[Federal Register Volume 89, Number 58 (Monday, March 25, 2024)]
[Rules and Regulations]
[Pages 20543-20545]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 2024-06196]


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DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 25

[Docket No. FAA-2024-0449; Special Conditions No. 25-860-SC]


Special Conditions: Airbus SAS Model A350 Series Airplanes; Seats 
With Inertia Locking Devices

AGENCY: Federal Aviation Administration (FAA), DOT.

ACTION: Final special conditions; request for comments.

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SUMMARY: These special conditions are issued for the Airbus SAS 
(Airbus) Model A350 series airplanes. These airplanes will have a novel 
or unusual design feature when compared to the state of technology 
envisioned in the applicable airworthiness standards. This design 
feature is seats with inertia locking devices (ILD). The applicable 
airworthiness regulations do not contain adequate or appropriate safety 
standards for this design feature. These 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.

[[Page 20544]]


DATES: This action is effective on Airbus on March 25, 2024. Send 
comments on or before May 9, 2024.

ADDRESSES: Send comments identified by Docket No. FAA-2024-0449 using 
any of the following methods:
     Federal eRegulations Portal: Go to 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.
     Docket: Background documents or comments received may be 
read at 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: Dan Jacquet, Cabin Safety Section, 
AIR-624, Technical Policy Branch, Policy & Standards Division, Federal 
Aviation Administration, 2200 South 216th Street, Des Moines, WA 98198, 
telephone 206-231-3208, email [email protected].

SUPPLEMENTARY INFORMATION: The substance of these special conditions 
has been published in the Federal Register for public comment in 
several prior instances with comments received that required no changes 
to previously issued special conditions. Therefore, the FAA finds, 
pursuant to 14 CFR 11.38(b), that new comments are unlikely, and notice 
and comment prior to this publication are unnecessary.

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 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 the individual listed in the For Further 
Information Contact section above. Comments the FAA receives, which are 
not specifically designated as CBI, will be placed in the public docket 
for these special conditions.

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, and will consider comments filed late if it is possible to do 
so without incurring delay. The FAA may change these special conditions 
based on the comments received.

Background

    On August 16, 2022, Airbus applied for an amendment to Type 
Certificate No. T000631B for seats with ILD in the Model A350 series 
airplanes. These airplanes are twin-engine, transport-category 
airplanes, with a maximum seating for 480 passengers, and a maximum 
take-off weight of 623,908 pounds.

Type Certification Basis

    Under the provisions of title 14, Code of Federal Regulations (14 
CFR) 21.101, Airbus must show that the Airbus Model A350 series 
airplanes, as changed, continue to meet the applicable provisions of 
the regulations listed in Type Certificate No. T000631B, 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 A350 series 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 A350 series airplanes must comply with the 
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 14 CFR 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 A350 series airplanes will incorporate the 
following novel or unusual design features:
    Seats with inertia locking devices.

Discussion

    Airbus will install, in Model A350 series airplanes, passenger 
seats that can be translated in the fore and aft direction by an 
electrically powered motor (actuator) that is attached to the seat 
primary structure. Under typical service-loading conditions, the motor 
internal brake is able to translate the seat and hold the seat in the 
translated position. However, under the inertial loads of emergency-
landing and loading conditions, specified in Sec.  25.562, the motor 
internal brake may not be able to maintain the seat in the required 
position. The ILD is an ``active'' device intended to control seat 
movement (i.e., a system that mechanically deploys during an impact 
event), by locking the gears of the motor assembly in place. The ILD 
mechanism is activated by the higher inertial load factors that could 
occur during an emergency landing event. Each seat place incorporates 
two ILDs, one on either side of the seat pan. Only one ILD is required 
to hold an

[[Page 20545]]

occupied seat in position during worst-case dynamic loading specified 
in Sec.  25.562.
    The ILD will self-activate only in the event of a predetermined 
airplane loading condition such as that occurring during crash or 
emergency landing and will prevent excessive seat forward translation. 
A minimum level of protection must be provided if the seat-locking 
device does not deploy.
    The normal means of satisfying the structural and occupant 
protection requirements of Sec.  25.562 result in a non-quantified, but 
nominally predictable, progressive structural deformation or reduction 
of injury severity for impact conditions less than the maximum 
specified by the rule. A seat using ILD technology, however, may 
involve a step change in protection for impacts below and above that at 
which the ILD activates and deploys to retain the seat pan in place. 
This could result in structural deformation or occupant injury being 
higher at an intermediate impact condition than that resulting from the 
maximum impact condition. It is acceptable for such step-change 
characteristics to exist, provided the resulting output does not exceed 
the maximum allowable criteria at any condition at which the ILD does 
or does not deploy, up to the maximum severity pulse specified by the 
requirements.
    The ideal triangular maximum severity pulse is defined in Advisory 
Circular (AC) 25.561-1B ``Dynamic Evaluation of Seat Restraint Systems 
and Occupant Protection on Transport Airplanes''. For the evaluation 
and testing of less-severe pulses for purposes of assessing the 
effectiveness of the ILD deployment setting, a similar triangular pulse 
should be used with acceleration, rise time, and velocity change scaled 
accordingly. The magnitude of the required pulse should not deviate 
below the ideal pulse by more than 0.5g until 1.33 t1 is reached, where 
t1 represents the time interval between 0 and t1 on the referenced 
pulse shape as shown in AC 25.561-1B. This is an acceptable method of 
compliance to the test requirements of the special conditions.
    Conditions 1 through 5 ensure that the ILD activates when intended, 
to provide the necessary protection of occupants. This includes 
protection of a range of occupants under various accident conditions. 
Conditions 6 through 10 address maintenance and reliability of the ILD, 
including any outside influences on the mechanism, to ensure it 
functions as intended.
    These 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 special conditions are applicable to the 
Airbus Model A350 series airplanes. Should Airbus apply at a later date 
for a change to the type certificate to include another model 
incorporating the same novel or unusual design feature, these special 
conditions would apply to that model as well.

Conclusion

    This action affects only a certain novel or unusual design feature 
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, and 
44704.

The Special Conditions

    Accordingly, pursuant to the authority delegated to me by the 
Administrator, the following special conditions are issued as part of 
the type certification basis for Airbus SAS Model A350 series 
airplanes.
    In addition to the requirements of Sec.  25.562, passenger seats 
incorporating inertia locking devices (ILD)s must meet the following:
    1. Level of Protection Provided by ILD--It must be demonstrated by 
test that the seats and attachments, when subject to the emergency-
landing dynamic conditions specified in Sec.  25.562, and with one ILD 
not deployed, do not experience structural failure that could result 
in:
    a. Separation of the seat from the airplane floor.
    b. Separation of any part of the seat that could form a hazard to 
the seat occupant or any other airplane occupant.
    c. Failure of the occupant restraint or any other condition that 
could result in the occupant separating from the seat.
    2. Protection Provided Below and Above the ILD Actuation 
Condition--If step-change effects on occupant protection exist for 
impacts below and above that at which the ILD deploys, tests must be 
performed to demonstrate that the occupant is shown to be protected at 
any condition at which the ILD does or does not deploy, up to the 
maximum severity pulse specified by Sec.  25.562. Test conditions must 
take into account any necessary tolerances for deployment.
    3. Protection Over a Range of Crash Pulse Vectors--The ILD must be 
shown to function as intended for all test vectors specified in Sec.  
25.562.
    4. Protection During Secondary Impacts--The ILD activation setting 
must be demonstrated to maximize the probability of the protection 
being available when needed, considering a secondary impact that is 
above the severity at which the device is intended to deploy up to the 
impact loading required by Sec.  25.562.
    5. Protection of Occupants other than 50th Percentile--Protection 
of occupants for a range of stature from a two-year-old child to a 
ninety-five-percentile male must be shown.
    6. Inadvertent Operation--It must be shown that any inadvertent 
operation of the ILD does not affect the performance of the device 
during a subsequent emergency landing.
    7. Installation Protection--It must be shown that the ILD 
installation is protected from contamination and interference from 
foreign objects.
    8. Reliability--The performance of the ILD must not be altered by 
the effects of wear, manufacturing tolerances, aging, or drying of 
lubricants, and corrosion.
    9. Maintenance and Functional Checks--The design, installation, and 
operation of the ILD must be such that it is possible to functionally 
check the device in place. Additionally, a functional-check method and 
a maintenance-check interval must be included in the seat installer's 
instructions for continued airworthiness (ICA) document.
    10. Release Function--If a means exists to release an inadvertently 
activated ILD, the release means must not introduce additional hidden 
failures that would prevent the ILD from functioning properly.

    Issued in Kansas City, Missouri, on March 19, 2024.
James David Foltz,
Manager, Technical Policy Branch, Policy and Standards Division, 
Aircraft Certification Service.
[FR Doc. 2024-06196 Filed 3-22-24; 8:45 am]
BILLING CODE 4910-13-P