developed consensus standards or other accepted means of compliance. In 
the past, the engine start battery could be used to meet the required 
load capacity based on an ELOS finding (as pointed out be Kestrel). The 
requirements found in this ELOS finding to former Sec.  23.1353(h) 
could be documented in a consensus standard as an acceptable means of 
compliance to the regulation. The same applies to the definition of the 
``primary source.'' The intent is not to increase

[[Page 96656]]

design requirements, but to make showing of compliance more flexible.
    Textron requested the FAA limit the applicability of proposed Sec.  
23.1330(c) to electrical systems by changing the title proposed Sec.  
23.1330 to ``Electrical system power generation, storage, and 
distribution.''
    The FAA disagrees with Textron's proposal as the Part 23 ARC 
discussed this issue, with a consensus agreeing the rule should apply 
to current technologies such as batteries and new technologies that may 
apply in the future. The language proposed by the FAA would implement 
the ARC's recommendation, and the FAA makes no changes to that language 
in the final rule based on Textron's proposal.
i. External and Cockpit Lighting (Proposed Sec.  23.1335/Now Sec.  
23.2530)
    In the NPRM, proposed Sec.  23.1335 (now Sec.  23.2530) would have 
required an applicant to design and install all lights to prevent 
adverse effects on the performance of flightcrew duties. Proposed Sec.  
23.1335 would have required position and anti-collision lights, if 
installed, to have the intensities, flash rate, colors, fields of 
coverage, and other characteristics to provide sufficient time for 
another airplane to avoid a collision. Proposed Sec.  23.1335 would 
have required position lights, if installed, to include a red light on 
the left side of the airplane, a green light on the right side of the 
airplane, spaced laterally as far apart as practicable, and a white 
light facing aft, located on an aft portion of the airplane or on the 
wing tips. Proposed Sec.  23.1335 would have required that an applicant 
to design and install any taxi and landing lights, if required by 
operational rules, so they provide sufficient light for night 
operations. Finally, for seaplanes or amphibian airplanes, proposed 
Sec.  23.1335 would have required riding lights to provide a white 
light visible in clear atmospheric conditions.
    Textron commented on proposed Sec.  23.1335(a), explaining it would 
have been difficult to design and install lights to ``prevent adverse 
effects'' on the performance of flightcrew duties in all cases. 
Therefore, Textron recommended the FAA require lights to be installed 
to ``minimize,'' rather than ``prevent,'' the possibility they will 
adversely affect the satisfactory performance of the flightcrew's 
duties.\53\
---------------------------------------------------------------------------

    \53\ This wording was proposed in the ARC final report for Sec.  
23.1383.
---------------------------------------------------------------------------

    The FAA agrees the term ``prevent'' would be difficult to comply 
with in all cases. The FAA also interprets the term ``prevent'' to be 
more restrictive than the former requirements, which used descriptive 
terms such as ``no dangerous glare'' in former Sec.  23.1383(a) and 
``not seriously affected'' in former Sec.  23.1383(b). The term 
``minimize'' more accurately reflects the former requirements of part 
23. For these reasons, the FAA revises the proposed rule language to 
require the applicant to design and install all lights to minimize any 
adverse effects on the performance of flightcrew duties.
    Kestrel commented that the proposed wording, ``as far as space 
allows,'' in proposed Sec.  23.1335(c) could be interpreted to mean 
that integrated wingtip navigation lights are no longer permitted, and 
the only way to meet the requirement is to install external navigation 
lights outboard of the wingtips. Kestrel recommended reverting to the 
language used in former Sec.  23.1385, which stated that navigation 
lights should be ``spaced laterally as far apart as practicable.''
    The FAA agrees with the commenter. The FAA intended proposed Sec.  
23.1335(c) (now Sec.  23.2530(c)) to capture the safety intent of 
former Sec.  23.1385(c) without an increase in burden for 
certification. Former Sec.  23.1385(c) required the left and right 
position lights to consist of a red and a green light ``spaced 
laterally as far apart as practicable.'' The FAA is reverting back to 
this language for the reasons identified by the commenter. Accordingly, 
Sec.  23.2530(c) now requires any position lights, if required by part 
91, to include a red light on the left side of the airplane and a green 
light on the right side of the airplane, spaced laterally as far apart 
as practicable.
    Kestrel and Air Tractor commented on proposed Sec.  23.1335(d), 
which would have required the installation of taxi and landing lights. 
Kestrel asked the FAA to align proposed paragraph (d) with former Sec.  
23.1383, which did not require the installation of both taxi and 
landing lights, but instead required ``sufficient light for each phase 
of night operations.'' Air Tractor suggested the FAA add rule language 
to paragraph (d) to make it applicable to taxi and landing lights, ``if 
installed,'' because the regulations do not require night operations.
    The FAA did not intend to require the design and installation of 
taxi and landing lights in proposed Sec.  23.1335(d) (now Sec.  
23.2530(d)). As explained in the NPRM, the FAA intended proposed Sec.  
23.1335(d) to capture the safety intent of former Sec.  23.1383, which 
required each taxi and landing light to be designed and installed so 
that it provided enough light for night operations. The FAA revises the 
proposed rule language to more clearly reflect its intent. Accordingly, 
Sec.  23.2530(d) now requires any taxi and landing lights to be 
designed and installed so they provide sufficient light for night 
operations.
    The Associations and ICON recommended the FAA not adopt proposed 
Sec.  23.1335(e). The Associations noted that the requirement is 
already addressed in regulations concerning maritime vessels, and could 
create a conflict should those maritime regulations be changed. The 
Associations also noted that there is no safety benefit in duplicate 
coverage. ICON commented that the FAA proposed to add a requirement for 
a riding light on seaplanes. ICON stated that the operational 
requirement for a vehicle to display a white light on the water is not 
an FAA requirement and should not be mandated as a vehicle design 
requirement by the FAA. ICON recommended the FAA let the agency 
controlling the body of water impose this operating rule on seaplanes. 
ICON further noted it should not be a design requirement because a 
pilot may choose to comply with the requirement by using a portable 
light rather than an installed device on an airplane.
    The FAA considered the commenters recommendations but notes 
proposed Sec.  23.1335(e) (now Sec.  23.2530(e)) is not a new 
requirement. As explained in the NPRM, proposed Sec.  23.1335(e) 
captures the safety intent of former Sec.  23.1399. Former Sec.  
23.1399 required each riding (anchor) light required for a seaplane or 
amphibian, to be installed so it can show a white light for at least 
two miles at night under clear atmospheric conditions; and show the 
maximum unbroken light practicable when the airplane is moored or 
drifting on the water. Former Sec.  23.1399 was adopted on February 1, 
1965, as a recodification of CAR 3.704.\54\ The FAA's intent was to 
remove the prescriptive requirements of former Sec.  23.1399 to means 
of compliance and imposing the safety requirement as a performance-
based standard in paragraph (e). Therefore, the FAA adopts paragraph 
(e) as proposed.
---------------------------------------------------------------------------

    \54\ See 29 FR 17955 (1964).
---------------------------------------------------------------------------

    While the commenters did not cite a specific regulation concerning 
vessels, the FAA has determined the commenters are referring to Title 
33 of the CFR (33 CFR), Navigation and Navigable Waters. 33 CFR part 83 
contains rules applicable to all vessels upon the inland waters of the 
United States,\55\ and defines a vessel as including every description 
of water craft-- including seaplanes--used or

[[Page 96657]]

capable of being used as a means of transportation on the water.\56\ 
Thus, while a seaplane is anchored or afloat upon the inland waters of 
the United States, it is subject to part 83. Although Sec.  83.30 
contains light requirements for anchored vessels, the FAA finds it 
necessary to require seaplanes to have a riding light that provides a 
white light visible in clear atmospheric conditions. The objective of 
Sec.  83.30 is to ensure vessels see other vessels. The objective of 
Sec.  23.2530(e) is to ensure seaplanes are able to see other seaplanes 
in the interest of safety, not to provide duplicate coverage. There is 
no apparent conflict between part 83 and Sec.  23.2530(e), nor has 
there been a known conflict in the last fifty years. Furthermore, Sec.  
83.31 states that where it is impractical for a seaplane to exhibit 
lights and shapes of the characteristics or in the positions prescribed 
in subpart C of part 83, which contains Sec.  83.30, that seaplane 
shall exhibit lights and shapes as closely similar in characteristics 
and position as possible.
---------------------------------------------------------------------------

    \55\ See 33 CFR 83.01.
    \56\ See 33 CFR 83.03.
---------------------------------------------------------------------------

    Also, former Sec.  23.1399(b) stated that externally-hung lights 
may be used. While the FAA removed this prescriptive requirement from 
the regulations, it may still be used as an acceptable means of 
compliance to Sec.  23.2530(e).
    Finally, Embraer suggested the FAA adopt guidance material and 
standards, such as ACs and Agency Process Recommendations, as reference 
to the certification project, provided these documents are compatible 
with the former part 23 requirements.
    The FAA notes that current published guidance, previously accepted 
industry standards, and the prescriptive requirements found in former 
part 23 will remain acceptable means of compliance for this final rule. 
The FAA will continue to develop guidance as deemed necessary, but 
intends to use industry-developed standards if they are found 
acceptable. The FAA is actively engaged with industry consensus groups 
developing suitable standards for this final rule.
j. Safety Equipment (Proposed Sec.  23.1400/Now Sec.  23.2535)
    In the NPRM, proposed Sec.  23.1400 (now Sec.  23.2535) would have 
required safety and survival equipment, required by the operating rules 
of this chapter, to be reliable, readily accessible, easily 
identifiable, and clearly marked to identify its method of operation.
    Air Tractor noted that the requirement for safety and survival 
equipment to be reliable may require some kind of testing or 
certification of fire extinguishers. The commenter questioned whether 
the current Underwriter's Laboratory (UL) rating of fire extinguishers 
would be sufficient.
    The FAA finds the UL rating for fire extinguishers will be an 
acceptable means of compliance under Sec.  23.2535, as it was an 
acceptable method of compliance under former Sec.  23.1411. As 
explained in the NPRM, the FAA intended proposed Sec.  23.1400 (now 
Sec.  23.2535) to capture the safety intent of former Sec.  23.1411. 
While the FAA removed the prescriptive language from former Sec.  
23.1411, it did not intend to change the current method of compliance 
for the required safety and survival equipment.
k. Flight In Icing Conditions (Proposed Sec.  23.1405/Now Sec.  
23.2540)
    In the NPRM, proposed Sec.  23.1405 (now Sec.  23.2540) would have 
required an applicant to demonstrate its ice protection system would 
provide for safe operation, if certification for flight in icing 
conditions is requested.\57\ Proposed Sec.  23.1405 would have required 
these airplanes to be protected from stalling when the autopilot is 
operating in a vertical mode. Proposed Sec.  23.1405 would have also 
required this demonstration be conducted in atmospheric icing 
conditions specified in part 1 of appendix C to part 25 of this 
chapter, and any additional icing conditions for which certification is 
requested.
---------------------------------------------------------------------------

    \57\ Part 23 Icing ARC recommendations, including 
recommendations on activation and operation of ice protection 
systems, would have been used as a means of compliance to proposed 
Sec.  23.1405(a)(1).
---------------------------------------------------------------------------

    In light of comments received, the FAA revises Sec.  23.2540 to 
move proposed paragraphs (a) and (b) to the introductory paragraph, and 
renumber proposed paragraphs (a)(1) and (2) as new paragraphs (a) and 
(b). This section discusses these changes in more detail.
    The NTSB stated that adopting proposed Sec. Sec.  23.230 (now Sec.  
23.2165) and 23.1405 will likely result in Safety Recommendation A-96-
54 being classified ``Closed--Acceptable Action.'' The NTSB agreed with 
the FAA's statement in the NPRM that proposed Sec.  23.1405 would 
address Safety Recommendations A-07-14 and-15.
    The Associations suggested a better correlation between proposed 
Sec. Sec.  23.230 and 23.1405 and added it may be appropriate to 
combine these sections.
    In light of this comment, the FAA is restructuring proposed Sec.  
23.1405 to be consistent with Sec.  23.2165. Proposed Sec.  23.1405(a) 
and Sec.  23.1405(b) were combined into the introductory sentence of 
Sec.  23.2540 and modified to read similarly to Sec.  23.2165. 
Accordingly, Sec.  23.2540 now requires an applicant who requests 
certification for flight in icing conditions defined in part 1 of 
appendix C to part 25, or an applicant who requests certification for 
flight in these icing conditions and any additional atmospheric icing 
conditions, to show compliance with paragraphs (a) and (b) in the icing 
conditions for which certification is requested.\58\
---------------------------------------------------------------------------

    \58\ See section III, B. Part 23, Airworthiness Standards, 
Subpart B of this preamble (explaining the clarifying change made to 
proposed Sec.  23.230(a)).
---------------------------------------------------------------------------

    The FAA is not, however, combining proposed Sec. Sec.  23.230 and 
23.1405. The FAA agrees with the Part 23 Icing ARC's and the Part 23 
ARC's recommendations to separate the performance and flight 
characteristics requirements for flight in icing conditions from the 
system requirements for flight in icing conditions.\59\ The FAA notes 
Sec.  23.2165 contains the requirement to safely avoid or exit icing 
conditions for which certification is not requested, whereas Sec.  
23.2540 does not contain such a requirement for systems. The FAA finds 
it appropriate to keep these sections separate as the distinction 
between the sections means that systems, such as the windshield or air 
data, do not have to be evaluated in icing conditions for which the 
airplane is not requesting certification.
---------------------------------------------------------------------------

    \59\ See docket number FAA-2015-1621.
---------------------------------------------------------------------------

    Textron and Kestrel commented on ice crystal conditions. Textron 
noted that the proposed rule would not have defined ice crystal 
conditions and asked the FAA where the term would be defined. Kestrel 
asked if the requirements of TSO C16a, ``Electrically Heated Pitot and 
Pitot-Static Tubes'', would be an acceptable means of compliance to the 
ice crystal requirements of proposed Sec.  23.1405.
    The FAA notes the phrase ``any additional atmospheric icing 
conditions'' in proposed Sec.  23.1405 includes ``ice crystal 
conditions''. However, the FAA is not defining ``ice crystal 
conditions'' in the final rule because it is more appropriately 
addressed in means of compliance.
    The FAA finds TSO C16a will be an acceptable means of compliance 
when it is revised to include SAE airworthiness standard AS 5562, ``Ice 
and Rain Minimum Qualification Standards for Pitot and Pitot-static 
Probes''. The FAA notes SAE AS 5562 is an acceptable means of 
compliance to the ice crystal requirements for pitot and static 
systems. The FAA points out, however, that SAE AS 5562 does not include 
ice crystal requirements for certain angle-of-

[[Page 96658]]

attack instruments, such as sensors that utilize differential static 
pressure.
    Kestrel questioned if the FAA would permit ice protection systems 
to be operational on an airplane not certified for Flight Into Known 
Ice (FIKI), as it does today via the guidelines established in Appendix 
4 of AC 23.1419-2D for ``non-hazard'' systems. Kestrel noted that it 
was unclear whether the FAA intends to continue the use of the ``non-
hazard'' classification because the NPRM does not explicitly mention 
``non-hazard'' systems. Kestrel believed that operational ice 
protection systems on non-FIKI-certified airplane do not need a special 
``non-hazard'' classification. Kestrel suggested ice protections 
systems could be considered supplemental systems, which are addressed 
by the installation and inadvertent operation requirements of proposed 
Sec. Sec.  23.1300 and 23.1315.
    Prior to this final rule, the FAA certified ``non-hazard'' systems 
in accordance with former Sec. Sec.  23.1301 and 23.1309(a)(2), (b), 
(c), and (d). As explained in the NPRM, the FAA intended proposed 
Sec. Sec.  23.1300(b) (now Sec.  23.2500(b)), 23.1305 (now Sec.  
23.2505), and 23.1315 (now Sec.  23.2510) to capture the safety intent 
of the applicable portions of former Sec.  23.1301 and Sec.  23.1309. 
Therefore, the FAA intends to certify these ``non-hazard'' systems in 
accordance with Sec. Sec.  23.2500(b), 23.2505, and 23.2510.
    The FAA received several comments on proposed Sec.  23.1405(a)(2). 
Garmin stated that proposed Sec.  23.1405(a)(2) should apply regardless 
of whether an airplane is certified for flight in icing conditions. 
Garmin recommended the FAA either move the proposed requirement to 
proposed Sec.  23.215 (now Sec.  23.2150) or delete it.
    The FAA agrees that an airplane must be protected from stalling 
when the autopilot is operating, regardless of whether the airplane is 
certified for flight in icing conditions. However, proposed Sec.  
23.1405(a)(2) (now Sec.  23.2540(b)) should not apply to airplanes 
where the applicant is not requesting certification for flight in icing 
conditions. The stall warning requirements of Sec.  23.2150 will 
provide low-airspeed awareness, with or without the autopilot engaged, 
for new airplanes not certified for icing. The FAA finds Sec.  
23.2165(a) will provide stall warning for new airplanes where the 
applicant is requesting certification for flight in icing conditions. 
For new airplanes, the FAA acknowledges that a stall warning system 
that complies with Sec. Sec.  23.2150 and 23.2165(a) will comply with 
Sec.  23.2540(b). Section 23.2540(b) will also be added to the 
certification basis of certain STCs and amended TCs on icing certified 
airplanes, as discussed below in this section.
    Textron and Rockwell Collins commented on the prescriptiveness of 
proposed Sec.  23.1405(a)(2). Textron added that proposed Sec.  
23.1405(a)(2), which was in place only for changed product rule 
considerations, appeared to be a band-aid solution and not in line with 
higher-level goals for the new rules. Textron suggested the FAA delete 
proposed paragraph (a)(2).
    The FAA finds that proposed Sec.  23.1405(a)(2), with the exception 
of specifying ``vertical mode,'' is performance-based and consistent 
with the higher-level goals of the proposal, because the standard does 
not specify how to achieve protection from a stall. The FAA expects 
means of compliance to include the Icing ARC's recommendations. The FAA 
deletes the reference to ``vertical mode'' from Sec.  23.2540(b) to 
make it less prescriptive, since it is expected the icing means of 
compliance will recognize that only vertical modes may result in 
airspeed loss. The FAA renumbers this section as part of the final 
rule. Proposed Sec.  23.1405(a)(2) is now Sec.  23.2540(b).
    Additionally, in response to Textron's comment, proposed Sec.  
23.1405(a)(2) (now Sec.  23.2540(b)) is intended to increase the safety 
of the existing fleet. While Sec.  23.2540(a) and (b) apply to new 
airplanes, the FAA intends Sec.  23.2540(b) to specifically target 
older airplanes adding an autopilot for the first time, modifying 
certain autopilots on airplanes with a negative service history in 
icing, or making significant changes that affect performance or flight 
characteristics and affect the autopilot. As stated in the NPRM, under 
the changed product rule, Sec.  23.2540(b) will be added to the 
certification basis of these types of STCs and amended TCs for icing 
certified airplanes. This will result in a targeted increase in safety 
without requiring compliance to an entire later amendment, including 
Sec.  23.2540(a). Compliance with Sec.  23.2540(a) would require the 
applicant to address areas unaffected by an autopilot STC. The Part 23 
Icing ARC Report (Icing ARC Report) provides examples of modifications 
in which new Sec.  23.2540(b) will be applicable. Numerous icing 
accidents have shown that unrecognized airspeed loss can occur with 
autopilots in altitude hold or vertical speed modes. Means of 
compliance other than modifications to the airplanes' stall warning 
system may be acceptable under Sec.  23.2540(b) for these STCs and 
amended TCs. The Task 9, ``Determine if implementation of NTSB Safety 
Recommendation A-10-12 is feasible for part 23 airplanes for operations 
in icing conditions,'' discussion in the Icing ARC Report provides 
additional background.
    Rockwell Collins stated that proposed Sec.  23.1405(a)(2) could be 
interpreted as requiring the autopilot to protect the airplane from 
stalling.
    To address the commenter's concern, the FAA revises the proposed 
rule language (now Sec.  23.2540(b)) to clarify that the airplane 
design must provide protection from stalling when the autopilot is 
operating.
    The NTSB disagreed that proposed Sec.  23.1405(a)(2) would address 
Safety Recommendation A-10-12, which concerns low-airspeed alerting 
systems. The NTSB stated that this safety recommendation would be more 
appropriately addressed in proposed Sec.  23.1500, ``Flightcrew 
Interface.''
    The FAA notes, as explained in the NPRM, proposed Sec.  
23.1405(a)(2) was based on NTSB safety recommendation A-10-12. This 
implied proposed Sec.  23.1405(a)(2) responded to recommendation A-10-
12. The FAA acknowledges Sec.  23.2540(b) is not the type of stall 
protection the NTSB recommended because it does not require the 
installation of low-airspeed alert systems. Instead, Sec.  23.2540(b) 
addresses a different and more urgent safety problem by requiring 
airplanes with autopilots to provide an adequate stall warning in icing 
conditions. Furthermore, Sec.  23.2540(b) is an airworthiness standard 
that establishes a minimum level of safety for all airplanes under part 
23. If the FAA were to adopt a requirement in part 23 that required 
applicants to install a low-speed alert system in their airplanes, that 
requirement would apply to all airplanes. The FAA did not propose such 
a requirement because safety recommendation A-10-12 applies only to 
commercial airplanes under part 91 subpart K, and parts 121, and 135. 
To properly respond to NTSB safety recommendation A-10-12, the FAA 
would have to change the operating rules, which is outside the scope of 
this rulemaking.
    Embraer and Garmin both commented on the term ``demonstration.'' 
Embraer recommended the FAA change ``in atmospheric icing conditions'' 
in proposed paragraph (b) to ``considering atmospheric icing 
conditions''. Embraer stated that its proposal aimed to make a broad 
statement, implying that there may be several means of addressing the 
icing conditions as shown in figures 1 through 6 of Appendix C to Part 
25. The commenter asserted the original text in the NPRM might be 
understood as

[[Page 96659]]

requiring only a flight test demonstration. Garmin commented on the 
importance of clarifying this term because the FAA Aircraft 
Certification Office has almost always insisted that ``demonstration'' 
means the applicant must perform it on an airplane.
    In light of these comments, the FAA is using the phrase ``must 
show'' rather than ``must demonstrate'' in the introductory sentence of 
Sec.  23.2540, which is consistent with the changes made to Sec.  
23.2165. This change is also consistent with the NPRM, which explained 
that demonstration, as a means of compliance, may include design and/or 
analysis and does not mean flight tests are required. However, for the 
foreseeable future, the FAA does expect means of compliance to include 
icing flight tests for applicants seeking icing certification for new 
TCs.
l. Pressurized System Elements (Proposed Sec.  23.1410/Now Sec.  
23.2545)
    In the NPRM, proposed Sec.  23.1410(a), (c) and (d) (now Sec.  
23.2545) would have required the minimum burst pressure of--
     Hydraulic systems be at least 2.5 times the design 
operating pressure with the proof pressure at least 1.5 times the 
maximum operating pressure;
     Pressurization system elements be at least 2.0 times, and 
proof pressure be at least 1.5 times, the maximum normal operating 
pressure; and
     Pneumatic system elements be at least 3.0 times, and proof 
pressure be at least 1.5 times, the maximum normal operating pressure.

Proposed Sec.  23.1410(e) would have required that other pressurized 
system elements to have pressure margins that take into account system 
design and operating conditions. Additionally, proposed Sec.  
23.1410(b) would have required engine driven accessories essential to 
safe operation to be distributed among multiple engines, on multiengine 
airplanes.
    In light of comments received, the FAA withdraws proposed Sec.  
23.1410(a) through (e) and adopts new language for Sec.  23.2545. This 
section discusses these changes in more detail.
    Garmin commented that proposed Sec.  23.1410 was still extremely 
prescriptive and suggested the FAA revise the rule to a higher safety 
objective, and burst and proof pressures should be in a consensus 
standard. Garmin proposed alternative, less prescriptive language. ANAC 
similarly stated that parts of proposed Sec.  23.1410 were too 
prescriptive and suggested that it might be more appropriate to set the 
``minimum burst'' and ``proof pressure'' values for the hydraulic, 
pressurization, and pneumatic systems using consensus standards. ANAC 
also proposed alternative language.
    The FAA agrees with ANAC's recommendation to set the proof and 
burst factors for hydraulic, pneumatic and pressurization systems in 
consensus standards or means of compliance. This is consistent with the 
FAA's goal of moving from prescriptive regulations to performance-based 
regulations. The FAA did not use Garmin's suggested language because it 
did not clearly state that the requirement was for ``proof'' and 
``burst'' pressure, and would have applied to ``pressurized system 
elements''. This may be more limited than using the phrase 
``pressurized system''. ANAC's suggested language was also not used 
because it was not inclusive of all pressurized systems. Consensus 
standards or means of compliance can be used to document the 
appropriate proof and burst factors, the operating pressure to be 
factored, pass/fail criteria for tests, and other information included 
in former Sec.  23.1435(a)(4), (b), Sec.  23.1438, and AC 23-17C.
    Textron noted it is unclear what the difference is between the 
terminology used to describe the system pressures upon which the 
factors in proposed Sec.  23.1410(a), (c), (d), and (e) are applied 
(i.e., ``design operation pressure,'' ``maximum operating pressure,'' 
and ``maximum normal operating pressure.''). ANAC made a similar 
observation, as it noted the phrase ``maximum operating pressure'' in 
proposed Sec.  23.1410(a) and the phrase ``maximum normal operating 
pressure'' in proposed Sec.  23.1410(b) and (c) might share the same 
interpretation. ANAC recommended a harmonization between these 
paragraphs in order to avoid misinterpretations for the consensus 
standards, while Textron suggested that using the ASTM to identify 
those differences would be more in keeping with the move from 
prescriptive to performance-based standards. ANAC also recommended 
merging proposed Sec.  23.1410(a), (c), and (d).
    The FAA agrees with merging proposed Sec.  23.1410 (a), (c) and (d) 
because they are similar and related. In addition, the FAA has decided 
to merge proposed Sec.  23.1410(e) with these requirements to address 
all systems containing fluids under pressure. Therefore, the FAA 
withdraws proposed paragraphs (a), (c), (d), and (e) and adopts new 
language in Sec.  23.2545 that requires pressurized systems to 
withstand appropriate proof and burst pressures.
    ANAC, Textron, and an individual commenter addressed proposed Sec.  
23.1410(b). ANAC recommended the provision be deleted. In addition to 
being prescriptive, ANAC noted the provision is already addressed in 
proposed Sec.  23.1315, which evaluates in a more systematic way the 
design and installation of a system or component according to their 
failure condition that is directly related to the airplane safe 
operation. Additionally, Textron said the provision is misplaced and 
should be moved to proposed subpart E, Sec.  23.900 or Sec.  23.910 
(now Sec.  23.2410). An individual commenter also recommended moving 
the provision to Sec.  23.900.
    Based on the comments, the FAA has decided that the safety intent 
of this requirement is adequately addressed in Sec.  23.2510 and Sec.  
23.2410. Section 23.2510 requires equipment separation and redundancy 
based on the severity of equipment failures. Section 23.2410 requires 
powerplant failures, including engine driven accessory failures, to be 
considered and mitigated--effectively requiring safety critical engine 
driven accessories to be distributed on multiengine airplanes. 
Therefore, the FAA withdraws proposed Sec.  23.1410(b) from the final 
rule; hence, there is no reason to place it elsewhere.
m. Equipment Containing High-Energy Rotors (Sec.  23.2550)
    The requirements of former Sec.  23.1461 were not fully 
incorporated into proposed Sec.  23.755(a)(3), so the FAA creates a new 
Sec.  23.2550 to correct this omission. The preamble section for Sec.  
23.2320 discusses this change in more detail.
8. Subpart G--Flightcrew Interface and Other Information
a. General Discussion
    In the NPRM, the FAA proposed substantial changes to former subpart 
G based on its assessment that many of the regulations contained in 
this subpart contain prescriptive requirements that are more 
appropriate for inclusion as means of compliance to the new part 23 
performance-based regulations. The FAA noted this approach would 
provide at least the same level of safety as current prescriptive 
requirements while providing greater flexibility for future designs. 
The FAA also expanded the scope of the subpart to address flightcrew 
interface requirements.
    Zee agreed with the FAA's proposal to expand subpart G to address 
not only current operating limitations and information, but also 
flightcrew interface. Zee noted that, based on current technology, the 
FAA anticipates new airplanes will heavily rely on

[[Page 96660]]

automation and systems that require new and novel pilot or flightcrew 
interface methods and procedures. The commenter noted further that more 
automated systems could dramatically reduce cockpit workload, which 
would be a great boon for the public who has shied away from personal 
aviation transportation due to increasing operational complexities of 
traditional airplanes.
    EASA commented that information from various other subparts in 
proposed part 23 should be included in subpart G to provide 
requirements on how the information should be provided. EASA noted that 
proposed subpart G could include requirements for subjects such as 
flightcrew interface; function and installation, flight, navigation, 
powerplant instruments, cockpit controls, instrument markings, control 
markings and placards, airplane flight manual, and instructions for 
continued airworthiness. EASA also noted these subjects were under 
consideration by EASA for inclusion as separate sections in a future 
proposal to revise CS 23.
    The FAA finds its proposed actions respond to the concerns of Zee, 
EASA, and others within the industry to better address the issue of 
flightcrew interface. The FAA recognizes that flightcrew interface 
issues have become increasingly more important as a result of recent 
technological developments in flight, navigation, surveillance, and 
powerplant control systems. The FAA partially agrees with EASA's 
comment that information from various other subparts in proposed part 
23 should be included in subpart G. However, the FAA finds the full 
extent of the material EASA proposes for inclusion would establish 
requirements that would be too prescriptive in nature and therefore not 
in accord with the overall objective of this rulemaking to replace the 
detailed prescriptive requirements with more general performance-based 
standards. The FAA does, however, acknowledge that certain sections of 
EASA A-NPA 2015-06 and NPA 2016-05 may better address those 
requirements where the FAA's proposed language may have been too 
general in nature and not sufficiently detailed to permit adequate 
means of compliance to be developed. In a number of instances, the FAA 
has adopted either the specific regulatory language used by EASA or 
similar equivalent language to better address those safety concerns and 
achieve greater harmonization. The specific instances where the FAA has 
adopted these revisions are discussed in the preamble to the sections 
in which those changes have been made.
    The FAA notes that EASA proposed the inclusion of three sections in 
its revision of CS 23, subpart G, which added substantial detail to 
that subpart. The FAA did not include corresponding sections within its 
proposed subpart G. Proposed CS 23.2605, ``Installation and operation 
information'', and proposed CS 23.2610, ``Flight, navigation, and 
powerplant instruments'', however, did correspond to proposed Sec.  
23.1305 and proposed Sec.  23.1310, respectively, in subpart F of the 
NPRM. Proposed CS 23.2615, ``Cockpit controls,'' was also in EASA's 
proposed subpart G, but did not have a corresponding section in the 
NPRM.
    The FAA agrees that placing the requirements contained in these 
sections into subpart G is more appropriate than addressing those 
requirements in subpart F, as these requirements more directly relate 
to flightcrew interface issues. Accordingly, the FAA is relocating 
proposed Sec.  23.1305 to subpart G, Sec.  23.2605, ``Installation and 
operation,'' and proposed Sec.  23.1310 to Sec.  23.2615, ``Flight, 
navigation, and powerplant instruments.'' While adopting the general 
safety intent embodied in EASA's proposed regulations, the FAA is not 
including the complete level of detail specified in those regulations 
because the FAA considers the additional information more appropriate 
as a means of compliance. While the FAA believes that cockpit controls 
should be addressed under subpart G, the FAA did not include a separate 
section in the final rule equivalent to proposed CS 23.2615 because the 
FAA has determined these requirements are more appropriate as a means 
of compliance to Sec.  23.2600.
b. Flightcrew Interface (Proposed Sec.  23.1500/Now Sec.  23.2600)
    In the NPRM, proposed Sec.  23.1500 (now Sec.  23.2600) would have 
required the pilot compartment and its equipment to allow each pilot to 
perform their duties, including taxi, takeoff, climb, cruise, descent 
approach and landing. The pilot compartment and its equipment would 
also have to allow a pilot to perform any maneuvers within the 
operating envelope of the airplane, without excessive concentration, 
skill, alertness, or fatigue. Proposed Sec.  23.1500 would have 
required an applicant to install flight, navigation, surveillance, and 
powerplant controls and displays so qualified flightcrew could monitor 
and perform all tasks associated with the intended functions of systems 
and equipment so as to make the possibility that a flightcrew error 
could result in a catastrophic event highly unlikely.
    Textron noted that proposed Sec.  23.1500 has ``minimal wording'' 
as compared to CS 23.460 and recommended the FAA harmonize proposed 
Sec.  23.1500 with EASA's proposed provisions.
    Textron also specifically recommended the FAA add the requirement 
in former Sec.  23.671(b) for controls to be arranged and identified to 
provide convenience in operation and to prevent the possibility of 
confusion and subsequent inadvertent operation, to proposed Sec.  
23.1500.
    The FAA has reviewed EASA A-NPA 2014-12 and NPA 2016-05 and finds 
the level of detail included in the crew interface requirements in both 
documents may be overly restrictive. The FAA finds Sec.  23.2600 
adequately address pilot compartment requirements and the requirements 
for the provision of necessary information and indications to the 
flightcrew. The FAA is not revising Sec.  23.2600 as EASA recommended, 
because the FAA is concerned that adding the extensive level of detail 
that EASA is considering for inclusion in subpart G would neither 
enhance the FAA's ability to respond to the introduction of new 
technology nor foster future innovation. The FAA notes the adoption of 
the EASA's recommended requirements would only serve to create issues 
similar to those that the FAA is attempting to address with this 
significant revision of part 23 airworthiness standards. However, the 
FAA recognizes Textron's concerns and agrees that cockpit controls 
should not only be convenient to operate, but also prevent the 
possibility of confusion and subsequent inadvertent operation. 
Nevertheless, the FAA finds the regulatory intent of former Sec.  
23.671 will be achieved because Textron's concerns will be addressed in 
any means of compliance developed and submitted for acceptance to 
demonstrate compliance with Sec.  23.2600.
    Air Tractor raised concerns that proposed Sec.  23.1500(b) added a 
requirement that the flightcrew be able to monitor and perform ``all'' 
tasks associated with the intended functions of systems and equipment. 
Air Tractor recommended the FAA insert the term ``required'' after 
``all'' to ensure the proposal would not require the performance and 
monitoring of non-required tasks. An individual commenter at the FAA's 
public meeting also shared concerns regarding use of the term ``all'' 
and asked if its use would preclude systems from monitoring tasks the 
flightcrew does not have to continuously monitor.
    The FAA agrees that use of the term ``all'' is too encompassing in 
this section

[[Page 96661]]

and could be misinterpreted to impose requirements that would exceed 
the safety intent of the rule. However, the FAA finds adding the term 
``required'' would make the rule's requirements narrower than the FAA 
intended. The FAA notes that airplanes are currently equipped with 
systems and equipment that are not necessarily required, yet the 
flightcrew must be able have the ability to monitor and perform all 
tasks associated with the intended functions of those systems and 
equipment to operate the airplane safely. Accordingly, the FAA has 
determined that including the term ``defined'' in Sec.  23.2600(b) will 
address both the concerns of Air Tractor and the FAA, and also allow 
for the installation of systems and equipment that can be used to 
monitor a function or parameter for the flightcrew. The FAA notes this 
term is currently used in Sec.  25.1302(a), which addresses flightcrew 
interface with systems and equipment installed in transport category 
airplanes. While the FAA recognizes that many of the requirements in 
Sec.  25.1302 are inappropriate for the certification of airplanes 
under part 23, the FAA finds its use of the concept of ``defined 
tasks'' is appropriate for application to part 23 flightcrew interface 
requirements.
    An individual commenter asserted that proposed Sec.  23.1500(b) is 
``convoluted and subject to varying interpretations.'' The commenter 
noted that one such interpretation could be the flightcrew would not be 
required to monitor and perform tasks and prevent errors that go beyond 
the intended functions of the installed systems and equipment. 
Accordingly, the commenter asserted that if there is no equipment 
installed to prevent CFIT, such as TAWS, there would be no requirement 
for monitoring and performing tasks and preventing errors associated 
with terrain clearance. The commenter also stated the rule could be 
interpreted to mean the tasks, monitoring, and error prevention 
requirements are those associated with a particular flight phase and 
flight conditions. For example, the commenter noted that there must be 
equipment to prevent CFIT (e.g., TAWS or other), at least for IFR-
certified airplanes, and it must meet the stated requirements. The 
commenter noted that many situations and types of equipment could be 
affected by the proposal and maintained that if these interpretations 
were accurate, there would be obvious cost, weight, practicability, and 
other implications that were not adequately addressed in the preamble 
or Regulatory Analysis.
    In the NPRM, the FAA stated that it proposed to expand subpart G to 
address not only current operating limitations and information, but 
also the concept of flightcrew interface. The FAA further noted that it 
was proposing to address the pilot interface issues found in subparts D 
and F in proposed Sec.  23.1500. Otherwise, subpart G retained the 
safety intent of the requirements in the former rules. This section 
does not impose additional equipment requirements, as suggested by the 
commenter's example, but it does require consideration of the 
flightcrew interface and human factors in the design and installation 
of equipment. The FAA notes the commenter's concern that the flightcrew 
would not be required to monitor and perform tasks, such as terrain 
avoidance, that are not directly addressed by installed systems and 
equipment.
    Several commenters raised concerns regarding the use of the term 
``highly unlikely'' in proposed Sec.  23.1500(b) that addresses the 
ability of the system and equipment design to avoid the possibility 
that a flightcrew error could result in a catastrophic event. One 
individual commenter specifically noted that ``highly unlikely'' is a 
new and undefined term. The commenter recognized that prevention of 
errors undoubtedly would increase safety, but noted there is a limit to 
how much system and equipment design error prevention is justified and 
practicable in any airplane, not just those certificated under the 
provisions of part 23. This commenter also contended it would be 
difficult to comply with a stringent reading of ``highly unlikely'' and 
asserted a review of accident history would reveal this. Garmin, Air 
Tractor, and BendixKing submitted similar comments regarding the 
potential for this proposed requirement to increase the burden on 
applicants. Each of these commenters proposed alternative regulatory 
language addressing their concerns.
    The Associations commented that the intent of this proposed 
requirement is to prevent likely flightcrew errors with flight, 
navigation, surveillance, and powerplant controls and displays and 
proposed language to meet this intent. Textron also noted the proposed 
requirement failed to exclude skill related errors, errors as a result 
of malicious intent, recklessness, and actions taken under duress. 
Textron contended that system designs should not be responsible for all 
possible flightcrew errors, but only for reasonable errors. Textron 
recommended proposed alternative regulatory language addressing its 
concern.
    Astronautics said the term ``highly unlikely,'' as it relates to 
``catastrophic,'' would cause confusion in the context of failure 
condition categorization and likelihood of occurrence. The commenter 
suggested replacing the term ``highly unlikely'' with recognized terms 
that categorize failure hazards and probabilities. Astronautics also 
suggested recognizing a flightcrew error may have differing degrees of 
severity by revising the proposed rule to include consideration of the 
three different degrees of failure in proposed Sec.  23.1315(b).
    The FAA agrees with many of the commenters concerns regarding the 
use of the term ``highly unlikely'' in addressing the probability of 
preventing flightcrew errors resulting from system and equipment 
designs that could lead to catastrophic events. The FAA also recognizes 
the difficulty in assessing complex flightcrew interface issues 
associated with the approval of control and display designs. Prior to 
the adoption of this rule, the FAA utilized very prescriptive 
requirements with associated guidance material based on its need to 
address traditional controls, displays, and flight operations in the 
certification process. Although the FAA expects that this prescriptive 
language for the evaluation of traditional controls and displays will 
serve as a means of compliance with the new performance-based 
requirements, the FAA determines the new performance-based requirements 
will also allow for alternative approaches to meeting flightcrew 
interface requirements for non-traditional airplanes, operations, and 
non-traditional controls and displays.
    As the FAA noted in the NPRM preamble, the smart use of automation 
and phase-of-flight-based displays could reduce pilot workload and 
increase pilot awareness. Accordingly, the FAA finds new technology can 
help the pilot in numerous ways, all with the effect of reducing pilot 
workload, which should help reduce accidents based on pilot error. The 
FAA intended to remove many of the barriers to the introduction of new 
technology while still retaining a clear performance-based requirement 
to which an applicant could demonstrate compliance. The FAA recognizes 
the potential for misinterpretation of the requirements with this new 
approach; however, the FAA's intent is not to increase the requirements 
set forth in former regulations, unless specifically stated in the 
preamble. The FAA expects the use of performance-based requirements to 
address flightcrew interface issues will result in the accelerated 
development of industry standards that will be used to improve the 
manner in which pilots

[[Page 96662]]

interface not only with information that has been traditionally 
provided to them but also with new information. Section 23.2600 is not 
intended to add any burden on the applicant and is expected to reduce 
time to market for new system and equipment designs, thereby, resulting 
in reduced costs.
    As several commenters noted, the terms ``highly unlikely'' and 
``catastrophic'' have specific meanings with respect to the 
certification of systems that typically are not used when addressing 
human interactions. Based on the commenters' recommendations, the FAA 
finds the best approach to adequately address flightcrew interface 
issues is to revise Sec.  23.2600 using language similar to that 
contained in former Sec.  23.1309(d), which states that systems and 
controls must be designed to minimize crew errors which could create 
additional hazards. This avoids the problems associated with the use of 
language more appropriate for evaluation of system and equipment 
failures.
    Shortly after the close of the comment period, EASA published NPA 
2016-05, which proposed requirements to address an oversight in the 
NPRM regarding the pilot visibility requirements originally contained 
in subpart D. The FAA has adopted EASA's proposed language both in 
paragraphs (a) and (c) to correct this oversight in the FAA's proposal, 
to ensure that pilot compartment visibility requirements are addressed. 
Adopting these requirements serves to ensure that pilot view 
requirements, and particularly those requirements that could result 
from the loss of vision through a windshield panel in a level 4 
airplane, are addressed. The FAA finds that these revisions impose no 
requirements in excess of those specified in the former Sec.  23.775 
and will maintain the level of safety set forth in part 23, through 
amendment 23-62, as originally intended in the proposal. As discussed 
in the context of proposed Sec.  23.755, the requirement for level 4 
airplanes that the flightcrew interface design must allow for continued 
safe flight and landing after the loss of vision through any one of the 
windshield panels has been moved to Sec.  23.2600(c).
c. Installation and Operation (Proposed Sec.  23.1305/Now Sec.  
23.2605)
    In the NPRM, proposed Sec.  23.1305 (now Sec.  23.2605) would have 
required each item of installed equipment--
     To perform its intended function;
     Be installed according to limitations specified for that 
equipment; and
     The equipment be labeled, if applicable, due to the size, 
location, or lack of clarity as to its intended function, as to its 
identification, function, or operation limitations, or any combination 
of these factors.

Proposed Sec.  23.1305 would have required a discernable means of 
providing system operating parameters required to operate the airplane, 
including warnings, cautions, and normal indications to the responsible 
crewmember. Proposed Sec.  23.1305 would have also required information 
concerning an unsafe operating condition be provided in a clear and 
timely manner to the crewmember responsible for taking corrective 
action.
    In light of comments received, the FAA revises proposed Sec.  
23.1305 by moving paragraphs (a)(2) through (c) to new Sec.  23.2605. 
This section discusses these changes in more detail.
    The function and installation rule language in proposed Sec.  
23.1305 was originally located in subpart F, Equipment. The logic 
behind the location of these requirements was that requirements for the 
display and control of a specific function would be in subpart G, while 
requirements for the hardware or software for the display or control 
are would be in subpart F. For this reason, proposed Sec.  23.1305, 
``Function and installation,'' included specific paragraphs from the 
requirements of former Sec. Sec.  23.1301, 23.1303, 23.1305, 23.1309, 
23.1322, 23.1323, 23.1326, 23.1327, 23.1329, 23.1331, 23.1335, 23.1337, 
23.1351, 23.1353, 23.1357, 23.1361, 23.1365, 23.1367, and 23.1416.
    The Associations recommended the FAA delete proposed Sec.  
23.1305(a)(2) and (a)(3). The commenters also suggested the FAA delete 
proposed Sec.  23.1305(b), as the flightcrew interface portion of the 
proposed rules already addressed the same subject area. Furthermore, 
EASA recommended moving the flightcrew interface requirements from 
proposed Sec.  23.1305(a)(2) through (c) to subpart G.
    The FAA agrees with the commenters that the paragraphs in proposed 
Sec.  23.1305 that address display and control for the flightcrew is 
better located in subpart G. Upon closer review, the FAA agrees with 
EASA's recommendation as it is consistent with the FAA's intent behind 
moving requirements from subpart F to subpart G. As proposed, subpart G 
did not have any sections that directly address these specific 
paragraphs. For that reason, the FAA adds new Sec.  23.2605, 
``Installation and operation'', which contains the language from 
proposed Sec.  23.1305(a)(2) through (c).
d. Instrument Markings, Control Markings, and Placards (Proposed Sec.  
23.1505/Now Sec.  23.2610)
    In the NPRM, proposed Sec.  23.1505 (new Sec.  23.2610) would have 
required each airplane to display in a conspicuous manner any placard 
and instrument marking necessary for operation. Proposed Sec.  23.2610 
would also have required an applicant to clearly mark each cockpit 
control, other than primary flight controls, as to its function and 
method of operation and include instrument marking and placard 
information in the AFM.
    Astronautics agreed that an applicant should ensure markings are 
adequate and meet the marking requirements specified in 14 CFR 45.11, 
``Marking of products.'' However, they asserted that the requirement 
for applicants to mark the controls and instruments themselves, as 
required by proposed Sec.  23.1505(b), is ``overly broad.'' The 
proposed requirement fails to account for existing markings such as 
those required by Sec.  45.15, ``Marking requirements for PMA articles, 
TSO articles, and critical parts.'' Astronautics noted that some 
controls, such as knobs and push buttons, are typically integrated 
parts of TSO articles. The commenter believed that proposed Sec.  
23.1505 could be interpreted to require an applicant to add or replace 
markings on instruments already marked pursuant to a TSO authorization 
or PMA. Astronautics recommended the FAA revise proposed Sec.  23.1505 
to specify that an applicant is not required to alter markings already 
required under Sec.  45.15.
    The FAA agrees with Astronautics that the proposal is overly 
prescriptive as to how information regarding function and method of 
operation is to be provided. Accordingly, the FAA removes the 
requirement from proposed paragraph (b) specifically requiring an 
applicant to mark cockpit controls and instruments and revises the 
proposal to require the airplane design clearly indicate the function 
of each cockpit control (other than primary flight controls). This 
revision will permit an applicant to utilize markings made pursuant to 
a TSO authorization or PMA without imposing a repetitive and 
potentially conflicting requirement.
    BendixKing requested the FAA delete the phrase ``. . . and method 
of operation'' from proposed Sec.  23.1505(b). The commenter believed 
that the marking of cockpit controls should be limited to labeling the 
function of the control and that including its method of operation as a 
marking requirement is neither bounded nor appropriate.

[[Page 96663]]

    The FAA agrees in part with BendixKing's comment. The FAA concurs 
that application of the proposed requirement to all cockpit controls 
(other than primary flight controls) is overbroad and could lead to an 
applicant including information on cockpit control markings that is 
excessive, unnecessary, and contrary to the agency's original intent. 
Accordingly, the FAA revises proposed paragraph (b) to eliminate the 
proposed requirement that an applicant mark cockpit controls with their 
method of operation. However, cockpit controls (other than primary 
flight controls) would continue to be required to clearly indicate 
their function. As under the former regulations, information on the 
method of operation of equipment is provided in the airplane flight 
manual and equipment manuals, which is sufficient to satisfy the 
objective of the proposal.
    Textron requested the FAA be more specific as to what placards 
(i.e., emergency, passenger safety, or operational placards) need to be 
included in the AFM pursuant to proposed Sec.  23.1505(c).
    The FAA recognizes that information may be provided to pilots and 
passengers using a variety of methods and considers it unnecessary to 
specifically prescribe those placards that must be included in the AFM. 
Additionally, a requirement to include specific placards would be 
counter to this rule's intent to remove prescriptive requirements from 
current regulatory text and replace those provisions with performance-
based regulations. The FAA finds that variations in airplane designs 
and the methods of providing information to pilots and passengers may 
necessitate the need for various types of placard information that 
would be more appropriate for inclusion as a means of compliance to the 
regulatory requirements, thereby providing applicants with more 
flexibility in meeting the underlying safety intent of the rule.
e. Flight, Navigation, and Powerplant Instruments (Proposed Sec.  
23.1310/Now Sec.  23.2615)
    In the NPRM, proposed Sec.  23.1310 (now Sec.  23.2615) would have 
required installed systems to provide the flightcrew member who sets or 
monitors flight parameters for the flight, navigation, and powerplant 
information necessary to do so during each phase of flight. Proposed 
Sec.  [thinsp]23.1310 would have required this information include 
parameters and trends, as needed for normal, abnormal, and emergency 
operation, and limitations, unless an applicant showed the limitation 
would not be exceeded in all intended operations. Proposed Sec.  
[thinsp]23.1310 would have prohibited indication systems that integrate 
the display of flight or powerplant parameters to operate the airplane 
or are required by the operating rules of this chapter, from inhibiting 
the primary display of flight or powerplant parameters needed by any 
flightcrew member in any normal mode of operation. Proposed Sec.  
[thinsp]23.1310 would have required these indication systems be 
designed and installed so information essential for continued safe 
flight and landing would be available to the flightcrew in a timely 
manner after any single failure or probable combination of failures.
    Several commenters raised concerns with proposed Sec.  
23.1310(a)(1), which would have required installed systems to provide 
the flightcrew member with parameters and trends, as needed. Air 
Tractor questioned whether round gauge instruments produce a trend and 
whether the FAA would use paragraph (a)(1) to mandate electric gauges. 
Similarly, Garmin contended that proposed Sec.  23.1310(a)(1) could be 
interpreted as requiring more information than was formerly required. 
Garmin noted the pilot often determines the trend by monitoring a 
gauge, but the trend itself may not be displayed. Garmin asked the FAA 
to clarify whether it intended paragraph (a)(1) to require trend 
information to be displayed, or information to be presented in a manner 
that enables the pilot to monitor the parameter and determine trends. 
Genesys Aerosystems commented that requiring ``trends'' rather than 
addressing ``trends'' in guidance materials would lead to more trends 
being required than needed.
    The FAA did not intend proposed Sec.  23.1310(a)(1) to require 
electric gauges. Traditional analog indicators, such as airspeed 
indicators or altimeters, have been shown to provide adequate trend 
indications and will still be acceptable. It may also be possible to 
have a system that automatically monitors the parameter of interest and 
warns the pilot of any trend that could lead to a failure. Paragraph 
(a)(1), however, does not allow a light that comes on at the same time 
that the failure occurs to replace analog indicators because such a 
light does not provide trend information prior to a failure. A warning 
light system that would comply must be sophisticated enough to read 
transients and trends, and give a useful warning to the pilot of a 
potential condition.
    The FAA agrees the proposed rule language could have been 
misinterpreted as requiring more information than former part 23. The 
FAA intended proposed Sec.  23.1310 to capture the safety intent of the 
former requirements, which was to provide flightcrew members the 
ability to obtain the information necessary to operate the airplane 
safely in flight, but not to exceed the safety intent of former part 
23. Therefore, proposed Sec.  23.1310(a)(1) was intended to require 
installed systems to provide adequate information to the flightcrew 
member to determine trends by monitoring a gauge or display. The FAA 
did not intend to expressly require an installed system to display the 
trend itself, because not all systems display trends. The FAA revises 
the proposed rule language to clarify its intent. Accordingly, Sec.  
23.2615(a)(1) now requires the information to be presented in a manner 
that enables the flightcrew member to monitor parameters and determine 
trends, as needed, to operate the airplane.
    Former Sec.  23.1311(a)(6) required electronic display indicators 
to incorporate, as appropriate, trend information to the parameter 
being displayed to the pilot. Section 23.2615(a)(1) is not meant to be 
an increase in burden from the former requirement and associated 
guidance regarding when trends are needed.
    Kestrel raised concerns that although proposed Sec.  23.1310 is 
less prescriptive, it did not minimally require the pilot to have 
available airspeed, altitude, direction, and attitude indicators as 
former Sec.  23.1303 prescribed. The commenter asked if the FAA 
envisions a scenario where this information would not be required. 
Kestrel was also concerned that the phrase ``as needed'' would lead to 
diverging FAA interpretations of proposed Sec.  23.1310(a)(1). The 
commenter asked the FAA to clarify its intent regarding the requirement 
to provide parameters and trends ``as needed.'' If this was not a fixed 
set of parameters, Kestrel asked for details on how this list would be 
determined.
    As explained in the NPRM, the former regulations that required 
airspeed, altimeter, and magnetic direction were redundant with the 
operating rules, specifically Sec. Sec.  91.205 and 135.149. 
Furthermore, they required prescriptive design solutions that were 
assumed to achieve an acceptable level of safety. These prescriptive 
solutions precluded finding more effective or more economical paths to 
providing acceptable safety. One of the stated goals of the proposal 
was to facilitate the introduction of new technologies into small 
airplanes. Concepts already envisioned with fly-by-wire system may

[[Page 96664]]

render the instruments that were required by former Sec.  23.1303 
irrelevant in the future. New Sec.  23.2615 reflects the intent to 
allow new technologies in the future, while maintaining a minimum 
safety requirement by capturing the safety intent of the former 
regulations and by relying on the operating rules and accepted means of 
compliance to prescribe the details. This philosophy also applies to 
the comment on the phrase ``as needed.'' The accepted means of 
compliance, which may include industry consensus standards, will define 
which parameters need trends.
    Astronautics asked the FAA to insert a comma after ``as needed'' in 
paragraph (a)(1) to clarify that ``as needed'' is a parenthetical 
phrase. The FAA agrees and corrects the grammar in the revised rule 
language.
    ANAC suggested the FAA not adopt proposed Sec.  23.1310(a) because 
it is covered by proposed Sec.  23.1305(b) and (c), which are broader 
in scope. In light of the performance-based context of the proposed 
rule, ANAC reasoned that defining specific requirements only for 
flight, navigation, and powerplant instruments was unnecessary. ANAC 
also recommended the FAA not adopt proposed Sec.  23.1310(b), which 
appeared to apply to specific technologies (integrated systems). ANAC 
noted the intent of paragraph (b) was already addressed in proposed 
Sec.  23.1305(b) and (c) (requiring timely information), and proposed 
Sec.  23.1315 (now Sec.  25.2510, requiring the capacity to maintain 
continued safety flight and landing after single or probable failures).
    The FAA notes ANAC's comment on proposed Sec.  23.1310(a) and (b), 
but paragraphs (a) and (b) are not redundant. Sections 23.2505 and 
23.2510 apply generally to installed equipment and systems. However, 
Sec. Sec.  23.2505 and 23.2510 do not apply if another section of part 
23 imposes requirements for specific installed equipment or systems. 
The FAA finds that flight, navigation, and powerplant instrumentation 
are significant enough to warrant their own requirements. Therefore, 
the FAA adopts Sec.  23.1310 (nowSec.  23.2615(a) and (b)) as proposed.
    ANAC also raised concerns that the phrase ``normal, abnormal, and 
emergency operation'' in paragraph (a) may be interpreted as a required 
classification of types of operations, meaning a system safety type 
analysis may be required for each indicator, classification of each 
condition, and three separate indications for each condition, which it 
deemed overly prescriptive. As an alternative to deleting proposed 
Sec.  23.1310(a)(1), ANAC recommended the FAA revise paragraph (a)(1) 
to require parameters and trends, as needed, ``to operate the 
airplane.''
    The FAA agrees with ANAC and revises paragraph (a)(1) accordingly.
    Genesys Aerosystems commented on proposed Sec.  23.1310(b), which 
was formerly covered only in guidance material. Genesys Aerosystems 
contended that paragraph (b) is a bit prescriptive and including it in 
the regulation could stifle future innovation.
    The FAA notes Genesys Aerosystems concern, but this requirement was 
previously covered under former Sec.  23.1311. Section 23.2615(b) 
captures the safety intent of former Sec.  23.1311, but removes the 
prescriptive requirements of former Sec.  23.1311(a)(5), which mandated 
secondary instruments as the means to providing information to the 
flightcrew essential for continued safe flight and landing. This would 
allow future innovations in system architecture and design to provide 
the flight parameters necessary to maintain safe flight.
    EASA recommended moving the pilot interface issues of proposed 
Sec.  23.1310 to subpart G.
    The FAA agrees with this recommendation because flightcrew 
interface issues are more appropriately addressed in subpart G, which 
contains requirements on flightcrew interface and other information. 
Therefore, the FAA moves the entire proposed Sec.  23.1310 to subpart G 
as new Sec.  23.2615.
f. Airplane Flight Manual (Proposed Sec.  23.1510/Now Sec.  23.2620)
    In the NPRM, proposed Sec.  23.1510 (now Sec.  23.2620) would have 
required an applicant to furnish an AFM with each airplane that 
contained the operating limitations and procedures, performance 
information, loading information, and any other information necessary 
for the operation of the airplane.\60\
---------------------------------------------------------------------------

    \60\ The NPRM erroneously stated that proposed Sec.  23.1510 was 
intended to consolidate current Sec. Sec.  23.1505 through 23.1527. 
See 81 FR at 13495. However, Sec.  23.1510 was actually intended to 
consolidate the AFM provisions in former Sec. Sec.  23.1581 through 
23.1589.
---------------------------------------------------------------------------

    Garmin noted that the purpose of the AFM is to provide the pilot 
with basic information required to safely fly the airplane and stated 
it appreciates and supports the FAA's proposal to remove the 
prescriptive detail about the AFM content from Sec.  23.1510. However, 
Garmin did express concern about use of the phrases ``[o]perating 
limits and procedures'' in proposed Sec.  23.1510(a) and ``[a]ny other 
information necessary for the operation of the airplane'' in proposed 
Sec.  23.1510(d). Garmin noted the possibility for confusion arising 
from the ambiguity of the terms ``operating'' and ``operation'' in 
former Sec. Sec.  23.1581(a)(2), 23.1581(a)(3), 23.1583(k), and 
23.1585(j). For example, Garmin pointed out that many current FAA 20-
series ACs specify that equipment operation limitations should be 
included in an AFM.\61\ Garmin contended the AFM was never intended as 
a catch-all for equipment or airspace operating limitations and that 
equipment operating limitations are more appropriately included in the 
equipment's pilot guide or operating manual provided by the equipment 
manufacturer.
---------------------------------------------------------------------------

    \61\ As an example, the commenter noted that: AC 20-138D 
(including change 1 and 2) for positioning and navigation equipment 
includes 77 instances of ``AFM,'' AC 20-165B for ADS-B Out equipment 
includes 8 instances of ``AFM,'' AC 20-149B for non-required safety 
enhancing FIS-B equipment includes 7 instances of ``A/RFM,'' and 
even AC 20-153B for aeronautical database LOAs includes 2 paragraphs 
requiring specific AFM content. The commenter noted that these 
counts do not include instances of ``airplane flight manual'' or 
other similar phrases.
---------------------------------------------------------------------------

    Garmin also suggested using the terms ``operating'' and 
``operation'' in proposed Sec.  23.1510(a) and (d) could be easily 
confused with operating rule limitations (e.g., Sec.  91.225 for ADS-B 
Out) or system-wide operating limitations (e.g., the displayed age of 
FIS-B weather products), which are not necessary to safely fly the 
airplane and would be more appropriately captured in the Aeronautical 
Information Manual (AIM).
    Therefore, Garmin recommended proposed Sec.  23.1510(a) state: 
``Airplane operating limitations and procedures.'' The Associations 
recommended the same revision. Garmin also suggested revising the NPRM 
preamble to state that the AFM is not intended to be used as a catch-
all for equipment operating limitations, or to be used for operating 
rule limitations or system-wide operating limitations, all of which are 
more appropriately included in guides and manuals.
    The FAA agrees with Garmin in that the AFM was never intended as a 
catch-all for equipment or airspace operating limitations. The 
requirement for ``operating limitations and procedures'' in the 
proposed Sec.  23.1510(a) was intended to capture information required 
to be included in the AFM by former Sec. Sec.  23.1583 and 23.1585.
    The FAA did not intend to expand Sec.  23.2620(a) to encompass 
information that is not required to be included in the AFM by former 
Sec. Sec.  23.1583 and 23.1585. To further clarify its intent, the FAA

[[Page 96665]]

adopts the commenters' suggestion and amends Sec.  23.2620(a)(1) to 
specify that this section requires ``airplane'' operating limitations 
and procedures.
    Proposed Sec.  23.1510(a)(4) would have required that ``any other 
information necessary for the operation of the airplane'' must be 
included in the AFM. The FAA agrees with the commenters' concern that 
the proposed language was too broad and could be interpreted as 
requiring information that has not traditionally been included in the 
AFM. The intent of this proposed provision was to retain the 
requirement of former Sec.  23.1581(a)(2), which require the AFM to 
include other information that is necessary for safe operation because 
of design, operating, or handling characteristics.'' Because the 
proposed language was unclear, the final rule will simply codify, 
without change, the language of former Sec.  23.1581(a)(2) into Sec.  
23.2620(a)(4).
    Garmin noted that while it was not specifically covered in the NPRM 
preamble, it appreciated that proposed Sec.  23.2620 no longer appears 
to require FAA approval of certain information contained in the AFM as 
required by former Sec.  23.1581(b). Garmin said this would eliminate 
delays associated with seeking an Aircraft Certification Office 
engineer's approval of AFM content for the TC or STC process, typically 
a one-time occurrence; or Flight Standards District Office inspector's 
approval of AFM content for post-certification installations, which 
occur frequently. Garmin explained that these approval delays translate 
into loss of revenue for the applicants. Garmin recommended the 
preamble specifically indicate there is no intent to require FAA 
approval of AFM content during certification or for post-certification 
installation.
    NATCA asked the FAA to clarify the Airworthiness Limitations 
Sections (ALS), as well as portions of the AFM, requiring FAA approval. 
NATCA indicated this clarification was need as approval of ALS and AFM 
content are ``inherently governmental functions.'' NATCA noted that all 
other sections of the continuing operating instructions, maintenance, 
and some flight manual sections are accepted.
    The FAA notes the requirement for the AFM in former Sec.  23.1581 
required each portion of the AFM containing information required by the 
FAA must be approved by the FAA, segregated, identified, and clearly 
distinguished from each unapproved portion of the AFM. The former 
requirements also provided an exception for reciprocating-powered 
airplanes that do not weigh more than 6,000 pounds if certain 
requirements were met.\62\ It was not the FAA's intent to discontinue 
the former requirement to approve select AFM information. The approval 
process allows the FAA to review an AFM to ensure it satisfies the 
applicable requirements; this rule will generally retain the existing 
requirement that FAA-required information provided in the AFM must be 
approved by the FAA. For this reason, the FAA has added paragraph (b) 
to clarify that the FAA will retain our authority to approve specific 
AFM information.
---------------------------------------------------------------------------

    \62\ Id. Sec.  23.1581(b)(2). To qualify for this exception, the 
following requirements must be satisfied: (1) Each part of the AFM 
containing the Limitations information must be limited to such 
information, and must be approved, identified, and clearly 
distinguished from each other part of the AFM; and (2) the remaining 
required information must be presented in its entirety in a manner 
acceptable to the FAA.
---------------------------------------------------------------------------

E. Miscellaneous Amendments (Sec. Sec.  21.9, 21.17, 21.24, 21.35, 
21.50, 21.101, SFAR 23, Appendix E to Part 43, and 91.323)
1. Production of Replacement and Modification Articles (Sec.  21.9)
    In the NPRM, the FAA proposed revising Sec.  21.9 by adding a new 
paragraph (a)(7) to provide applicants with an alternative method to 
obtain FAA approval to produce replacement and modification articles 
that are reasonably likely to be installed on type certificated 
aircraft. The FAA also proposed revising paragraphs (b) and (c) to 
specify that these articles would be suitable for use in a type 
certificated product. Lastly, the FAA also proposed allowing an 
applicant to submit production information for a specific article, but 
would not require the producer of the article to apply for approval of 
the article's design or obtain approval of its quality system. Under 
the proposed changes, approval to produce a modification or replacement 
article under proposed Sec.  21.9(a)(7) would not constitute a 
production approval as defined in Sec.  21.1(b)(6). In the NPRM, the 
FAA indicated it would limit use of this procedure to articles whose 
improper operation or failure would not cause a hazard. Additionally, 
the approval would be granted on a case-by-case basis, specific to the 
installation proposed, accounting for potential risk and considering 
the safety continuum.
    The FAA specifically solicited comments regarding whether the 
proposed change would safely facilitate retrofit of low risk articles 
and whether there are alternative methods to address the perceived 
retrofit barrier.
    All commenters expressed some level of support for the proposed 
changes to Sec.  21.9. Several commenters asked the FAA to provide 
guidance to clarify how the proposed changes will work.
    The FAA agrees with the commenters that additional details and 
clarification are needed to further define the process for obtaining 
approval under Sec.  21.9(a)(7) and will provide the necessary policy 
and guidance material. Generally, the process for obtaining FAA 
approval under Sec.  21.9(a)(7) is intended to be scalable in nature in 
that different degrees of substantiation may be required, depending on 
the complexity of the article for which approval is sought. For 
example, a non-required, low-risk article could be simple enough that a 
design approval and quality system might not be required; however, a 
more complex article might also require a Sec.  21.8(d) design approval 
and some form of quality system. Examples of the requirements for more 
complex projects include FAA policy memorandum AIR100-14-110-PM01, 
``Approval of Non-Required Angle-of-Attack (AOA) Indicator Systems, and 
FAA policy statement PS-AIR-21.8-1602, Approval of Non-Required Safety 
Enhancing Equipment (NORSEE).'' For simple articles, a reduction in 
scale could be negotiated with the FAA to provide an appropriate level 
of safety. Audits of the manufacturer's facility would be at the 
discretion of the appropriate MIDO. Typically, a MIDO audit would not 
be required unless there is evidence that indicates improper quality 
control issues that require a MIDO's involvement, as described in the 
FAA Policy Statement PS-AIR-21.8-1602.\63\
---------------------------------------------------------------------------

    \63\ Policy No. PS-AIR-21.8-1602 has been placed in docket 
number FAA-20150-1621.
---------------------------------------------------------------------------

    Astronautics Corporation commented that whether an article is 
``required'' or ``non-required'' depends on the kind of operation the 
applicant requests for certification. Garmin also questioned why the 
qualifying articles have to be non-required and asked the FAA to 
consider expanding use of the proposed Sec.  21.9(a)(7) process to 
include low-risk required articles when the applicant has an approved 
quality system. Garmin contended that low risk to the aircraft or its 
occupants should be sufficient criteria to allow application to both 
required and non-required equipment.
    Astronautics Corporation is correct in its observation that the 
approval means for an article could potentially affect the ``kinds of 
operation'' authorized for an aircraft. The FAA's intent is not to 
bypass existing certification process for required equipment, but to 
provide an alternative process for non-required, low-risk articles. For 
example, a weather

[[Page 96666]]

display approved under Sec.  21.9(a)(7) may have extensive information 
available, but this information would be considered supplemental and 
could not be used to satisfy operational requirements. If the FAA 
determines that certain equipment is required for safety, then existing 
certification processes must be followed to ensure the required safety 
equipment is functioning properly.
    Garmin also asked what would be needed for approval of the 
installation of articles produced under Sec.  21.9(a)(7) and whether 
new FAA policy would be needed each time there is a new equipment 
standard proposed to allow its installation.
    Section 21.9(a)(7) concerns only the production of articles, not 
their installation. The required process for obtaining installation 
approval remains unchanged by this rule.
    Garmin asserted that the term ``low risk'' is subjective and asked 
the FAA to clarify the intent of this term. Specifically, Garmin asked 
if a system with a minor failure condition would fall into the low-risk 
category.
    The FAA intends the term ``low risk,'' for the purposes of Sec.  
21.9(a)(7), to apply to non-required articles with a hazard 
classification no greater than minor. In this context, a ``minor'' 
failure condition would result in only a slight reduction in functional 
capabilities or safety margins.
    Air Tractor asked whether the changes to Sec.  21.9 will apply 
equally to TC and STC holders and applicants for those certificates, 
which the commenter said it believed the changes should.
    It is the FAA's intent that an article approved under Sec.  
21.9(a)(7) can be subsequently approved for installation by a TC or STC 
holder based on the installation data provided by the TC or STC holder.
    Additionally, the FAA has decided not to except articles approved 
under Sec.  21.9(a)(7) from the prohibition on representing an article 
as suitable for installation on a type-certificated product found in 
Sec.  21.9(b) and Sec.  21.9(c); therefore, the FAA is not adopting the 
NPRM's proposed changes to Sec.  21.9(b) and Sec.  21.9(c). The current 
Sec.  21.9 creates an exception from this prohibition for articles 
produced under a TC or an FAA production approval because these 
articles have approved installation data that justify a representation 
of suitability. The proposed changes in the NPRM would have allowed 
articles that are not produced under a TC or production approval to be 
sold or represented as suitable for installation on type-certificated 
products without approved installation data. A representation that an 
article is ``suitable for installation'' could be misinterpreted as 
``approved for installation.'' The FAA notes that approval under Sec.  
21.9(a)(7) does not constitute approval for installation of the 
article; however, a person may state that an article approved under 
Sec.  21.9(a)(7) may be installed in a type-certificated aircraft 
provided it has been determined suitable for installation by an 
appropriately-rated mechanic using appropriate means.
2. Designation of Applicable Regulations (Sec.  21.17)
    In the NPRM, the FAA proposed amending Sec.  21.17(a) by removing 
the reference to Sec.  23.2 because Sec.  23.2 would be deleted by this 
rule.
    NATCA commented that elimination of the reference to retroactive 
rules, former Sec.  23.2, leaves holes in certification basis for the 
existing fleet of airplanes. This commenter noted that while Sec.  23.2 
is not listed as a basis for certification for many existing airplanes, 
the provision nevertheless applies due to the date of manufacture of 
some airplanes. NATCA also raised concerns it would be burdensome to 
revise Type Certificate Data Sheets (TCDS) to reflect the change; 
therefore, NATCA requested that this regulation address the addition of 
seatbelts as a retroactive, date of manufacture, requirement.
    The FAA notes NATCA's concern; however, the provisions of current 
Sec.  23.2 are duplicated in Sec.  91.205 and therefore remain 
applicable based on date of manufacture. The revision of TCDS will be 
unnecessary because any reference to current Sec.  23.2 in an existing 
TCDS will include reference to the applicable amendment and continue to 
be enforceable.
    The NTSB commented that the FAA should retain Sec.  23.2 because it 
is a regulatory mechanism to apply special retroactive requirements to 
newly-manufactured items after the item has been issued a TC.
    The FAA notes the NTSB's comment, but this rule does not affect the 
FAA's ability to promulgate other special retroactive requirements 
using the normal rulemaking process.
    The FAA removes Sec.  23.2 and revises Sec.  21.17(a) by removing 
the reference to Sec.  23.2, as proposed.
    Although the NPRM did not propose changes to Sec.  21.17(b), which 
addresses the designation of applicable regulations to special classes 
of airplane, NATCA asked whether the FAA would continue to accept 
EASA's CS-VLA and CS 22 sailplanes and powered sailplanes, as special, 
stand-alone classes of airplanes, or whether the intent was to include 
these airplanes in part 23 as EASA proposed.
    The FAA intends to continue to allow CS-VLA and CS 22 airplanes to 
be approved as special, stand-alone classes of airplanes while also 
allowing eligibility for certification in accordance with part 23 using 
accepted means of compliance.
3. Issuance of Type Certificate: Primary Category Aircraft (Sec.  
21.24)
    In the NPRM, the FAA proposed amending Sec.  21.24 by revising 
paragraph (a)(1)(i) to modify the phrase ``as defined by Sec.  23.49'' 
to include reference to amendment 23-62 (76 FR 75736, December 2, 
2011), effective on January 31, 2012. The FAA explained that revision 
would be necessary to maintain a complete definition of stall speed in 
Sec.  21.24, as the former Sec.  23.49 is removed by this rule.
    The Associations said it is unnecessary to amend Sec.  
21.24(a)(1)(i) as proposed. These commenters noted there are many 
references to items such as stall speed that do not need to reference a 
previous amendment regulation for the steps to determine stall speed. 
The commenters contended it would be sufficient to include the intent 
in the preamble discussion.
    The FAA agrees the reference to Sec.  23.49, amendment 23-62, in 
Sec.  21.24 is unnecessary. VSO is defined in Sec.  1.2. The 
conditions and techniques for determining stall speed have been 
consistent for decades. Furthermore, AC 23-8C has a thorough discussion 
on how to do stall testing. Rather than referencing a regulation from a 
previous amendment, the FAA is revising Sec.  21.24 to refer to 
VSO stall speed as determined under part 23.
    The Associations also asked the FAA to include electric propulsion 
in the primary category aircraft once the FAA determines acceptable 
standards by inserting the phrase ``or with electric propulsion 
systems'' after the phrase ``naturally aspired engine.''
    The commenters' request to include electric propulsion systems in 
the primary category is beyond the scope of this rulemaking. Therefore, 
the FAA defers the request for consideration in future part 21 
rulemaking activity.
    NATCA argued the establishment of Primary Category Aircraft in 
current Sec.  21.24 has been an almost useless addition to part 21, 
resulting in problems without providing any benefit. As an example, 
NATCA referenced without elaboration the Seabird Seeker.\64\ NATCA also 
noted that very

[[Page 96667]]

few airplanes have been certified under existing Sec.  21.24, except 
perhaps those seeking to obtain EASA approval for CS-LSA (Light Sport 
Aeroplanes). The commenter said the proposed changes to part 23 support 
the use of industry specifications as a certification basis within part 
23, thereby eliminating the need to retain procedural regulations for 
Primary Category Aircraft. NATCA recommended FAA focus on harmonizing 
the standards for Very Light Aircraft and Light Sport Aircraft with 
bilateral partners, particularly EASA. The commenter observed that 
United States manufacturers are at a disadvantage to obtain CS-LSA 
approval in Europe.
---------------------------------------------------------------------------

    \64\ It appears the Seabird Seeker is a light utility airplane 
built by Seabird Aviation Australia that was prohibited from being 
sold in the United States until receiving part 23 TC in 2015.
---------------------------------------------------------------------------

    NATCA maintained that these types of airplanes are meant to be 
included in the part 23 rewrite and therefore recommended the FAA 
remove new type certification under Sec.  21.24 once the part 23 
revisions becomes final. Specifically, NATCA recommended the FAA 
rewrite Sec. Sec.  21.24 and 21.184 to eliminate Primary Category 
certifications, or keep with an effective date to account for existing 
fleet, and create procedural requirements in part 21 and maybe part 23 
to recognize something equivalent to EASA's CS-LSA.
    The FAA considered NATCA's proposal to remove Sec.  21.24, in 
effect, eliminating primary category certification. Although Very Light 
Aircraft and Light Sport Aircraft could be certified under the new part 
23, eliminating Sec.  21.24 is beyond the scope of this rulemaking 
because it would also remove a means of certification for certain 
rotorcraft that qualify for the primary category. These rotorcraft will 
not be able to take advantage of the new part 23 because it applies 
only to the certification of airplanes. Additionally, Sec.  21.24 and 
the new part 23 do not conflict; they are alternative paths for 
certification.
    Additionally, proposed Sec.  21.24(i) abbreviated ``January'' as 
``Jan''. This rule replaces ``Jan'' with ``January''.
4. Flight Tests (Sec.  21.35)
    The NPRM proposed amending Sec.  21.35(b)(2) to delete reference to 
reciprocating engines and expanding the exempted airplanes to include 
all low-speed part 23 airplanes 6,000 pounds or less. This proposed 
change would align the requirements for function and reliability 
testing with the proposed changes in part 23 that do not distinguish 
between propulsion types. This change would allow the FAA flexibility 
to address new propulsion types.
    All commenters objected to the use of a 6,000-pound weight limit as 
a threshold for exemption from testing in proposed Sec.  21.35(b)(2). 
Each commenter noted that the stated intent of the part 23 revision is, 
in part, to move away from weight and propulsion type classifications. 
Each commenter also requested the FAA remove the 6,000-pound weight 
limit.
    Air Tractor proposed eliminating the need for function and 
reliability testing entirely and suggested the market will sort out 
function and reliability issues by means of natural economic controls.
    The Associations suggested the FAA use a parameter other than 
maximum weight as a discriminator. Recognizing that the 6,000-pound 
weight limit appears to be based on the airplane's complexity and 
considering the acceptable level of risk, these commenters suggested 
using a low[hyphen]speed airplane, which is a measure of complexity, 
and airworthiness level 2 or less, which are newly accepted measures of 
risk, to provide the same level of safety. The commenters noted this 
discriminator would also better align with the part 23 design rules. 
Therefore, the Associations recommended replacing the phrase ``of 6,000 
pound or less maximum weight'' with ``meeting part 23 airworthiness 
level 1 or 2.''
    The FAA disagrees with Air Tractor's proposal to eliminate all 
Function and Reliability (F&R) testing, because elimination of F&R 
testing for high-speed, complex airplanes, carrying larger numbers of 
passengers is not in keeping with the FAA's statutory mandate to 
prescribe minimum standards in the interest of safety for the design 
and performance of airplanes.
    The FAA agrees with Textron and the Associations to remove the 
6,000-pound discriminator in favor of values based on complexity and 
risk. Accordingly, the FAA has decided to replace the exception from 
F&R testing for airplanes weighing 6,000 pounds and below with an 
exception for airplanes with performance level of low-speed and 
certification level of 2 or less. The 6,000-pound discriminator was 
based on the FAA's assumptions regarding the complexity and risk 
associated with airplanes of that weight. However, as the commenters 
point out, their recommended parameters reflect the same assumptions 
regarding complexity and risk. Although this change may provide an 
exception for airplanes of up to 19,000 pounds, these airplanes would 
still be within the allowable risk and complexity parameters.
5. Instructions for Continued Airworthiness and Manufacturer's 
Maintenance Manuals Having Airworthiness Limitations Sections (Sec.  
21.50)
    In the NPRM, proposed Sec.  21.50(b) would have replaced the 
reference Sec.  23.1529 with Sec.  23.1515 to align with the proposed 
part 23 numbering convention.
    The FAA has decided not to renumber Sec.  23.1529, which requires 
applicants for a TC or a change to a TC under part 23 to prepare 
Instructions for Continued Airworthiness; therefore, this section 
retains the reference to Sec.  23.1529 in this rule. However, the FAA 
will keep the proposed addition of the phrase ``for Continued 
Airworthiness'' in the second sentence of Sec.  21.50 to clarify that 
the second sentence in paragraph (b) refers to Instructions for 
Continued Airworthiness.
6. Designation of Applicable Regulations (Sec.  21.101)
    The NPRM proposed amending Sec.  21.101(b) to remove reference to 
Sec.  23.2 because Sec.  23.2 was proposed to be removed from part 23 
and the requirements of former Sec.  23.2 are addressed in the 
operating rules. The NPRM, in order to align Sec.  21.101 with the 
proposed part 23 certification levels, proposed amending Sec.  
21.101(c) to include simple airplanes, level 1, low-speed airplanes, 
and level 2, low-speed airplanes. The NPRM did not propose to revise 
Sec.  21.101 to address airplanes certified under former part 23, 
amendment 23-62, or prior amendments. Section 21.101 will continue to 
allow for compliance with the certification requirements at amendment 
23-62 or earlier when compliance to the latest amendment of part 23 is 
determined by the FAA to be impractical.
    The Associations said the FAA should remove the phrase ``to a 
simple'' from the first sentence of Sec.  21.101(c), regardless of the 
later utilization of the term as these aircraft are completely 
encompassed by low[hyphen]speed, level 1 airplanes. The FAA agrees and 
revises the rule language to remove ``to a simple'' from Sec.  
21.101(c).
    Textron commented that the purpose of the part 23 rewrite is to 
move away from prescriptive classifications like weight and propulsion 
type, and therefore asked FAA to remove the 6,000-pound weight-based 
division in proposed Sec.  21.101(c). Textron also noted the FAA 
provided no justifications for retaining the 6,000-pound weight-based 
division. Textron also suggested adding

[[Page 96668]]

the word ``airplane'' after ``simple'' and after ``level 1 low speed'' 
for clarity.
    The FAA considered Textron's comment. However, the 6,000-pound 
weight division cannot be removed because it continues to apply to 
legacy airplanes and modifications to those airplanes. A legacy 
airplane would only be identified by a certification level if it was 
re-certified to be fully compliant with the new rule. Therefore, the 
proposed wording is intended to capture both legacy airplanes and newly 
type certified airplanes. The FAA agrees that adding the word 
``airplane'' after ``level 1 low speed'' in paragraph (c) will improve 
the sentence's clarity.
    NATCA observed that there do not appear to be FAA directives or 
guidance on how to apply the part 23 rewrite to existing airplanes. As 
an example, NATCA asked how this rewrite would apply to a Piper Seneca 
V, an amendment 23-6 airplane. The commenter contended the FAA already 
struggles with the existing regulations and guidance. NATCA also asked 
how the proposed changes will be implemented on existing TC and STC 
products and how the certification basis will be captured. NATCA asked 
FAA to issue new directives, orders, and ACs specifically addressing 
application of part 23, relative to the Changed Product Rule, to 
prevent a situation in which each ACO (and applicant) comes up with 
their own creative interpretation of the regulation.
    The FAA has developed internal training and guidance material to 
assist FAA employees. Specific to the application of the Changed 
Product Rule (Sec.  21.101), there should be minimal variation from 
existing procedures and guidance material. The certification basis for 
changed products will be captured by section and amendment in 
accordance with existing procedures, and section-specific certification 
levels identified for those amendments issued concurrent with, or 
subsequent to, this rulemaking.
7. Special Federal Regulation 23 (SFAR No. 23)
    This final rule removes SFAR No. 23 as unnecessary because an 
applicant may no longer certify an airplane to SFAR No. 23. SFAR No. 23 
was first superseded by SFAR 41 and then by commuter category in part 
23, amendment 23-34. The FAA's intent to remove SFAR No. 23 was 
reflected in the amendatory language in the NPRM.
8. Altimeter System Test and Inspection (Appendix E to Part 43)
    In the NPRM, the FAA proposed to revise paragraph (a)(2) of 
appendix E to part 43 by removing the reference to Sec.  23.1325,\65\ 
which would cease to exist in the proposed rule, and by requiring each 
person performing the altimeter system tests and inspections required 
by Sec.  91.411 to perform a proof test to demonstrate the integrity of 
the static pressure system in a manner acceptable to the Administrator. 
This proposed change would have affected owners and operators of part 
23 certificated airplanes in controlled airspace under IFR, who must 
comply with Sec.  91.411.
---------------------------------------------------------------------------

    \65\ In the NPRM, the FAA proposed to capture the safety intent 
of Sec.  23.1325 in proposed Sec. Sec.  23.1300, 23.1310, and 
23.1315.
---------------------------------------------------------------------------

    Kestrel noted that existing appendix E to part 43 references Sec.  
23.1325 for leakage tolerances; however, the proposed rule would not 
have included Sec.  23.1325 and the specified tolerances. Kestrel asked 
if the FAA plans to address the specified tolerances in guidance, or if 
it will permit the varying tolerances between similar airplane.
    The FAA agrees and will address the leakage tolerances in guidance. 
As explained in the NPRM, the FAA is revising AC 43-6, Altitude 
Reporting Equipment and Transponder System Maintenance and Inspection 
Practices, to include a static pressure system proof test acceptable to 
the Administrator. The revised AC will incorporate the same static 
leakage standards that were formerly prescribed in Sec.  23.1325. 
However, as ACs are not the only means of compliance, it is possible 
that someone could ultimately propose an alternative means that the FAA 
could find acceptable, which would lead to a difference between similar 
airplane. But no such methods have been proposed to date.
9. Increased Maximum Certification Weights for Certain Airplanes 
Operated in Alaska (Sec.  91.323)
    The NPRM proposed amendments to Sec. Sec.  91.205, 91.313, 91.323, 
and 91.531. The only section that received comments was Sec.  91.323. 
increased maximum certification weights for certain airplanes operated 
in Alaska.
    The FAA proposed to amend Sec.  91.323 by removing the reference to 
Sec.  23.337 because the FAA proposed revising and consolidating Sec.  
23.337 with other structural requirements. The FAA proposed adding the 
relevant prescriptive requirement of Sec.  23.337 to Sec.  
91.323(b)(3).
    Air Tractor noted that the weight in Sec.  91.323(b)(3) has been 
changed to reflect a maneuvering load factor that is now independent of 
the load factor in part 23, but matches the previous Sec.  23.337 
definition. The commenter contended that there is now an increased 
likelihood that the load factor considered under this new rule will not 
match the load factors that were used in the original certification of 
the design, because it is possible that some consensus standard will 
impose some other creative interpretation. The commenter suggested that 
safety would be better preserved if Sec.  91.323 were required to 
reference the load factors that were used in the original 
certification.
    Air Tractor's concern is based on an incorrect interpretation of 
the FAA's proposed amendment to Sec.  91.323. Section 91.323 applies 
only to aircraft that have been type certificated under Airworthiness 
Bulletin 7A or under normal category of part 4a of the former Civil Air 
Regulations (CAR). The FAA's proposed amendment to Sec.  91.323 would 
not permit any additional aircraft to be operated in accordance with 
Sec.  91.323. It would only preserve the approval of increased maximum 
certification weights for airplanes that were designed and built to a 
higher design requirement than CAR 3 and 14 CFR part 23. Approving an 
increase in the maximum certificated weight of an airplane pursuant to 
Sec.  91.323, based on the equation from former Sec.  23.337(a)(1), 
allows operation at the same weights had the airplane been certificated 
in accordance with CAR 3.
10. Additional Emergency Equipment (Sec.  121.310)
    In the NPRM, the FAA proposed to amend Sec.  121.310(b)(2)(iii) by 
updating the reference to Sec.  23.811(b). Current Sec.  
121.130(b)(2)(iii) references Sec.  23.811(b) of part 23, amendment 23-
62. Because the FAA is replacing part 23, amendment 23-62 with new part 
23, the FAA proposed to update the reference to Sec.  23.811(b) by 
specifying that each passenger emergency exit marking and each locating 
sign must be manufactured to meet the requirements of Sec.  23.811(b) 
of this chapter in effect on June 16, 1994. However, upon further 
reflection, the FAA has decided not to reference a section that will no 
longer exist in the CFR on August 30, 2017. Instead, the FAA is 
incorporating the requirements of Sec.  23.811(b) in Sec.  
121.310(b)(2)(iii). Accordingly, Sec.  121.310(b)(2)(iii) now requires, 
for a nontransport category turbopropeller powered airplane type 
certificated after December 31, 1964, that each passenger emergency 
exit marking and each locating sign be manufactured to have white 
letters 1 inch high on a red background 2 inches high, be self-
illuminated or independently, internally electrically illuminated, and 
have a

[[Page 96669]]

minimum brightness of at least 160 microlamberts. The color may be 
reversed if the passenger compartment illumination is essentially the 
same.
11. Additional Airworthiness Requirements (Sec.  135.169)
    In the NPRM, the FAA proposed to allow a small airplane in the 
normal category, in Sec.  135.169(b)(8), to operate within the rules 
governing commuter and on demand operations. Proposed Sec.  
135.169(b)(8) would have required the new normal category airplane to 
use a means of compliance accepted by the Administrator equivalent to 
the airworthiness standards applicable to the certification of 
airplanes in the commuter category found in part 23, amendment 23-62.
    Upon further reflection, the FAA has decided not to reference part 
23, amendment 23-62 in Sec.  135.169(b)(8) because part 23, amendment 
23-62 will not exist in the CFR when new normal category airplanes are 
being type certificated under new part 23. The FAA intended proposed 
Sec.  135.169(b)(8) to ensure a continued higher level of safety for 
commercial operations by requiring a new normal category airplane under 
part 23 to use a means of compliance equivalent to the airworthiness 
standards that applied to airplanes certified in the commuter category. 
As explained in the NPRM, this final rule sunsets the commuter category 
for newly type certificated airplanes and creates a new normal 
category, certification level 4 airplane as equivalent to the commenter 
category by applying it to 10-19 passengers. In order to retain the 
FAA's intent while omitting the reference to part 23 at amendment 23-
62, the FAA is revising the proposed rule language to clarify that 
Sec.  135.169(b)(8) applies to a normal category airplane equivalent to 
the commuter category. Accordingly, Sec.  135.169(b)(8) now allows 
consideration of a small airplane that is type certificated in the 
normal category, as a multi-engine certification level 4 airplane, to 
operate within the rules governing commuter and on demand operations.
    Because new part 23 maintains the level of safety associated with 
current part 23, except for areas addressing loss of control and icing 
where a higher level of safety is established, the FAA expects that any 
multi-engine, level 4 airplane approved for commercial operations with 
10 or more passengers will meet, at a minimum, the performance required 
for airplanes type certificated in the commuter category.

IV. Regulatory Notices and Analyses

A. Regulatory Evaluation Summary

    Changes to Federal regulations must undergo several economic 
analyses. First, Executive Order 12866 and Executive Order 13563 direct 
that each Federal agency shall propose or adopt a regulation only upon 
a reasoned determination that the benefits of the intended regulation 
justify its costs. Second, the Regulatory Flexibility Act of 1980 (Pub. 
L. 96-354) requires agencies to analyze the economic impact of 
regulatory changes on small entities. Third, the Trade Agreements Act 
(Pub. L. 96-39) prohibits agencies from setting standards that create 
unnecessary obstacles to the foreign commerce of the United States. In 
developing U.S. standards, this Trade Act requires agencies to consider 
international standards and, where appropriate, that they be the basis 
of U.S. standards. Fourth, the Unfunded Mandates Reform Act of 1995 
(Pub. L. 104-4) requires agencies to prepare a written assessment of 
the costs, benefits, and other effects of proposed or final rules that 
include a Federal mandate likely to result in the expenditure by State, 
local, or tribal governments, in the aggregate, or by the private 
sector, of $100 million or more annually (adjusted for inflation with 
base year of 1995). This portion of the preamble summarizes the FAA's 
analysis of the economic impacts of this final rule. We suggest readers 
seeking greater detail read the full regulatory evaluation, a copy of 
which we have placed in the docket for this rulemaking.
    In conducting these analyses, FAA has determined that this final 
rule: (1) Has benefits that justify its costs, (2) is not an 
economically ``significant regulatory action'' as defined in section 
3(f) of Executive Order 12866, (3) is not ``significant'' as defined in 
DOT's Regulatory Policies and Procedures; (4) has a significant 
positive economic impact on small entities; (5) will not create 
unnecessary obstacles to the foreign commerce of the United States; and 
(6) will not impose an unfunded mandate on state, local, or tribal 
governments, or on the private sector by exceeding the threshold 
identified above. These analyses are summarized below.
1. Total Benefits and Costs of This Rule
    The following table shows the estimated benefits and costs of the 
final rule. Another way to consider the expected net benefit to the 
society is if the rule saves only one human life by improving stall 
characteristics and stall warnings, this alone would result in benefits 
which substantially outweigh the costs.

                      Estimated Benefits and Costs
                            [2015 $ Millions]
------------------------------------------------------------------------
                                                      Safety benefits +
                              Stall & spin + other  cost savings = total
                                      costs               benefits
------------------------------------------------------------------------
Total.......................  $0.8 + $3.1 = $3.9..  $17.9 + $9.9 = $27.8
Present value at 7%.........  0.8 + 3.1 = 3.9.....  6.1 + 4.9 = 11.0
Present value at 3%.........  0.8 + 3.1 = 3.9.....  11.1 + 7.1 = 18.3
------------------------------------------------------------------------
* These numbers are subject to rounding error.

2. Who is potentially affected by this rule?
    The proposal will affect U.S. manufacturers and operators of new 
part 23 type certificated airplanes.
3. Assumptions
    The benefit and cost analysis for the regulatory evaluation is 
based on the following factors/assumptions:
     The analysis is conducted in constant dollars with 2015 as 
the base year.
     The final rule will be effective in 2017.
     The primary analysis period for costs and benefits extends 
for 20 years, from 2017 through 2036. This period was selected because 
annual costs and benefits will have reached a steady state by 2036.
     Future part 23 type certifications and deliveries are 
estimated from historical part 23 type certifications and deliveries.
     Costs for the new part 23 type certifications forecasted 
in the ``Fleet Discussion'' section will all occur in year 1 of the 
analysis interval.

[[Page 96670]]

     Airplane deliveries from the forecasted part 23 type 
certificates will start in year 5 of the analysis interval. Therefore, 
accident reduction benefits will begin five years after the rule is in 
effect.
     The FAA uses a three and seven percent discount rate for 
the benefits and costs as prescribed by OMB in Circular A-4.
     The baseline for estimating the costs and benefits of the 
rule will be part 23, through the current amendment level.
     Based on FAA Small Airplane Directorate expert judgment, 
the FAA estimates 335 FAA part 23 certification engineers will require 
additional training as a result of this final rule. The FAA assumes 
that the same number of industry part 23 certification engineers will 
also require additional training as a result of this final rule.
     The FAA estimates this rulemaking will add 16 hours of 
training to FAA and industry part 23 certification engineers.
     Since this training program will be on-line, we estimate 
no travel costs for the engineers.
     FAA pay-band tables and the Bureau of Labor Statistics 
(BLS) determines the hourly wages used to estimate the costs to the FAA 
and applicants.
     Using the U.S. Department of Transportation guidance, the 
wage multiplier for employee benefits is 1.17.
4. Benefits of This Rule
    The major safety benefit of this rule is to add stall 
characteristics and stall warnings that will result in airplane designs 
that are more resistant to inadvertently departing controlled flight. 
The largest number of accidents for small airplanes is a stall or 
departure based loss of control (LOC) in flight. This rule will have 
cost savings by streamlining the certification process and encouraging 
new and innovative technology. Streamlining the certification process 
will reduce the issuance of special conditions, exemptions, and 
equivalent level of safety findings.
5. Costs of This Rule
    The final rules major costs are the engineer training costs and the 
certification database creation costs. Additional costs will also 
accrue from the controllability and stall sections that will increase 
scope over current requirements and manual upgrade costs.
    In the following table, we summarize the total estimated compliance 
costs by category. The FAA notes that since we assumed that all costs 
occurred in Year 1 of the analysis interval, the 2015-dollar costs 
equal the present value costs.

                     Total Cost Summary by Category
                     [In 2015 present value dollars]
------------------------------------------------------------------------
                                                          Total costs in
                      Type of cost                         present value
                                                           at 7 percent
------------------------------------------------------------------------
Sec.   23.2150(c) Controllability.......................        $277,318
Sec.   23.2150(b) Stall characteristics, stall warning,          500,595
 and spins..............................................
Engineer Training Costs.................................       1,167,379
Certification Database Costs............................       1,295,290
Manual Upgrade Costs....................................         700,833
                                                         ---------------
  Total Costs...........................................       3,941,414
------------------------------------------------------------------------
* These numbers are subject to rounding error.

B. Final Regulatory Flexibility Determination

    The Regulatory Flexibility Act of 1980 (Pub. L. 96-354) (RFA) 
establishes ``as a principle of regulatory issuance that agencies shall 
endeavor, consistent with the objectives of the rule and of applicable 
statutes, to fit regulatory and informational requirements to the scale 
of the businesses, organizations, and governmental jurisdictions 
subject to regulation. To achieve this principle, agencies are required 
to solicit and consider flexible regulatory proposals and to explain 
the rationale for their actions to assure that such proposals are given 
serious consideration.'' The RFA covers a wide-range of small entities, 
including small businesses, not-for-profit organizations, and small 
governmental jurisdictions.
    Agencies must perform a review to determine whether a rule will 
have a significant economic impact on a substantial number of small 
entities. If the agency determines that it will, the agency must 
prepare a regulatory flexibility analysis as described.
    The FAA believes that this final rule could have a significant 
positive economic impact on a substantial number of entities because we 
believe this rule could enable the creation of new part 23 type 
certificates and new manufacturers. The FAA has been working with U.S. 
and foreign small aircraft manufacturers since 2007 to review the life 
cycle of part 23 airplanes and determine what needed improvement.
    The purpose of this analysis is to provide the reasoning underlying 
the FAA determination.
    Section 604(a) of the Act specifies the content of a FRFA.
    Each FRFA must contain:
     A statement of the need for, and objectives of, the rule;
     a statement of the significant issues raised by the public 
comments in response to the initial regulatory flexibility analysis, a 
statement of the assessment of the agency of such issues, and a 
statement of any changes made in the proposed rule as a result of such 
comments;
     the response of the agency to any comments filed by the 
Chief Counsel for Advocacy of the Small Business Administration in 
response to the proposed rule, and a detailed statement of any change 
made to the proposed rule in the final rule as a result of the 
comments;
     a description of and an estimate of the number of small 
entities to which the rule will apply or an explanation of why no such 
estimate is available;
     a description of the projected reporting, recordkeeping 
and other compliance requirements of the rule, including an estimate of 
the classes of small entities which will be subject to the requirement 
and the type of professional skills necessary for preparation of the 
report or record; and
     a description of the steps the agency has taken to 
minimize the significant economic impact on small entities consistent 
with the stated objectives of applicable statutes, including a 
statement of the factual, policy, and legal reasons for selecting the 
alternative adopted in the final rule and why each one of the other 
significant alternatives to the rule considered by the agency which 
affect the impact on small entities was rejected.
1. Reasons Why the Rule Is Needed
    The FAA promulgates this action to amend the airworthiness 
standards for new part 23 type certificated airplanes to reflect the 
current needs of the small airplane industry, accommodate future 
trends, address emerging technologies, and enable the creation of new 
part 23 manufacturers and new type certificated airplanes. The rule's 
changes to part 23 are necessary to eliminate the current workload of 
exemptions, special conditions, and equivalent levels of safety 
findings necessary to certificate new part 23 airplanes. These part 23 
changes will also promote safety by enacting new regulations for 
controllability and stall standards and promote the introduction of new 
technologies in part 23 airplanes.
2. Significant Issues Raised by the Public Comments in Response to the 
Initial Regulatory Flexibility Analysis
    With regard to assessing the impact on small, numerous firms were 
left out

[[Page 96671]]

of the FAA's analysis. Analysis concerning the impact on small firms 
ultimately included data from only 5 firms, one of which has not been 
in operation for 8 years, and another that no longer exists, but is 
struggling to set up business under new ownership. It would seem that 
the FAA should have knowledge of every company that still has active 
manufacturing activities (active production certificates), and that the 
data that was included was exceptionally non-representative of the 
overall industry. Further, by eliminating from consideration all firms 
that are not US-owned a distorted view of the true impact on the 
general aviation industry in our country is presented.
    FAA Response: Under the Small Business Regulatory Flexibility Act, 
for each initial regulatory flexibility analysis, agencies are required 
to provide a description of and, where feasible, an estimate of the 
number of small entities to which the proposed rule would apply. Many, 
if not most, small entities do not provide public data such as 
publically available employment data in order to determine if a 
business is small under the SBA guidelines, or publically available 
revenue data, in order to determine if a business is disproportionately 
burdened by the proposed or final rulemaking. The FAA does not have the 
means or authority to require small entities to report their employment 
or revenue data and therefore we do not have knowledge of every company 
that still has active manufacturing activities. The small business 
entities that the FAA analyzed provided data on their employment and 
revenue either through the U.S. DOT Form 41 rules, SEC rules, or 
through news releases the companies made public.
    The FAA conducted research and found that all five businesses' we 
examined at the time of our analysis were small and either actively 
manufacturing aircraft or they were under new ownership and had 
publically announced they were in the process of working towards 
setting up an aircraft manufacturing line. The FAA notes the rule also 
reduces the certification time for small part 23 parts manufacturers. 
The FAA conclusion that the proposed rule may have a significant 
positive impact on small entities extends well beyond our sample.
    Further, FAA regulations apply to US-owned business and to any 
foreign owned business that manufactures a product in the U.S. or 
markets their products/services in the U.S. Foreign owned business' 
voluntarily complies with the rules and regulations promulgated by the 
FAA. Thus the FAA expects that the final rule would impact a 
substantial number of small entities.
    The comment regarding numerous firms being left out of the FAA's 
small business analysis was from a company who certificates most of 
their aircraft with a restricted category special air worthiness 
certificate. A restricted category special airworthiness certificate is 
issued to operate aircraft that have been type certificated in the 
restricted category. Operation of restricted category aircraft is 
limited to special purposes identified in the applicable type design. 
Restricted category aircraft manufacturers do not follow part 23 in its 
entirety, rather they follow parts of part 21, part 21 subpart H, part 
45, section 91.313, part 91 subpart D, section 91.715, and part 375 and 
can choose whatever other certification bases requirements, based on 
FAA approval, to certificate their aircraft for the aircraft's special 
operations. Therefore, since restricted category aircraft manufacturers 
do not comply part 23 in its entirety for their type certifications, 
these manufacturers are not included in our analysis.
    In addition, many part suppliers may benefit from this performance-
based rule through an expected quicker approval process. The objective 
of this rule is to allow industry more flexibility and lower cost 
methods to certify future part 23 airplanes at a sufficiently lower 
certification cost which can be driven by industry innovation and more 
small entities will have additional opportunities that do not exist 
today.
3. FAA Response to Any Comments Filed by the Chief Counsel for Advocacy 
of the Small Business Administration in Response to the Proposed Rule
    The Chief Counsel for Advocacy did not file comments for the 
proposed rule.
4. A Description of and an Estimate of the Number of Small Entities to 
Which the Rule Will Apply or an Explanation of Why No Such Estimate Is 
Available
    For the initial regulatory flexibility analysis (IRFA), the FAA 
conducted a review to determine whether a rule will have a significant 
economic impact on a substantial number of small entities. The IRFA 
concluded that the proposed rule could have a significant economic 
impact on a substantial number of entities because we believe this rule 
could enable the creation of new part 23 type certificates and new 
manufacturers.
    The FAA is unable to estimate the total number of small entities to 
which the rule will apply because many, if not most, small part 23 
aircraft manufacturing entities do not provide public data such as 
publically available employment data in order to determine if a 
business is small under the SBA guidelines, and publically available 
revenue data, in order to determine if a business is disproportionately 
burdened by the final rulemaking. The FAA also believes that the final 
rule will enable new part 23 aircraft manufacturing industries, while 
maintaining a safe operating environment. In addition, many part 
suppliers may benefit from this performance-based rule through an 
expected quicker approval process.
5. A Description of the Projected Reporting, Recordkeeping and Other 
Compliance Requirements of the Rule, Including an Estimate of the 
Classes of Small Entities Which Will Be Subject to the Requirement and 
the Type of Professional Skills Necessary for Preparation of the Report 
or Record
    The final rule will reduce the number of special conditions, 
equivalent level of safety (ELOS), and exemptions and therefore will 
reduce paperwork and processing time for both the FAA and industry. The 
rule would also maintain the fundamental safety requirements from the 
current part 23 regulations but allow more flexibility in airplane 
designs, faster adoption of safety enhancing technology, and reduce the 
regulatory cost burden. To estimate savings driven by this change, the 
FAA counted the special conditions, ELOS, and exemption applications 
submitted to the FAA for part 23 aircraft between 2012 and 2014 and 
divided the number by two years for an average of 37 applications per 
year. The Aviation Rulemaking Committee (ARC) report offered a similar 
average of 37 applications per year. Additionally, the FAA counted the 
number of pages per application to obtain an average number of pages 
per application. For special conditions, there were approximately 21 
pages, 16 pages for an exemption, and 15 pages per ELOS application. 
The FAA assumes that the applicant and each FAA office that reviews the 
application spend 8 hours on research, coordination, and review per 
page. The ARC also noted ``an ELOS finding or exemption can take the 
FAA between 4 to 12 months to develop and approve. The applicant spends 
roughly the same amount of time as the FAA in proposing what they need 
and responding to FAA questions for SC, exemption, or ELOS. As 
explained in number four above, the FAA is unable to estimate the total 
number of small entities to which the rule will apply. The completion 
of these reports will not require professional skills beyond basic 
literacy and aviation

[[Page 96672]]

skills required to work for a part 23 aircraft manufacturer.
6. A Description of the Steps the Agency Has Taken To Minimize the 
Significant Economic Impact on Small Entities Consistent With the 
Stated Objectives of Applicable Statutes, Including a Statement of the 
Factual, Policy, and Legal Reasons for Selecting the Alternative 
Adopted in the Final Rule and Why Each One of the Other Significant 
Alternatives to the Rule Considered by the Agency Which Affect the 
Impact on Small Entities Was Rejected
    The Federal Aviation Administration (FAA) is revising the 
airworthiness standards for normal, utility, acrobatic, and commuter 
category part 23 airplanes and believes this action will provide a set 
of requirements that will allow more flexibility in part 23 airplane 
designs and faster adoption of safety enhancing technology while 
maintaining a higher level of safety. The current issue with part 23 is 
the prescriptive regulatory framework does not readily allow the 
adoption of new and innovative technology. This rulemaking will solve 
this issue by putting in place a performance-based regulatory structure 
that will result in the FAA accepting new means of compliance based 
upon industry consensus standards.
    This rulemaking project will comply with the Congressional mandated 
Small Airplane Revitalization Act of 2013, which requires the FAA to 
issue a final rule that revises the certification requirements for 
small airplanes by creating a regulatory regime that will improve 
safety and decrease certification costs. This action will increase the 
FAA's ability to address future technology and be relieving for all 
part 23 manufacturers regardless of their size and number of employees.
    For the initial regulatory flexibility analysis, the FAA analyzed 
two alternatives and solicited and received no comments on the 
alternative analysis. The two alternatives the FAA analyzed follows.
Alternative 1
    The FAA will continue to issue special conditions, exemptions, and 
equivalent level of safety findings to certificate part 23 airplanes. 
As this approach will not follow congressional direction, we choose not 
to continue with the status quo.
Alternative 2
    The FAA will continue to enforce the current regulations that 
affect stall and controllability. The FAA rejected this alternative 
because the accident rate for part 23 airplanes identified a safety 
issue that had to be addressed.
    Thus, this rule's benefits small entities by allowing new designs 
and parts with lower certifications costs.

C. International Trade Impact Assessment

    The Trade Agreements Act of 1979 (Pub. L. 96-39), as amended by the 
Uruguay Round Agreements Act (Pub. L. 103-465), prohibits Federal 
agencies from establishing standards or engaging in related activities 
that create unnecessary obstacles to the foreign commerce of the United 
States. Pursuant to these Acts, the establishment of standards is not 
considered an unnecessary obstacle to the foreign commerce of the 
United States, so long as the standard has a legitimate domestic 
objective, such as the protection of safety, and does not operate in a 
manner that excludes imports that meet this objective. The statute also 
requires consideration of international standards and, where 
appropriate, that they be the basis for U.S. standards. The FAA has 
assessed the potential effect of this final rule and determined that 
the standards are necessary for aviation safety and will not create 
unnecessary obstacles to the foreign commerce of the United States.

D. Unfunded Mandates Assessment

    Title II of the Unfunded Mandates Reform Act of 1995 (Pub. L. 104-
4) requires each Federal agency to prepare a written statement 
assessing the effects of any Federal mandate in a proposed or final 
agency rule that may result in an expenditure of $100 million or more 
(in 1995 dollars) in any one year by State, local, and tribal 
governments, in the aggregate, or by the private sector; such a mandate 
is deemed to be a ``significant regulatory action.'' The FAA currently 
uses an inflation-adjusted value of $155.0 million in lieu of $100 
million. This final rule does not contain such a mandate; therefore, 
the requirements of Title II of the Act do not apply.

E. Paperwork Reduction Act

    The Paperwork Reduction Act of 1995 (44 U.S.C. 3507(d)) requires 
that the FAA consider the impact of paperwork and other information 
collection burdens imposed on the public. The information requirements 
for aircraft certification are covered by existing OMB No. 2120-0018. 
Burdens associated with special conditions, ELOS, and exemptions are 
not quantified in this collection because the need to seek relief under 
one of these options is dependent on each applicant and is difficult to 
quantify. It is expected that this rulemaking will reduce the number of 
special conditions, ELOS, and exemptions filed, thus reducing paperwork 
and processing time for both the FAA and industry. It would also 
maintain the fundamental safety requirements from the current part 23 
regulations but allow more flexibility in airplane designs, faster 
adoption of safety enhancing technology, and reduce the regulatory cost 
burden.
    To estimate savings driven by this change, the FAA counted the 
special conditions, ELOS, and exemption applications submitted to the 
FAA for part 23 aircraft between 2012 and 2014 and divided the number 
by three years for an average of 37 applications per year.\66\ 
Additionally, the FAA counted the number of pages per application to 
obtain an average number of pages per application. For special 
conditions, there were approximately 21 pages, 16 pages for an 
exemption, and 15 pages per ELOS application. The FAA assumes that the 
applicant and each FAA office that reviews the application spend 8 
hours on research, coordination, and review per page. The ARC also 
noted ``an ELOS finding or exemption can take the FAA between 4 to 12 
months to develop and approve. The applicant spends roughly the same 
amount of time as the FAA in proposing what they need and responding to 
FAA questions for SC, exemption, or ELOS.'' \67\
---------------------------------------------------------------------------

    \66\ https://my.faa.gov/org/linebusiness/avs/offices/air/tools/cert.html.
    \67\ Ibid., 54.
---------------------------------------------------------------------------

    The number of applications is multiplied by the number of pages and 
by the hourly wage for the applicant and different FAA offices to 
account for the cost to the FAA and the applicant. The following table 
shows annual hours and cost by special condition, exemption, and ELOS.

[[Page 96673]]

 
------------------------------------------------------------------------
                                                   Annual total
                                         -------------------------------
                                             Man hours         Cost
------------------------------------------------------------------------
Savings from Special Conditions (SC)....           8,826        $553,962
Savings from Exemptions.................           1,620         101,596
Savings from Equivalent Level of Safety            5,268         330,691
 (ELOS).................................
------------------------------------------------------------------------

    Using these yearly cost estimates in the table above, over 20 years 
$6.6 million in man-hours will be spent on applying for and processing 
special conditions, exemptions, and ELOS. However under the rule, the 
need to demonstrate compliance through special conditions, exemptions, 
or ELOS will largely be eliminated. Instead new products will simply 
need to demonstrate compliance by following consensus standards 
acceptable to the Administrator, or by submitting their own proposed 
means of compliance using the process outlined in AC 23.10.\68\ As a 
conservative estimate, the FAA estimates that special conditions, 
exemptions, and ELOS will be reduced by half for a savings to the FAA 
and applicant of roughly $3.3 million ($1.6 million present value). The 
total cost and hour savings by year is shown in the table below.
---------------------------------------------------------------------------

    \68\ See Section VI. Discussion of the Regulatory Amendments of 
the preamble for a discussion of how this might be accomplished.

------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
                                                                              FAA SAD                         FAA ACO                        Applicant                         Total
                                                                 -------------------------------------------------------------------------------------------------------------------------------
                                                                     Man-hours        Savings        Man-hours        Savings        Man-hours        Savings        Man-hours        Savings
------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
Total...........................................................          34,920      $2,613,227          34,920      $1,789,953          34,920      $2,171,813         104,760      $6,574,993
0.5*Total.......................................................          17,460       1,306,613          17,460         904,977          17,460       1,085,907          52,380       3,287,497
------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
These numbers are subject to rounding error.

    In addition to this savings, there would also be additional 
paperwork burden associated with Sec.  23.2150(c). This rulemaking will 
not require a new control number, but does need an update to the 
control number that currently covers part 23. A PRA questionnaire has 
been updated with new requirements from this rule, and submitted to our 
PRA officer. This provision could result in a change to a limitation or 
a performance number in the flight manual, which will require an update 
to the training courseware or flight manual. Industry ARC members 
believe that this change could cost from $100,119 to $150,179 in 2015 
dollars. Therefore, the FAA uses $125,149 (($100,119 + $150,179)/2) as 
an average cost for this change. This will be a one-time cost per new 
type certification.
    There will also be additional paperwork associated with this 
requirement that is not part of the costs discussed above. The FAA 
estimates the paperwork costs for these provisions by multiplying the 
number of hours the FAA estimates for each page of paperwork, by the 
number of pages for the training courseware, or flight manual, by the 
hourly rate of the person responsible for the update. The FAA estimates 
that this section will add a total of four pages to the training 
courseware and flight manual. The FAA also estimates that it will take 
a part 23 certification engineer eight hours to complete the one page 
required for each new type certification. The eight hours to complete a 
page includes the research, coordination, and review each document 
requires. Therefore, the FAA estimates the total paperwork costs for 
Sec.  23.2150(c) will be about $1,990 in 2015 dollars. The FAA assumes 
that this section will add costs to only one of the new part 23 
turbojet airplane type certificates estimated in the Fleet Discussion 
section of the regulatory evaluation. The following table shows the 
total paperwork costs for the changes to Sec.  23.2150(c).

----------------------------------------------------------------------------------------------------------------
                                                                  Changes to
                Airplane type                      Hours        flight manual      Paper work         Total
----------------------------------------------------------------------------------------------------------------
Turbojet....................................           2,044         $125,149           $1,990         $127,139
----------------------------------------------------------------------------------------------------------------

    Conversations with the industry ARC members indicate that there may 
need to be some changes to the engineering manuals to describe how the 
accepted means of compliance must be related to the regulations. 
Depending on the complexity of each company's manual, industry 
estimates that these changes could run from about $50,060 up to 
$200,238 in 2015 dollars. This will be a one-time cost per new type 
certification.
    As we received no comments to the paperwork analysis in the NPRM, 
we use the same assumptions in the final rule regarding manual 
complexity. The manufacturers of the two new part 23 reciprocating 
engine airplane type certifications, discussed in the Fleet Discussion 
section of the regulatory evaluation, will spend $50,060 to make the 
changes to the engineering manual. We also assume that the one new part 
23 turboprop airplane certification and the two new part 23 turbojet 
airplane certifications, discussed in the Fleet Discussion section of 
the regulatory evaluation, will use the more complex and costly 
approach of $200,238.
    The FAA notes that either the simple approach or the more complex 
approach to updating the manuals could also either take place in-house 
or could be contracted out to a consultant. The following table shows 
the total paperwork costs for the changes to the engineering manuals in 
2015 dollars.

[[Page 96674]]

----------------------------------------------------------------------------------------------------------------
                                     Number of
                                   estimated new      Simple          Complex
          Airplane type                type          approach        approach          Hours           Total
                                   certificates
----------------------------------------------------------------------------------------------------------------
Recip...........................               2         $50,060              $0           1,610        $100,119
Turboprop.......................               1               0         200,238           3,219         200,238
Turbojet........................               2               0         200,238           6,439         400,476
                                 -------------------------------------------------------------------------------
    Total.......................  ..............  ..............  ..............          11,268         700,833
----------------------------------------------------------------------------------------------------------------
These numbers are subject to rounding error.

F. International Compatibility and Cooperation

    In keeping with U.S. obligations under the Convention on 
International Civil Aviation, it is FAA policy to conform to 
International Civil Aviation Organization (ICAO) Standards and 
Recommended Practices to the maximum extent practicable. The FAA has 
reviewed the corresponding ICAO Standards and Recommended Practices and 
has identified the following differences with these proposed 
regulations. The ICAO Standards for small airplanes use weight and 
propulsion to differentiate between some requirements. The proposed 
regulations use certification levels and performance to differentiate 
between some requirements. Furthermore, part 23 will still allow the 
certification of airplanes up to 19,000 pounds. If this proposal is 
adopted, the FAA intends to file these differences with ICAO. Executive 
Order (EO) 13609, Promoting International Regulatory Cooperation, (77 
FR 26413, May 4, 2012) promotes international regulatory cooperation to 
meet shared challenges involving health, safety, labor, security, 
environmental, and other issues and reduce, eliminate, or prevent 
unnecessary differences in regulatory requirements. The FAA has 
analyzed this action under the policy and agency responsibilities of 
Executive Order 13609, Promoting International Regulatory Cooperation. 
The agency has determined that this action would eliminate differences 
between U.S. aviation standards and those of other CAAs by aligning the 
revised part 23 standards with the new CS 23 standards that are being 
developed concurrently by EASA. Several other CAAs are participating in 
this effort and intend to either adopt the new part 23 or CS 23 
regulations or revise their airworthiness standards to align with these 
new regulations.
    The Part 23 ARC included participants from several foreign CAAs and 
international members from almost every GA manufacturer of both 
airplanes and avionics. It also included several Light-Sport Aircraft 
manufacturers who are interested in certificating their products using 
the airworthiness standards contained in part 23. The rulemaking and 
means of compliance are international efforts. Authorities from Europe, 
Canada, Brazil, China, and New Zealand all are working to produce 
similar rules. These rules, while not identical, are intended to allow 
the use of the same set of industry developed means of compliance. 
Industry has told that FAA that it is very costly to address the 
differences that some contrived means of compliance imposes. If there 
is substantial agreement between the major CAAs to use the same 
industry means of compliance, then U.S. manufactures expect a 
significant saving for exporting their products.
    Furthermore, this project is a harmonization project between the 
FAA and EASA.
    EASA has worked a parallel rulemaking program for CS 23. The FAA 
provided comments to the EASA A-NPA. EASA and other authorities will 
have an opportunity to comment on this NPRM when it is published. These 
efforts will allow the FAA, EASA and other authorities to work toward a 
harmonized set of regulations when the final rules are published.

G. Environmental Analysis

    FAA Order 1050.1F identifies FAA actions that are categorically 
excluded from preparation of an environmental assessment or 
environmental impact statement under the National Environmental Policy 
Act in the absence of extraordinary circumstances. The FAA has 
determined this rulemaking action qualifies for the categorical 
exclusion identified in paragraph 5-6.6 and involves no extraordinary 
circumstances.

H. Regulations Affecting Intrastate Aviation in Alaska

    Section 1205 of the FAA Reauthorization Act of 1996 (110 Stat. 
3213) requires the Administrator, when modifying 14 CFR regulations in 
a manner affecting intrastate aviation in Alaska, to consider the 
extent to which Alaska is not served by transportation modes other than 
aviation, and to establish appropriate regulatory distinctions. Because 
this rule would apply to GA airworthiness standards, it could, if 
adopted, affect intrastate aviation in Alaska. The FAA, therefore, 
specifically requests comments on whether there is justification for 
applying the proposed rule differently in intrastate operations in 
Alaska.

V. Executive Order Determination

A. Executive Order 13132, Federalism

    The FAA has analyzed this rule under the principles and criteria of 
Executive Order 13132, Federalism. The agency has determined that this 
action would not have a substantial direct effect on the States, or the 
relationship between the Federal Government and the States, or on the 
distribution of power and responsibilities among the various levels of 
government, and, therefore, would not have Federalism implications.

B. Executive Order 13211, Regulations That Significantly Affect Energy 
Supply, Distribution, or Use

    The FAA analyzed this rule under Executive Order 13211, Actions 
Concerning Regulations that Significantly Affect Energy Supply, 
Distribution, or Use (May 18, 2001). The agency has determined that it 
would not be a ``significant energy'' action under the executive order 
and would not be likely to have a significant adverse effect on the 
supply, distribution, or use of energy.

VI. How To Obtain Additional Information

A. Rulemaking Documents

    An electronic copy of rulemaking documents may be obtained from the 
Internet by--
    1. Searching the Federal eRulemaking Portal (http://www.regulations.gov) for Docket FAA-2015-1621;
    2. Visiting the FAA's Regulations and Policies Web page at http://www.faa.gov/regulations_policies/; or
    3. Accessing the Government Printing Office's Web page at http://www.gpo.gov/fdsys/.

[[Page 96675]]

    Copies may also be obtained by sending a request to the Federal 
Aviation Administration, Office of Rulemaking, ARM-1, 800 Independence 
Avenue SW., Washington, DC 20591, or by calling (202) 267-9680.

B. Comments Submitted to the Docket

    Comments received may be viewed by going to http://www.regulations.gov and following the online instructions to search the 
docket number (FAA-2015-1621) for this action. Anyone is able to search 
the electronic form of all comments received into any of the FAA's 
dockets by the name of the individual submitting the comment (or 
signing the comment, if submitted on behalf of an association, 
business, labor union, etc.).

C. Small Business Regulatory Enforcement Fairness Act

    The Small Business Regulatory Enforcement Fairness Act (SBREFA) of 
1996 requires FAA to comply with small entity requests for information 
or advice about compliance with statutes and regulations within its 
jurisdiction. A small entity with questions regarding this document, 
may contact its local FAA official, or the person listed under the FOR 
FURTHER INFORMATION CONTACT heading at the beginning of the preamble. 
To find out more about SBREFA on the Internet, visit http://www.faa.gov/regulations_policies/rulemaking/sbre_act/.

Appendix 1 to the Preamble--Former to New Regulations Cross-Reference 
Table

    The below cross-reference table is intended to permit easy 
access from former to new regulations. The preamble is organized 
topical, section-by-section, former to new regulations. This table 
should assist the reader in following the section discussions 
contained in the preamble. If the intent of a former regulation was 
incorporated into multiple new regulations, only the most pertinent 
new regulations were listed.

----------------------------------------------------------------------------------------------------------------
            Former section                   Former title             New section               New title
----------------------------------------------------------------------------------------------------------------
                                               Subpart A--General
----------------------------------------------------------------------------------------------------------------
23.1.................................  Applicability..........  23.2000................  Applicability.
23.2.................................  Special retroactive      23.2...................  Interim Airworthiness
                                        requirements.                                     Requirements.
23.3.................................  Airplane categories....  23.2005................  Certification of normal
                                                                                          category airplanes
                                                                23.2010................  Accepted means of
                                                                                          compliance.
----------------------------------------------------------------------------------------------------------------
                                                Subpart B--Flight
----------------------------------------------------------------------------------------------------------------
23.21................................  Proof of compliance....  23.2100................  Weight and center of
                                                                                          gravity.
23.23................................  Load distribution        23.2100................  Weight and center of
                                        limits.                                           gravity.
23.25................................  Weight limits..........  23.2100................  Weight and center of
                                                                                          gravity.
23.29................................  Empty weight and         23.2100................  Weight and center of
                                        corresponding center                              gravity.
                                        of gravity.
23.31................................  Removable ballast......  23.2100................  Weight and center of
                                                                                          gravity.
23.33................................  Propeller speed and      23.2400................  Powerplant
                                        pitch limits.                                     installation.
23.45................................  Performance--General...  23.2105................  Performance data.
23.49................................  Stalling speed.........  23.2110................  Stall Speed.
23.51................................  Takeoff speeds.........  23.2115................  Takeoff performance.
23.53................................  Takeoff performance....  23.2115................  Takeoff performance.
23.55................................  Accelerate-stop          23.2115................  Takeoff performance.
                                        distance.
23.57................................  Takeoff path...........  23.2115................  Takeoff performance.
23.59................................  Takeoff distance and     23.2115................  Takeoff performance.
                                        takeoff run.
23.61................................  Takeoff flight path....  23.2115................  Takeoff performance.
23.63................................  Climb: General.........  23.2120................  Climb requirements.
23.65................................  Climb: All engines       23.2120................  Climb requirements.
                                        operating.
23.66................................  Takeoff climb: one       23.2125................  Climb information.
                                        engine inoperative.
23.67................................  Climb: One engine        23.2120................  Climb requirements.
                                        inoperative.
23.69................................  Enroute climb/descent..  23.2125................  Climb information.
23.71................................  Glide: single engine     23.2125................  Climb information.
                                        airplanes.
23.73................................  Reference landing        23.2130................  Landing.
                                        approach speed.
23.75................................  Landing distance.......  23.2130................  Landing.
23.77................................  Balked landing.........  23.2120................  Climb requirements.
23.141...............................  Flight Characteristics-  23.2135................  Controllability.
                                        General.
23.143...............................  Controllability and      23.2135................  Controllability.
                                        Maneuverability--Gener
                                        al.
23.145...............................  Longitudinal control...  23.2135................  Controllability.
23.147...............................  Directional and lateral  23.2135................  Controllability.
                                        control.
23.149...............................  Minimum control speed..  23.2135................  Controllability.
23.151...............................  Acrobatic maneuvers....  23.2135................  Controllability.
23.153...............................  Control during landings  23.2135................  Controllability.
23.155...............................  Elevator control force   23.2135................  Controllability.
                                        in maneuvers.
23.157...............................  Rate of roll...........  23.2135................  Controllability.
23.161...............................  Trim...................  23.2140................  Trim.
23.171...............................  Stability--General.....  23.2145................  Stability.
23.173...............................  Static longitudinal      23.2145................  Stability.
                                        stability.
23.175...............................  Demonstration of static  23.2145................  Stability.
                                        longitudinal stability.
23.177...............................  Static directional and   23.2145................  Stability.
                                        lateral stability.

[[Page 96676]]

 
23.179...............................  Instrument stick force   23.2145................  Stability.
                                        measurements.
23.181...............................  Dynamic stability......  23.2145................  Stability.
23.201...............................  Wings level stall......  23.2150................  Stall characteristics,
                                                                                          stall warning, and
                                                                                          spins.
23.203...............................  Turning Flight and       23.2150................  Stall characteristics,
                                        accelerated turning                               stall warning, and
                                        stalls.                                           spins.
23.207...............................  Stall Warning..........  23.2150................  Stall characteristics,
                                                                                          stall warning, and
                                                                                          spins.
23.221...............................  Spinning...............  23.2150................  Stall characteristics,
                                                                                          stall warning, and
                                                                                          spins.
23.231...............................  Longitudinal stability   23.2155................  Ground and water
                                        and control.                                      handling
                                                                                          characteristics.
23.233...............................  Directional stability    23.2155................  Ground and water
                                        and control.                                      handling
                                                                                          characteristics.
23.235...............................  Operation on unpaved     23.2155................  Ground and water
                                        surfaces.                                         handling
                                                                                          characteristics.
23.237...............................  Operation on water.....  23.2155................  Ground and water
                                                                                          handling
                                                                                          characteristics.
23.239...............................  Spray characteristics..  23.2155................  Ground and water
                                                                                          handling
                                                                                          characteristics.
23.251...............................  Vibration and buffeting  23.2160................  Vibration, buffeting,
                                                                                          and high-speed
                                                                                          characteristics.
23.253...............................  High-speed               23.2160................  Vibration, buffeting,
                                        characteristics.                                  and high-speed
                                                                                          characteristics.
23.255...............................  Out of trim              23.2160................  Vibration, buffeting,
                                        characteristics.                                  and high-speed
                                                                                          characteristics.
                                                                23.2165................  Performance and flight
                                                                                          characteristics
                                                                                          requirements for
                                                                                          flight in icing
                                                                                          conditions.
----------------------------------------------------------------------------------------------------------------
                                              Subpart C--Structure
----------------------------------------------------------------------------------------------------------------
23.301...............................  Loads..................  23.2210, 23.2230.......  Structural design
                                                                                          loads, Limit and
                                                                                          ultimate loads.
(a)..................................  .......................  23.2230................  Limit and ultimate
                                                                                          loads.
(b)..................................  .......................  23.2210................  Structural design
                                                                                          loads.
(c)..................................  .......................  23.2210................  Structural design
                                                                                          loads.
(d)..................................  .......................  23.2210................  Structural design
                                                                                          loads.
23.302...............................  Canard or tandem wing    23.2210................  Structural design
                                        configurations.                                   loads.
23.303...............................  Factors of safety......  23.2230................  Limit and ultimate
                                                                                          loads.
23.305...............................  Strength and             23.2235................  Structural strength.
                                        deformation.
                                                                23.2205................  Interaction of systems
                                                                                          and structures.
23.307...............................  Proof of structure.....  23.2235................  Structure strength.
23.321...............................  Flight Loads--General..  23.2210................  Structural design
                                                                                          loads.
(a)..................................  .......................  23.2210................  Structural design
                                                                                          loads.
(b)..................................  .......................  23.2200................  Structural design
                                                                                          envelope.
(c)..................................  .......................  23.2200................  Structural design
                                                                                          envelope.
23.331...............................  Symmetrical flight       23.2210................  Structural design
                                        conditions.                                       loads.
23.333...............................  Flight envelope........  23.2200................  Structural design
                                                                                          envelope.
(a)..................................  .......................  23.2200................  Structural design
                                                                                          envelope.
(b)..................................  .......................  23.2200................  Structural design
                                                                                          envelope.
(c)..................................  .......................  23.2215................  Flight load conditions.
(d)..................................  .......................  23.2200................  Structural design
                                                                                          envelope.
23.335...............................  Design airspeeds.......  23.2200................  Structural design
                                                                                          envelope.
23.337...............................  Limit maneuvering load   23.2200................  Flight load conditions.
                                        factors.
(a)..................................  .......................  23.2200................  Structural design
                                                                                          envelope.
(b)..................................  .......................  23.2200................  Structural design
                                                                                          envelope.
(c)..................................  .......................  Means of Compliance....
23.341...............................  Gust load factors......  23.2215................  Flight load conditions.
23.343...............................  Design fuel loads......  23.2200................  Structural design
                                                                                          envelope.
(a)..................................  .......................  23.2200................  Structural design
                                                                                          envelope.
(b)..................................  .......................  23.2200................  Structural design
                                                                                          envelope.
(c)..................................  .......................  Means of Compliance....
23.345...............................  High lift devices......  23.2225................  Component loading
                                                                                          conditions.
23.347...............................  Unsymmetrical flight     23.2215................  Flight load conditions.
                                        loads.
23.349...............................  Rolling conditions.....  23.2215................  Flight load conditions.
23.351...............................  Yawing conditions......  23. 215................  Flight load conditions.
23.361...............................  Engine torque..........  23.2225................  Component loading
                                                                                          conditions.
23.363...............................  Side load on engine      23.2225................  Component loading
                                        mount.                                            conditions.
23.365...............................  Pressurized cabin loads  23.2225................  Flight load conditions.
(e)..................................  .......................  23.2240................  Structural durability.

[[Page 96677]]

 
23.367...............................  Unsymmetrical loads due  23.2215................  Flight load conditions.
                                        to engine failure.
23.369...............................  Rear lift truss........  Means of Compliance....
23.371...............................  Gyroscopic and           23.2225................  Component loading
                                        aerodynamic loads.                                conditions.
23.373...............................  Speed control devices..  23.2225................  Component loading
                                                                                          conditions.
23.391...............................  Control surface loads..  23.2225................  Component loading
                                                                                          conditions.
23.393...............................  Loads parallel to hinge  23.2225................  Component loading
                                        line.                                             conditions.
23.395...............................  Control system loads...  23.2225................  Component loading
                                                                                          conditions.
23.397...............................  Limit control forces     23.2225................  Component loading
                                        and torques.                                      conditions.
23.399...............................  Dual control system....  23.2225................  Component loading
                                                                                          conditions.
23.405...............................  Secondary control        23.2225................  Component loading
                                        system.                                           conditions.
23.407...............................  Trim tab effects.......  23.2225................  Component loading
                                                                                          conditions.
23.409...............................  Tabs...................  23.2225................  Component loading
                                                                                          conditions.
23.415...............................  Ground gust conditions.  23.2225................  Component loading
                                                                                          conditions.
23.421...............................  Balancing loads........  Means of Compliance....
23.423...............................  Maneuvering loads......  23.2215................  Flight load conditions.
23.425...............................  Gust loads.............  23.2215................  Flight load conditions.
23.427...............................  Unsymmetrical loads due  23.2215................  Flight load conditions.
                                        to engine failure.
23.441...............................  Maneuvering loads......  23.2215................  Flight load conditions.
23.443...............................  Gust loads.............  23.2215................  Flight load conditions.
23.445...............................  Outboard fins or         Means of Compliance....
                                        winglets.
23.455...............................  Ailerons...............  23.2225................  Component loading
                                                                                          conditions.
23.459...............................  Special devices........  23.2225................  Component loading
                                                                                          conditions.
23.471...............................  Ground Loads--General..  23.2220................  Ground and water load
                                                                                          conditions.
23.473...............................  Ground load conditions   23.2220................  Ground and water load
                                        and assumptions.                                  conditions.
23.477...............................  Landing gear             23.2220................  Ground and water load
                                        arrangement.                                      conditions.
23.479...............................  Level landing            23.2220................  Ground and water load
                                        conditions.                                       conditions.
23.481...............................  Tail down landing        23.2220................  Ground and water load
                                        conditions.                                       conditions.
23.483...............................  One-wheel landing        23.2220................  Ground and water load
                                        conditions.                                       conditions.
23.485...............................  Side load conditions...  23.2220................  Ground and water load
                                                                                          conditions.
23.493...............................  Braked roll conditions.  23.2220................  Ground and water load
                                                                                          conditions.
23.497...............................  Supplementary            23.2220................  Ground and water load
                                        conditions for tail                               conditions.
                                        wheels.
23.499...............................  Supplementary            23.2220................  Ground and water load
                                        conditions for nose                               conditions.
                                        wheels.
23.505...............................  Supplementary            23.2220................  Ground and water load
                                        conditions for                                    conditions.
                                        skiplanes.
23.507...............................  Jacking loads..........  23.2220................  Ground and water load
                                                                                          conditions.
23.509...............................  Towing loads...........  23.2220................  Ground and water load
                                                                                          conditions.
23.511...............................  Ground load:             23.2220................  Ground and water load
                                        Unsymmetrical loads on                            conditions.
                                        multiple-wheel units.
23.521...............................  Water load conditions..  23.2220................  Ground and water load
                                                                                          conditions.
23.523...............................  Design weights and       23.2220................  Ground and water load
                                        center of gravity                                 conditions.
                                        positions.
23.525...............................  Application of loads...  23.2220................  Ground and water load
                                                                                          conditions.
23.527...............................  Hull and main float      23.2220................  Ground and water load
                                        load factors.                                     conditions.
23.529...............................  Hull and main float      23.2220................  Ground and water load
                                        landing conditions.                               conditions.
23.531...............................  Hull and main float      23.2220................  Ground and water load
                                        takeoff conditions.                               conditions.
23.533...............................  Hull and main float      23.2220................  Ground and water load
                                        bottom pressures.                                 conditions.
23.535...............................  Auxiliary float loads..  23.2220................  Ground and water load
                                                                                          conditions.
23.537...............................  Seawing loads..........  23.2220................  Ground and water load
                                                                                          conditions.
23.561...............................  Emergency Landing        23.2270................  Emergency conditions.
                                        Conditions--General.

[[Page 96678]]

 
23.562...............................  Emergency landing        23.2270................  Emergency conditions.
                                        dynamic conditions.
23.571...............................  Metallic pressurized     23.2240................  Structural durability.
                                        cabin structures.
23.572...............................  Metallic wing,           23.2240................  Structural durability.
                                        empennage, and
                                        associated structures.
23.573...............................  Damage tolerance and     23.2240................  Structural durability.
                                        fatigue evaluation of
                                        structure.
23.574...............................  Metallic damage          23.2240................  Structural durability.
                                        tolerance and fatigue
                                        evaluation of commuter
                                        category airplanes.
23.575...............................  Inspections and other    23.2240................  Structural durability.
                                        procedures.
----------------------------------------------------------------------------------------------------------------
                                       Subpart D--Design and Construction
----------------------------------------------------------------------------------------------------------------
23.601...............................  General................  23.2250................  Design and construction
                                                                                          principles.
23.603...............................  Materials and            23.2250, 23.2260.......  Design and construction
                                        workmanship.                                      principles, Materials
                                                                                          and processes.
23.605...............................  Fabrication methods....  23.2260................  Materials and
                                                                                          processes.
23.607...............................  Fasteners..............  23.2250, 23.2255.......  Design and construction
                                                                                          principles, Protection
                                                                                          of structure.
23.609...............................  Protection of Structure  23.2255................  Protection of
                                                                                          structure.
23.611...............................  Accessibility..........  23.2255................  Protection of
                                                                                          structure.
23.613...............................  Material strength        23.2260................  Materials and
                                        properties and design                             processes.
                                        values.
23.619...............................  Special factors........  23.2265................  Special factors of
                                                                                          safety.
23.621...............................  Casting factors........  23.2265................  Special factors of
                                                                                          safety.
23.623...............................  Bearing factors........  23.2265................  Special factors of
                                                                                          safety.
23.625...............................  Fitting factors........  23.2265................  Special factors of
                                                                                          safety.
23.627...............................  Fatigue strength.......  23.2240................  Structural durability.
23.629...............................  Flutter................  23.2245................  Aeroelasticity.
23.641...............................  Proof of strength......  Means of Compliance....
23.651...............................  Proof of strength......  Means of Compliance....
23.655...............................  Installation...........  23.2300(a)(2)..........  Flight control systems.
23.657...............................  Hinges.................  23.2265................  Special factors of
                                                                                          safety.
23.659...............................  Mass balance...........  23.2215, 23.2335.......  Flight load conditions,
                                                                                          Structural strength.
23.671...............................  Control systems--
                                        General.
(a)..................................  .......................  23.2300(a)(1) &          Flight control systems
                                                                 23.2600(a).              & Flightcrew
                                                                                          interface.
(b)..................................  .......................  23.2600, 23.2605.......  Flightcrew interface,
                                                                                          Installation and
                                                                                          operation.
23.672...............................  Stability augmentation
                                        and automatic and
                                        power-operated systems.
(a)..................................  .......................  23.2605(c).............  Installation and
                                                                                          operation.
(b)..................................  .......................  23.2300(a)(2)..........  Flight control systems.
(c)..................................  .......................  23.2510, 23.2300(a)(2).  Installation and
                                                                                          operation, Flight
                                                                                          control systems.
23.673...............................  Primary flight controls  .......................  Definition.
23.675...............................  Stops..................  23.2300(a)(2)..........  Flight control systems.
23.677...............................  Trim systems...........
(a)..................................  .......................  23.2300(b) & 23.2600...  Flight control systems
                                                                                          & Flightcrew
                                                                                          interface.
(b)..................................  .......................  23.2300(a)(2)..........  Flight control systems.
(c)..................................  .......................  23.2245................  Aeroelasticity.
(d)..................................  .......................  23.2515................  Equipment, systems and
                                                                                          installations.
23.679...............................  Control system locks...
(a), (b).............................  .......................  23.2605(c).............  Installation and
                                                                                          operation.
(c)..................................  .......................  23.2300(a)(2)..........  Flight control systems.
23.681...............................  Limit load static tests
(a)..................................  .......................  23.2225(b), 23.2235....  Component loading
                                                                                          conditions, Structural
                                                                                          strength.
(b)..................................  .......................  23.2265................  Special factors of
                                                                                          safety.
23.683...............................  Operation tests........  23.2250(d),              Design and construction
                                                                 23.2300(a)(2).           principles, Flight
                                                                                          control systems.
23.685...............................  Control system details.  23.2300(a)(2)..........  Flight control systems.
23.687...............................  Spring devices.........  23.2245, 23.2250 &       Aeroelasticity.
                                                                 23.2300(a)(2).           Structural design &
                                                                                          Flight control
                                                                                          systems.
23.689...............................  Cable systems..........  23.2250(c).............  Design and construction
                                                                                          principles.
(a)(3)...............................  .......................  23.2255(c).............  Protection of
                                                                                          structure.

[[Page 96679]]

 
23.691...............................  Artificial stall
                                        barrier system.
(a), (b).............................  .......................  23.2250................  Design and construction
                                                                                          principles.
(c)..................................  .......................  23.2605(c).............  Installation and
                                                                                          operation.
(d), (e), (f)........................  .......................  23.2300(a)(2)..........  Flight control systems.
(g)..................................  .......................  23.2510................  Equipment, systems, and
                                                                                          installations.
23.693...............................  Joints.................  23.2265................  Special factors of
                                                                                          safety.
23.697...............................  Wing flap controls.....  23.2300(a).............  Flight control systems.
23.699...............................  Wing flap position       23.2600(b).............  Flightcrew interface.
                                        indicator.
23.701...............................  Flap interconnection...  23.2300(a)(2), 23.2510.  Flight control systems
                                                                                          & Equipment, systems,
                                                                                          and installations.
23.703...............................  Takeoff warning system.  23.2605(c).............  Installation and
                                                                                          operation.
23.721...............................  General................  23.2305(a)(2),           Landing gear systems,
                                                                 23.2430(a)(6).           Fuel systems.
23.723...............................  Shock absorption tests.  23.2235, 23.2250(c)....  Structural strength,
                                                                                          Design and
                                                                                          construction
                                                                                          principles.
23.725...............................  Limit drop tests.......  23.2235................  Structural strength.
23.726...............................  Ground load dynamic      23.2235................  Structural strength.
                                        tests.
23.727...............................  Reserve energy           23.2235, 23.2250(c)....  Structural strength,
                                        absorption drop tests.                            Design and
                                                                                          construction
                                                                                          principles.
23.729...............................  Landing gear extension
                                        and retraction system.
(a)..................................  .......................  23.2235................  Structural strength.
(b)..................................  .......................  23.2305(c)(1)..........  Landing gear systems.
(c)..................................  .......................  23.2305(c)(2)..........  Landing gear systems.
(d)..................................  .......................  23.2505................  Function and
                                                                                          installation.
(e)..................................  .......................  23.2600................  Flightcrew interface.
(f)..................................  .......................  23.2605(c).............  Installation and
                                                                                          operation.
(g)..................................  .......................  23.2305(a)(2)..........  .......................
23.731...............................  Wheels.................  23.2220, 23.2250(c)....  Ground and water load
                                                                                          conditions, Design and
                                                                                          construction
                                                                                          principles.
23.733...............................  Tires..................
(a)..................................  .......................  23.2250(c).............  Design and construction
                                                                                          principles.
(b)..................................  .......................  23.2610................  Instrument markings,
                                                                                          control markings, and
                                                                                          placards.
(c)..................................  .......................  23.2250(c).............  Design and construction
                                                                                          principles.
23.735...............................  Brakes.................
(a), (b), (c), (e)...................  .......................  23.2305(b).............  Landing gear systems.
(b)..................................  .......................  23.2250(c).............  Design and construction
                                                                                          principles.
(d)..................................  .......................  23.2510................  Equipment, systems, and
                                                                                          installations.
23.737...............................  Skis...................  23.2235................  Structural strength.
23.745...............................  Nose/Tail wheel          23.2305 & 23.2600(a)...  Landing gear systems &
                                        steering.                                         Flightcrew interface.
23.751...............................  Main float buoyancy....  23.2310................  Buoyancy for seaplanes
                                                                                          and amphibians.
23.753...............................  Main float design......  23.2220................  Ground and water load
                                                                                          conditions.
23.755...............................  Hulls..................  23.2310................  Buoyancy for seaplanes
                                                                                          and amphibians.
23.757...............................  Auxiliary floats.......  23.2310................  Buoyancy for seaplanes
                                                                                          and amphibians.
23.771...............................  Pilot compartment......
(a)..................................  .......................  23.2600................  Flightcrew interface.
(b)..................................  .......................  23.2320(a)(1)..........  Occupant physical
                                                                                          environment.
(c)..................................  .......................  23.2320(a)(2)..........  Occupant physical
                                                                                          environment.
23.773...............................  Pilot compartment view.  23.2600(a).............  Flightcrew interface.
23.775...............................  Windshields and windows
(a)..................................  .......................  23.2320(a)(3)..........  Occupant physical
                                                                                          environment.
(b), (c), (d)........................  .......................  23.2250................  Design and construction
                                                                                          principles.
(e)..................................  .......................  23.2600(a).............  Flightcrew interface.
(f)..................................  .......................  23.2540................  Flight in icing
                                                                                          conditions.
(g)..................................  .......................  23.2510................  Equipment, systems and
                                                                                          installations.
(h)(1)...............................  .......................  23.2320(b).............  Occupant physical
                                                                                          environment.
(h)(2)...............................  .......................  23.2600(c).............  Flightcrew interface.

[[Page 96680]]

 
23.777...............................  Cockpit controls.......  23.2600, 23.2610.......  Flightcrew interface,
                                                                                          Instrument markings,
                                                                                          control markings and
                                                                                          placards.
23.779...............................  Motion and effect of     23.2600................  Flightcrew interface.
                                        cockpit controls.
23.781...............................  Cockpit control knob     23.2600................  Flightcrew interface.
                                        shape.
23.783...............................  Doors..................
(a), (b), (c)(2), (c)(3), (c)(4),      .......................  23.2315(a).............  Means of egress and
 (c)(5), (c)(6), (d), (f), (g).                                                           emergency exits.
(b)..................................  .......................  23.2250................  Design and construction
                                                                                          principles.
(c)(1), (e)..........................  .......................  23.2250(e).............  Design and construction
                                                                                          principles.
(e)(3)...............................  .......................  23.2605(c).............  Installation and
                                                                                          operation.
23.785...............................  Seats, berths, litters,  23.2265 and 23.2270....  Special factors of
                                        safety belts, and                                 safety, Emergency
                                        shoulder harnesses.                               conditions.
23.787...............................  Baggage and cargo        23.2270(e) & 23.2315(a)  Emergency conditions &
                                        compartments.                                     Means of egress and
                                                                                          emergency exits.
23.791...............................  Passenger information    23.2320(a)(1)..........  Occupant physical
                                        signs.                                            environment.
23.803...............................  Emergency evacuation...  23.2315(a).............  Means of egress and
                                                                                          emergency exits.
23.805...............................  Flightcrew emergency     23.2315(a).............  Means of egress and
                                        exits.                                            emergency exits.
23.807...............................  Emergency exits........
(a), (b)(1), (b)(2), (b)(3), (b)(4),   .......................  23.2315(a).............  Means of egress and
 (d)(1), (d)(3), (d)(4), (c), (e).                                                        emergency exits.
(b)(5), (b)(6).......................  .......................  23.2315(b).............  Means of egress and
                                                                                          emergency exits.
(d)(2)...............................  .......................  23.2250(e).............  Design and construction
                                                                                          principles.
23.811...............................  Emergency exit marking.  23.2315(a).............  Means of egress and
                                                                                          emergency exits.
23.812...............................  Emergency lighting.....  23.2315(a).............  Means of egress and
                                                                                          emergency exits.
23.813...............................  Emergency exit access..  23.2315(a).............  Means of egress and
                                                                                          emergency exits.
23.815...............................  Width of aisle.........  23.2315(a).............  Means of egress and
                                                                                          emergency exits.
23.831...............................  Ventilation............
(a), (b), (c)........................  .......................  23.2320(c).............  Occupant physical
                                                                                          environment.
(c)..................................  .......................  23.2600(a).............  Flightcrew interface.
(d)..................................  .......................  23.2510................  Equipment, systems and
                                                                                          installations.
23.841...............................  Pressurized cabins.....
(a), (b)(4), (d)(1)..................  .......................  23.2320(c).............  Occupant physical
                                                                                          environment.
(b)(1), (b)(2), (b)(8), (c), (d)(2),   .......................  23.2320(d).............  Occupant physical
 (d)(3).                                                                                  environment.
(b)(3)...............................  .......................  23.2320(c), (d)........  Occupant physical
                                                                                          environment.
(b)(5), (b)(6), (d)(4), (d)(5).......  .......................  23.2605................  Installation and
                                                                                          operation.
(b)(7)...............................  .......................  23.2610................  Instrument markings,
                                                                                          control markings, and
                                                                                          placards.
(b)(8), (c), (d)(2), (d)(3)..........  .......................  23.2510................  Equipment, systems and
                                                                                          installations.
(d)(5)...............................  .......................  23.2505................  Function and
                                                                                          installation.
23.843...............................  Pressurization tests...
(a)..................................  .......................  23.2225(c), 23.2236....  Component loading
                                                                                          conditions, Structural
                                                                                          strength.
(b)..................................  .......................  23.2320 & 23.2505......  Occupant physical
                                                                                          environment & Function
                                                                                          and installation.
23.851...............................  Fire extinguishers.....
(a) and (b)..........................  .......................  23.2325................  Fire protection.
(c)..................................  .......................  Means Of Compliance....
23.853...............................  Passenger and crew       .......................  .......................
                                        compartment interiors.
(a), (d)(3)(i), (d)(3)(iii),           .......................  23.2325................  Fire protection.
 (d)(3)(iv), (e), (f).
(b)(c) and (d)(1)(2).................  .......................  Means Of Compliance....
23.855...............................  Cargo and baggage        23.2325................  Fire protection.
                                        compartment fire
                                        protection.
23.856...............................  Thermal/acoustic         23.2325................  Fire protection.
                                        insulation materials.
23.859...............................  Combustion heater fire
                                        protection.
(a)..................................  .......................  23.2325(h).............  Fire protection.

[[Page 96681]]

 
(b) thru (i).........................  .......................  23.2250(c).............  Design and construction
                                                                                          principles.
23.863...............................  Flammable fluid fire     23.2325(g).............  Fire protection.
                                        protection.
23.865...............................  Fire protection of       23.23330...............  Fire protection in
                                        flight controls,                                  designated fire zones
                                        engine mounts, and                                and adjacent areas.
                                        other flight structure.
23.867...............................  Electrical bonding and   23.2335................  Lightning protection.
                                        protection against
                                        lightning and static
                                        electricity.
23.871...............................  Leveling means.........  Means Of Compliance....
----------------------------------------------------------------------------------------------------------------
                                              Subpart E--Powerplant
----------------------------------------------------------------------------------------------------------------
23.901(a) and (f)....................  Installation...........  23.2400(a).............  Powerplant
                                                                                          Installation.
(b), (c), and (d)(2).................  .......................  23.2400(c).............  Powerplant
                                                                                          Installation.
(d)(1) and (e).......................  .......................  23.2400(e).............  Powerplant
                                                                                          Installation.
23.903(a)(1).........................  Engines................  23.2400(b).............  Powerplant
                                                                                          Installation.
(a)(2)...............................  .......................  23.2400(c).............  Powerplant
                                                                                          Installation.
(b)..................................  .......................  23.2400(c), 23.2410(a),  Powerplant
                                                                 (b) and 23.2425(a).      installation,
                                                                                          Powerplant
                                                                                          installation hazard
                                                                                          assessment; Powerplant
                                                                                          operational
                                                                                          characteristics.
(c)..................................  .......................  23.2410(a) and (c).....  Powerplant installation
                                                                                          hazard assessment.
(d) thru (g).........................  .......................  23.00(d), 23.2410(a)     Powerplant
                                                                 and 23.2425(b).          installation,
                                                                                          Powerplant
                                                                                          installation hazards
                                                                                          assessment, Powerplant
                                                                                          operational
                                                                                          characteristics.
23.904...............................  Automatic power reserve  23.2405................  Automatic power or
                                        system.                                           thrust control
                                                                                          systems.
23.905(a)............................  Propellers.............  23.2400(b).............  Powerplant
                                                                                          installation.
(b)..................................  .......................  23.2400(e).............  Powerplant
                                                                                          installation.
(c)..................................  .......................  23.2425(b).............  Powerplant operational
                                                                                          characteristics.
(d), (e) and (f).....................  .......................  23.2400(c).............  Powerplant
                                                                                          installation.
(g)..................................  .......................  23.2400(c), (e)........  Powerplant
                                                                                          installation.
(h)..................................  .......................  23.2400(c)(3)..........  Powerplant
                                                                                          installation.
23.907...............................  Propeller vibration and  23.2400(c)(4), (e).....  Powerplant
                                        fatigue.                                          installation.
23.909(a)............................  Turbocharger systems...  23.2400(e) and           Powerplant
                                                                 23.2425(a).              installation,
                                                                                          Powerplant operational
                                                                                          characteristics.
(b)..................................  .......................  23.2410(a).............  Powerplant installation
                                                                                          hazards assessment.
(c)..................................  .......................  23.2400(c)(3) and        Powerplant
                                                                 23.2410(a).              installation,
                                                                                          Powerplant
                                                                                          installation hazards
                                                                                          assessment.
(d)..................................  .......................  23.2400(c).............  Powerplant
                                                                                          installation.
(e)..................................  .......................  23.2400(e), 23.2420 and  Powerplant
                                                                 23.2620.                 installation,
                                                                                          Powerplant operational
                                                                                          characteristics,
                                                                                          Airplane flight
                                                                                          manual.
23.925...............................  Propeller clearance....  23.2400(c)(2)..........  Powerplant
                                                                                          installation.
23.929...............................  Engine installation ice  23.2415(b).............  Powerplant ice
                                        protection.                                       protection.
23.933...............................  Reversing systems......  23.2420................  Reversing systems.
23.934...............................  Turbojet and turbofan    23.2400(c), (e) and      Powerplant
                                        engine thrust reverser   23.2425(a).              installation,
                                        systems tests.                                    Powerplant operational
                                                                                          characteristics.
23.937...............................  Turbopropeller-drag      23.10(a)...............  Powerplant installation
                                        limiting systems.                                 hazard assessment.
23.939...............................  Powerplant operating     23.2400(c)(4), (e) and   Powerplant
                                        characteristics.         23.2425(a).              installation,
                                                                                          Powerplant operational
                                                                                          characteristics.
23.943...............................  Negative acceleration..  23.2400(c)(1), (c)(3)    Powerplant
                                                                 and 23.2425(a).          installation,
                                                                                          Powerplant operational
                                                                                          characteristics.
23.951 (a), (b) and (c)..............  Fuel System--General...  23.2400(c)(1), (3) and   Powerplant
                                                                 23.2430(a)(3).           installation, Fuel
                                                                                          systems.
(d)..................................  .......................  .......................  Intent covered under
                                                                                          Part 34.
23.953...............................  Fuel system              23.2410(a), (c),         Powerplant installation
                                        independence.            23.2430(a)(1) and        hazards assessment,
                                                                 23.2440(d).              Fuel systems,
                                                                                          Powerplant fire
                                                                                          protection.
23.954...............................  Fuel system lightning    23.2430(a)(2)..........  Fuel systems.
                                        protection.
23.955...............................  Fuel flow..............  23.2400(c)(1), (3),      Powerplant
                                                                 23.2410(a) and           installation,
                                                                 23.2430(a)(3), (4).      Powerplant
                                                                                          installation hazard
                                                                                          assessment, Fuel
                                                                                          systems.

[[Page 96682]]

 
23.957(a)............................  Flow between             23.2430(a)(2), (b)(3)..  Fuel systems.
                                        interconnected tanks.
(b)..................................  .......................  23.2400(c)(1), (3),      Powerplant
                                                                 23.2430(b)(3).           installation, Fuel
                                                                                          systems--.
23.959...............................  Unusable fuel supply...  23.2430(a)(4) and        Fuel systems and
                                                                 23.2410(a).              Powerplant
                                                                                          installation hazard
                                                                                          assessment.
23.961...............................  Fuel system hot weather  23.2430(a)(3)..........  Fuel systems.
                                        operation.
23.963(a)............................  Fuel tank: general.....  23.2430(a)(1)..........  Fuel systems.
(b) and (c)..........................  .......................  23.2400(c).............  Powerplant
                                                                                          installation.
(d)..................................  .......................  23.2430(b)(4)..........  Fuel systems.
(e)..................................  .......................  23.2430(a)(4)..........  Fuel systems.
23.965...............................  Fuel tank tests........  23.2430(b)(1)..........  Fuel systems.
23.967...............................  Fuel tank installation.
(a)..................................  .......................  23.2400(c) and           Powerplant
                                                                 23.2430(a), (b).         installation, Fuel
                                                                                          systems.
(b)..................................  .......................  23.2400(d).............  Fuel systems.
(c) and (d)..........................  .......................  23.2430(b)(2)..........  Fuel systems.
(e)..................................  .......................  23.2430(a)(6)..........  Fuel systems.
23.969...............................  Fuel tank expansion      23.2430(b)(3)..........  Fuel systems.
                                        space.
23.971...............................  Fuel tank sump.........  23.2430(a)(7)..........  Fuel systems.
23.973...............................  Fuel tank filler         23.2430(c).............  Fuel systems.
                                        connection.
23.975...............................  Fuel tank vents and      23.2400(c)(1), (3),      Powerplant
                                        carburetor vapor vents.  23.2415 and              installation,
                                                                 23.2430(a)(3), (b)(3).   Powerplant ice
                                                                                          protection, Fuel
                                                                                          systems.
23.977...............................  Fuel tank outlet.......  23.2430(a)(7)..........  Fuel systems.
23.979...............................  Pressure fueling         23.2400(c) and           Powerplant
                                        systems.                 23.2430(c).              installation, Fuel
                                                                                          systems.
23.991(a), (b) and (d)...............  Fuel pumps.............  23.2410(a) and           Powerplant installation
                                                                 23.2430(a)(1), (3).      hazard assessment,
                                                                                          Fuel systems.
(a), (b), (c)........................  .......................  23.2430(a)(1), (3) and   Fuel systems.
                                                                 23.2410(a).
(c)..................................  .......................  23.2605................  Installation and
                                                                                          operation.
23.993...............................  Fuel system lines and    23.2430(a)(6)..........  Fuel systems.
                                        fittings.
23.994...............................  Fuel system components.  23.2430(a)(6)..........  Fuel systems.
23.995...............................  Fuel valves and          23.2440(d).............  Powerplant fire
                                        controls.                                         protection.
23.997(a)............................  Fuel strainer or filter  23.2400(c)(3)..........  Fuel systems.
(b)..................................  .......................  23.2430(a)(7)..........  Fuel systems.
(c)..................................  .......................  23.2400(c)(1)..........  Powerplant
                                                                                          installation.
(d)..................................  .......................  23.2400(e) and           Powerplant
                                                                 23.2430(a)(7).           installation, Fuel
                                                                                          systems.
(e)..................................  .......................  23.2430(a)(3)..........  Fuel systems.
23.999...............................  Fuel system drains.....  23.2400(c)(3),           Powerplant
                                                                 23.2430(a)(5).           installation, Fuel
                                                                                          systems.
23.1001(a) thru (f)..................  Fuel jettisoning system  23.2400(c)(1), (3) and   Powerplant
                                                                 23.2430(b)(5).           installation, Fuel
                                                                                          systems.
(g)..................................  .......................  23.2610................  Instrument markings,
                                                                                          controls markings, and
                                                                                          placards.
(h)..................................  .......................  23.2410(a).............  Powerplant installation
                                                                                          hazard assessment.
23.1011..............................  General................  23.2400(c), (e) and      Powerplant installation
                                                                 23.2410(a).              and Powerplant
                                                                                          installation hazard
                                                                                          assessment.
23.1013..............................  Oil tanks..............  23.2400(c).............  Powerplant
                                                                                          installation.
23.1015..............................  Oil tank tests.........  23.2400(c).............  Powerplant
                                                                                          installation.
23.1017..............................  Oil lines and fittings.  23.2400(c).............  Powerplant
                                                                                          installation.
23.1019..............................  Oil strainer or filter.  23.2400(c), (e) and      Powerplant
                                                                 23.2600(b).              installation.
23.1021..............................  Oil system drains......  23.2400(c).............  Powerplant
                                                                                          installation.
23.1023..............................  Oil radiators..........  23.2400(c).............  Powerplant
                                                                                          installation.
23.1027..............................  Propeller feathering     23.2400(c) and           Powerplant installation
                                        system.                  23.2410(a).              and Hazard assessment.
23.1041..............................  Cooling--General.......  23.2400(c) and (e).....  Powerplant
                                                                                          installation.
23.1043..............................  Cooling tests..........  23.2400(c), (e)........  Powerplant
                                                                                          installation.
23.1045..............................  Cooling test procedures  23.2400(c), (e)........  Powerplant
                                        for turbine engine                                installation.
                                        powered airplanes.
23.1047..............................  Cooling test procedures  23.2400(c), (e)........  Powerplant
                                        for reciprocating                                 installation.
                                        engine powered
                                        airplanes.
23.1061..............................  Installation...........  23.2400(c).............  Powerplant
                                                                                          installation.
23.1063..............................  Coolant tank tests.....  23.2400(c).............  Powerplant
                                                                                          installation.
23.1091..............................  Air induction system...  23.2435(a).............  Powerplant induction
                                                                                          and exhaust systems.
23.1093..............................  Induction system icing   23.2415(a).............  Powerplant ice
                                        protection.                                       protection.
23.1095..............................  Carburetor deicing       23.2415(a).............  Powerplant ice
                                        fluid flow rate.                                  protection.

[[Page 96683]]

 
23.1097..............................  Carburetor deicing       23.2400(c) and           Powerplant installation
                                        fluid system capacity.   23.2415(a).              and Powerplant ice
                                                                                          protection.
23.1099..............................  Carburetor deicing       23.2400(c) and           Powerplant installation
                                        fluid system detail      23.2415(a).              and Powerplant ice
                                        design.                                           protection.
23.1101(a)...........................  Induction air preheater  23.2400(c), 23.2435(b).  Powerplant installation
                                        design.                                           and Powerplant
                                                                                          induction and exhaust
                                                                                          systems.
(b) and (c)..........................  .......................  23.2400(c).............  Powerplant
                                                                                          installation.
23.1103(a) thru (d)..................  Induction system ducts.  23.2400(c) and           Powerplant installation
                                                                 23.2435(a).              and Powerplant
                                                                                          induction and exhaust
                                                                                          systems.
(e) and (f)..........................  .......................  23.2400(c) and           Powerplant installation
                                                                 23.2440(c).              and Powerplant fire
                                                                                          protection.
23.1105..............................  Induction system         23.2400(c) and           Powerplant installation
                                        screens.                 23.2415(a).              and Powerplant ice
                                                                                          protection.
23.1107..............................  Induction system         23.2400(c).............  Powerplant
                                        filters.                                          installation.
23.1109..............................  Turbocharger bleed air   23.2400(c)(1), (3) and   Powerplant installation
                                        system.                  23.2410(a).              and Powerplant
                                                                                          installation hazard
                                                                                          assessment.
23.1111(a) and (c)...................  Turbine engine bleed     23.2400(c)(3)..........  Powerplant
                                        air system.                                       installation.
(b)..................................  .......................  23.2400(c) and           Powerplant installation
                                                                 23.2435(a).              and Powerplant
                                                                                          induction and exhaust
                                                                                          systems.
23.1121..............................  Exhaust System--General  23.2400(c), (d) and      Powerplant installation
                                                                 23.2435(b).              and Powerplant
                                                                                          induction and exhaust
                                                                                          systems.
23.1123..............................  Exhaust system.........  23.2435(b).............  Powerplant induction
                                                                                          and exhaust systems.
23.1125..............................  Exhaust heat exchangers  23.2400(c) and           Powerplant installation
                                                                 23.2435(b).              and Powerplant
                                                                                          induction and exhaust
                                                                                          systems.
23.1141(a)...........................  Powerplant controls:     23.2600................  Flightcrew interface.
                                        General.
(b), (c) and (d).....................  .......................  23.2400(c) and 23.2500.  Powerplant installation
                                                                                          and Airplane level
                                                                                          systems requirements.
(e)..................................  .......................  23.2410(a).............  Powerplant installation
                                                                                          hazard assessment.
(f)..................................  .......................  23.2440(c)(2)..........  Powerplant fire
                                                                                          protection.
(g)..................................  .......................  23.2600 and 23.2615....  Flightcrew interface
                                                                                          and Flight, Navigation
                                                                                          and Powerplant
                                                                                          Instruments.
23.1142..............................  Auxiliary power unit     23.2425(b), 23.2600,     Powerplant operational
                                        controls.                23.2605 and 23.2615.     characteristics,
                                                                                          Flightcrew interface,
                                                                                          Installation and
                                                                                          operation, and Flight,
                                                                                          Navigation and
                                                                                          Powerplant
                                                                                          Instruments.
23.1143(a) thru (f)..................  Engine controls........  23.2600................  Flightcrew interface.
(g)..................................  .......................  23.2410(a).............  Powerplant installation
                                                                                          hazard assessment.
23.1145..............................  Ignition switches......  23.2425(a) and 23.2600.  Powerplant operational
                                                                                          characteristics and
                                                                                          Flightcrew interface.
23.1147..............................  Mixture controls.......  23.2410(a) and 23.2600.  Powerplant installation
                                                                                          hazard assessment and
                                                                                          Flightcrew interface.
23.1149..............................  Propeller speed and      23.2600................  Flightcrew interface.
                                        pitch controls.
23.1153..............................  Propeller feathering     23.2600................  Flightcrew interface.
                                        controls.
23.1155..............................  Turbine engine reverse   23.2600................  Flightcrew interface.
                                        thrust and propeller
                                        pitch settings below
                                        the flight regime.
23.1157..............................  Carburetor air           23.2600................  Flightcrew interface.
                                        temperature controls.
23.1163..............................  Powerplant accessories.  23.2400(c), (e) and      Powerplant installation
                                                                 23.2410(a).              and Powerplant
                                                                                          installation hazard
                                                                                          assessment.
23.1165..............................  Engine ignition systems  23.2400(c), 23.2425(b)   Powerplant
                                                                 and 23.2605.             installation,
                                                                                          Powerplant operational
                                                                                          characteristics, and
                                                                                          Installation and
                                                                                          operation.
23.1181..............................  Designated fire zones:   23.2440(a).............  Powerplant fire
                                        Regions included.                                 protection.
23.1182..............................  Nacelle areas behind     23.2440(c).............  Powerplant fire
                                        firewalls.                                        protection.
23.1183..............................  Lines, fittings, and     23.2440(c).............  Powerplant fire
                                        components.                                       protection.
23.1189..............................  Shutoff means..........  23.2440(d).............  Powerplant fire
                                                                                          protection.
23.1191..............................  Firewalls..............  23.2440(a), (b) and (c)  Powerplant fire
                                                                                          protection.

[[Page 96684]]

 
23.1192..............................  Engine accessory         23.2440(a) and (b).....  Powerplant fire
                                        compartment diaphragm.                            protection.
23.1193..............................  Cowling and nacelle....  23.2400(c), 23.2440(a)   Powerplant
                                                                 and (b).                 installation,
                                                                                          Powerplant fire
                                                                                          protection.
23.1195..............................  Fire extinguishing       23.2440(f).............  Powerplant fire
                                        systems.                                          protection.
23.1197..............................  Fire extinguishing       23.2400(d) and           Powerplant fire
                                        agents.                  23.2440(f).              protection.
23.1199..............................  Extinguishing agent      23.2400(c).............  Powerplant
                                        containers.                                       installation.
23.1201..............................  Fire extinguishing       23.2400(c), 23.2440(c)   Powerplant
                                        system materials.        and 23.2500.             installation,
                                                                                          Powerplant fire
                                                                                          protection, and
                                                                                          Airplane systems level
                                                                                          requirements.
23.1203(a)...........................  Fire detector system...  23.2440(e).............  Powerplant fire
                                                                                          protection.
(a)..................................  .......................  23.2440(e).............  Powerplant fire
                                                                                          protection.
(b) and (c)..........................  .......................  23.2400(c).............  Powerplant
                                                                                          installation.
(d)..................................  .......................  23.2600................  Flight crew interface.
(e)..................................  .......................  23.2440(c) and 23.2500.  Powerplant fire
                                                                                          protection and
                                                                                          Airplane systems level
                                                                                          requirements.
----------------------------------------------------------------------------------------------------------------
                                              Subpart F--Equipment
----------------------------------------------------------------------------------------------------------------
23.1301..............................  Function and
                                        installation.
(a)..................................  .......................  23.2250(a), 23.2500(a),  Design and construction
                                                                 23.2505.                 principles, Airplane
                                                                                          level systems
                                                                                          requirements, Function
                                                                                          and installation.
(b)..................................  .......................  23.2605................  Installation and
                                                                                          operation.
(c)..................................  .......................  23.2505................  Function and
                                                                                          installation.
23.1303..............................  Flight and navigation    23.2500, 23.2615, 23.2   Airplane level systems
                                        instruments.             and 23.2525.             requirements; Flight,
                                                                                          navigation, and
                                                                                          powerplant
                                                                                          instruments; Function
                                                                                          and installation;
                                                                                         System power
                                                                                          generation, storage,
                                                                                          and distribution.
23.1305..............................  Powerplant instruments.  23.2500, 23.2615 and     Airplane level systems
                                                                 23.2605.                 requirements; Flight,
                                                                                          navigation, and
                                                                                          powerplant
                                                                                          instruments;
                                                                                          Installation and
                                                                                          operation.
23.1306..............................  Electrical and           23.2515................  Electrical and
                                        electronic system                                 electronic system
                                        lightning protection.                             lightning protection.
23.1307..............................  Miscellaneous equipment  23.2500 and 23.2610....  Airplane level systems
                                                                                          requirements; Flight,
                                                                                          navigation, and
                                                                                          powerplant
                                                                                          instruments.
23.1308..............................  High-Intensity Radiated  23.2520................  High-intensity Radiated
                                        Fields (HIRF)                                     Fields (HIRF)
                                        protection.                                       protection.
23.1309..............................  Equipment, systems, and  23.2510................  Equipment, systems, and
                                        installations.                                    installations.
(a)(1)...............................  .......................  23.2500(a).............  Airplane level systems
                                                                                          requirements.
(a)(2)...............................  .......................  23.2500(b).............  Airplane level systems
                                                                                          requirements.
(b)..................................  .......................  .......................  --Deleted--.
(c)..................................  .......................  23.2510................  Equipment, systems, and
                                                                                          installations.
(d)..................................  .......................  23.2605................  Installation and
                                                                                          operation.
23.1310..............................  Power source capacity    23.2525................  System power
                                        and distribution.                                 generation, storage,
                                                                                          and distribution.
23.1311..............................  Electronic display       23.2500 and 23.2615....  Airplane level systems
                                        instrument systems.                               requirements; Flight,
                                                                                          navigation, and
                                                                                          powerplant
                                                                                          instruments.
23.1321..............................  Arrangement and          23.2500 and 23.2610....  Airplane level systems
                                        visibility.                                       requirements; Flight,
                                                                                          navigation, and
                                                                                          powerplant
                                                                                          instruments.
23.1322..............................  Warning, caution, and    23.2605................  Flight, navigation, and
                                        advisory lights.                                  powerplant
                                                                                          instruments.
23.1323..............................  Airspeed indicating      23.2250, 23.2500,        Design and construction
                                        system.                  23.2505, 23.2615, and    principles; Airplane
                                                                 23.2510.                 level systems
                                                                                          requirements; Function
                                                                                          and installation;
                                                                                          Flight, navigation,
                                                                                          and powerplant
                                                                                          instruments; and
                                                                                          Equipment, systems,
                                                                                          and installations.
(d)..................................  .......................  23.2250, 23.2540(a)....  Design and construction
                                                                                          principles, Flight in
                                                                                          icing conditions.

[[Page 96685]]

 
23.1325..............................  Static pressure system.  23.2500, 23.2615, and    Airplane level systems
                                                                 23.2510.                 requirements; Flight,
                                                                                          navigation, and
                                                                                          powerplant
                                                                                          instruments; and
                                                                                          Equipment, systems,
                                                                                          and installations.
(a), (b), (c), (d), (e)..............  .......................  23.2250................  Design and construction
                                                                                          principles.
(b)(3) and (g).......................  .......................  23.2540(a).............  Flight in icing
                                                                                          conditions.
23.1326..............................  Pitot heat indication    23.2605................  Installation and
                                        systems.                                          operation.
23.1327..............................  Magnetic direction       23.2500, 23.2505 and     Airplane level systems
                                        indicator.               23.2615.                 requirements; Function
                                                                                          and installation;
                                                                                          Flight, navigation,
                                                                                          and powerplant
                                                                                          instruments.
23.1329..............................  Automatic pilot system.  23.2500, 23.2505,        Airplane level systems
                                                                 232510, and 23.2605.     requirements; Function
                                                                                          and installation;
                                                                                          Equipment, systems,
                                                                                          and installations;
                                                                                          Installation and
                                                                                          operation.
(a)..................................  .......................  23.2500 and 23.2510....  Airplane level systems
                                                                                          requirements;
                                                                                          Equipment, systems,
                                                                                          and installations.
(b)..................................  .......................  23.2300 and 23.2600....  Flight control systems;
                                                                                          Flightcrew interface.
(c)..................................  .......................  23.2605................  Installation and
                                                                                          operation.
(d)..................................  .......................  23.2300 and 23.2600....  Flight control systems;
                                                                                          Flightcrew interface.
(e), (f), (g)........................  .......................  23.2500 and 23.2510....  Airplane level systems
                                                                                          requirements;
                                                                                          Equipment, systems,
                                                                                          and installations.
(h)..................................  .......................  23.2605................  Installation and
                                                                                          operation.
23.1331..............................  Instruments using a
                                        power source.
(a)..................................  .......................  23.2605................  Installation and
                                                                                          operation.
(b) and (c)..........................  .......................  23.2510 and 23.2525....  Equipment, systems, and
                                                                                          installations; System
                                                                                          power generation,
                                                                                          storage, and
                                                                                          distribution.
23.1335..............................  Flight director systems  23.2500, 23.2505,        Airplane level systems;
                                                                 23.2510, 23.2600, and    Function and
                                                                 23.2605.                 installation;
                                                                                          Equipment systems and
                                                                                          installations;
                                                                                          Flightcrew interface;
                                                                                          and Installation and
                                                                                          operation.
23.1337..............................  Powerplant instruments
                                        installation.
(a)..................................  .......................  23.2325................  Fire protection.
                                                                23.2430................  Fuel systems.
(b)..................................  .......................  23.2605................  Installation and
                                                                                          operation.
                                                                23.2610................  Flight, navigation, and
                                                                                          powerplant
                                                                                          instruments.
                                                                23.2510................  Equipment, systems, and
                                                                                          installations.
(c)..................................  .......................  23.2510................  Equipment, systems, and
                                                                                          installations.
(d)..................................  .......................  23.2605................  Installation and
                                                                                          operation.
                                                                23.2615................  Flight, navigation, and
                                                                                          powerplant
                                                                                          instruments.
23.1351..............................  Electrical Systems--
                                        General.
(a)..................................  .......................  23.2525................  System power
                                                                                          generation, storage,
                                                                                          and distribution.
(b)..................................  .......................  23.2500, 23.2525.......  Airplane level systems
                                                                                          requirements: System
                                                                                          power generation,
                                                                                          storage, and
                                                                                          distribution.
(c)..................................  .......................  23.2525, 23.2605.......  System power
                                                                                          generation, storage,
                                                                                          and distribution;
                                                                                          Installation and
                                                                                          operation.
(d)..................................  .......................  23.2605................  Installation and
                                                                                          operation.
(e)..................................  .......................  23.2500, 23.2325.......  Airplane level systems
                                                                                          requirements: Fire
                                                                                          protection.
(f), (g).............................  .......................  23.2500................  Airplane level systems
                                                                                          requirements.
23.1353..............................  Storage battery design   23.2525................  System power
                                        and installation.                                 generation, storage,
                                                                                          and distribution.

[[Page 96686]]

 
23.1357..............................  Circuit protective       23.2500, 23.2505,        Airplane level systems
                                        devices.                 23.2510, and 23.2525.    requirements; Function
                                                                                          and installation;
                                                                                          Equipment, systems,
                                                                                          and installations; and
                                                                                          System power
                                                                                          generation, storage,
                                                                                          and distribution.
23.1359..............................  Electrical system fire
                                        protection.
(a)..................................  .......................  23.2330, 23.2325.......  Fire protection in
                                                                                          designated fire zones;
                                                                                          Fire protection.
(b)..................................  .......................  23.2330................  Fire protection in
                                                                                          designated fire zones.
(c)..................................  .......................  23.2325................  Fire protection.
23.1361..............................  Master switch            23.2500 and 23.2505....  Airplane level systems
                                        arrangement.                                      requirements; Function
                                                                                          and installation.
23.1365..............................  Electrical cables and    23.2505................  Function and
                                        equipment.                                        installation.
(b)..................................  .......................  23.2330................  Fire protection in
                                                                                          designated fire zones.
23.1367..............................  Switches...............
(a) and (b)..........................  .......................  23.2505................  Function and
                                                                                          installation.
(c) and (d)..........................  .......................  23.2600................  Flightcrew interface.
23.1381..............................  Instrument lights......
(a) and (b)..........................  .......................  23.2600................  Flightcrew interface.
(c)..................................  .......................  23.2500................  Airplane level systems
                                                                                          requirements.
23.1383(a), (b), (c).................  Taxi and landing lights  23.2530................  External and cockpit
                                                                                          lighting.
(d)..................................  Taxi and landing lights  23.2325................  Fire protection.
23.1385(a), (b), (c).................  Position light system    23.2530................  External and cockpit
                                        installation.                                     lighting.
(d)..................................  Position light system    23.2325................  Fire protection.
                                        installation.
23.1387..............................  Position light system    23.2530................  External and cockpit
                                        dihedral angles.                                  lighting.
23.1389..............................  Position light           23.2530................  External and cockpit
                                        distribution and                                  lighting.
                                        intensities.
23.1391..............................  Minimum intensities in   23.2530................  External and cockpit
                                        the horizontal plane                              lighting.
                                        of position lights.
23.1393..............................  Minimum intensities in   23.2530................  External and cockpit
                                        any vertical plane of                             lighting.
                                        position lights.
23.1395..............................  Maximum intensities in   23.2530................  External and cockpit
                                        overlapping beams of                              lighting.
                                        position lights.
23.1397..............................  Color specifications...  23.2530................  External and cockpit
                                                                                          lighting.
23.1399..............................  Riding light...........  23.2530................  External and cockpit
                                                                                          lighting.
23.1401..............................  Anticollision light
                                        system.
(a), (a)(1)..........................  .......................  23.2530................  External and cockpit
                                                                                          lighting.
(a)(2)...............................  .......................  Means Of Compliance....
(b) thru (f).........................  .......................  23.2530................  External and cockpit
                                                                                          lighting.
23.1411..............................  Safety Equipment-
                                        General.
(a), (b)(1)..........................  .......................  23.2535................  Safety equipment.
(b)(2)...............................  .......................  23.2270................  Emergency conditions.
23.1415..............................  Ditching equipment.....  23.2535................  Safety equipment.
(a), (c), (d)........................  .......................  23.2535................  Safety equipment.
(b)..................................  .......................  Means Of Compliance....
23.1416..............................  Pneumatic de-icer boot   23.2500................  Airplane level systems
                                        system.                                           requirements.
                                                                23.2505................  Function and
                                                                                          installation.
(c)..................................  .......................  23.2605(b).............  Installation and
                                                                                          operation.
23.1419..............................  Ice protection.........  23.2165(a)(1)..........  Performance and flight
                                                                                          characteristics
                                                                                          requirements for
                                                                                          flight in icing
                                                                                          conditions.
                                                                23.2540(a).............  Flight in icing
                                                                                          conditions.
(d)..................................  .......................  23.2600(a).............  Flightcrew interface.
23.1431..............................  Electronic equipment...  23.2510................  Equipment, systems and
                                                                                          installations.
23.1435..............................  Hydraulic systems......
(a)(1)...............................  .......................  23.2235................  Structural strength.
(a)(2)...............................  .......................  23.2600................  Flightcrew interface.
(a)(3)(c)............................  .......................  23.2250................  Design and construction
                                                                                          principles.
(a)(4), (b)..........................  .......................  23.2545................  Pressurized system
                                                                                          elements.
(c)..................................  .......................  23.2440(c).............  Powerplant fire
                                                                                          protection.
23.1437..............................  Accessories for          23.2410 & 23.2515......  Powerplant installation
                                        multiengine airplanes.                            hazard assessment and
                                                                                          Equipment, systems and
                                                                                          installations.
23.1438..............................  Pressurization and       23.2545................  Pressurized system
                                        pneumatic systems.                                elements.

[[Page 96687]]

 
23.1441..............................  Oxygen equipment and     23.2320(e).............  Occupant physical
                                        supply.                                           environment.
(c)..................................  .......................  23.2605(b).............  Installation and
                                                                                          operation.
23.1443..............................  Minimum mass flow of     23.2320(e).............  Occupant physical
                                        supplemental oxygen.                              environment.
23.1445..............................  Oxygen distribution      23.2320(e).............  Occupant physical
                                        system.                                           environment.
(a), (b).............................  .......................  23.2250(c).............  Design and construction
                                                                                          principles.
23.1447..............................  Equipment standards for  23.2320(e).............  Occupant physical
                                        oxygen dispensing                                 environment.
                                        units.
23.1449..............................  Means for determining    23.2320(e).............  Occupant physical
                                        use of oxygen.                                    environment.
23.1450..............................  Chemical oxygen
                                        generators.
(a)(b)...............................  .......................  23.2320(e).............  Occupant physical
                                                                                          environment.
(c)..................................  .......................  23.2610................  Instrument markings,
                                                                                          control markings, and
                                                                                          placards.
23.1451..............................  Fire protection for      23.2320(e).............  Occupant physical
                                        oxygen equipment.                                 environment.
23.1453..............................  Protection of oxygen     23.2320(e) & 23.2545...  Occupant physical
                                        equipment from rupture.                           environment &
                                                                                          Pressurized system
                                                                                          elements.
23.1457..............................  Cockpit voice recorders  23.1457................  No Change.
23.1459..............................  Flight recorders.......  23.1459................  No Change.
23.1461..............................  Equipment containing     23.2550................  Equipment containing
                                        high-energy rotors.                               high-energy rotors.
----------------------------------------------------------------------------------------------------------------
                                Subpart G--Operating Limitations and Information
----------------------------------------------------------------------------------------------------------------
23.1501..............................  General................  23.2610................  Instrument, control
                                                                                          markings, and
                                                                                          placards.
23.1505..............................  Airspeed limitations...  23.2610................  Instrument markings,
                                                                                          control markings, and
                                                                                          placards.
23.1507..............................  Operating maneuvering    23.2610................  Instrument markings,
                                        speed.                                            control markings, and
                                                                                          placards.
23.1511..............................  Flap extended speed....  23.2610................  Instrument markings,
                                                                                          control markings, and
                                                                                          placards.
23.1513..............................  Minimum control speed..  23.2610................  Instrument markings,
                                                                                          control markings, and
                                                                                          placards.
23.1519..............................  Weight and center of     23.2610................  Instrument markings,
                                        gravity.                                          control markings, and
                                                                                          placards.
23.1521..............................  Powerplant limitations.  23.2610................  Instrument markings,
                                                                                          control markings, and
                                                                                          placards.
23.1522..............................  Auxiliary power unit     23.2610................  Instrument markings,
                                        limitations.                                      control markings, and
                                                                                          placards.
23.1523..............................  Minimum flight crew....  23.2610................  Instrument markings,
                                                                                          control markings, and
                                                                                          placards.
23.1524..............................  Maximum passenger        23.2610................  Instrument markings,
                                        seating configuration.                            control markings, and
                                                                                          placards.
23.1525..............................  Kinds of operation.....  23.2610................  Airplane level system
                                                                                          requirements.
                                                                23.2610................  Instrument markings,
                                                                                          control markings, and
                                                                                          placards.
23.1527..............................  Maximum operating        23.2610................  Instrument markings,
                                        altitude.                                         control markings, and
                                                                                          placards.
23.1529..............................  Instructions for         23.1529................  Instructions for
                                        continued                                         continued
                                        airworthiness.                                    airworthiness.
23.1541..............................  Marking and Placards--   23.2610................  Instrument markings,
                                        General.                                          control markings, and
                                                                                          placards.
23.1543..............................  Instrument marking:      23.2610................  Instrument markings,
                                        General.                                          control markings, and
                                                                                          placards.
23.1545..............................  Airspeed indicator.....  23.2610................  Instrument markings,
                                                                                          control markings, and
                                                                                          placards.
23.1547..............................  Magnetic direction       23.2610................  Instrument markings,
                                        indicator.                                        control markings, and
                                                                                          placards.
23.1549..............................  Powerplant and           23.2610................  Instrument markings,
                                        auxiliary power unit                              control markings, and
                                        instruments.                                      placards.
23.1551..............................  Oil quantity indicator.  23.2610................  Instrument markings,
                                                                                          control markings, and
                                                                                          placards.
23.1553..............................  Fuel quantity indicator  23.2610................  Instrument markings,
                                                                                          control markings, and
                                                                                          placards.
23.1555..............................  Control markings.......  23.2610................  Instrument markings,
                                                                                          control markings, and
                                                                                          placards.
23.1557..............................  Miscellaneous marking    23.2610................  Instrument markings,
                                        and placards.                                     control markings, and
                                                                                          placards.
23.1559..............................  Operating limitations    23.2610................  Instrument markings,
                                        placard.                                          control markings, and
                                                                                          placards.

[[Page 96688]]

 
23.1561..............................  Safety equipment.......  23.2610................  Instrument markings,
                                                                                          control markings, and
                                                                                          placards.
23.1563..............................  Airspeed placards......  23.2610................  Instrument markings,
                                                                                          control markings, and
                                                                                          placards.
23.1567..............................  Flight maneuver placard  23.2610................  Instrument markings,
                                                                                          control markings, and
                                                                                          placards.
23.1581..............................  Airplane Flight Manual   23.2620................  Airplane flight manual.
                                        and Approved Manual
                                        Material--General.
23.1583..............................  Operating limitations..  23.2620................  Airplane flight manual.
23.1585..............................  Operating procedures...  23.2620................  Airplane flight manual.
23.1587..............................  Performance information  23.2620................  Airplane flight manual.
23.1589..............................  Loading information....  23.2620................  Airplane flight manual.
Appendix A...........................  Simplified Design Load   Means Of Compliance....
                                        Criteria.
Appendix B...........................  [Reserved].............
Appendix C...........................  Basic Landing            Means Of Compliance....
                                        Conditions.
Appendix D...........................  Wheel Spin-Up and        Means Of Compliance....
                                        Spring-Back Loads.
Appendix E...........................  [Reserved].............
Appendix F...........................  Test Procedure.........  Means Of Compliance....
Appendix G...........................  Instructions for         Appendix A.............  Instructions for
                                        Continued                                         Continued
                                        Airworthiness.                                    Airworthiness.
Appendix H...........................  Installation of An       Means Of Compliance....
                                        Automatic Power
                                        Reserve (APR) System.
Appendix I...........................  Seaplane Loads.........  Means Of Compliance....
Appendix J...........................  HIRF Environments and    Means Of Compliance....
                                        Equipment HIRF Test
                                        Levels.
----------------------------------------------------------------------------------------------------------------

Appendix 2 to the Preamble--Abbreviations and Acronyms Frequently Used 
in This Document

AC Advisory Circular
AD Airworthiness Directive
AFM Airplane Flight Manual
A-NPA Advance Notice of Proposed Amendment
ARC Aviation Rulemaking Committee
ASTM ASTM International
FCAA Foreign Civil Aviation Authority
CAR 3 Civil Aviation Regulations, Part 3
Cf Confer (to identify a source or a usage citation for a word or 
phrase)
CPS Certification Process Study
CS Certification Specification
CS-VLA Certification Specification-Very Light Aeroplanes
DER Designated Engineering Representative
EASA European Aviation Safety Agency
ELOS Equivalent Level of Safety
FR Federal Register
GA General Aviation
HIRF High-Intensity Radiated Field
IFR Instrument Flight Rules
IMC Instrument Meteorological Conditions
KCAS Knots Calibrated Airspeeds
LOC Loss of Control
NATCA National Air Traffic Controllers Association
NPA Notice of Proposed Amendment
NPRM Notice of Proposed Rulemaking
NTSB National Transportation Safety Board
OMB Office of Management and Budget
SAE SAE International
SARA Small Airplane Revitalization Act of 2013
SLD Supercooled Large Droplet
STC Supplemental Type Certificate
TC Type Certificate
TCDS Type Certificate Data Sheet
VA Design Maneuvering Speed
VC Design Cruising Speed
VD Design Dive Speed
VMC Minimum Control Speed
VMO/MMO Maximum Operating Limit Speed
VNO Maximum Structural Cruising Speed
VFR Visual Flight Rules
VSO Stalling speed or the minimum steady flight speed in 
the landing configuration

List of Subjects

14 CFR Part 21

    Aircraft, Aviation safety, Recording and recordkeeping 
requirements.

14 CFR Part 23

    Aircraft, Aviation Safety, Signs and symbols.

14 CFR Part 35

    Aircraft, Aviation safety.

14 CFR Part 43

    Aircraft, Aviation safety, Reporting and recordkeeping 
requirements.

14 CFR Part 91

    Air traffic control, Aircraft, Airmen, Airports, Aviation safety, 
Reporting and recordkeeping requirements.

14 CFR Part 121

    Aircraft, Airmen, Aviation safety, Reporting and recordkeeping 
requirements.

14 CFR Part 135

    Aircraft, Airmen, Aviation safety, Reporting and recordkeeping 
requirements.

The Amendment

    In consideration of the foregoing, the Federal Aviation 
Administration amends chapter I of title 14, Code of Federal 
Regulations as follows:

PART 21--CERTIFICATION PROCEDURES FOR PRODUCTS AND ARTICLES

0
1. The authority citation for part 21 is revised to read as follows:

    Authority:  42 U.S.C. 7572; 49 U.S.C. 106(f), 106(g), 40105, 
40113, 44701-44702, 44704, 44707, 44709, 44711, 44713, 44715, 45303.

0
2. In Sec.  21.9, revise paragraphs (a)(5), (a)(6), and add paragraph 
(a)(7) to read as follows:

Sec.  21.9   Replacement and modification articles.

    (a) * * *
    (5) Produced by an owner or operator for maintaining or altering 
that owner or operator's product;
    (6) Fabricated by an appropriately rated certificate holder with a 
quality system, and consumed in the repair or alteration of a product 
or article in accordance with part 43 of this chapter; or
    (7) Produced in any other manner approved by the FAA.
* * * * *

0
3. In Sec.  21.17, revise paragraph (a) introductory text to read as 
follows:

[[Page 96689]]

Sec.  21.17   Designation of applicable regulations.

    (a) Except as provided in Sec. Sec.  25.2, 27.2, 29.2, and in parts 
26, 34, and 36 of this subchapter, an applicant for a type certificate 
must show that the aircraft, aircraft engine, or propeller concerned 
meets--
* * * * *

0
4. In Sec.  21.24, revise paragraph (a)(1)(i) to read as follows:

Sec.  21.24   Issuance of type certificate: primary category aircraft.

    (a) * * *
    (1) * * *
    (i) Is unpowered; is an airplane powered by a single, naturally 
aspirated engine with a 61-knot or less Vso stall speed as 
determined under part 23 of this chapter; or is a rotorcraft with a 6-
pound per square foot main rotor disc loading limitation, under sea 
level standard day conditions;
* * * * *

0
5. In Sec.  21.35, revise paragraph (b)(2) to read as follows:

Sec.  21.35   Flight tests.

* * * * *
    (b) * * *
    (2) For aircraft to be certificated under this subchapter, except 
gliders and low-speed, certification level 1 or 2 airplanes, as defined 
in part 23 of this chapter, to determine whether there is reasonable 
assurance that the aircraft, its components, and its equipment are 
reliable and function properly.
* * * * *

0
6. In Sec.  21.50, revise paragraph (b) to read as follows:

Sec.  21.50   Instructions for continued airworthiness and 
manufacturer's maintenance manuals having airworthiness limitations 
sections.

* * * * *
    (b) The holder of a design approval, including either a type 
certificate or supplemental type certificate for an aircraft, aircraft 
engine, or propeller for which application was made after January 28, 
1981, must furnish at least one set of complete Instructions for 
Continued Airworthiness to the owner of each type aircraft, aircraft 
engine, or propeller upon its delivery, or upon issuance of the first 
standard airworthiness certificate for the affected aircraft, whichever 
occurs later. The Instructions for Continued Airworthiness must be 
prepared in accordance with Sec. Sec.  [thinsp]23.1529, 25.1529, 
25.1729, 27.1529, 29.1529, 31.82, 33.4, 35.4, or part 26 of this 
subchapter, or as specified in the applicable airworthiness criteria 
for special classes of aircraft defined in Sec.  [thinsp]21.17(b), as 
applicable. If the holder of a design approval chooses to designate 
parts as commercial, it must include in the Instructions for Continued 
Airworthiness a list of commercial parts submitted in accordance with 
the provisions of paragraph (c) of this section. Thereafter, the holder 
of a design approval must make those instructions available to any 
other person required by this chapter to comply with any of the terms 
of those instructions. In addition, changes to the Instructions for 
Continued Airworthiness shall be made available to any person required 
by this chapter to comply with any of those instructions.
* * * * *

0
7. In Sec.  21.101 revise paragraphs (b) introductory text, and (c) to 
read as follows:

Sec.  21.101   Designation of applicable regulations.

* * * * *
    (b) Except as provided in paragraph (g) of this section, if 
paragraphs (b)(1), (2), or (3) of this section apply, an applicant may 
show that the change and areas affected by the change comply with an 
earlier amendment of a regulation required by paragraph (a) of this 
section, and of any other regulation the FAA finds is directly related. 
However, the earlier amended regulation may not precede either the 
corresponding regulation included by reference in the type certificate, 
or any regulation in Sec. Sec.  25.2, 27.2, or 29.2 of this chapter 
that is related to the change. The applicant may show compliance with 
an earlier amendment of a regulation for any of the following:
* * * * *
    (c) An applicant for a change to an aircraft (other than a 
rotorcraft) of 6,000 pounds or less maximum weight, to a non-turbine 
rotorcraft of 3,000 pounds or less maximum weight, to a level 1 low-
speed airplane, or to a level 2 low-speed airplane may show that the 
change and areas affected by the change comply with the regulations 
included in the type certificate. However, if the FAA finds that the 
change is significant in an area, the FAA may designate compliance with 
an amendment to the regulation incorporated by reference in the type 
certificate that applies to the change and any regulation that the FAA 
finds is directly related, unless the FAA also finds that compliance 
with that amendment or regulation would not contribute materially to 
the level of safety of the product or would be impractical.
* * * * *

0
8. Revise part 23 to read as follows:

PART 23--AIRWORTHINESS STANDARDS: NORMAL CATEGORY AIRPLANES

Sec.
23.1457 Cockpit voice recorders.
23.1459 Flight data recorders.
23.1529 Instructions for continued airworthiness.
Subpart A--General
23.2000 Applicability and definitions.
23.2005 Certification of normal category airplanes.
23.2010 Accepted means of compliance.
Subpart B--Flight

Performance

23.2100 Weight and center of gravity.
23.2105 Performance data.
23.2110 Stall speed.
23.2115 Takeoff performance.
23.2120 Climb requirements.
23.2125 Climb information.
23.2130 Landing.

Flight Characteristics

23.2135 Controllability.
23.2140 Trim.
23.2145 Stability.
23.2150 Stall characteristics, stall warning, and spins.
23.2155 Ground and water handling characteristics.
23.2160 Vibration, buffeting, and high-speed characteristics.
23.2165 Performance and flight characteristics requirements for 
flight in icing conditions.
Subpart C--Structures
23.2200 Structural design envelope.
23.2205 Interaction of systems and structures.

Structural Loads

23.2210 Structural design loads.
23.2215 Flight load conditions.
23.2220 Ground and water load conditions.
23.2225 Component loading conditions.
23.2230 Limit and ultimate loads.

Structural Performance

23.2235 Structural strength.
23.2240 Structural durability.
23.2245 Aeroelasticity.

Design

23.2250 Design and construction principles.
23.2255 Protection of structure.
23.2260 Materials and processes.
23.2265 Special factors of safety.

Structural Occupant Protection

23.2270 Emergency conditions.
Subpart D--Design and Construction
23.2300 Flight control systems.
23.2305 Landing gear systems.
23.2310 Buoyancy for seaplanes and amphibians.

[[Page 96690]]

Occupant System Design Protection

23.2315 Means of egress and emergency exits.
23.2320 Occupant physical environment.

Fire and High Energy Protection

23.2325 Fire protection.
23.2330 Fire protection in designated fire zones and adjacent areas.
23.2335 Lightning protection.
Subpart E--Powerplant
23.2400 Powerplant installation.
23.2405 Automatic power or thrust control systems.
23.2410 Powerplant installation hazard assessment.
23.2415 Powerplant ice protection.
23.2420 Reversing systems.
23.2425 Powerplant operational characteristics.
23.2430 Fuel system.
23.2435 Powerplant induction and exhaust systems.
23.2440 Powerplant fire protection.
Subpart F--Equipment
23.2500 Airplane level systems requirements.
23.2505 Function and installation.
23.2510 Equipment, systems, and installations.
23.2515 Electrical and electronic system lightning protection.
23.2520 High-intensity Radiated Fields (HIRF) protection.
23.2525 System power generation, storage, and distribution.
23.2530 External and cockpit lighting.
23.2535 Safety equipment.
23.2540 Flight in icing conditions.
23.2545 Pressurized system elements.
23.2550 Equipment containing high-energy rotors.
Subpart G--Flightcrew Interface and Other Information
23.2600 Flightcrew interface.
23.2605 Installation and operation.
23.2610 Instrument markings, control markings, and placards.
23.2615 Flight, navigation, and powerplant instruments.
23.2620 Airplane flight manual.

Appendix A to Part 23--Instructions for Continued Airworthiness

    Authority:  49 U.S.C. 106(f), 106(g), 40113, 44701-44702, 44704, 
Pub. L. 113-53, 127 Stat. 584 (49 U.S.C. 44704) note.

Sec.  23.1457   Cockpit voice recorders.

    (a) Each cockpit voice recorder required by the operating rules of 
this chapter must be approved and must be installed so that it will 
record the following:
    (1) Voice communications transmitted from or received in the 
airplane by radio.
    (2) Voice communications of flightcrew members on the flight deck.
    (3) Voice communications of flightcrew members on the flight deck, 
using the airplane's interphone system.
    (4) Voice or audio signals identifying navigation or approach aids 
introduced into a headset or speaker.
    (5) Voice communications of flightcrew members using the passenger 
loudspeaker system, if there is such a system and if the fourth channel 
is available in accordance with the requirements of paragraph 
(c)(4)(ii) of this section.
    (6) If datalink communication equipment is installed, all datalink 
communications, using an approved data message set. Datalink messages 
must be recorded as the output signal from the communications unit that 
translates the signal into usable data.
    (b) The recording requirements of paragraph (a)(2) of this section 
must be met by installing a cockpit-mounted area microphone, located in 
the best position for recording voice communications originating at the 
first and second pilot stations and voice communications of other 
crewmembers on the flight deck when directed to those stations. The 
microphone must be so located and, if necessary, the preamplifiers and 
filters of the recorder must be so adjusted or supplemented, so that 
the intelligibility of the recorded communications is as high as 
practicable when recorded under flight cockpit noise conditions and 
played back. Repeated aural or visual playback of the record may be 
used in evaluating intelligibility.
    (c) Each cockpit voice recorder must be installed so that the part 
of the communication or audio signals specified in paragraph (a) of 
this section obtained from each of the following sources is recorded on 
a separate channel:
    (1) For the first channel, from each boom, mask, or handheld 
microphone, headset, or speaker used at the first pilot station.
    (2) For the second channel from each boom, mask, or handheld 
microphone, headset, or speaker used at the second pilot station.
    (3) For the third channel--from the cockpit-mounted area 
microphone.
    (4) For the fourth channel from:
    (i) Each boom, mask, or handheld microphone, headset, or speaker 
used at the station for the third and fourth crewmembers.
    (ii) If the stations specified in paragraph (c)(4)(i) of this 
section are not required or if the signal at such a station is picked 
up by another channel, each microphone on the flight deck that is used 
with the passenger loudspeaker system, if its signals are not picked up 
by another channel.
    (5) And that as far as is practicable all sounds received by the 
microphone listed in paragraphs (c)(1), (2), and (4) of this section 
must be recorded without interruption irrespective of the position of 
the interphone-transmitter key switch. The design shall ensure that 
sidetone for the flightcrew is produced only when the interphone, 
public address system, or radio transmitters are in use.
    (d) Each cockpit voice recorder must be installed so that:
    (1)(i) It receives its electrical power from the bus that provides 
the maximum reliability for operation of the cockpit voice recorder 
without jeopardizing service to essential or emergency loads.
    (ii) It remains powered for as long as possible without 
jeopardizing emergency operation of the airplane.
    (2) There is an automatic means to simultaneously stop the recorder 
and prevent each erasure feature from functioning, within 10 minutes 
after crash impact.
    (3) There is an aural or visual means for preflight checking of the 
recorder for proper operation.
    (4) Any single electrical failure external to the recorder does not 
disable both the cockpit voice recorder and the flight data recorder.
    (5) It has an independent power source--
    (i) That provides 10 1 minutes of electrical power to 
operate both the cockpit voice recorder and cockpit-mounted area 
microphone;
    (ii) That is located as close as practicable to the cockpit voice 
recorder; and
    (iii) To which the cockpit voice recorder and cockpit-mounted area 
microphone are switched automatically in the event that all other power 
to the cockpit voice recorder is interrupted either by normal shutdown 
or by any other loss of power to the electrical power bus.
    (6) It is in a separate container from the flight data recorder 
when both are required. If used to comply with only the cockpit voice 
recorder requirements, a combination unit may be installed.
    (e) The recorder container must be located and mounted to minimize 
the probability of rupture of the container as a result of crash impact 
and consequent heat damage to the recorder from fire.
    (1) Except as provided in paragraph (e)(2) of this section, the 
recorder container must be located as far aft as practicable, but need 
not be outside of the pressurized compartment, and may not be located 
where aft-mounted engines may crush the container during impact.
    (2) If two separate combination digital flight data recorder and 
cockpit voice

[[Page 96691]]

recorder units are installed instead of one cockpit voice recorder and 
one digital flight data recorder, the combination unit that is 
installed to comply with the cockpit voice recorder requirements may be 
located near the cockpit.
    (f) If the cockpit voice recorder has a bulk erasure device, the 
installation must be designed to minimize the probability of 
inadvertent operation and actuation of the device during crash impact.
    (g) Each recorder container must--
    (1) Be either bright orange or bright yellow;
    (2) Have reflective tape affixed to its external surface to 
facilitate its location under water; and
    (3) Have an underwater locating device, when required by the 
operating rules of this chapter, on or adjacent to the container, which 
is secured in such manner that they are not likely to be separated 
during crash impact.

Sec.  23.1459   Flight data recorders.

    (a) Each flight recorder required by the operating rules of this 
chapter must be installed so that--
    (1) It is supplied with airspeed, altitude, and directional data 
obtained from sources that meet the aircraft level system requirements 
and the functionality specified in Sec.  23.2500;
    (2) The vertical acceleration sensor is rigidly attached, and 
located longitudinally either within the approved center of gravity 
limits of the airplane, or at a distance forward or aft of these limits 
that does not exceed 25 percent of the airplane's mean aerodynamic 
chord;
    (3)(i) It receives its electrical power from the bus that provides 
the maximum reliability for operation of the flight data recorder 
without jeopardizing service to essential or emergency loads;
    (ii) It remains powered for as long as possible without 
jeopardizing emergency operation of the airplane;
    (4) There is an aural or visual means for preflight checking of the 
recorder for proper recording of data in the storage medium;
    (5) Except for recorders powered solely by the engine-driven 
electrical generator system, there is an automatic means to 
simultaneously stop a recorder that has a data erasure feature and 
prevent each erasure feature from functioning, within 10 minutes after 
crash impact;
    (6) Any single electrical failure external to the recorder does not 
disable both the cockpit voice recorder and the flight data recorder; 
and
    (7) It is in a separate container from the cockpit voice recorder 
when both are required. If used to comply with only the flight data 
recorder requirements, a combination unit may be installed. If a 
combination unit is installed as a cockpit voice recorder to comply 
with Sec.  23.1457(e)(2), a combination unit must be used to comply 
with this flight data recorder requirement.
    (b) Each non-ejectable record container must be located and mounted 
so as to minimize the probability of container rupture resulting from 
crash impact and subsequent damage to the record from fire. In meeting 
this requirement, the record container must be located as far aft as 
practicable, but need not be aft of the pressurized compartment, and 
may not be where aft-mounted engines may crush the container upon 
impact.
    (c) A correlation must be established between the flight recorder 
readings of airspeed, altitude, and heading and the corresponding 
readings (taking into account correction factors) of the first pilot's 
instruments. The correlation must cover the airspeed range over which 
the airplane is to be operated, the range of altitude to which the 
airplane is limited, and 360 degrees of heading. Correlation may be 
established on the ground as appropriate.
    (d) Each recorder container must--
    (1) Be either bright orange or bright yellow;
    (2) Have reflective tape affixed to its external surface to 
facilitate its location under water; and
    (3) Have an underwater locating device, when required by the 
operating rules of this chapter, on or adjacent to the container, which 
is secured in such a manner that they are not likely to be separated 
during crash impact.
    (e) Any novel or unique design or operational characteristics of 
the aircraft shall be evaluated to determine if any dedicated 
parameters must be recorded on flight recorders in addition to or in 
place of existing requirements.

Sec.  23.1529   Instructions for continued airworthiness.

    The applicant must prepare Instructions for Continued 
Airworthiness, in accordance with appendix A of this part, that are 
acceptable to the Administrator. The instructions may be incomplete at 
type certification if a program exists to ensure their completion prior 
to delivery of the first airplane or issuance of a standard certificate 
of airworthiness, whichever occurs later.

Subpart A--General

Sec.  23.2000   Applicability and definitions.

    (a) This part prescribes airworthiness standards for the issuance 
of type certificates, and changes to those certificates, for airplanes 
in the normal category.
    (b) For the purposes of this part, the following definition 
applies:
    Continued safe flight and landing means an airplane is capable of 
continued controlled flight and landing, possibly using emergency 
procedures, without requiring exceptional pilot skill or strength. Upon 
landing, some airplane damage may occur as a result of a failure 
condition.

Sec.  23.2005   Certification of normal category airplanes.

    (a) Certification in the normal category applies to airplanes with 
a passenger-seating configuration of 19 or less and a maximum 
certificated takeoff weight of 19,000 pounds or less.
    (b) Airplane certification levels are:
    (1) Level 1--for airplanes with a maximum seating configuration of 
0 to 1 passengers.
    (2) Level 2--for airplanes with a maximum seating configuration of 
2 to 6 passengers.
    (3) Level 3--for airplanes with a maximum seating configuration of 
7 to 9 passengers.
    (4) Level 4--for airplanes with a maximum seating configuration of 
10 to 19 passengers.
    (c) Airplane performance levels are:
    (1) Low speed--for airplanes with a VNO and 
VMOMONO or 
VMO > 250 KCAS or a MMO > 0.6.
    (d) Airplanes not certified for aerobatics may be used to perform 
any maneuver incident to normal flying, including--
    (1) Stalls (except whip stalls); and
    (2) Lazy eights, chandelles, and steep turns, in which the angle of 
bank is not more than 60 degrees.
    (e) Airplanes certified for aerobatics may be used to perform 
maneuvers without limitations, other than those limitations established 
under subpart G of this part.

Sec.  23.2010   Accepted means of compliance.

    (a) An applicant must comply with this part using a means of 
compliance, which may include consensus standards, accepted by the 
Administrator.
    (b) An applicant requesting acceptance of a means of compliance 
must provide the means of compliance to the FAA in a form and manner 
acceptable to the Administrator.

[[Page 96692]]

Subpart B--Flight

Performance

Sec.  23.2100   Weight and center of gravity.

    (a) The applicant must determine limits for weights and centers of 
gravity that provide for the safe operation of the airplane.
    (b) The applicant must comply with each requirement of this subpart 
at critical combinations of weight and center of gravity within the 
airplane's range of loading conditions using tolerances acceptable to 
the Administrator.
    (c) The condition of the airplane at the time of determining its 
empty weight and center of gravity must be well defined and easily 
repeatable.

Sec.  23.2105   Performance data.

    (a) Unless otherwise prescribed, an airplane must meet the 
performance requirements of this subpart in--
    (1) Still air and standard atmospheric conditions at sea level for 
all airplanes; and
    (2) Ambient atmospheric conditions within the operating envelope 
for levels 1 and 2 high-speed and levels 3 and 4 airplanes.
    (b) Unless otherwise prescribed, the applicant must develop the 
performance data required by this subpart for the following conditions:
    (1) Airport altitudes from sea level to 10,000 feet (3,048 meters); 
and
    (2) Temperatures above and below standard day temperature that are 
within the range of operating limitations, if those temperatures could 
have a negative effect on performance.
    (c) The procedures used for determining takeoff and landing 
distances must be executable consistently by pilots of average skill in 
atmospheric conditions expected to be encountered in service.
    (d) Performance data determined in accordance with paragraph (b) of 
this section must account for losses due to atmospheric conditions, 
cooling needs, and other demands on power sources.

Sec.  23.2110   Stall speed.

    The applicant must determine the airplane stall speed or the 
minimum steady flight speed for each flight configuration used in 
normal operations, including takeoff, climb, cruise, descent, approach, 
and landing. The stall speed or minimum steady flight speed 
determination must account for the most adverse conditions for each 
flight configuration with power set at--
    (a) Idle or zero thrust for propulsion systems that are used 
primarily for thrust; and
    (b) A nominal thrust for propulsion systems that are used for 
thrust, flight control, and/or high-lift systems.

Sec.  23.2115   Takeoff performance.

    (a) The applicant must determine airplane takeoff performance 
accounting for--
    (1) Stall speed safety margins;
    (2) Minimum control speeds; and
    (3) Climb gradients.
    (b) For single engine airplanes and levels 1, 2, and 3 low-speed 
multiengine airplanes, takeoff performance includes the determination 
of ground roll and initial climb distance to 50 feet (15 meters) above 
the takeoff surface.
    (c) For levels 1, 2, and 3 high-speed multiengine airplanes, and 
level 4 multiengine airplanes, takeoff performance includes a 
determination the following distances after a sudden critical loss of 
thrust--
    (1) An aborted takeoff at critical speed;
    (2) Ground roll and initial climb to 35 feet (11 meters) above the 
takeoff surface; and
    (3) Net takeoff flight path.

Sec.  23.2120   Climb requirements.

    The design must comply with the following minimum climb performance 
out of ground effect:
    (a) With all engines operating and in the initial climb 
configuration--
    (1) For levels 1 and 2 low-speed airplanes, a climb gradient of 8.3 
percent for landplanes and 6.7 percent for seaplanes and amphibians; 
and
    (2) For levels 1 and 2 high-speed airplanes, all level 3 airplanes, 
and level 4 single-engines a climb gradient after takeoff of 4 percent.
    (b) After a critical loss of thrust on multiengine airplanes--
    (1) For levels 1 and 2 low-speed airplanes that do not meet single-
engine crashworthiness requirements, a climb gradient of 1.5 percent at 
a pressure altitude of 5,000 feet (1,524 meters) in the cruise 
configuration(s);
    (2) For levels 1 and 2 high-speed airplanes, and level 3 low-speed 
airplanes, a 1 percent climb gradient at 400 feet (122 meters) above 
the takeoff surface with the landing gear retracted and flaps in the 
takeoff configuration(s); and
    (3) For level 3 high-speed airplanes and all level 4 airplanes, a 2 
percent climb gradient at 400 feet (122 meters) above the takeoff 
surface with the landing gear retracted and flaps in the approach 
configuration(s).
    (c) For a balked landing, a climb gradient of 3 percent without 
creating undue pilot workload with the landing gear extended and flaps 
in the landing configuration(s).

Sec.  23.2125   Climb information.

    (a) The applicant must determine climb performance at each weight, 
altitude, and ambient temperature within the operating limitations--
    (1) For all single-engine airplanes;
    (2) For levels 1 and 2 high-speed multiengine airplanes and level 3 
multiengine airplanes, following a critical loss of thrust on takeoff 
in the initial climb configuration; and
    (3) For all multiengine airplanes, during the enroute phase of 
flight with all engines operating and after a critical loss of thrust 
in the cruise configuration.
    (b) The applicant must determine the glide performance for single-
engine airplanes after a complete loss of thrust.

Sec.  23.2130   Landing.

    The applicant must determine the following, for standard 
temperatures at critical combinations of weight and altitude within the 
operational limits:
    (a) The distance, starting from a height of 50 feet (15 meters) 
above the landing surface, required to land and come to a stop.
    (b) The approach and landing speeds, configurations, and 
procedures, which allow a pilot of average skill to land within the 
published landing distance consistently and without causing damage or 
injury, and which allow for a safe transition to the balked landing 
conditions of this part accounting for:
    (1) Stall speed safety margin; and
    (2) Minimum control speeds.

Flight Characteristics

Sec.  23.2135   Controllability.

    (a) The airplane must be controllable and maneuverable, without 
requiring exceptional piloting skill, alertness, or strength, within 
the operating envelope--
    (1) At all loading conditions for which certification is requested;
    (2) During all phases of flight;
    (3) With likely reversible flight control or propulsion system 
failure; and
    (4) During configuration changes.
    (b) The airplane must be able to complete a landing without causing 
substantial damage or serious injury using the steepest approved 
approach gradient procedures and providing a reasonable margin below 
Vref or above approach angle of attack.
    (c) VMC is the calibrated airspeed at which, following 
the sudden critical loss of thrust, it is possible to maintain control 
of the airplane. For multiengine airplanes, the applicant must 
determine VMC, if applicable, for the most critical 
configurations used in takeoff and landing operations.

[[Page 96693]]

    (d) If the applicant requests certification of an airplane for 
aerobatics, the applicant must demonstrate those aerobatic maneuvers 
for which certification is requested and determine entry speeds.

Sec.  23.2140   Trim.

    (a) The airplane must maintain lateral and directional trim without 
further force upon, or movement of, the primary flight controls or 
corresponding trim controls by the pilot, or the flight control system, 
under the following conditions:
    (1) For levels 1, 2, and 3 airplanes in cruise.
    (2) For level 4 airplanes in normal operations.
    (b) The airplane must maintain longitudinal trim without further 
force upon, or movement of, the primary flight controls or 
corresponding trim controls by the pilot, or the flight control system, 
under the following conditions:
    (1) Climb.
    (2) Level flight.
    (3) Descent.
    (4) Approach.
    (c) Residual control forces must not fatigue or distract the pilot 
during normal operations of the airplane and likely abnormal or 
emergency operations, including a critical loss of thrust on 
multiengine airplanes.

Sec.  23.2145   Stability.

    (a) Airplanes not certified for aerobatics must--
    (1) Have static longitudinal, lateral, and directional stability in 
normal operations;
    (2) Have dynamic short period and Dutch roll stability in normal 
operations; and
    (3) Provide stable control force feedback throughout the operating 
envelope.
    (b) No airplane may exhibit any divergent longitudinal stability 
characteristic so unstable as to increase the pilot's workload or 
otherwise endanger the airplane and its occupants.

Sec.  23.2150   Stall characteristics, stall warning, and spins.

    (a) The airplane must have controllable stall characteristics in 
straight flight, turning flight, and accelerated turning flight with a 
clear and distinctive stall warning that provides sufficient margin to 
prevent inadvertent stalling.
    (b) Single-engine airplanes, not certified for aerobatics, must not 
have a tendency to inadvertently depart controlled flight.
    (c) Levels 1 and 2 multiengine airplanes, not certified for 
aerobatics, must not have a tendency to inadvertently depart controlled 
flight from thrust asymmetry after a critical loss of thrust.
    (d) Airplanes certified for aerobatics that include spins must have 
controllable stall characteristics and the ability to recover within 
one and one-half additional turns after initiation of the first control 
action from any point in a spin, not exceeding six turns or any greater 
number of turns for which certification is requested, while remaining 
within the operating limitations of the airplane.
    (e) Spin characteristics in airplanes certified for aerobatics that 
includes spins must recover without exceeding limitations and may not 
result in unrecoverable spins--
    (1) With any typical use of the flight or engine power controls; or
    (2) Due to pilot disorientation or incapacitation.

Sec.  23.2155   Ground and water handling characteristics.

    For airplanes intended for operation on land or water, the airplane 
must have controllable longitudinal and directional handling 
characteristics during taxi, takeoff, and landing operations.

Sec.  23.2160   Vibration, buffeting, and high-speed characteristics.

    (a) Vibration and buffeting, for operations up to VD/
MD, must not interfere with the control of the airplane or 
cause excessive fatigue to the flightcrew. Stall warning buffet within 
these limits is allowable.
    (b) For high-speed airplanes and all airplanes with a maximum 
operating altitude greater than 25,000 feet (7,620 meters) pressure 
altitude, there must be no perceptible buffeting in cruise 
configuration at 1g and at any speed up to VMO/
MMO, except stall buffeting.
    (c) For high-speed airplanes, the applicant must determine the 
positive maneuvering load factors at which the onset of perceptible 
buffet occurs in the cruise configuration within the operational 
envelope. Likely inadvertent excursions beyond this boundary must not 
result in structural damage.
    (d) High-speed airplanes must have recovery characteristics that do 
not result in structural damage or loss of control, beginning at any 
likely speed up to VMO/MMO, following--
    (1) An inadvertent speed increase; and
    (2) A high-speed trim upset for airplanes where dynamic pressure 
can impair the longitudinal trim system operation.

Sec.  23.2165   Performance and flight characteristics requirements for 
flight in icing conditions.

    (a) An applicant who requests certification for flight in icing 
conditions defined in part 1 of appendix C to part 25 of this chapter, 
or an applicant who requests certification for flight in these icing 
conditions and any additional atmospheric icing conditions, must show 
the following in the icing conditions for which certification is 
requested under normal operation of the ice protection system(s):
    (1) Compliance with each requirement of this subpart, except those 
applicable to spins and any that must be demonstrated at speeds in 
excess of--
    (i) 250 knots CAS;
    (ii) VMO/MMO or VNE; or
    (iii) A speed at which the applicant demonstrates the airframe will 
be free of ice accretion.
    (2) The means by which stall warning is provided to the pilot for 
flight in icing conditions and non-icing conditions is the same.
    (b) If an applicant requests certification for flight in icing 
conditions, the applicant must provide a means to detect any icing 
conditions for which certification is not requested and show the 
airplane's ability to avoid or exit those conditions.
    (c) The applicant must develop an operating limitation to prohibit 
intentional flight, including takeoff and landing, into icing 
conditions for which the airplane is not certified to operate.

Subpart C--Structures

Sec.  23.2200   Structural design envelope.

    The applicant must determine the structural design envelope, which 
describes the range and limits of airplane design and operational 
parameters for which the applicant will show compliance with the 
requirements of this subpart. The applicant must account for all 
airplane design and operational parameters that affect structural 
loads, strength, durability, and aeroelasticity, including:
    (a) Structural design airspeeds, landing descent speeds, and any 
other airspeed limitation at which the applicant must show compliance 
to the requirements of this subpart. The structural design airspeeds 
must--
    (1) Be sufficiently greater than the stalling speed of the airplane 
to safeguard against loss of control in turbulent air; and
    (2) Provide sufficient margin for the establishment of practical 
operational limiting airspeeds.
    (b) Design maneuvering load factors not less than those, which 
service

[[Page 96694]]

history shows, may occur within the structural design envelope.
    (c) Inertial properties including weight, center of gravity, and 
mass moments of inertia, accounting for--
    (1) Each critical weight from the airplane empty weight to the 
maximum weight; and
    (2) The weight and distribution of occupants, payload, and fuel.
    (d) Characteristics of airplane control systems, including range of 
motion and tolerances for control surfaces, high lift devices, or other 
moveable surfaces.
    (e) Each critical altitude up to the maximum altitude.

Sec.  23.2205   Interaction of systems and structures.

    For airplanes equipped with systems that modify structural 
performance, alleviate the impact of this subpart's requirements, or 
provide a means of compliance with this subpart, the applicant must 
account for the influence and failure of these systems when showing 
compliance with the requirements of this subpart.

Structural Loads

Sec.  23.2210   Structural design loads.

    (a) The applicant must:
    (1) Determine the applicable structural design loads resulting from 
likely externally or internally applied pressures, forces, or moments 
that may occur in flight, ground and water operations, ground and water 
handling, and while the airplane is parked or moored.
    (2) Determine the loads required by paragraph (a)(1) of this 
section at all critical combinations of parameters, on and within the 
boundaries of the structural design envelope.
    (b) The magnitude and distribution of the applicable structural 
design loads required by this section must be based on physical 
principles.

Sec.  23.2215   Flight load conditions.

    The applicant must determine the structural design loads resulting 
from the following flight conditions:
    (a) Atmospheric gusts where the magnitude and gradient of these 
gusts are based on measured gust statistics.
    (b) Symmetric and asymmetric maneuvers.
    (c) Asymmetric thrust resulting from the failure of a powerplant 
unit.

Sec.  23.2220   Ground and water load conditions.

    The applicant must determine the structural design loads resulting 
from taxi, takeoff, landing, and handling conditions on the applicable 
surface in normal and adverse attitudes and configurations.

Sec.  23.2225   Component loading conditions.

    The applicant must determine the structural design loads acting on:
    (a) Each engine mount and its supporting structure such that both 
are designed to withstand loads resulting from--
    (1) Powerplant operation combined with flight gust and maneuver 
loads; and
    (2) For non-reciprocating powerplants, sudden powerplant stoppage.
    (b) Each flight control and high-lift surface, their associated 
system and supporting structure resulting from--
    (1) The inertia of each surface and mass balance attachment;
    (2) Flight gusts and maneuvers;
    (3) Pilot or automated system inputs;
    (4) System induced conditions, including jamming and friction; and
    (5) Taxi, takeoff, and landing operations on the applicable 
surface, including downwind taxi and gusts occurring on the applicable 
surface.
    (c) A pressurized cabin resulting from the pressurization 
differential--
    (1) From zero up to the maximum relief pressure combined with gust 
and maneuver loads;
    (2) From zero up to the maximum relief pressure combined with 
ground and water loads if the airplane may land with the cabin 
pressurized; and
    (3) At the maximum relief pressure multiplied by 1.33, omitting all 
other loads.

Sec.  23.2230   Limit and ultimate loads.

    The applicant must determine--
    (a) The limit loads, which are equal to the structural design loads 
unless otherwise specified elsewhere in this part; and
    (b) The ultimate loads, which are equal to the limit loads 
multiplied by a 1.5 factor of safety unless otherwise specified 
elsewhere in this part.

Structural Performance

Sec.  23.2235   Structural strength.

    The structure must support:
    (a) Limit loads without--
    (1) Interference with the safe operation of the airplane; and
    (2) Detrimental permanent deformation.
    (b) Ultimate loads.

Sec.  23.2240   Structural durability.

    (a) The applicant must develop and implement inspections or other 
procedures to prevent structural failures due to foreseeable causes of 
strength degradation, which could result in serious or fatal injuries, 
or extended periods of operation with reduced safety margins. Each of 
the inspections or other procedures developed under this section must 
be included in the Airworthiness Limitations Section of the 
Instructions for Continued Airworthiness required by Sec.  23.1529.
    (b) For Level 4 airplanes, the procedures developed for compliance 
with paragraph (a) of this section must be capable of detecting 
structural damage before the damage could result in structural failure.
    (c) For pressurized airplanes:
    (1) The airplane must be capable of continued safe flight and 
landing following a sudden release of cabin pressure, including sudden 
releases caused by door and window failures.
    (2) For airplanes with maximum operating altitude greater than 
41,000 feet, the procedures developed for compliance with paragraph (a) 
of this section must be capable of detecting damage to the pressurized 
cabin structure before the damage could result in rapid decompression 
that would result in serious or fatal injuries.
    (d) The airplane must be designed to minimize hazards to the 
airplane due to structural damage caused by high-energy fragments from 
an uncontained engine or rotating machinery failure.

Sec.  23.2245   Aeroelasticity.

    (a) The airplane must be free from flutter, control reversal, and 
divergence--
    (1) At all speeds within and sufficiently beyond the structural 
design envelope;
    (2) For any configuration and condition of operation;
    (3) Accounting for critical degrees of freedom; and
    (4) Accounting for any critical failures or malfunctions.
    (b) The applicant must establish tolerances for all quantities that 
affect flutter.

Design

Sec.  23.2250   Design and construction principles.

    (a) The applicant must design each part, article, and assembly for 
the expected operating conditions of the airplane.
    (b) Design data must adequately define the part, article, or 
assembly configuration, its design features, and any materials and 
processes used.
    (c) The applicant must determine the suitability of each design 
detail and part having an important bearing on safety in operations.
    (d) The control system must be free from jamming, excessive 
friction, and excessive deflection when the airplane is subjected to 
expected limit airloads.
    (e) Doors, canopies, and exits must be protected against 
inadvertent opening in

[[Page 96695]]

flight, unless shown to create no hazard when opened in flight.

Sec.  23.2255   Protection of structure.

    (a) The applicant must protect each part of the airplane, including 
small parts such as fasteners, against deterioration or loss of 
strength due to any cause likely to occur in the expected operational 
environment.
    (b) Each part of the airplane must have adequate provisions for 
ventilation and drainage.
    (c) For each part that requires maintenance, preventive 
maintenance, or servicing, the applicant must incorporate a means into 
the aircraft design to allow such actions to be accomplished.

Sec.  23.2260  Materials and processes.

    (a) The applicant must determine the suitability and durability of 
materials used for parts, articles, and assemblies, accounting for the 
effects of likely environmental conditions expected in service, the 
failure of which could prevent continued safe flight and landing.
    (b) The methods and processes of fabrication and assembly used must 
produce consistently sound structures. If a fabrication process 
requires close control to reach this objective, the applicant must 
perform the process under an approved process specification.
    (c) Except as provided in paragraphs (f) and (g) of this section, 
the applicant must select design values that ensure material strength 
with probabilities that account for the criticality of the structural 
element. Design values must account for the probability of structural 
failure due to material variability.
    (d) If material strength properties are required, a determination 
of those properties must be based on sufficient tests of material 
meeting specifications to establish design values on a statistical 
basis.
    (e) If thermal effects are significant on a critical component or 
structure under normal operating conditions, the applicant must 
determine those effects on allowable stresses used for design.
    (f) Design values, greater than the minimums specified by this 
section, may be used, where only guaranteed minimum values are normally 
allowed, if a specimen of each individual item is tested before use to 
determine that the actual strength properties of that particular item 
will equal or exceed those used in the design.
    (g) An applicant may use other material design values if approved 
by the Administrator.

Sec.  23.2265  Special factors of safety.

    (a) The applicant must determine a special factor of safety for 
each critical design value for each part, article, or assembly for 
which that critical design value is uncertain, and for each part, 
article, or assembly that is--
    (1) Likely to deteriorate in service before normal replacement; or
    (2) Subject to appreciable variability because of uncertainties in 
manufacturing processes or inspection methods.
    (b) The applicant must determine a special factor of safety using 
quality controls and specifications that account for each--
    (1) Type of application;
    (2) Inspection method;
    (3) Structural test requirement;
    (4) Sampling percentage; and
    (5) Process and material control.
    (c) The applicant must multiply the highest pertinent special 
factor of safety in the design for each part of the structure by each 
limit and ultimate load, or ultimate load only, if there is no 
corresponding limit load, such as occurs with emergency condition 
loading.

Structural Occupant Protection

Sec.  23.2270  Emergency conditions.

    (a) The airplane, even when damaged in an emergency landing, must 
protect each occupant against injury that would preclude egress when--
    (1) Properly using safety equipment and features provided for in 
the design;
    (2) The occupant experiences ultimate static inertia loads likely 
to occur in an emergency landing; and
    (3) Items of mass, including engines or auxiliary power units 
(APUs), within or aft of the cabin, that could injure an occupant, 
experience ultimate static inertia loads likely to occur in an 
emergency landing.
    (b) The emergency landing conditions specified in paragraph (a)(1) 
and (a)(2) of this section, must--
    (1) Include dynamic conditions that are likely to occur in an 
emergency landing; and
    (2) Not generate loads experienced by the occupants, which exceed 
established human injury criteria for human tolerance due to restraint 
or contact with objects in the airplane.
    (c) The airplane must provide protection for all occupants, 
accounting for likely flight, ground, and emergency landing conditions.
    (d) Each occupant protection system must perform its intended 
function and not create a hazard that could cause a secondary injury to 
an occupant. The occupant protection system must not prevent occupant 
egress or interfere with the operation of the airplane when not in use.
    (e) Each baggage and cargo compartment must--
    (1) Be designed for its maximum weight of contents and for the 
critical load distributions at the maximum load factors corresponding 
to the flight and ground load conditions determined under this part;
    (2) Have a means to prevent the contents of the compartment from 
becoming a hazard by impacting occupants or shifting; and
    (3) Protect any controls, wiring, lines, equipment, or accessories 
whose damage or failure would affect safe operations.

Subpart D--Design and Construction

Sec.  23.2300   Flight control systems.

    (a) The applicant must design airplane flight control systems to:
    (1) Operate easily, smoothly, and positively enough to allow proper 
performance of their functions.
    (2) Protect against likely hazards.
    (b) The applicant must design trim systems, if installed, to:
    (1) Protect against inadvertent, incorrect, or abrupt trim 
operation.
    (2) Provide a means to indicate--
    (i) The direction of trim control movement relative to airplane 
motion;
    (ii) The trim position with respect to the trim range;
    (iii) The neutral position for lateral and directional trim; and
    (iv) The range for takeoff for all applicant requested center of 
gravity ranges and configurations.

Sec.  23.2305   Landing gear systems.

    (a) The landing gear must be designed to--
    (1) Provide stable support and control to the airplane during 
surface operation; and
    (2) Account for likely system failures and likely operation 
environments (including anticipated limitation exceedances and 
emergency procedures).
    (b) All airplanes must have a reliable means of stopping the 
airplane with sufficient kinetic energy absorption to account for 
landing. Airplanes that are required to demonstrate aborted takeoff 
capability must account for this additional kinetic energy.
    (c) For airplanes that have a system that actuates the landing 
gear, there is--
    (1) A positive means to keep the landing gear in the landing 
position; and
    (2) An alternative means available to bring the landing gear in the 
landing position when a non-deployed system position would be a hazard.

[[Page 96696]]

Sec.  23.2310   Buoyancy for seaplanes and amphibians.

    Airplanes intended for operations on water, must--
    (a) Provide buoyancy of 80 percent in excess of the buoyancy 
required to support the maximum weight of the airplane in fresh water; 
and
    (b) Have sufficient margin so the airplane will stay afloat at rest 
in calm water without capsizing in case of a likely float or hull 
flooding.

Occupant System Design Protection

Sec.  23.2315   Means of egress and emergency exits.

    (a) With the cabin configured for takeoff or landing, the airplane 
is designed to:
    (1) Facilitate rapid and safe evacuation of the airplane in 
conditions likely to occur following an emergency landing, excluding 
ditching for level 1, level 2 and single engine level 3 airplanes.
    (2) Have means of egress (openings, exits or emergency exits), that 
can be readily located and opened from the inside and outside. The 
means of opening must be simple and obvious and marked inside and 
outside the airplane.
    (3) Have easy access to emergency exits when present.
    (b) Airplanes approved for aerobatics must have a means to egress 
the airplane in flight.

Sec.  23.2320  Occupant physical environment.

    (a) The applicant must design the airplane to--
    (1) Allow clear communication between the flightcrew and 
passengers;
    (2) Protect the pilot and flight controls from propellers; and
    (3) Protect the occupants from serious injury due to damage to 
windshields, windows, and canopies.
    (b) For level 4 airplanes, each windshield and its supporting 
structure directly in front of the pilot must withstand, without 
penetration, the impact equivalent to a two-pound bird when the 
velocity of the airplane is equal to the airplane's maximum approach 
flap speed.
    (c) The airplane must provide each occupant with air at a 
breathable pressure, free of hazardous concentrations of gases, vapors, 
and smoke during normal operations and likely failures.
    (d) If a pressurization system is installed in the airplane, it 
must be designed to protect against--
    (1) Decompression to an unsafe level; and
    (2) Excessive differential pressure.
    (e) If an oxygen system is installed in the airplane, it must--
    (1) Effectively provide oxygen to each user to prevent the effects 
of hypoxia; and
    (2) Be free from hazards in itself, in its method of operation, and 
its effect upon other components.

Fire and High Energy Protection

Sec.  23.2325  Fire protection.

    (a) The following materials must be self-extinguishing--
    (1) Insulation on electrical wire and electrical cable;
    (2) For levels 1, 2, and 3 airplanes, materials in the baggage and 
cargo compartments inaccessible in flight; and
    (3) For level 4 airplanes, materials in the cockpit, cabin, 
baggage, and cargo compartments.
    (b) The following materials must be flame resistant--
    (1) For levels 1, 2 and 3 airplanes, materials in each compartment 
accessible in flight; and
    (2) Any equipment associated with any electrical cable installation 
and that would overheat in the event of circuit overload or fault.
    (c) Thermal/acoustic materials in the fuselage, if installed, must 
not be a flame propagation hazard.
    (d) Sources of heat within each baggage and cargo compartment that 
are capable of igniting adjacent objects must be shielded and insulated 
to prevent such ignition.
    (e) For level 4 airplanes, each baggage and cargo compartment 
must--
    (1) Be located where a fire would be visible to the pilots, or 
equipped with a fire detection system and warning system; and
    (2) Be accessible for the manual extinguishing of a fire, have a 
built-in fire extinguishing system, or be constructed and sealed to 
contain any fire within the compartment.
    (f) There must be a means to extinguish any fire in the cabin such 
that--
    (1) The pilot, while seated, can easily access the fire 
extinguishing means; and
    (2) For levels 3 and 4 airplanes, passengers have a fire 
extinguishing means available within the passenger compartment.
    (g) Each area where flammable fluids or vapors might escape by 
leakage of a fluid system must--
    (1) Be defined; and
    (2) Have a means to minimize the probability of fluid and vapor 
ignition, and the resultant hazard, if ignition occurs.
    (h) Combustion heater installations must be protected from 
uncontained fire.

Sec.  23.2330  Fire protection in designated fire zones and adjacent 
areas.

    (a) Flight controls, engine mounts, and other flight structures 
within or adjacent to designated fire zones must be capable of 
withstanding the effects of a fire.
    (b) Engines in a designated fire zone must remain attached to the 
airplane in the event of a fire.
    (c) In designated fire zones, terminals, equipment, and electrical 
cables used during emergency procedures must be fire-resistant.

Sec.  23.2335  Lightning protection.

    The airplane must be protected against catastrophic effects from 
lightning.

Subpart E--Powerplant

Sec.  23.2400  Powerplant installation.

    (a) For the purpose of this subpart, the airplane powerplant 
installation must include each component necessary for propulsion, 
which affects propulsion safety, or provides auxiliary power to the 
airplane.
    (b) Each airplane engine and propeller must be type certificated, 
except for engines and propellers installed on level 1 low-speed 
airplanes, which may be approved under the airplane type certificate in 
accordance with a standard accepted by the FAA that contains 
airworthiness criteria the Administrator has found appropriate and 
applicable to the specific design and intended use of the engine or 
propeller and provides a level of safety acceptable to the FAA.
    (c) The applicant must construct and arrange each powerplant 
installation to account for--
    (1) Likely operating conditions, including foreign object threats;
    (2) Sufficient clearance of moving parts to other airplane parts 
and their surroundings;
    (3) Likely hazards in operation including hazards to ground 
personnel; and
    (4) Vibration and fatigue.
    (d) Hazardous accumulations of fluids, vapors, or gases must be 
isolated from the airplane and personnel compartments, and be safely 
contained or discharged.
    (e) Powerplant components must comply with their component 
limitations and installation instructions or be shown not to create a 
hazard.

Sec.  23.2405  Automatic power or thrust control systems.

    (a) An automatic power or thrust control system intended for in-
flight use must be designed so no unsafe condition will result during 
normal operation of the system.

[[Page 96697]]

    (b) Any single failure or likely combination of failures of an 
automatic power or thrust control system must not prevent continued 
safe flight and landing of the airplane.
    (c) Inadvertent operation of an automatic power or thrust control 
system by the flightcrew must be prevented, or if not prevented, must 
not result in an unsafe condition.
    (d) Unless the failure of an automatic power or thrust control 
system is extremely remote, the system must--
    (1) Provide a means for the flightcrew to verify the system is in 
an operating condition;
    (2) Provide a means for the flightcrew to override the automatic 
function; and
    (3) Prevent inadvertent deactivation of the system.

Sec.  23.2410  Powerplant installation hazard assessment.

    The applicant must assess each powerplant separately and in 
relation to other airplane systems and installations to show that any 
hazard resulting from the likely failure of any powerplant system, 
component, or accessory will not--
    (a) Prevent continued safe flight and landing or, if continued safe 
flight and landing cannot be ensured, the hazard has been minimized;
    (b) Cause serious injury that may be avoided; and
    (c) Require immediate action by any crewmember for continued 
operation of any remaining powerplant system.

Sec.  23.2415  Powerplant ice protection.

    (a) The airplane design, including the induction and inlet system, 
must prevent foreseeable accumulation of ice or snow that adversely 
affects powerplant operation.
    (b) The powerplant installation design must prevent any 
accumulation of ice or snow that adversely affects powerplant 
operation, in those icing conditions for which certification is 
requested.

Sec.  23.2420  Reversing systems.

    Each reversing system must be designed so that--
    (a) No unsafe condition will result during normal operation of the 
system; and
    (b) The airplane is capable of continued safe flight and landing 
after any single failure, likely combination of failures, or 
malfunction of the reversing system.

Sec.  23.2425   Powerplant operational characteristics.

    (a) The installed powerplant must operate without any hazardous 
characteristics during normal and emergency operation within the range 
of operating limitations for the airplane and the engine.
    (b) The pilot must have the capability to stop the powerplant in 
flight and restart the powerplant within an established operational 
envelope.

Sec.  23.2430   Fuel systems.

    (a) Each fuel system must--
    (1) Be designed and arranged to provide independence between 
multiple fuel storage and supply systems so that failure of any one 
component in one system will not result in loss of fuel storage or 
supply of another system;
    (2) Be designed and arranged to prevent ignition of the fuel within 
the system by direct lightning strikes or swept lightning strokes to 
areas where such occurrences are highly probable, or by corona or 
streamering at fuel vent outlets;
    (3) Provide the fuel necessary to ensure each powerplant and 
auxiliary power unit functions properly in all likely operating 
conditions;
    (4) Provide the flightcrew with a means to determine the total 
useable fuel available and provide uninterrupted supply of that fuel 
when the system is correctly operated, accounting for likely fuel 
fluctuations;
    (5) Provide a means to safely remove or isolate the fuel stored in 
the system from the airplane;
    (6) Be designed to retain fuel under all likely operating 
conditions and minimize hazards to the occupants during any survivable 
emergency landing. For level 4 airplanes, failure due to overload of 
the landing system must be taken into account; and
    (7) Prevent hazardous contamination of the fuel supplied to each 
powerplant and auxiliary power unit.
    (b) Each fuel storage system must--
    (1) Withstand the loads under likely operating conditions without 
failure;
    (2) Be isolated from personnel compartments and protected from 
hazards due to unintended temperature influences;
    (3) Be designed to prevent significant loss of stored fuel from any 
vent system due to fuel transfer between fuel storage or supply 
systems, or under likely operating conditions;
    (4) Provide fuel for at least one-half hour of operation at maximum 
continuous power or thrust; and
    (5) Be capable of jettisoning fuel safely if required for landing.
    (c) Each fuel storage refilling or recharging system must be 
designed to--
    (1) Prevent improper refilling or recharging;
    (2) Prevent contamination of the fuel stored during likely 
operating conditions; and
    (3) Prevent the occurrence of any hazard to the airplane or to 
persons during refilling or recharging.

Sec.  23.2435   Powerplant induction and exhaust systems.

    (a) The air induction system for each powerplant or auxiliary power 
unit and their accessories must--
    (1) Supply the air required by that powerplant or auxiliary power 
unit and its accessories under likely operating conditions;
    (2) Be designed to prevent likely hazards in the event of fire or 
backfire;
    (3) Minimize the ingestion of foreign matter; and
    (4) Provide an alternate intake if blockage of the primary intake 
is likely.
    (b) The exhaust system, including exhaust heat exchangers for each 
powerplant or auxiliary power unit, must--
    (1) Provide a means to safely discharge potential harmful material; 
and
    (2) Be designed to prevent likely hazards from heat, corrosion, or 
blockage.

Sec.  23.2440   Powerplant fire protection.

    (a) A powerplant, auxiliary power unit, or combustion heater that 
includes a flammable fluid and an ignition source for that fluid must 
be installed in a designated fire zone.
    (b) Each designated fire zone must provide a means to isolate and 
mitigate hazards to the airplane in the event of fire or overheat 
within the zone.
    (c) Each component, line, fitting, and control subject to fire 
conditions must--
    (1) Be designed and located to prevent hazards resulting from a 
fire, including any located adjacent to a designated fire zone that may 
be affected by fire within that zone;
    (2) Be fire resistant if carrying flammable fluids, gas, or air or 
required to operate in event of a fire; and
    (3) Be fireproof or enclosed by a fire proof shield if storing 
concentrated flammable fluids.
    (d) The applicant must provide a means to prevent hazardous 
quantities of flammable fluids from flowing into, within or through 
each designated fire zone. This means must--
    (1) Not restrict flow or limit operation of any remaining 
powerplant or auxiliary power unit, or equipment necessary for safety;
    (2) Prevent inadvertent operation; and
    (3) Be located outside the fire zone unless an equal degree of 
safety is provided with a means inside the fire zone.
    (e) A means to ensure the prompt detection of fire must be provided 
for each designated fire zone--

[[Page 96698]]

    (1) On a multiengine airplane where detection will mitigate likely 
hazards to the airplane; or
    (2) That contains a fire extinguisher.
    (f) A means to extinguish fire within a fire zone, except a 
combustion heater fire zone, must be provided for--
    (1) Any fire zone located outside the pilot's view;
    (2) Any fire zone embedded within the fuselage, which must also 
include a redundant means to extinguish fire; and
    (3) Any fire zone on a level 4 airplane.

Subpart F--Equipment

Sec.  23.2500   Airplane level systems requirements.

    This section applies generally to installed equipment and systems 
unless a section of this part imposes requirements for a specific piece 
of equipment, system, or systems.
    (a) The equipment and systems required for an airplane to operate 
safely in the kinds of operations for which certification is requested 
(Day VFR, Night VFR, IFR) must be designed and installed to--
    (1) Meet the level of safety applicable to the certification and 
performance level of the airplane; and
    (2) Perform their intended function throughout the operating and 
environmental limits for which the airplane is certificated.
    (b) The systems and equipment not covered by paragraph (a), 
considered separately and in relation to other systems, must be 
designed and installed so their operation does not have an adverse 
effect on the airplane or its occupants.

Sec.  23.2505   Function and installation.

    When installed, each item of equipment must function as intended.

Sec.  23.2510   Equipment, systems, and installations.

    For any airplane system or equipment whose failure or abnormal 
operation has not been specifically addressed by another requirement in 
this part, the applicant must design and install each system and 
equipment, such that there is a logical and acceptable inverse 
relationship between the average probability and the severity of 
failure conditions to the extent that:
    (a) Each catastrophic failure condition is extremely improbable;
    (b) Each hazardous failure condition is extremely remote; and
    (c) Each major failure condition is remote.

Sec.  23.2515   Electrical and electronic system lightning protection.

    An airplane approved for IFR operations must meet the following 
requirements, unless an applicant shows that exposure to lightning is 
unlikely:
    (a) Each electrical or electronic system that performs a function, 
the failure of which would prevent the continued safe flight and 
landing of the airplane, must be designed and installed such that--
    (1) The function at the airplane level is not adversely affected 
during and after the time the airplane is exposed to lightning; and
    (2) The system recovers normal operation of that function in a 
timely manner after the airplane is exposed to lightning unless the 
system's recovery conflicts with other operational or functional 
requirements of the system.
    (b) Each electrical and electronic system that performs a function, 
the failure of which would significantly reduce the capability of the 
airplane or the ability of the flightcrew to respond to an adverse 
operating condition, must be designed and installed such that the 
system recovers normal operation of that function in a timely manner 
after the airplane is exposed to lightning.

Sec.  23.2520   High-intensity Radiated Fields (HIRF) protection.

    (a) Each electrical and electronic systems that perform a function, 
the failure of which would prevent the continued safe flight and 
landing of the airplane, must be designed and installed such that--
    (1) The function at the airplane level is not adversely affected 
during and after the time the airplane is exposed to the HIRF 
environment; and
    (2) The system recovers normal operation of that function in a 
timely manner after the airplane is exposed to the HIRF environment, 
unless the system's recovery conflicts with other operational or 
functional requirements of the system.
    (b) For airplanes approved for IFR operations, each electrical and 
electronic system that performs a function, the failure of which would 
significantly reduce the capability of the airplane or the ability of 
the flightcrew to respond to an adverse operating condition, must be 
designed and installed such that the system recovers normal operation 
of that function in a timely manner after the airplane is exposed to 
the HIRF environment.

Sec.  23.2525   System power generation, storage, and distribution.

    The power generation, storage, and distribution for any system must 
be designed and installed to--
    (a) Supply the power required for operation of connected loads 
during all intended operating conditions;
    (b) Ensure no single failure or malfunction of any one power 
supply, distribution system, or other utilization system will prevent 
the system from supplying the essential loads required for continued 
safe flight and landing; and
    (c) Have enough capacity, if the primary source fails, to supply 
essential loads, including non-continuous essential loads for the time 
needed to complete the function required for continued safe flight and 
landing.

Sec.  23.2530   External and cockpit lighting.

    (a) The applicant must design and install all lights to minimize 
any adverse effects on the performance of flightcrew duties.
    (b) Any position and anti-collision lights, if required by part 91 
of this chapter, must have the intensities, flash rate, colors, fields 
of coverage, and other characteristics to provide sufficient time for 
another aircraft to avoid a collision.
    (c) Any position lights, if required by part 91 of this chapter, 
must include a red light on the left side of the airplane, a green 
light on the right side of the airplane, spaced laterally as far apart 
as practicable, and a white light facing aft, located on an aft portion 
of the airplane or on the wing tips.
    (d) Any taxi and landing lights must be designed and installed so 
they provide sufficient light for night operations.
    (e) For seaplanes or amphibian airplanes, riding lights must 
provide a white light visible in clear atmospheric conditions.

Sec.  23.2535   Safety equipment.

    Safety and survival equipment, required by the operating rules of 
this chapter, must be reliable, readily accessible, easily 
identifiable, and clearly marked to identify its method of operation.

Sec.  23.2540   Flight in icing conditions.

    An applicant who requests certification for flight in icing 
conditions defined in part 1 of appendix C to part 25 of this chapter, 
or an applicant who requests certification for flight in these icing 
conditions and any additional atmospheric icing conditions, must show 
the following in the icing conditions for which certification is 
requested:
    (a) The ice protection system provides for safe operation.
    (b) The airplane design must provide protection from stalling when 
the autopilot is operating.

Sec.  23.2545   Pressurized systems elements.

    Pressurized systems must withstand appropriate proof and burst 
pressures.

[[Page 96699]]

Sec.  23.2550   Equipment containing high-energy rotors.

    Equipment containing high-energy rotors must be designed or 
installed to protect the occupants and airplane from uncontained 
fragments.

Subpart G--Flightcrew Interface and Other Information

Sec.  23.2600   Flightcrew interface.

    (a) The pilot compartment, its equipment, and its arrangement to 
include pilot view, must allow each pilot to perform his or her duties, 
including taxi, takeoff, climb, cruise, descent, approach, landing, and 
perform any maneuvers within the operating envelope of the airplane, 
without excessive concentration, skill, alertness, or fatigue.
    (b) The applicant must install flight, navigation, surveillance, 
and powerplant controls and displays so qualified flightcrew can 
monitor and perform defined tasks associated with the intended 
functions of systems and equipment. The system and equipment design 
must minimize flightcrew errors, which could result in additional 
hazards.
    (c) For level 4 airplanes, the flightcrew interface design must 
allow for continued safe flight and landing after the loss of vision 
through any one of the windshield panels.

Sec.  23.2605   Installation and operation.

    (a) Each item of installed equipment related to the flightcrew 
interface must be labelled, if applicable, as to it identification, 
function, or operating limitations, or any combination of these 
factors.
    (b) There must be a discernible means of providing system operating 
parameters required to operate the airplane, including warnings, 
cautions, and normal indications to the responsible crewmember.
    (c) Information concerning an unsafe system operating condition 
must be provided in a timely manner to the crewmember responsible for 
taking corrective action. The information must be clear enough to avoid 
likely crewmember errors.

Sec.  23.2610   Instrument markings, control markings, and placards.

    (a) Each airplane must display in a conspicuous manner any placard 
and instrument marking necessary for operation.
    (b) The design must clearly indicate the function of each cockpit 
control, other than primary flight controls.
    (c) The applicant must include instrument marking and placard 
information in the Airplane Flight Manual.

Sec.  23.2615   Flight, navigation, and powerplant instruments.

    (a) Installed systems must provide the flightcrew member who sets 
or monitors parameters for the flight, navigation, and powerplant, the 
information necessary to do so during each phase of flight. This 
information must--
    (1) Be presented in a manner that the crewmember can monitor the 
parameter and determine trends, as needed, to operate the airplane; and
    (2) Include limitations, unless the limitation cannot be exceeded 
in all intended operations.
    (b) Indication systems that integrate the display of flight or 
powerplant parameters to operate the airplane or are required by the 
operating rules of this chapter must--
    (1) Not inhibit the primary display of flight or powerplant 
parameters needed by any flightcrew member in any normal mode of 
operation; and
    (2) In combination with other systems, be designed and installed so 
information essential for continued safe flight and landing will be 
available to the flightcrew in a timely manner after any single failure 
or probable combination of failures.

Sec.  23.2620   Airplane flight manual.

    The applicant must provide an Airplane Flight Manual that must be 
delivered with each airplane.
    (a) The Airplane Flight Manual must contain the following 
information--
    (1) Airplane operating limitations;
    (2) Airplane operating procedures;
    (3) Performance information;
    (4) Loading information; and
    (5) Other information that is necessary for safe operation because 
of design, operating, or handling characteristics.
    (b) The following sections of the Airplane Flight Manual must be 
approved by the FAA in a manner specified by the administrator--
    (1) For low-speed, level 1 and 2 airplanes, those portions of the 
Airplane Flight Manual containing the information specified in 
paragraph (a)(1) of this section; and
    (2) For high-speed level 1 and 2 airplanes and all level 3 and 4 
airplanes, those portions of the Airplane Flight Manual containing the 
information specified in paragraphs (a)(1) thru (a)(4) of this section.

Appendix A to Part 23--Instructions for Continued Airworthiness

A23.1 General

    (a) This appendix specifies requirements for the preparation of 
Instructions for Continued Airworthiness as required by this part.
    (b) The Instructions for Continued Airworthiness for each 
airplane must include the Instructions for Continued Airworthiness 
for each engine and propeller (hereinafter designated ``products''), 
for each appliance required by this chapter, and any required 
information relating to the interface of those appliances and 
products with the airplane. If Instructions for Continued 
Airworthiness are not supplied by the manufacturer of an appliance 
or product installed in the airplane, the Instructions for Continued 
Airworthiness for the airplane must include the information 
essential to the continued airworthiness of the airplane.
    (c) The applicant must submit to the FAA a program to show how 
changes to the Instructions for Continued Airworthiness made by the 
applicant or by the manufacturers of products and appliances 
installed in the airplane will be distributed.

A23.2 Format

    (a) The Instructions for Continued Airworthiness must be in the 
form of a manual or manuals as appropriate for the quantity of data 
to be provided.
    (b) The format of the manual or manuals must provide for a 
practical arrangement.

A23.3 Content

    The contents of the manual or manuals must be prepared in the 
English language. The Instructions for Continued Airworthiness must 
contain the following manuals or sections and information:
    (a) Airplane maintenance manual or section.
    (1) Introduction information that includes an explanation of the 
airplane's features and data to the extent necessary for maintenance 
or preventive maintenance.
    (2) A description of the airplane and its systems and 
installations including its engines, propellers, and appliances.
    (3) Basic control and operation information describing how the 
airplane components and systems are controlled and how they operate, 
including any special procedures and limitations that apply.
    (4) Servicing information that covers details regarding 
servicing points, capacities of tanks, reservoirs, types of fluids 
to be used, pressures applicable to the various systems, location of 
access panels for inspection and servicing, locations of lubrication 
points, lubricants to be used, equipment required for servicing, tow 
instructions and limitations, mooring, jacking, and leveling 
information.
    (b) Maintenance Instructions.
    (1) Scheduling information for each part of the airplane and its 
engines, auxiliary power units, propellers, accessories, 
instruments, and equipment that provides the recommended periods at 
which they should be cleaned, inspected, adjusted, tested, and 
lubricated, and the degree of inspection, the applicable wear 
tolerances, and work recommended at these periods. However, the 
applicant may refer to an accessory, instrument, or equipment 
manufacturer as the source of this information if the applicant 
shows that the item has an exceptionally high degree of complexity 
requiring specialized maintenance techniques, test

[[Page 96700]]

equipment, or expertise. The recommended overhaul periods and 
necessary cross reference to the Airworthiness Limitations section 
of the manual must also be included. In addition, the applicant must 
include an inspection program that includes the frequency and extent 
of the inspections necessary to provide for the continued 
airworthiness of the airplane.
    (2) Troubleshooting information describing probable 
malfunctions, how to recognize those malfunctions, and the remedial 
action for those malfunctions.
    (3) Information describing the order and method of removing and 
replacing products and parts with any necessary precautions to be 
taken.
    (4) Other general procedural instructions including procedures 
for system testing during ground running, symmetry checks, weighing 
and determining the center of gravity, lifting and shoring, and 
storage limitations.
    (c) Diagrams of structural access plates and information needed 
to gain access for inspections when access plates are not provided.
    (d) Details for the application of special inspection techniques 
including radiographic and ultrasonic testing where such processes 
are specified by the applicant.
    (e) Information needed to apply protective treatments to the 
structure after inspection.
    (f) All data relative to structural fasteners such as 
identification, discard recommendations, and torque values.
    (g) A list of special tools needed.
    (h) In addition, for level 4 airplanes, the following 
information must be furnished--
    (1) Electrical loads applicable to the various systems;
    (2) Methods of balancing control surfaces;
    (3) Identification of primary and secondary structures; and
    (4) Special repair methods applicable to the airplane.

A23.4 Airworthiness limitations section.

    The Instructions for Continued Airworthiness must contain a 
section titled Airworthiness Limitations that is segregated and 
clearly distinguishable from the rest of the document. This section 
must set forth each mandatory replacement time, structural 
inspection interval, and related structural inspection procedure 
required for type certification. If the Instructions for Continued 
Airworthiness consist of multiple documents, the section required by 
this paragraph must be included in the principal manual. This 
section must contain a legible statement in a prominent location 
that reads ``The Airworthiness Limitations section is FAA approved 
and specifies maintenance required under Sec. Sec.  43.16 and 91.403 
of Title 14 of the Code of Federal Regulations unless an alternative 
program has been FAA approved.''

PART 35--AIRWORTHINESS STANDARDS: PROPELLERS

0
9. The authority citation for part 35 is revised to read as follows:

    Authority: 49 U.S.C. 106(f), 106(g), 40113, 44701-44702, 44704.

0
10. In Sec.  35.1, revise paragraph (c) to read as follows:

Sec.  35.1   Applicability.

* * * * *
    (c) An applicant is eligible for a propeller type certificate and 
changes to those certificates after demonstrating compliance with 
subparts A, B, and C of this part. However, the propeller may not be 
installed on an airplane unless the applicant has shown compliance with 
either Sec.  23.2400(c) or Sec.  25.907 of this chapter, as applicable, 
or compliance is not required for installation on that airplane.
* * * * *

0
11. In Sec.  35.37, revise paragraph (c)(1) to read as follows:

Sec.  35.37   Fatigue limits and evaluation.

* * * * *
    (c) * * *
    (1) The intended airplane by complying with Sec.  23.2400(c) or 
Sec.  25.907 of this chapter, as applicable; or
* * * * *

PART 43--MAINTENANCE, PREVENTIVE MAINTENANCE, REBUILDING, AND 
ALTERATION

0
12. The authority citation for part 43 is revised to read as follows:

    Authority: 42 U.S.C. 7572; 49 U.S.C. 106(f), 106(g), 40105, 
40113, 44701-44702, 44704, 44707, 44709, 44711, 44713, 44715, 45303.

0
13. In part 43, appendix E, revise the introductory text and paragraph 
(a)(2) to read as follows:

Appendix E to Part 43--Altimeter System Test and Inspection

    Each person performing the altimeter system tests and 
inspections required by Sec.  91.411 of this chapter must comply 
with the following:
    (a) * * *
    (2) Perform a proof test to demonstrate the integrity of the 
static pressure system in a manner acceptable to the Administrator. 
For airplanes certificated under part 25 of this chapter, determine 
that leakage is within the tolerances established by Sec.  25.1325.
* * * * *

PART 91--GENERAL OPERATING AND FLIGHT RULES

0
14. The authority citation for part 91 continues to read as follows:

    Authority: 49 U.S.C. 106(f), 106(g), 1155, 40101, 40103, 40105, 
40113, 40120, 44101, 44111, 44701, 44704, 44709, 44711, 44712, 
44715, 44716, 44717, 44722, 46306, 46315, 46316, 46504, 46506-46507, 
47122, 47508, 47528-47531, 47534, articles 12 and 29 of the 
Convention on International Civil Aviation (61 Stat. 1180), (126 
Stat. 11).

0
15. In Sec.  91.205, revise paragraphs (b)(13) and (b)(14), and remove 
and reserve paragraph (b)(16) to read as follows:

Sec.  91.205   Powered civil aircraft with standard category U.S. 
airworthiness certificates: Instrument and equipment requirements.

* * * * *
    (b) * * *
    (13) An approved safety belt with an approved metal-to-metal 
latching device, or other approved restraint system for each occupant 2 
years of age or older.
    (14) For small civil airplanes manufactured after July 18, 1978, an 
approved shoulder harness or restraint system for each front seat. For 
small civil airplanes manufactured after December 12, 1986, an approved 
shoulder harness or restraint system for all seats. Shoulder harnesses 
installed at flightcrew stations must permit the flightcrew member, 
when seated and with the safety belt and shoulder harness fastened, to 
perform all functions necessary for flight operations. For purposes of 
this paragraph--
    (i) The date of manufacture of an airplane is the date the 
inspection acceptance records reflect that the airplane is complete and 
meets the FAA-approved type design data; and
    (ii) A front seat is a seat located at a flightcrew member station 
or any seat located alongside such a seat.
* * * * *
    (16) [Reserved]
* * * * *

0
16. In Sec.  91.313, revise paragraph (g) introductory text to read as 
follows:

Sec.  91.313   Restricted category civil aircraft: Operating 
limitations.

* * * * *
    (g) No person may operate a small restricted-category civil 
airplane manufactured after July 18, 1978, unless an approved shoulder 
harness or restraint system is installed for each front seat. The 
shoulder harness or restraint system installation at each flightcrew 
station must permit the flightcrew member, when seated and with the 
safety belt and shoulder harness fastened or the restraint system 
engaged, to perform all functions necessary for flight operation. For 
purposes of this paragraph--
* * * * *

0
17. In Sec.  91.323, revise paragraph (b)(3) to read as follows:

[[Page 96701]]

Sec.  91.323   Increased maximum certificated weights for certain 
airplanes operated in Alaska.

* * * * *
    (b) * * *
    (3) The weight at which the airplane meets the positive maneuvering 
load factor n, where n=2.1+(24,000/(W+10,000)) and W=design maximum 
takeoff weight, except that n need not be more than 3.8; or
* * * * *

0
18. In Sec.  91.531, revise paragraphs (a)(1) and (a)(3) to read as 
follows:

Sec.  91.531   Second in command requirements.

    (a) * * *
    (1) A large airplane or normal category level 4 airplane, except 
that a person may operate an airplane certificated under SFAR 41 
without a pilot who is designated as second in command if that airplane 
is certificated for operation with one pilot.
* * * * *
    (3) A commuter category airplane or normal category level 3 
airplane, except that a person may operate those airplanes 
notwithstanding paragraph (a)(1) of this section, that have a passenger 
seating configuration, excluding pilot seats, of nine or less without a 
pilot who is designated as second in command if that airplane is type 
certificated for operations with one pilot.
* * * * *

PART 121--OPERATING REQUIREMENTS: DOMESTIC, FLAG, AND SUPPLEMENTAL 
OPERATIONS

0
19. The authority citation for part 121 continues to read as follows:

    Authority: 49 U.S.C. 106(f), 106(g), 40103, 40113, 40119, 41706, 
42301 preceding note added by Pub. L. 112-95, Sec. 412, 126 Stat. 
89, 44101, 44701-44702, 44705, 44709-44711, 44713, 44716-44717, 
44722, 44729, 44732; 46105; Pub. L. 111-216, 124 Stat. 2348 (49 
U.S.C. 44701 note); Pub. L. 112-95, 126 Stat. 62 (49 U.S.C. 44732 
note).

0
20. In Sec.  121.310, revise paragraph (b)(2)(iii) to read as follows:

Sec.  121.310   Additional emergency equipment.

* * * * *
    (b) * * *
    (2) * * *
    (iii) For a nontransport category turbopropeller powered airplane 
type certificated after December 31, 1964, each passenger emergency 
exit marking and each locating sign must be manufactured to have white 
letters 1 inch high on a red background 2 inches high, be self-
illuminated or independently, internally electrically illuminated, and 
have a minimum brightness of at least 160 microlamberts. The color may 
be reversed if the passenger compartment illumination is essentially 
the same. On these airplanes, no sign may continue to be used if its 
luminescence (brightness) decreases to below 100 microlamberts.
* * * * *

PART 135--OPERATING REQUIREMENTS: COMMUTER AND ON DEMAND OPERATIONS 
AND RULES GOVERNING PERSONS ON BOARD SUCH AIRCRAFT

0
21. The authority citation for part 135 continues to read as follows:

    Authority: 49 U.S.C. 106(f), 106(g), 41706, 40113, 44701-44702, 
44705, 44709, 44711-44713, 44715-44717, 44722, 44730, 45101-45105; 
Pub. L. 112-95, 126 Stat. 58 (49 U.S.C. 44730).

0
22. In Sec.  135.169, revise paragraphs (b) introductory text, (b)(6), 
and (b)(7), and add paragraph (b)(8) to read as follows:

Sec.  135.169   Additional airworthiness requirements.

* * * * *
    (b) No person may operate a small airplane that has a passenger-
seating configuration, excluding pilot seats, of 10 seats or more 
unless it is type certificated--
* * * * *
    (6) In the normal category and complies with section 1.(b) of 
Special Federal Aviation Regulation No. 41;
    (7) In the commuter category; or
    (8) In the normal category, as a multi-engine certification level 4 
airplane as defined in part 23 of this chapter.
* * * * *

    Issued under authority provided by 49 U.S.C. 106(f), 44701(a), 
44703 and Pub. L. 113-53 (127 Stat. 584; 49 U.S.C. 44704 note) in 
Washington, DC, on December 12, 2016.
Michael P. Huerta,
Administrator.
[FR Doc. 2016-30246 Filed 12-21-16; 4:15 pm]
 BILLING CODE 4910-13-P
```