Rule2024-29442
Special Conditions: Airbus Models A321 neo ACF and A321 neo XLR; Single-Occupant Oblique Seats With Pretensioner Restraint Systems
Primary source
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Published
December 13, 2024
Effective
December 13, 2024
Issuing agencies
Transportation DepartmentFederal Aviation Administration
Abstract
These special conditions are issued for the Airbus Model A321 neo ACF and A321 neo XLR airplanes. These airplanes 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 incorporates oblique (side-facing) passenger seats which may include a 3-point restraint system with pretensioner. These oblique seats may be installed at an angle of 18 to 45 degrees to the aircraft centerline and have surrounding furniture that introduces occupant and loading concerns. 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.
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<title>Federal Register, Volume 89 Issue 240 (Friday, December 13, 2024)</title>
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[Federal Register Volume 89, Number 240 (Friday, December 13, 2024)]
[Rules and Regulations]
[Pages 100727-100730]
From the Federal Register Online via the Government Publishing Office [<a href="http://www.gpo.gov">www.gpo.gov</a>]
[FR Doc No: 2024-29442]
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DEPARTMENT OF TRANSPORTATION
Federal Aviation Administration
14 CFR Part 25
[Docket No. FAA-2024-2387; Special Conditions No. 25-871-SC]
Special Conditions: Airbus Models A321 neo ACF and A321 neo XLR;
Single-Occupant Oblique Seats With Pretensioner Restraint Systems
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 Model A321
neo ACF and A321 neo XLR airplanes. These airplanes 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 incorporates oblique (side-facing)
passenger seats which may include a 3-point restraint system with
pretensioner. These oblique seats may be installed at an angle of 18 to
45 degrees to the aircraft centerline and have surrounding furniture
that introduces occupant and loading concerns. 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.
DATES: This action is effective on Airbus S.A.S. on December 13, 2024.
Send comments on or before January 27, 2025.
ADDRESSES: Send comments identified by Docket No. FAA-2024-2387 using
any of the following methods:
<bullet> Federal eRegulations Portal: Go to <a href="http://www.regulations.gov">www.regulations.gov</a> and
follow the online instructions for sending your comments
electronically.
<bullet> 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.
<bullet> 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.
<bullet> Fax: Fax comments to Docket Operations at 202-493-2251.
Docket: Background documents or comments received may be read at
<a href="http://www.regulations.gov">www.regulations.gov</a> 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: Shannon Lennon, Cabin Safety Section,
AIR-624, Technical Policy Branch, Policy and Standards Division,
Aircraft Certification Service, Federal Aviation Administration, 2200
South 216th Street, Des Moines, Washington 98198; telephone (206) 231-
3209; fax (206) 231-3827; email <a href="/cdn-cgi/l/email-protection#c390aba2adadacaded8fa6adadacad83a5a2a2eda4acb5"><span class="__cf_email__" data-cfemail="d88bb0b9b6b6b7b6f694bdb6b6b7b698beb9b9f6bfb7ae">[email protected]</span></a>.
SUPPLEMENTARY INFORMATION: The substance of these special conditions
has been published in the Federal
[[Page 100728]]
Register for public comment in several prior instances with no
substantive comments received. 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 <a href="http://www.regulations.gov">www.regulations.gov</a>, 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. The FAA may change these special conditions based on the
comments received.
Background
On September 23, 2024, Airbus S.A.S. applied for an amendment to
Type Certificate No. (TC no.) A28NM to include new Models A321 neo ACF
and A321 neo XLR airplanes. Airbus Model A321 neo ACF and Model A321
neo XLR airplanes, which are derivatives of the Model A321 currently
approved under TC no. A28NM, are twin-engine transport category
airplanes with a maximum passenger capacity of 244. The maximum takeoff
weight of the Airbus Model A321 neo ACF is approximately 213,848
pounds, while the Airbus Model A321 neo XLR has a maximum takeoff
weight of approximately 222,667 pounds.
Type Certification Basis
Under the provisions of title 14, Code of Federal Regulations (14
CFR) 21.101, Airbus S.A.S must show that Models A321 neo ACF and A321
neo XLR airplanes, as changed, continue to meet the applicable
provisions of the regulations listed in TC 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 Models A321 neo ACF and
A321 neo 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, Airbus Models A321 neo ACF and A321 neo XLR 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
Airbus Models A321 neo ACF and A321 neo XLR airplanes will
incorporate a novel or unusual design feature: single occupant oblique
(side-facing) passenger seats that may include a 3-point restraint
system with pretensioner. These oblique seats may be installed at an
angle of 18 to 45 degrees relative to the aircraft centerline and have
surrounding furniture that introduces occupant and loading concerns.
Discussion
Title 14, Code of Federal Regulations (14 CFR) 25.785(d) requires
that each occupant of a seat that makes more than an 18 degree angle
with the vertical plane containing the airplane centerline must be
protected from head injury by a safety belt and an energy absorbing
rest that will support the arms, shoulders, head, and spine, or by a
safety belt and shoulder harness that will prevent the head from
contacting any injurious object.
The proposed Airbus Model A321 neo ACF and A321 neo XLR seat
installations are novel in that the current requirements do not
adequately address protection of the occupant's neck and spine for
seating configurations that are positioned at angles greater than 18
degrees up to and including 45 degrees from the airplane centerline.
The installation of passenger seats at angles of 18 to 45 degrees to
the airplane centerline is unique due to the seat/occupant interface
with the surrounding furniture that introduces occupant alignment/
loading concerns with or without the installation of a 3-point or
airbag restraint systems. The existing special conditions for Airbus
Model A321 neo ACF series airplane oblique seat installations (Special
Conditions No. 25-779-SC) also do not address oblique seats with 3-
point restraint systems equipped with pretensioners. Therefore, in
order to provide a level of safety equivalent to that afforded to
occupants of forward and aft facing seating, additional airworthiness
standards in the form of new special conditions are necessary.
The FAA has been conducting and sponsoring research on appropriate
injury criteria for oblique (side-facing) seat installations. To
reflect current research findings, the FAA issued Policy Statement PS-
AIR-25-27, ``Technical Criteria for Approving Side-Facing Seats,''
dated July 11, 2018, which defines injury criteria for oblique seats.
FAA-sponsored research has found that an un-restrained flailing of
the
[[Page 100729]]
upper torso, even when the pelvis and torso are nearly aligned, can
produce serious spinal and torso injuries. At lower impact severities,
even with significant misalignment between the torso and pelvis, these
injuries did not occur. Tests with an FAA H-III anthropomorphic test
dummy (ATD) have identified a level of lumbar spinal tension
corresponding to the no-injury impact severity. This level of tension
is included as a limit in the special conditions. The spine tension
limit selected is conservative with respect to other aviation injury
criteria since it corresponds to a no-injury loading condition.
Other restraint systems, in lieu of single lap belt restraint
systems have been used to comply with the occupant injury criteria of
Sec. 25.562(c)(5). For instance, shoulder harnesses have been widely
used on flight-attendant seats, flight-deck seats, in business jets,
and in general-aviation airplanes to reduce occupant head injury in the
event of an emergency landing. Special conditions, pertinent
regulations, and published guidance exist that relate to other
restraint systems. However, the use of pretensioners in the restraint
system on transport category airplane seats to comply with the occupant
injury criteria of Sec. 25.562(c)(5) is a novel design.
Pretensioner technology involves a step-change in loading
experienced by the occupant for impacts below and above that at which
the device deploys, because activation of the shoulder harness, at the
point at which the pretensioner engages, interrupts upper-torso
excursion. Such excursion could result in the head-injury criteria
(HIC) being higher at an intermediate impact condition than that
resulting from the maximum impact condition corresponding to the test
conditions specified in Sec. 25.562. See condition 7 in these special
conditions.
The ideal triangular maximum-severity pulse is defined in Advisory
Circular (AC) 25.562-1B, ``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 pretensioner 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 25.562-1B. This is an acceptable method of
compliance to the test requirements of the special conditions.
Additionally, the pretensioner might not provide protection, after
actuation, during secondary impacts. Therefore, the case where a small
impact is followed by a large impact should be addressed. If the
minimum deceleration severity at which the pretensioner is set to
deploy is unnecessarily low, the protection offered by the pretensioner
may be lost by the time a second, larger impact occurs.
Conditions 1 through 7 address occupant protection in consideration
of the oblique-facing seats. Conditions 8 through 10 ensure that the
pretensioner system activates when intended and protects a range of
occupants under various accident conditions. Conditions 11 through 16
address maintenance and reliability of the pretensioner system,
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 A321 neo ACF and Model A321 neo XLR airplanes. Should
Airbus S.A.S. apply at a later date for a change to the type
certificate to include another model incorporating 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 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 the Airbus Model A321 neo ACF and A321
neo XLR series airplanes.
In addition to the requirements of Sec. 25.562, passenger seats
installed at an angle between 18 degrees and 45 degrees from the
aircraft centerline must meet the following conditions:
1. Body-to-Wall and Body-to-Furnishing Contact:
If a seat is installed aft of a structure (e.g., interior wall or
furnishings) that does not provide a homogenous contact surface for the
expected range of occupants and yaw angles, then additional analysis
and tests may be required to demonstrate that the injury criteria are
met for the area that an occupant could contact. For example, if, in
addition to a pretensioner restraint system, an airbag device is
present, different yaw angles could result in different airbag-device
performance, then additional analysis or separate tests may be
necessary to evaluate performance.
2. Neck Injury Criteria:
The seating system must protect the occupant from experiencing
serious neck injury. In addition to a pretensioner restraint system, if
an airbag device also is present, the assessment of neck injury must be
conducted with the airbag device activated, unless there is reason to
also consider that the neck injury potential would be higher for
impacts below the airbag-device deployment threshold.
(a) The Nij (calculated in accordance with 49 CFR 571.208) must be
below 1.0, where Nij = Fz/Fzc + My/Myc, and Nij critical values are:
(1) Fzc = 1530 lbs. for tension
(2) Fzc = 1385 lbs. for compression
(3) Myc = 229 lb-ft in flexion
(4) Myc = 100 lb-ft in extension
(b) In addition, peak Fz must be below 937 lbs. in tension and 899
lbs. in compression.
(c) Rotation of the head about its vertical axis relative to the
torso is limited to 105 degrees in either direction from forward
facing.
(d) The neck must not impact any surface that would produce
concentrated loading on the neck.
3. Spine and Torso Injury Criteria:
(a) The lumbar spine tension (Fz) cannot exceed 1,200 lbs.
(b) Significant concentrated loading on the occupant's spine, in
the area between the pelvis and shoulders during impact, including
rebound, is not acceptable. During this type of contact, the interval
for any rearward (X direction) acceleration exceeding 20g must be less
than 3 milliseconds as measured by the thoracic instrumentation
specified in 49 CFR part 572, subpart E, filtered in accordance with
SAE International
[[Page 100730]]
(SAE) recommended practice J211/1, ``Instrumentation for Impact Test-
Part 1-Electronic Instrumentation.''
(c) The occupant must not interact with the armrest or other seat
components in any manner significantly different than would be expected
for a forward-facing seat installation.
4. Pelvis Criteria:
Any part of the load-bearing portion of the bottom of the ATD
pelvis must not translate beyond the edges of the seat bottom seat-
cushion supporting structure.
5. Femur Criteria:
Axial rotation of the upper leg (about the Z-axis of the femur per
SAE Recommended Practice J211/1) must be limited to 35 degrees from the
nominal seated position. Evaluation during rebound does not need to be
considered.
6. ATD and Test Conditions:
Longitudinal tests conducted to measure the injury criteria above
must be performed with the FAA Hybrid III ATD, as described in SAE
1999-01-1609, ``A Lumber Spine Modification to the Hybrid III ATD for
Aircraft Seat Tests.'' The tests must be conducted with an undeformed
floor, at the most-critical yaw cases for injury, and with all lateral
structural supports (e.g. armrests or walls) installed.
Note: The applicant must demonstrate that the installation of
seats via plinths or pallets meets all applicable requirements.
Compliance with the guidance contained in policy memorandum PS-ANM-
100-2000-00123, ``Guidance for Demonstrating Compliance with Seat
Dynamic Testing for Plinths and Pallets,'' dated February 2, 2000,
may be applied.
7. Head Injury Criteria:
The HIC value must not exceed 1000 at any condition at which the
pretensioner does or does not deploy, up to the maximum severity pulse
that corresponds to the test conditions specified in Sec. 25.562.
Tests must be performed to demonstrate this, taking into account any
necessary tolerances for deployment.
When an airbag is present in addition to the pretensioner restraint
system, and the anthropomorphic test dummy (ATD) has no apparent
contact with the seat/structure but has contact with the airbag, a HIC
unlimited score in excess of 1000 is acceptable provided the HIC15
score (calculated in accordance with 49 CFR 571.208) for the contact is
less than 700. ATD head contact with the seat or other structure,
through the airbag, or contact subsequent to contact with the airbag,
requires a HIC value that does not exceed 1000.
8. Protection During Secondary Impacts:
The pretensioner activation setting must be demonstrated to
maximize the probability of the protection being available when needed,
considering secondary impacts.
9. Protection of Occupants Other than 50th Percentile:
Protection of occupants for a range of stature from a 2-year-old
child to a 95th percentile male must be shown. For shoulder harnesses
that include pretensioners, protection of occupants other than a 50th
percentile male may be shown by test or analysis. In addition, the
pretensioner must not introduce a hazard to passengers due to the
following seat configurations:
(a) The seat occupant is holding an infant.
(b) The seat occupant is a child in a child-restraint device.
(c) The seat occupant is a pregnant woman.
10. Occupants Adopting the Brace Position:
Occupants in the traditional brace position when the pretensioner
activates must not experience adverse effects from the pretensioner
activation.
11. Inadvertent Pretensioner Actuation:
(a) The probability of inadvertent pretensioner actuation must be
shown to be extremely remote (i.e., average probability per flight hour
of less than 10<SUP>-7</SUP>).
(b) The system must be shown not susceptible to inadvertent
pretensioner actuation as a result of wear and tear, or inertia loads
resulting from in-flight or ground maneuvers likely to be experienced
in service.
(c) The seated occupant must not be seriously injured as a result
of inadvertent pretensioner actuation.
(d) Inadvertent pretensioner activation must not cause a hazard to
the airplane, nor cause serious injury to anyone who may be positioned
close to the retractor or belt (e.g., seated in an adjacent seat or
standing adjacent to the seat).
12. Availability of the Pretensioner Function Prior to Flight:
The design must provide means for a crewmember to verify the
availability of the pretensioner function prior to each flight, or the
probability of failure of the pretensioner function must be
demonstrated to be extremely remote (i.e., average probability per
flight hour of less than 10<SUP>-7</SUP>) between inspection intervals.
13. Incorrect Seat Belt Orientation:
The system design must ensure that any incorrect orientation
(twisting) of the seat belt does not compromise the pretensioner
protection function.
14. Contamination Protection:
The pretensioner mechanisms and controls must be protected from
external contamination associated with that which could occur on or
around passenger seating.
15. Prevention of Hazards:
The pretensioner system must not induce a hazard to passengers in
case of fire, nor create a fire hazard, if activated.
16. Functionality After Loss of Power:
The system must function properly after loss of normal airplane
electrical power, and after a transverse separation in the fuselage at
the most critical location. A separation at the location of the system
does not have to be considered.
Issued in Kansas City, Missouri, on December 9, 2024.
Patrick R. Mullen,
Manager, Technical Policy Branch, Policy and Standards Division,
Aircraft Certification Service.
[FR Doc. 2024-29442 Filed 12-12-24; 8:45 am]
BILLING CODE 4910-13-P
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