[Federal Register Volume 89, Number 66 (Thursday, April 4, 2024)]
[Rules and Regulations]
[Pages 23504-23507]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 2024-06894]


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DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 25

[Docket No. FAA-2024-0448; Special Conditions No. 25-859-SC]


Special Conditions: Jet Aviation AG, The Boeing Company Model 
737-8 Series Airplane; Dynamic Test Requirements for Single Occupant 
Oblique Seats With or Without Airbags and/or 3-Point Restraints

AGENCY: Federal Aviation Administration (FAA), DOT.

ACTION: Final special conditions; request for comments.

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[[Page 23505]]

SUMMARY: These special conditions are issued for The Boeing Company 
(Boeing) Model 737-8 series airplane. This airplane, as modified by Jet 
Aviation AG (Jet Aviation), 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 oblique (side-facing) single-occupant seats equipped with 
airbag devices or 3-point restraints. 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 Jet Aviation on April 4, 2024. Send 
comments on or before May 20, 2024.

ADDRESSES: Send comments identified by Docket No. FAA-2024-0448 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.
     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: John Shelden, 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 and fax 
206-231-3214; 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 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 proposed 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 December 19, 2022, Jet Aviation applied for a supplemental type 
certificate for the installation of oblique (side-facing) passenger 
seats with or without airbag devices or 3-point restraints in the 
Boeing Model 737-8 series airplanes. The Boeing Model 737-8 series 
airplane is a twin-engine, transport category airplane with a maximum 
takeoff weight of approximately 182,200 lbs. The airplane, as modified 
by Jet Aviation, will have a maximum seating capacity of 32.

Type Certification Basis

    Under the provisions of title 14, Code of Federal Regulations (14 
CFR) 21.101, Jet Aviation must show that the Model 737-8 series 
airplanes, as changed, continue to meet the applicable provisions of 
the regulations listed in Type Certificate No. A16WE 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 (i.e., 14 CFR part 25) do not contain adequate or 
appropriate safety standards for the Boeing Model 737-8 series airplane 
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, the special conditions would also apply to the 
other model under Sec.  21.101.
    In addition to the applicable airworthiness regulations and special 
conditions, the Boeing Model 737-8 series airplane 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 Boeing Model 737-8 series airplane, as modified by Jet 
Aviation,

[[Page 23506]]

will incorporate a seating configuration that is novel or unusual due 
to the installation of oblique (side-facing) passenger seats and 
surrounding furniture that introduces occupant alignment and loading 
concerns. These oblique seats may be installed at an angle of 18 to 45 
degrees to the aircraft centerline and may include a 3-point restraint 
system and/or airbags, for occupant restraint and injury protection.

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 Boeing Model 737-8 airplane seat installation is 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 system, or 
both.
    In order to provide a level of safety that is 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. FAA-sponsored research has found that an un-restrained 
flailing of the 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.
    As noted in the special conditions, because each airbag restraint 
system is essentially a single use device, there is the potential that 
it could deploy under crash conditions that are not sufficiently severe 
as to require head injury protection from the airbag restraint system. 
Since an actual crash is frequently composed of a series of impacts 
before the airplane comes to rest, this could render the airbag 
restraint system useless if a larger impact follows the initial impact. 
This situation does not exist with energy absorbing pads or upper torso 
restraints, which tend to provide protection according to the severity 
of the impact. Therefore, the installation of the airbag restraint 
system should be such that the airbag restraint system will provide 
protection when it is required and will not expend its protection when 
it is not needed.
    Because these airbag restraint systems may or may not activate 
during various crash conditions, the injury criteria listed in these 
special conditions and in Sec.  25.562 must be met in an event that is 
slightly below the activation level of the airbag restraint system. If 
an airbag restraint system is included with the oblique seats, the 
system must meet the requirements in one of the airbag (inflatable 
restraint) special conditions applicable to the Boeing Model 737 series 
airplanes. These special conditions supplement part 25 and, more 
specifically, supplement Sec. Sec.  25.562 and 25.785.
    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 
Boeing Model 737-8 series airplane modified by Jet Aviation. Should Jet 
Aviation apply at a later date for a supplemental type certificate to 
modify any other model included on Type Certificate No. A16WE to 
incorporate the same novel or unusual design feature, or should Jet 
Aviation apply for a change to the supplemental type certificate to 
include another model 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 and affects only the applicant who applied to the FAA for 
approval of these features on the airplane.

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

    [squf] 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 Boeing Company Model 737-8 
series airplanes modified by Jet Aviation AG.
    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:

1. Head Injury Criteria (HIC)

    Compliance with Sec.  25.562(c)(5) is required, except that, if the 
anthropomorphic test dummy (ATD) has no apparent contact with the seat/
structure but has contact with an airbag, a HIC unlimited score in 
excess of 1000 is acceptable, provided the HIC15 score (calculated in 
accordance with 49 CFR 571.208) for that contact is less than 700.

2. Body-to-Wall/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 
different yaw angles could result in different airbag device 
performance, then additional analysis or separate tests may be 
necessary to evaluate performance.

3. Neck Injury Criteria

    The seating system must protect the occupant from experiencing 
serious neck injury. 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.

[[Page 23507]]

    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:

i. Fzc = 1530 lbs. for tension
ii. Fzc = 1385 lbs. for compression
iii. Myc = 229 lb-ft in flexion
iv. 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.

4. Spine and Torso Injury Criteria

    a. The lumbar spine tension (Fz) cannot exceed 1200 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 (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.

5. 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.

6. 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.

7. 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 Lumbar 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: Jet Aviation AG 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, 
is acceptable to the FAA.

8. Inflatable Airbag Restraint Systems Special Conditions

    If inflatable airbag restraint systems are installed, the airbag 
systems must meet the requirements in Special Conditions 25-386-SC, or 
other airbag system special conditions which are applicable to the 
Boeing Model 737 series airplanes.

    Issued in Kansas City, Missouri, on March 22, 2024.
Patrick R. Mullen,
Manager, Technical Policy Branch, Policy and Standards Division, 
Aircraft Certification Service.
[FR Doc. 2024-06894 Filed 4-3-24; 8:45 am]
BILLING CODE 4910-13-P