Special Conditions: Airbus Models A321 neo ACF and A321 neo XLR; Single-Occupant Oblique Seats With Pretensioner Restraint Systems, 100727-100730 [2024-29442]
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Federal Register / Vol. 89, No. 240 / Friday, December 13, 2024 / Rules and Regulations
rest compartment in the event of a fire
in the cargo compartment.
19. Means must be provided to
prevent access into the Class C cargo
compartment during all airplane
operations and to ensure that the
maintenance door is closed during all
airplane flight operations.
20. All enclosed stowage
compartments within the crew rest that
are not limited to stowage of emergency
equipment or airplane-supplied
equipment (e.g., bedding) must meet the
design criteria given in the table below.
As indicated by the table below, this
special condition does not address
enclosed stowage compartments greater
than 200 ft3 in interior volume. The inflight accessibility of very large,
100727
enclosed stowage compartments and the
subsequent impact on the
crewmembers’ ability to effectively
reach any part of the compartment with
the contents of a hand fire extinguisher
will require additional fire protection
considerations similar to those required
for inaccessible compartments such as
Class C cargo compartments.
Stowage compartment interior volumes
Fire protection features
Less than 25
Materials of Construction 1 .............
Detectors 2 ......................................
Liner 3 .............................................
Locating Device 4 ...........................
ft3
25 ft3 to 57 ft3
Yes ................................................
No .................................................
No .................................................
No .................................................
57 ft3 to 200 ft3
Yes ................................................
Yes ................................................
No .................................................
Yes ................................................
Yes.
Yes.
Yes.
Yes.
1 Material: The material used to construct each enclosed stowage compartment must at least be fire resistant and must meet the flammability
standards established for interior components per the requirements of § 25.853. For compartments less than 25 ft3 in interior volume, the design
must ensure the ability to contain a fire likely to occur within the compartment under normal use.
2 Detectors: Enclosed stowage compartments equal to or exceeding 25 ft3 in interior volume must be provided with a smoke or fire detection
system to ensure that a fire can be detected within a one-minute detection time. Flight tests must be conducted to show compliance with this requirement. Each system (or systems) must provide:
(a) A visual indication in the flight deck within one minute after the start of a fire;
(b) An aural warning in the crew rest compartment; and
(c) A warning in the main passenger cabin. This warning must be readily detectable by a flight attendant, taking into consideration the positioning of flight attendants throughout the main passenger compartment during various phases of flight.
3 Liner: If it can be shown that the material used to construct the stowage compartment meets the flammability requirements of a liner for a
Class B cargo compartment, then no liner would be required for enclosed stowage compartments equal to or greater than 25 ft3 in interior volume but less than 57 ft3 in interior volume. For all enclosed stowage compartments equal to or greater than 57 ft3 in interior volume but less than
or equal to 200 ft3, a liner must be provided that meets the requirements of § 25.855 at Amendment 25–60 for a class B cargo compartment.
4 Location Detector: Crew rest areas which contain enclosed stowage compartments exceeding 25 ft3 interior volume and which are located
away from one central location such as the entry to the crew rest area or a common area within the crew rest area would require additional fire
protection features and/or devices to assist the firefighter in determining the location of a fire.
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. 2024–29432 Filed 12–12–24; 8:45 am]
BILLING CODE 4910–13–P
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
This action is effective on Airbus
S.A.S. on December 13, 2024. Send
comments on or before January 27,
2025.
DATES:
Federal Aviation
Administration (FAA), DOT.
ACTION: Final special conditions; request
for comments.
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AGENCY:
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
SUMMARY:
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16:42 Dec 12, 2024
Jkt 265001
category airplanes. This design feature
incorporates oblique (side-facing)
passenger seats which may include a 3point 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.
Send comments identified
by Docket No. FAA–2024–2387 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
ADDRESSES:
PO 00000
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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:
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 Shannon.Lennon@
faa.gov.
The
substance of these special conditions
has been published in the Federal
SUPPLEMENTARY INFORMATION:
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Federal Register / Vol. 89, No. 240 / Friday, December 13, 2024 / Rules and Regulations
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
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.
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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.
VerDate Sep<11>2014
16:42 Dec 12, 2024
Jkt 265001
Background
Novel or Unusual Design Features
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.
Airbus Models A321 neo ACF and
A321 neo XLR airplanes will
incorporate a novel or unusual design
feature: single occupant oblique (sidefacing) 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.
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 § 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 § 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 § 11.38, and they become part of
the type certification basis under
§ 21.101.
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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 3point 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 SideFacing Seats,’’ dated July 11, 2018,
which defines injury criteria for oblique
seats.
FAA-sponsored research has found
that an un-restrained flailing of the
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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 § 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 § 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 uppertorso 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 § 25.562. See condition 7 in
these special conditions.
The ideal triangular maximumseverity 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.
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Jkt 265001
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.
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100729
In addition to the requirements of
§ 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-toFurnishing 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
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(SAE) recommended practice J211/1,
‘‘Instrumentation for Impact Test-Part 1Electronic 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 mostcritical yaw cases for injury, and with
all lateral structural supports (e.g.
armrests or walls) installed.
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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 § 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:
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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¥7).
(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¥7) 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:
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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
DEPARTMENT OF TRANSPORTATION
Federal Aviation Administration
14 CFR Part 27
[Docket No. FAA–2024–0875; Special
Conditions No. 27–058–SC]
Special Conditions: Skyryse, Robinson
Helicopter Company Model R66
Helicopter; Interaction of Systems and
Structures
Federal Aviation
Administration (FAA), DOT.
ACTION: Final special conditions.
AGENCY:
These special conditions are
issued for the Robinson Helicopter
Company (Robinson) Model R66
helicopter. This helicopter, as modified
by Skyryse, will have a novel or unusual
design feature when compared to the
state of technology envisioned in the
airworthiness standards for normal
category helicopters. This design feature
is a novel control input and fly-by-wire
(FBW) system. 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: Effective December 13, 2024.
FOR FURTHER INFORMATION CONTACT:
Daniel Moore, Airframe Section, AIR–
622, Technical Policy Branch, Policy
and Standards Division, Aircraft
SUMMARY:
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]]>Agencies
[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 [www.gpo.gov]
[FR Doc No: 2024-29442]
-----------------------------------------------------------------------
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.
-----------------------------------------------------------------------
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:
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: 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 [email protected].
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 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. 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 10-7).
(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 10-7) 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
