[Federal Register Volume 61, Number 129 (Wednesday, July 3, 1996)]
[Proposed Rules]
[Pages 35056-35061]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 96-17034]



[[Page 35055]]


_______________________________________________________________________

Part VII





Department of Transportation





_______________________________________________________________________



Federal Aviation Administration



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14 CFR Part 25



Revision of Hydraulic Systems Airworthiness Standards To Harmonize With 
European Airworthiness Standards for Transportation Category Airplanes, 
and Proposed Advisory Circular for Hydraulic System Certification Tests 
and Analysis; Proposed Rule and Notice

Federal Register / Vol. 61, No. 129 / Wednesday, July 3, 1996 / 
Proposed Rules

[[Page 35056]]



DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 25

[Docket No. 28617; Notice 96-6]
RIN 2120-AF79


Revision of Hydraulic Systems Airworthiness Standards To 
Harmonize With European Airworthiness Standards for Transport Category 
Airplanes

AGENCY: Federal Aviation Administration (FAA), DOT.

ACTION: Notice of proposed rulemaking.

-----------------------------------------------------------------------

SUMMARY: This document proposes to amend the airworthiness standards 
for transport category airplanes to harmonize hydraulic systems design 
and test requirements with standards proposed for the European Joint 
Aviation Requirements (JAR). These proposals were developed in 
cooperation with the Joint Aviation Authorities (JAA) of Europe and the 
U.S. and European aviation industry through the Aviation Rulemaking 
Advisory Committee (ARAC). These changes are intended to benefit the 
public interest by standardizing certain requirements, concepts, and 
procedures contained in the airworthiness standards without reducing, 
but potentially enhancing, the current level of safety.

DATES: Comments must be received on or before October 1, 1996.

ADDRESSES: Comments on this notice may be mailed in triplicate to: 
Federal Aviation Administration, Office of the Chief Counsel, 
Attention: Rules Docket (AGC-200), Docket No. 28617, 800 Independence 
Avenue SW., Washington, DC 20591; or delivered in triplicate to: Room 
915G, 800 Independence Avenue SW., Washington, DC 20591.
    Comments delivered must be marked Docket No. 28617. Comments may 
also be sent electronically to the following internet address: 
<a href="/cdn-cgi/l/email-protection#204e524d50434d5453604d41494c0e48510e4641410e474f56"><span class="__cf_email__" data-cfemail="b7d9c5dac7d4dac3c4f7dad6dedb99dfc699d1d6d699d0d8c1">[email protected]</span></a>. Comments may be examined in Room 915G 
weekdays, except Federal holidays, between 8:30 a.m. and 5:00 p.m. In 
addition, the FAA is in maintaining an information docket of comments 
in the Transport Airplane Directorate (ANM-100), Federal Aviation 
Administration, Northwest Mountain Region, 1601 Lind Avenue SW., 
Renton, WA 98055-4056. Comments in the information docket may be 
examined weekdays, except Federal holidays, between 7:30 a.m. and 4:00 
p.m.

FOR FURTHER INFORMATION CONTACT:
Mahinder K. Wahi, Flight Test and Systems Branch, ANM-111, Transport 
Airplane Directorate, Aircraft Certification Service, FAA, 1601 Lind 
Avenue SW., Renton, WA 98055-4056; telephone (206) 227-2142; facsimile 
(206) 227-1320.

SUPPLEMENTARY INFORMATION:

Comment Invited

    Interested persons are invited to participate in this proposed 
rulemaking by submitting such written data, views, or arguments as they 
may desire. Comments relating to any environmental, energy, or economic 
impact that might result from adopting the proposals contained in this 
notice are invited. Substantive comments should be accompanied by cost 
estimates. Commenters should identify the regulatory docket or notice 
number and submit comments in triplicate to the Rules Docket address 
above. All comments received on or before the closing date for comments 
will be considered by the Administrator before taking action on this 
proposed rulemaking. The proposals contained in this notice may be 
changed in light of comments received. All comments received will be 
available in the Rules Docket, both before and after the comment period 
closing date, for examination by interested persons. A report 
summarizing each substantive public contact with FAA personnel 
concerning this rulemaking will be filed in the docket. Persons wishing 
the FAA to acknowledge receipt of their comments must submit with those 
comments a self-addressed, stamped postcard on which is stated: 
``Comments to Docket No. 28617.'' The postcard will be date stamped and 
returned to the commenter.

Availability of the NPRM

    An electronic copy of this document may be downloaded using a modem 
and suitable communications software from the FAA regulations section 
of the Fedworld electronic bulletin board service (telephone: 703-321-
3339), the Federal Register's electronic bulletin board service 
(telephone 202-512-1661), or the FAA's Aviation Rulemaking Advisory 
Committee Bulletin Board service (telephone: 202-267-5948).
    Internet users may reach the FAA's web page at http://www.faa.gov 
or the Federal Register's web page at http://www.access.gpo/su-docs for 
access to recently published rulemaking documents.
    Any person may obtain a copy of this notice of submitting a request 
to the Federal Aviation Administration (FAA), Office of Rulemaking, 
ARM-1, 800 Independence Avenue, S.W., Washington, D.C. 20591 or by 
calling (202) 267-9680. Communications must identify the notice number 
or docket number of this notice.
    Persons interested in being placed on a mailing list for future 
rulemaking documents should also request a copy of Advisory Circular 
No. 11-2A, Notice of Proposed Rulemaking Distribution System, which 
describes the application procedure.

Background

    The airworthiness standards for transport category airplanes are 
contained in 14 CFR part 25. Manufacturers of transport category 
airplanes must show that each airplane they produce of a different type 
design complies with the relevant standards of part 25. These standards 
apply to airplanes manufactured within the U.S. for use by U.S. 
registered operators and to airplanes manufactured in other countries 
and imported under a bilateral airworthiness agreement.
    In Europe, the Joint Aviation Requirements (JAR) were developed by 
the Joint Aviation Authorities (JAA) to provide a common set of 
airworthiness standards for use within the European aviation community. 
The airworthiness standards for European type certification of 
transport category airplanes, JAR-25, are based on part 25 of Title 14. 
Airplanes certificated to the JAR-25 standards, including airplanes 
manufactured in the U.S. for export to Europe, receive type 
certificates that are accepted by the aircraft certification 
authorities of 23 European countries.
    Although part 25 and JAR-25 are very similar, they are not 
identical. Differences between the FAR and the JAR can result in 
substantial additional costs when airplanes are type certificated to 
both standards. These additional costs, however, frequently do not 
bring about an increase in safety. For example, part 25 and JAR-25 may 
use different means to accomplish the same safety intent. In this case, 
the manufacturer is usually burdened with meeting both requirements, 
although the level of safety is not increased correspondingly. 
Recognizing that a common set of standards would not only economically 
benefit the aviation industry, but would also maintain the necessary 
high level of safety, the FAA and JAA consider harmonization to be a 
high priority.
    In 1988, the FAA, in cooperation with the JAA and other 
organizations representing the American and European aerospace 
industries, began a

[[Page 35057]]

process to harmonize the airworthiness requirements of the United 
States and the airworthiness requirements of Europe, especially in the 
areas of Flight Test and Structures.
    In 1992, the FAA harmonization effort was undertaken by the ARAC. A 
working group of industry and government hydraulic systems specialists 
of Europe and the United States was chartered by notice in the Federal 
Register (57 FR 58843, December 12, 1992). The working group was tasked 
to develop a draft notice of proposed rulemaking (NPRM) and any 
collateral documents, such as advisory circulars, concerning new or 
revised requirements for hydraulic systems, and the associated test 
conditions for hydraulic systems, installed in transport category 
airplanes (Sec. 25.1435). The JAA is to develop a similar proposal to 
amend JAR-25, as necessary, to achieve harmonization.
    The rulemaking proposal contained in this notice is based on a 
recommendation developed by the Hydraulic Systems Harmonization Working 
Group, and was presented to the FAA by the ARAC as a recommendation.

The Aviation Rulemaking Advisory Committee

    The ARAC was formally established by the FAA on January 22, 1991 
(56 FR 2190) to provide advice and recommendations concerning the full 
range of the FAA's safety-related rulemaking activity. This advice was 
sought to develop better rules in less overall time using fewer FAA 
resources than are currently needed. The committee provides the 
opportunity for the FAA to obtain firsthand information and insight 
from interested parties regarding proposed new rules or revisions of 
existing rules.
    There are 64 member organizations on the committee, representing a 
wide range of interests within the aviation community. Meetings of the 
committee are open to the public, except as authorized by section 10(d) 
of the Federal Advisory Committee Act.
    The ARAC establishes working groups to develop proposals to 
recommend to the FAA for resolving specific issues. Tasks assigned to 
working groups are published in the Federal Register. Although working 
group meetings are not generally open to the public, all interested 
parties are invited to participate as working group members. Working 
groups report directly to the ARAC, and the ARAC must accept a working 
group proposal before that proposal can be presented to the FAA as an 
advisory committee recommendation.
    The activities of the ARAC will not, however, circumvent the public 
rulemaking procedures. After an ARAC recommendation is received and 
found acceptable by the FAA, the agency proceeds with the normal public 
rulemaking procedures. Any ARAC participation in a rulemaking package 
will be fully disclosed in the public docket.

Discussion of the Proposals

    The FAA proposes to amend Sec. 25.1435 to harmonize this section 
with JAR-25. The JAA intend to publish a Notice of Proposed Amendment 
(NPA), also developed by the Hydraulic Systems Harmonization Working 
Group, to revise JAR-25 as necessary to ensure harmonization in those 
areas for which the proposed amendments differ from the current JAR-25, 
Change 14. When it is published, the NPA will be placed in the docket 
for this rulemaking.
    Generally, the FAA proposes to: (1) Add appropriate existing-JAR 
requirements to achieve harmonization; (2) Move some of the existing 
regulatory text to an advisory circular; (3) Consolidate and/or 
separate requirement subparagraphs for clarity; and (4) Revise airplane 
static proof pressure test requirements to require a complete 
functional (dynamic) airplane test at a lower pressure. A new proposed 
Advisory Circular (AC) 25.1435-1 has been developed by the ARAC to 
ensure consistent application of these proposed revised standards. 
Public comments concerning the AC 25.1435-1 are invited by separate 
notice published elsewhere in this issue of the Federal Register. The 
JAA intend to publish an Advisory Material Joint (AMJ), also developed 
by the Harmonization Working Group, to accompany their NPA. The 
proposed AC and the proposed AMJ contain harmonized advisory 
information. The following is a discussion of the specific proposals 
prescribed in this NPRM.
    Proposal 1. The FAA proposes to replace current Sec. 25.1435(a)(1) 
to add the existing requirements of JAR 25.1435(a)(10) and associated 
Appendix K requirements regarding design load factors for proof and 
ultimate pressure conditions for elements of the hydraulic system (see 
proposal 2 below regarding current Sec. 25.1435(a)(1)). The proof and 
ultimate pressure conditions would be defined as the design operating 
pressure times the factors of safety. This would be done to address 
unusually high pressures which may be seen in service, material defects 
and differences, manufacturing/construction tolerances and the 
consequences of failures (e.g. pressure vessel failure). The proposed 
load factors, ranging between 1.5 and 4.0, relate to the design 
operating pressure (DOP) and would apply to tubes, fittings, pressure 
vessels containing gas at high pressure (e.g., accumulators) and at low 
pressure (e.g. hydraulic reservoirs), hoses, and all other elements.
    By adopting these JAR minimum factors of safety standards which 
currently are not specifically stated in the FAR, the FAA intends to 
maintain an existing level of safety because normal U.S. Industry 
practices meet or exceed these standards.
    DOP is the normal maximum steady pressure. Excluded are reasonable 
tolerances and transient pressure effects such as may arise from 
acceptable pump ripple or reaction to system functioning or flow 
demands that may affect fatigue. In localized areas of systems and 
system elements the DOP may be different from the DOP for the system as 
a whole due to the range or normally anticipated airplane operational, 
dynamic and environmental conditions. Such differences would be 
required to be taken into account. The term ``design operating 
pressure'' would be discussed in AC 25.1435-1.
    Proposal 2. The FAA proposes to redesignate the current 
Sec. 25.1435(a)(1) as Sec. 25.1435(a)(2), delete the word ``loads'' 
from ``pressure loads'' (``loads'' is redundant) and edit some text to 
avoid repetition. The term ``limit structural load'', and a recommended 
minimum time to hold pressure would be discussed in AC 25.1435-1.
    Proposal 3. The FAA proposes to redesignate the current 
Sec. 25.1435(a)(2) as a new Sec. 25.1435(a)(3), delete the word 
``loads'' from ``pressure loads'' (``loads'' is redundant) and edit 
some text to avoid repetition. The term ``ultimate structural load'' 
and a minimum time to hold pressure would be discussed in AC 25.1435-1.
    Proposal 4. The FAA proposes to add a new Sec. 25.1435(a)(4) that 
would contain the current requirements of Sec. 25.1435(b)(2)(i) and 
(b)(2)(ii) regarding induced loads, pressure transients, and fatigue as 
well as the current JAR 25.1435(a)(11) requirements regarding fatigue 
design considerations accounting for fluctuating or repeated external 
or internal loads and pressure transients. These loads could be 
structurally or environmentally induced. By delineating these 
requirements, the FAA intends to ensure that each element is designed 
to provide fatigue resistance capability consistent with anticipated 
element usage, thus maintaining the current

[[Page 35058]]

level of safety. The terms ``fatigue'', and ``externally induced 
loads'' would be discussed in AC 25.1435-1.
    Proposal 5. The FAA proposes to add a new Sec. 25.1435(a)(5) that 
would contain the current requirements of Sec. 25.1435(b)(2)(i) through 
(b)(2)(v), except those addressed under proposal 4 above, as well as 
parts of the current JAR 25.1435 (a)(5) and (a)(6) requirements 
addressing excessive vibration, abrasion, corrosion, mechanical damage, 
and the ability to withstand inertia loads. These requirements would be 
consolidated and simplified by stating that each element must be 
designed to perform as intended under all environmental conditions for 
which the airplane is certificated. An acceptable means of compliance 
would be included in AC 25.1435-1.
    Proposal 6. The FAA proposes to add a modified version of the 
existing JAR 25.1435(a)(2) as Sec. 25.1435(a)(1), requiring means to 
indicate appropriate system parameters at a flight crewmember station 
if (1) the system performs a function necessary for continued safe 
flight and landing, or (2) in the event of hydraulic system 
malfunction, corrective action by the crew is required to ensure 
continued safe flight and landing. The existing JAR 25.1435(a)(2) 
requires fluid quantity and pressure indication under specified 
circumstances; prior to Amendment 25-72, Sec. 25.2435 contained an 
identical requirement. It was considered at the time that this 
requirement is covered by Sec. 25.1309(c), which requires that warning 
information must be provided to alert the crew to unsafe system 
operating conditions, and to enable them to take appropriate corrective 
action, and the Sec. 25.1435 requirement was therefore deleted. It is, 
however, now recognized that there is value in defining indication 
requirements for hydraulic systems and implications of their loss. The 
existing level of safety would not be impacted since the FAA is 
proposing the adopt an existing industry practice. The term 
``appropriate system parameters'' would be discussed in AC 25.1435-1. 
(Note: see proposal 12 below with respect to status of current 
Sec. 25.1435(b)(1) requirements).
    Proposal 7. The FAA proposes to replace the current 
Sec. 25.1435(b)(2) by adding a modified version of the current JAR 
25.1435 (a)(4) and (a)(7) to require that each system have means to 
ensure that system pressures remain within the design capabilities of 
each element. Prior to Amendment 25-72, Sec. 25.1435 contained a 
requirement that was identical to the current JAR requirement, but it 
was characterized as both containing arbitrary pressure transient 
limits and unnecessary because the intent is covered under 
Sec. 25.1309. The requirement was therefore deleted from Sec. 25.1435. 
The proposed version deletes the arbitrary limits but would require 
that the intent be specifically addressed by Sec. 25.1435(b)(2) to 
ensure consideration of the pressure and volume related transients that 
are unique to the hydraulic systems. There would be no impact on level 
of safety since an existing industry practice is being adopted. An 
acceptable means of compliance with Sec. 25.1435(b)(2) would be 
included in AC 25.1435-1.
    Proposal 8. The FAA proposes to add a new Sec. 25.1435(b)(3) which 
would contain a modified version of the existing JAR 25.1435(a)(5) 
requirements regarding the means to minimize harmful or hazardous 
concentrations of the hydraulic fluid or vapors, if liberated in any 
form, into the crew and passenger compartments during flight. Prior to 
Amendment 25-72, Sec. 25.1435 contained an identical requirement. It 
was considered at the time that Sec. 25.831(b) covers this requirement 
under a general statement that the ventilation air must be free of 
hazardous or harmful gases or vapors. However, Sec. 25.831(b) specifies 
allowable limits for carbon monoxide and carbon dioxide, but no other 
products. It could be construed that those two gases are the only 
hazardous products. Section 25.1435 would therefore be revised to state 
the specific requirement with respect to the hydraulic fluid or vapors.
    The JAR requirement currently states, in relevant part, that 
``there must be a means to prevent harmful or hazardous concentration 
of fluid. * * *'' In recognition of the fact that absolute prevention 
of such concentrations is not an achievable objective, the FAA proposes 
that the hydraulic system must have ``means to minimize the release of 
harmful or hazardous concentrations * * *'' To show compliance with 
this requirement, an applicant would have to show, both that the 
likelihood of releases has been minimized, and that, if there is such a 
release, the concentrations from the release would also be minimized. 
The level of safety would remain unaffected because it's an existing 
industry practice to address this issue. An acceptable means of 
compliance with Sec. 25.1435(b)(3) and a discussion of the terms 
``harmful'' and ``hazardous'' would be included in AC 25.1435-1.
    Proposal 9. The FAA proposes to redesignate the existing 
Sec. 25.1435(c) as Sec. 25.1435(b)(4); this is identical to the 
existing JAR 25.1435(c) requirements regarding use of flammable 
hydraulic fluid and fire protection. A discussion of the term 
``flammable hydraulic fluid'' would be included in AC 25.1435-1.
    Proposal 10. The FAA proposes to add a new Sec. 25.1435(b)(5), 
containing the current JAR 25.1435(d) requirements that the airplane 
manufacturer must specify the approved hydraulic fluid(s) suitable to 
be used in the system(s) and ensure that the system(s) meet the 
applicable placarding requirements of the current Sec. 25.1541. 
Although it is a standard U.S. industry practice to identify the 
compatible hydraulic fluid on each component's name plate, the practice 
may not be universal. In order to minimize the potential use of 
incompatible fluids, seals, etc. in any system, it is necessary to 
include this requirement. A discussion of mixability of hydraulic 
fluids would be included in AC 25.1435-1.
    Proposal 11. Current Sec. 25.1435(b)(2) requirements for hydraulic 
system compliance by test and analysis would be separated into 
Secs. 25.1435 (c), (c)(1) and (c)(2); the list of environmental factors 
[current Sec. 25.1435 (b)(2)(ii) through (b)(2)(v)] would be moved to 
AC 25.1435-1; and, text in the aforementioned sections would be 
clarified. In addition, analysis would be permitted in place of or to 
supplement testing, where shown to be reliable and appropriate. A 
discussion on endurance and fatigue testing, and simulated failures 
would be included in AC 25.1435-1.
    Proposal 12. Current Sec. 25.1435(b)(1) requirements for static 
testing of a complete hydraulic system to 1.5 times the design 
operating pressure (without deformation of any part of the system that 
would prevent performance of intended function) would be replaced with 
a new Sec. 25.1435(c)(3) requirement that ``the complete hydraulic 
system must be functionally tested on the airplane over the range of 
motion of all associated user systems.'' Also, the section would 
require that ``the test must be conducted at the system relief pressure 
or 1.25 times the DOP if a system pressure relief device is not part of 
the system design.'' This proposal reflected the recently granted 
petition for exemption to the Boeing Company, Regulatory Docket No. 
27384. The petition, any comments received, and a copy of the final 
disposition are filed in the assigned regulatory docket and are 
available for examination in the Rules Docket (AGC 200), room 915G, FAA 
Headquarters Building (FOB 10A), 800 Independence Avenue SW., 
Washington, DC 20591; telephone (202) 267-3132. A discussion on relief

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pressure settings and an acceptable means of compliance with 
Sec. 25.1435(c)(3) would be included in AC 25.1435-1.
    The FAA considers that the proposed functional (i.e., dynamic) test 
more closely approximates actual operating conditions than the existing 
static test. This is because for the static test, several parts of the 
system and associated relief valves (including return lines) may need 
to be disabled to allow system pressurization at 1.5 times the design 
operating pressure because the relief valves are designed to open at a 
pressure lower than 1.5 times the design operating pressure. Although 
the proposed test pressure would be lower than 1.5 times the design 
operating pressure, all elements would still be required to be able to 
withstand at least 1.5 times the design operating pressure per current 
Sec. 25.1435(a)(2) (proposed Sec. 25.1435(a)(3)), at least retaining 
and potentially enhancing the current level of safety by identification 
of additional dynamic interference problems.

Regulatory Evaluation Summary

Regulatory Evaluation, Regulatory Flexibility Determination, and Trade 
Impact Assessment

    Changes to federal regulations must undergo several economic 
analyses. First, Executive Order 12866 directs Federal agencies to 
promulgate new regulations or modify existing regulations only if the 
potential benefits to society outweigh the potential costs. Second, the 
Regulatory Flexibility Act of 1980 requires agencies to analyze the 
economic impact of regulatory changes on small entities. Finally, the 
Office of Management and Budget directs agencies to assess the effect 
of regulatory changes on international trade. In conducting these 
assessments, the FAA has determined that this proposed rule: (1) Would 
generate benefits exceeding its costs and is not ``significant'' as 
defined in Executive Order 12866; (2) Is not ``significant'' as defined 
in DOT's Policies and Procedures; (3) would not have a significant 
impact on a substantial number of small entities; and (4) would lessen 
restraints on international trade. These analyses, available in the 
docket, are summarized below.
    Although several revisions would be made to Sec. 25.1435, only 
three of them would impose additional costs (see below--proposals 1, 4, 
and 12, with the latter having potential cost savings for some 
manufacturers). Most of the changes codify current industry practice or 
conform Sec. 25.1435 to corresponding sections of the JAR. Adoption of 
the proposed changes would increase harmonization and commonality 
between American and European airworthiness standards. Harmonization 
would eliminate unnecessary duplication of airworthiness requirements, 
thus reducing manufacturers' certification costs. One manufacturer of 
part 25 large airplanes estimated such cost-savings could range between 
$60,000 and 600,000 per type certification (pertaining to hydraulic 
systems only); a manufacturer of part 25 small airplanes estimated such 
savings at $30,000 to $90,000 per type certification; Potential safety 
benefits resulting from specification of minimum accepted standards 
would supplement these cost-savings.
    Proposal 1. These changes codify existing industry standards. As 
such, they would not result in additional costs for most manufacturers, 
However, one manufacturer of small transport category airplanes 
estimated increased testing costs of approximately $25,000 per type 
certification Codification of the proposed standards would ensure that 
current safety levels are retained.
    Proposals 2, 3, and 9. There would be no additional costs 
associated with these minor changes.
    Proposal 4. Although some of the changes described are new 
requirements in the FAR, most American manufacturers of large transport 
category airplanes are already in compliance with the similar current 
European standards, which had to be met in order to market airplanes in 
JAA member countries. The modified testing and analysis regime is 
already in place. Initial first-time costs have already been incurred; 
such costs have diminished in recent certifications. Consequently, 
actual incremental costs would be negligible. One manufacturer, 
however, indicated that additional testing and analysis costs, ranging 
between $100,000 and $200,000 per type certification, would be incurred 
for the first one or two type certifications. Learning curve 
efficiencies would likely reduce these costs thereafter. Manufacturers 
of small transport category airplanes, on the other hand, expect no or 
negligible additional costs attributable to the new fatigue-related 
proposals. Codification of the proposed standards would ensure that 
minimum acceptable fatigue requirements are specified with potential 
for safety enhancement.
    Proposals 5, 6, 7, 8, and 10. These changes codify existing 
industry standards and would not result in additional certification/
production costs. Codification of the proposed standards would ensure 
that current safety levels are retained.
    Proposal 11. There would be no additional costs associated with 
these revisions. The use of analysis in lieu of or supplemental to 
testing may reduce certification costs in some cases.
    Proposal 12. Most manufacturers of part 25 airplanes would not 
experience additional costs associated with dynamic testing of 
hydraulic systems. In fact, testing time and associated costs could be 
reduced to some small extent since, unlike static testing, the proposed 
dynamic testing would not entail disabling any system(s) or otherwise 
reconfiguring the airplane. One manufacturer of part 25 large airplanes 
estimated potential savings between $100,000 and $200,000 per type 
certification in this regard (another estimated such savings at only 
$25,000). However, a manufacturer of part 25 small transport category 
airplanes estimates $25,000 in additional testing, analysis, and report 
preparation costs per type certification attributable to this proposal. 
The proposed requirements would at least retain, and potentially 
enhance, the current level of safety by identification of additional 
dynamic interference problems.

Summary of Costs and Benefits

    Manufacturers of part 25 small airplanes could experience 
additional costs totalling approximately $50,000 per type certification 
resulting from proposals 1 (design load factors) and 12 (dynamic 
testing). The estimated $30,000-$90,000 harmonization cost savings, 
coupled with potential safety benefits from proposals 4 and 12, would 
exceed these costs.
    For manufacturers of part 25 large airplanes, the cost differential 
could range from a $25,000-$200,000 reduction (resulting from proposal 
12) to a $100,000-$200,000 increase (resulting from proposal 4). The 
proposal 12 cost savings coupled with the estimated $60,000-$600,000 
harmonization cost savings would exceed the additional costs of 
proposal 4; potential safety benefits from proposals 4 and 12 would 
supplement the cost-savings.
    The FAA finds the proposed rule, therefore, to be cost-beneficial 
for both part 25 small and large transport manufacturers.

Regulatory Flexibility Determination

    The Regulatory Flexibility Act of 1980 (RFA) was enacted by 
Congress to ensure that small entities are not unnecessarily or 
disproportionately burdened by government regulations. The RFA requires 
a Regulatory

[[Page 35060]]

Flexibility Analysis if a rule would have a significant economic 
impact, either detrimental or beneficial, on a substantial number of 
small entities. FAA Order 2100.14A, Regulatory Flexibility Criteria and 
Guidance, prescribes standards for complying with RFA review 
requirements in FAA rulemaking actions. The order defines ``small 
entities'' in terms of size thresholds, ``significant economic impact'' 
in terms of annualized cost threshold, and ``substantial number'' as a 
number which is not less than eleven and which is more than one-third 
of the small entities subject to the proposed or final rule.
    The proposed rule would affect manufacturers of transport category 
airplanes produced under future new airplane type certifications. For 
manufacturers, Order 2100.14A specifies a size threshold for 
classification as a small entity as 75 or fewer employees. Since no 
transport category airplane manufacturer has 75 or fewer employees, the 
proposed rule would not have a significant economic impact on a 
substantial number of small manufacturers.

International Trade Impact Assessment

    The proposed rule would not constitute a barrier to international 
trade, including the export of American airplanes to foreign countries, 
and the import of foreign airplanes into the United States. Instead, 
the proposed changes to the FAR would harmonize with corresponding 
existing or proposed standards in the JAR, thereby lessening restraints 
on trade.

Federalism Implications

    The amended regulations proposed in this rulemaking would not have 
substantial direct effects on the States, on the relationship between 
the national government and the States, or on the distribution of power 
and responsibilities among the various levels of government. Therefore, 
in accordance with Executive Order 12612, it is determined that this 
proposal would not have sufficient federalism implications to warrant 
preparing a Federalism Assessment.

International Compatibility

    In keeping with U.S. obligations under the Convention on 
International Civil Aviation, it is FAA policy to comply with 
International Civil Aviation Organization (ICAO) standards and 
recommended practices to the maximum extent practicable. The FAA has 
determined that this rule does not conflict with any international 
agreement of the United States.

Paperwork Reduction Act

    In accordance with the Paperwork Reduction Act of 1980 (Pub. L. 96-
511), there are no requirements for information collection associated 
with this proposed rule.

Conclusion

    Because the proposed changes to standardize specific hydraulic 
systems test requirements of part 25 are not expected to result in 
substantial economic cost, the FAA has determined that this proposed 
regulation would not be significant under Executive Order 12866. 
Because this is an issue which has not prompted a great deal of public 
concern, the FAA has determined that this action is not significant 
under DOT Regulatory Policies and Procedures (44 FR 11034, February 25, 
1979). In addition since there are no small entities affected by this 
proposed rulemaking, the FAA certifies, under the criteria of the 
Regulatory Flexibility Act, that this rule, if adopted, will not have a 
significant economic impact, positive or negative, on a substantial 
number of small entities. An initial regulatory evaluation of the 
proposal, including a Regulatory Flexibility Determination and Trade 
Impact Analysis, has been placed in the docket. A copy may be obtained 
by contacting the person identified under for further information 
contact.

List of Subjects in 14 CFR Part 25

    Aircraft, Aviation safety, Reporting and recordkeeping 
requirements.

The Proposed Amendments

    Accordingly, the Federal Aviation Administration proposes to amend 
14 CFR part 25 as follows:

PART 25--AIRWORTHINESS STANDARDS--TRANSPORT CATEGORY AIRPLANES

    1. The authority citation for part 25 continues to read as follows:

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

    2. Section 25.1435 is revised to read as follows:


Sec. 25.1435  Hydraulic systems.

    (a) Element design. Each element of the hydraulic system must be 
designed to:
    (1) Withstand the proof pressure without leakage or permanent 
deformation that prevents it from performing its intended function, and 
the ultimate pressure without rupture. The proof and ultimate pressures 
are defined in terms of the design operating pressure (DOP) as follows:

------------------------------------------------------------------------
                                                        Proof   Ultimate
                       Element                         (xDOP)    (xDOP) 
------------------------------------------------------------------------
1. Tubes & fittings.................................       1.5       3.0
2. Pressure vessels containing gas:                                     
  High pressure (e.g., accumulators)................       3.0       4.0
  Low pressure (e.g., reservoirs)...................       1.5       3.0
3. Hoses............................................       2.0       4.0
4. All other elements...............................       1.5       2.0
------------------------------------------------------------------------

    (2) Withstand, without deformation that would prevent it from 
performing its intended function, the design operating pressure in 
combination with limit structural loads that may be imposed;
    (3) Withstand, without rupture, the design operating pressure 
multiplied by a factor of 1.5 in combination with ultimate structural 
load that can reasonably occur simultaneously;
    (4) Withstand the fatigue effects of all cyclic pressures, 
including transients, and associated externally induced loads, taking 
into account the consequences of element failure; and
    (5) Perform as intended under all environmental conditions for 
which the airplane is certificated.
    (b) System design. Each hydraulic system must:
    (1) Have means located at a flightcrew station to indicate 
appropriate system parameters.
    (i) It performs a function necessary for continued safe flight and 
landing; or
    (ii) In the event of hydraulic system malfunction, corrective 
action by the crew to ensure continued safe flight and landing is 
necessary;
    (2) Have means to ensure that system pressures, including transient 
pressures and pressures from fluid volumetric changes in elements that 
are likely to remain closed long enough for such changes to occur, are 
within the design capabilities of each element, such that they meet the 
requirements defined in Sec. 25.1435(a)(1) through (a)(5);
    (3) Have means to minimize the release of harmful of hazardous 
concentrations of hydraulic fluid or vapors into the crew and passenger 
compartments during flight;
    (4) Meet the applicable requirements of Secs. 25.863, 25.1183, 
25.1185, and 25.1189 if a flammable hydraulic fluid is used; and
    (5) Be designed to use any suitable hydraulic fluid specified by 
the airplane manufacturer, which must be identified by appropriate 
markings as required by Sec. 25.1541.
    (c) Tests. To demonstrate compliance with Sec. 25.1435 and support 
compliance with Sec. 25.1309, tests must be conducted on the hydraulic 
system(s), and/or

[[Page 35061]]

subsystem(s) and elements, except that analysis may be used in place of 
or to supplement testing, where the analysis is shown to be reliable 
and appropriate. All internal and external influences must be taken 
into account to an extent necessary to evaluate their effects, and to 
assure reliable system and element functioning and integration. Failure 
or unacceptable deficiency of an element or system must be corrected 
and be sufficiently retested, where necessary.
    (1) The system(s), subsystem(s), or element(s) must be subjected to 
performance, fatigue, and endurance tests representative of airplane 
ground flight operations.
    (2) The complete system must be tested to determine proper 
functional performance and relation to the other systems, including 
simulation of relevant failure conditions, and to support or validate 
element design.
    (3) The complete hydraulic system(s) must be functionally tested on 
the airplane in normal operation over the range of motion of all 
associated user systems. The test must be conducted at the system 
relief pressure 1.25 times the DOP if a system pressure relief device 
is not part of the system design. Clearances between hydraulic system 
elements and other systems or structural elements must remain adequate 
and there must be no detrimental effects.

    Issued in Washington, DC, on June 26, 1996.
Ava L. Robinson,
Acting Director, Aircraft Certification Service.
[FR Doc. 96-17034 Filed 7-2-96; 8:45 am]
BILLING CODE 4910-13-M


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