Document ID: FAA-2022-0349-0001
Agency: faa
Document Type: Proposed Rule
Title: Special Condition: Airbus Model A321neo XLR Airplane; Flight-Envelope Protection Functions-General
Posted Date: 2022-11-17T05:00Z

[Federal Register Volume 87, Number 221 (Thursday, November 17, 2022)]
[Proposed Rules]
[Pages 68942-68944]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 2022-24772]

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DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 25

[Docket No. FAA-2022-0349; Notice No. 25-22-05-SC]

Special Conditions: Airbus Model A321neo XLR Airplane; Flight-
Envelope Protection Functions--General

AGENCY: Federal Aviation Administration (FAA), DOT.

ACTION: Notice of proposed special conditions.

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SUMMARY: This action proposes special conditions for the the Airbus 
Model A321neo XLR airplanes. These airplanes will have a novel or 
unusual design feature when compared to the state of technology 
envisioned in the airworthiness standards for transport-category 
airplanes. This design feature is an electronic flight-control system 
that provides flight-envelope protections. The applicable airworthiness 
regulations do not contain

[[Page 68943]]

adequate or appropriate safety standards for this design feature. These 
proposed special conditions contain the additional safety standards 
that the Administrator considers necessary to establish a level of 
safety equivalent to that established by the existing airworthiness 
standards.

DATES: Send comments on or before January 3, 2023.

ADDRESSES: Send comments identified by Docket No. FAA-2022-0349 using 
any of the following methods:
     Federal eRegulations Portal: Go to https://www.regulations.gov/ and follow the online instructions for sending 
your comments electronically.
     Mail: Send comments to Docket Operations, M-30, U.S. 
Department of Transportation (DOT), 1200 New Jersey Avenue SE, Room 
W12-140, West Building Ground Floor, Washington, DC, 20590-0001.
     Hand Delivery or Courier: Take comments to Docket 
Operations in Room W12-140 of the West Building Ground Floor at 1200 
New Jersey Avenue SE, Washington, DC, between 9 a.m. and 5 p.m., Monday 
through Friday, except Federal holidays.
     Fax: Fax comments to Docket Operations at 202-493-2251.
    Privacy: Except for Confidential Business Information (CBI) as 
described in the following paragraph, and other information as 
described in title 14, Code of Federal Regulations (14 CFR) 11.35, the 
FAA will post all comments received without change to https://www.regulations.gov/, including any personal information you provide. 
The FAA will also post a report summarizing each substantive verbal 
contact received about these special conditions.
    Confidential Business Information: Confidential Business 
Information (CBI) is commercial or financial information that is both 
customarily and actually treated as private by its owner. Under the 
Freedom of Information Act (FOIA) (5 U.S.C. 552), CBI is exempt from 
public disclosure. If your comments responsive to these special 
conditions contain commercial or financial information that is 
customarily treated as private, that you actually treat as private, and 
that is relevant or responsive to these special conditions, it is 
important that you clearly designate the submitted comments as CBI. 
Please mark each page of your submission containing CBI as ``PROPIN.'' 
The FAA will treat such marked submissions as confidential under the 
FOIA, and the indicated comments will not be placed in the public 
docket of these special conditions. Send submissions containing CBI to 
Troy Brown, Performance and Environment Section, AIR-625, Technical 
Innovation Policy Branch, Policy and Innovation Division, Aircraft 
Certification Service, Federal Aviation Administration, 1801 S. Airport 
Rd., Wichita, KS 67209-2190; telephone and fax 405-666-1050; email 
[email protected]. Comments the FAA receives, which are not 
specifically designated as CBI, will be placed in the public docket for 
these special conditions.
    Docket: Background documents or comments received may be read at 
https://www.regulations.gov/ at any time. Follow the online 
instructions for accessing the docket or go to Docket Operations in 
Room W12-140 of the West Building Ground Floor at 1200 New Jersey 
Avenue SE, Washington, DC, between 9 a.m. and 5 p.m., Monday through 
Friday, except Federal holidays.

FOR FURTHER INFORMATION CONTACT: Troy Brown, Performance and 
Environment Section, AIR-625, Technical Innovation Policy Branch, 
Policy and Innovation Division, Aircraft Certification Service, Federal 
Aviation Administration, 1801 S. Airport Rd., Wichita, KS 67209-2190; 
telephone and fax 405-666-1050; email [email protected].

SUPPLEMENTARY INFORMATION:

Comments Invited

    The FAA invites interested people to take part in this rulemaking 
by sending written comments, data, or views. The most helpful comments 
reference a specific portion of the special conditions, explain the 
reason for any recommended change, and include supporting data.
    The FAA will consider all comments received by the closing date for 
comments. The FAA may change these special conditions based on the 
comments received.

Background

    On September 16, 2019, Airbus applied for an amendment to Type 
Certificate No. A28NM to include the new Model A321neo XLR airplanes, 
which include the Model A321-271NY and A321-253NY airplanes. These 
airplanes are twin-engine, transport-category airplanes with seating 
for 244 passengers and a maximum takeoff weight of 222,000 pounds.

Type Certification Basis

    Under the provisions of 14 CFR 21.101, Airbus must show that the 
Model A321neo XLR airplanes meet the applicable provisions of the 
regulations listed in Type Certificate No. A28NM, or the applicable 
regulations in effect on the date of application for the change, except 
for earlier amendments as agreed upon by the FAA.
    If the Administrator finds that the applicable airworthiness 
regulations (e.g., 14 CFR part 25) do not contain adequate or 
appropriate safety standards for the Airbus Model A321neo XLR airplanes 
because of a novel or unusual design feature, special conditions are 
prescribed under the provisions of Sec.  21.16.
    Special conditions are initially applicable to the model for which 
they are issued. Should the type certificate for that model be amended 
later to include any other model that incorporates the same novel or 
unusual design feature, or should any other model already included on 
the same type certificate be modified to incorporate the same novel or 
unusual design feature, these special conditions would also apply to 
the other model under Sec.  21.101.
    In addition to the applicable airworthiness regulations and special 
conditions, the Airbus Model A321neo XLR airplanes must comply with the 
fuel-vent and exhaust-emission requirements of 14 CFR part 34, and the 
noise-certification requirements of 14 CFR part 36.
    The FAA issues special conditions, as defined in Sec.  11.19, in 
accordance with Sec.  11.38, and they become part of the type 
certification basis under Sec.  21.101.

Novel or Unusual Design Features

    The Airbus Model A321neo XLR airplanes will incorporate the 
following novel or unusual design feature:
    An electronic flight-control system that provides flight envelope 
protections.

Discussion

    Many new transport-category airplanes use advanced electronic 
flight-control systems (EFCS), which incorporate flight-envelope 
protection (limiting) designed to prevent the pilot from inadvertently 
or intentionally exceeding any number of flight-envelope parameters. 
Depending on a particular EFCS design, these limiting features may or 
may not be active in all normal and alternate flight-control modes, and 
may or may not be capable of being overridden by the pilot.
    The FAA currently applies 14 CFR 25.143 to airplanes incorporating 
EFCS. The purpose of Sec.  25.143 is to verify that operational 
maneuvers conducted within the operational envelope can be accomplished 
smoothly with average piloting skill, and without encountering a stall 
warning or other characteristics that might interfere with normal 
maneuvering, or without exceeding

[[Page 68944]]

structural limits. The airplane response to control input should be 
predictable to the pilot. However, Sec.  25.143 does not adequately 
ensure that airplanes incorporating EFCS with flight-envelope 
protections will have a level of safety equivalent to that of existing 
standards.
    Envelope-protection functions are intended to reduce the likelihood 
of excursions, either commanded or uncommanded, to unintended or 
potentially hazardous airplane operating states. As a consequence of 
preventing excursions, these functions can also restrict aircraft 
maneuverability, and may introduce non-traditional behavior. The 
proposed special conditions will ensure that flight-envelope protection 
functions support safe operation, and do not interfere with required 
maneuvering in normal and emergency operations, and in forseeable 
atmospheric conditions.
    The FAA previously issued separate special conditions for general 
limiting, normal load-factor limiting, high-speed limiting, and pitch 
and roll limiting for airplanes incorporating flight-envelope 
protection features. However, the FAA tasked the Aviation Rulemaking 
Advisory Committee (ARAC) in April 2014 (79 FR 20295) to develop 
recommended standards for fly-by-wire flight controls for general 
flight-envelope protection (limiting) similar to those provided for 
conventional control functions in 14 CFR 25.143. The ARAC 
recommended,\1\ among other things, performance-based requirements that 
would encompass general limiting, normal load-factor limiting, high-
speed limiting, and pitch and roll limiting which the FAA previously 
issued as separate special conditions. These proposed special 
conditions are based on that ARAC recommendation.
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    \1\ FAA Aviation Rulemaking Advisory Committee, FTHWG Topic 1 
Envelope Protection, Recommendation Report-Rev. A, March, 2017, 
https://www.faa.gov/regulations_policies/rulemaking/committees/documents/media/09%20-%20FTHWG_Final_Report_Phase_2_RevA__Apr_2017.pdf.
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    These proposed special conditions provide the same level of safety 
as the prescriptive, design-specific special conditions the FAA has 
issued in the past for general limiting, normal load-factor limiting, 
high-speed limiting, and pitch and roll limiting, thus the FAA need not 
issue separate special conditions to address each of these areas.
    These proposed special conditions are in addition to the 
requirements of Sec.  25.143. These proposed special conditions contain 
the additional safety standards that the Administrator considers 
necessary to establish a level of safety equivalent to that established 
by the existing airworthiness standards.

Applicability

    As discussed above, these proposed special conditions apply to 
Airbus Model A321neo XLR airplanes. Should Airbus apply later for a 
change to the type certificate to include another model incorporating 
the same novel or unusual design feature, the special conditions would 
apply to that model as well.

Conclusion

    This action affects only certain novel or unusual design features 
on one model series of airplanes. It is not a rule of general 
applicability.

List of Subjects in 14 CFR Part 25

    Aircraft, Aviation safety, Reporting and recordkeeping 
requirements.

Authority Citation

    The authority citation for these special conditions is as follows:

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

The Proposed Special Conditions

    Accordingly, the Federal Aviation Administration (FAA) proposes the 
following special conditions as part of the type certification basis 
for Airbus Model A321neo XLR airplanes equipped with EFCS.
    In addition to Sec.  25.143, the following requirements apply:
    (a) Envelope protection functions must not unduly limit the 
maneuvering capability of the airplane, nor interfere with its ability 
to perform maneuvers required for normal and emergency operations.
    (b) Onset characteristics of each flight-envelope protection 
function must be appropriate to the phase of flight and type of 
maneuver, and must not conflict with the ability of the pilot to 
satisfactorily control the airplane flight path, speed, and attitude.
    (c) Excursions of a limited flight parameter beyond its nominal 
design-limit value due to dynamic maneuvering, airframe and system 
tolerances, and non-steady atmospheric conditions must not result in 
unsafe flight characteristics or conditions.
    (d) Operation of flight-envelope protection functions must not 
adversely affect aircraft control during expected levels of atmospheric 
disturbances, nor impede the application of recovery procedures in case 
of wind shear.
    (e) Simultaneous action of flight-envelope protection functions 
must not result in adverse coupling or adverse priority.
    (f) In case of abnormal attitude or excursion of flight parameters 
outside the protected boundaries, operation of flight-envelope 
protection functions must not hinder airplane recovery.

    Issued in Kansas City, Missouri, on November 8, 2022.
Patrick R. Mullen,
Manager, Technical Innovation Policy Branch, Policy and Innovation 
Division, Aircraft Certification Service.
[FR Doc. 2022-24772 Filed 11-16-22; 8:45 am]
BILLING CODE 4910-13-P