[Federal Register Volume 86, Number 48 (Monday, March 15, 2021)]
[Rules and Regulations]
[Pages 14234-14237]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 2021-05307]


-----------------------------------------------------------------------

DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 25

[Docket No. FAA-2020-0817; Special Conditions No. 25-779-SC]


Special Conditions: Airbus Model A321neo ACF Airplane; Dynamic 
Test Requirements for Single-Occupant Oblique (Side-Facing) Seats With 
3-Point Restraints

AGENCY: Federal Aviation Administration (FAA), DOT.

ACTION: Final special conditions; request for comments.

-----------------------------------------------------------------------

SUMMARY: These special conditions are issued for the Airbus Model 
A321neo Cabin Flex (ACF) airplane. This airplane 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 single-occupant oblique seats with 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 Airbus on March 15, 2021. Send 
comments on or before April 29, 2021.

ADDRESSES: Send comments identified by Docket No. FAA-2020-0817 using 
any of the following methods:
     Federal eRegulations Portal: Go to http://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

[[Page 14235]]

a.m. and 5 p.m., Monday through Friday, except Federal holidays.
     Fax: Fax comments to Docket Operations at 202-493-2251.
    Privacy: Except for Confidential Business Information (CBI) as 
described in the following paragraph, and other information as 
described in 14 CFR 11.35, the FAA will post all comments received 
without change, to http://www.regulations.gov/, including any personal 
information you provide. The FAA will also post a report summarizing 
each substantive verbal contact received about this proposal.
    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 this Notice contain 
commercial or financial information that is customarily treated as 
private, that you actually treat as private, and that is relevant or 
responsive to this Notice, 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 this Notice. Submissions 
containing CBI should be sent to Shannon Lennon, Human-Machine 
Interface Section, AIR-626, Transport Standards Branch, Policy and 
Innovation Division, Aircraft Certification Service, Federal Aviation 
Administration, 2200 South 216th Street, Des Moines, Washington 98198; 
telephone and fax 206-231-3209; email [email protected]. Comments 
the FAA receives, which are not specifically designated as CBI, will be 
placed in the public docket for this rulemaking.
    Docket: Background documents or comments received may be read at 
http://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, Human-Machine 
Interface Section, AIR-626, Transport Standards Branch, Policy and 
Innovation Division, Aircraft Certification Service, Federal Aviation 
Administration, 2200 South 216th Street, Des Moines, Washington 98198; 
telephone and fax 206-231-3209; email [email protected].

SUPPLEMENTARY INFORMATION: The substance of these special conditions 
previously has been published in the Federal Register for public 
comment. These special conditions have been derived without substantive 
change from those previously issued. It is unlikely that prior public 
comment would result in a significant change from the substance 
contained herein. Therefore, the FAA has determined that prior public 
notice and comment are unnecessary, and finds that, for the same 
reason, good cause exists for adopting these special conditions upon 
publication in the Federal Register.

Comments Invited

    The FAA invites you to send any written relevant data, views, or 
arguments about this proposal. Send your comments to an address listed 
under ADDRESSES. Include ``Docket No. FAA-2020-0817'' at the beginning 
of your comments. 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 and 
may amend these special conditions because of those comments.

Background

    On December 19, 2019, Airbus applied for a change to Type 
Certificate No. A28NM for single-occupant oblique seats with 3-point 
restraints in the Airbus Model A321neo ACF airplane. This airplane, 
which is a derivative of the Airbus Model A321-200 airplane currently 
approved under Type Certificate No. A28NM, is a twin-engine, transport-
category airplane with seating for 244 passengers and a maximum takeoff 
weight of 213,848 pounds.

Type Certification Basis

    Under the provisions of title 14, Code of Federal Regulations (14 
CFR) 21.101, Airbus must show that the Model A321neo ACF airplane, as 
changed, continues to meet the applicable provisions of the regulations 
listed in Type Certificate No. A28NM or the applicable regulations in 
effect on the date of application for the change, except for earlier 
amendments as agreed upon by the FAA.
    If the Administrator finds that the applicable airworthiness 
regulations (e.g., 14 CFR part 25) do not contain adequate or 
appropriate safety standards for the Airbus Model A321neo ACF 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, these special conditions would also apply to 
the other model under Sec.  21.101.
    In addition to the applicable airworthiness regulations and special 
conditions, the Airbus Model A321neo ACF airplane must comply with the 
fuel-vent and exhaust-emission requirements of 14 CFR part 34, and the 
noise-certification requirements of 14 CFR part 36.
    The FAA issues special conditions, as defined in 14 CFR 11.19, in 
accordance with Sec.  11.38, and they become part of the type 
certification basis under Sec.  21.101.

Novel or Unusual Design Features

    The Airbus Model A321neo ACF airplane will incorporate the 
following novel or unusual design features:
    Single-occupant oblique seats with 3-point restraints.

Discussion

    The FAA has been conducting and sponsoring research on appropriate 
injury criteria for oblique seat installations. However, the FAA 
research program is not complete, and the FAA may update these criteria 
as further research results are obtained. To reflect current research 
findings, the FAA issued policy statement PS-ANM-25-03-R1, ``Technical 
Criteria for Approving Side-Facing Seats,'' November 5, 2012, which 
updates injury criteria for fully side-facing seats; and policy 
statement PS-AIR-25-27, ``Technical Criteria for Approving Oblique 
Seats,'' July 11, 2018, to define injury criteria for oblique seats. 
These policies provide background and technical information, as well as 
applicable injury criteria.
    The installation of obliquely oriented passenger seats is novel 
such that the current certification basis does not adequately address 
protection of the occupant's neck and spine for seat configurations 
that are oriented at an angle greater than 18 degrees from the airplane 
longitudinal centerline.
    The installation of passenger seats at angles of 18 to 45 degrees 
to the airplane centerline is unusual in transport-

[[Page 14236]]

category airplanes due to the seat and occupant interface with the 
surrounding furniture that introduces occupant alignment and loading 
concerns with or without the installation of a 3-point restraint system 
or additional airbag restraint system. Note that, while the applicant 
did not specifically cite airbag systems as part of the seat restraint 
system, this discussion and related special conditions address airbag 
information in the event that an airbag system is installed as part of 
the seat restraint system.
    FAA-sponsored research has found that an unrestrained 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, 
including with significant misalignment between the torso and pelvis, 
the injuries did not occur. Tests with an FAA Hybrid III 
anthropomorphic test device (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 because it corresponds to a no-injury loading 
condition.
    Shoulder harnesses (3-point restraint systems) have been widely 
used on flight-attendant seats, flight-deck seats, business jets, and 
general aviation airplanes to reduce occupant head injury in the 
unlikely event of an emergency landing. The use of 3-point restraint 
systems on transport-category airplane passenger seats is rare; 
however, pertinent regulations and published guidance for this type of 
restraint system exist.
    The existing regulations, however, do not adequately address the 
proposed business-class seating configuration of oblique seats with 3-
point restraints because they do not consider unique occupant alignment 
and loading concerns due to obliquely oriented passengers. Therefore, 
special conditions are required.
    These special conditions provide head injury criteria, neck injury 
criteria, spine injury criteria, and body-to-wall contact criteria. 
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 A321neo ACF airplane. Should Airbus apply at a later date 
for a change to the type certificate to include another model 
incorporating the same novel or unusual design feature, these special 
conditions would apply to that model as well.

Conclusion

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

List of Subjects in 14 CFR Part 25

    Aircraft, Aviation safety, Reporting and recordkeeping 
requirements.

Authority Citation

    The authority citation for these special conditions is as follows:

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

The Special Conditions

    Accordingly, pursuant to the authority delegated to me by the 
Administrator, the following special conditions are issued as part of 
the type certification basis for Airbus Model A321neo ACF airplane.
    In addition to the requirements of Sec.  25.562, passenger seats 
installed at an angle between 18 degrees and 45 degrees from the 
aircraft bow-to-stern centerline must meet the following:
    1. Head Injury Criteria (HIC):
    Compliance with Sec.  25.562(c)(5) is required, except that, when 
an airbag device is present in addition to the 3-point restraint 
system, and the anthropomorphic test device (ATD) has no apparent 
contact with the seat or structure but has contact with an airbag, the 
HIC unlimited scored 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.
    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.
    2. Body-to-Wall/Furnishing Contact:
    If a seat is installed aft of 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 an 
airbag device is present, and different yaw angles could result in 
different airbag-device performance, then additional analysis or 
separate test(s) may be necessary to evaluate performance.
    3. Neck Injury Criteria:
    a. The seating system must protect the occupant from experiencing 
serious neck injury. If an airbag device 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.
    b. 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
    c. In addition, peak Fz must be below 937 lb. in tension 
and 899 lb. in compression.
    d. Rotation of the head about its vertical axis relative to the 
torso is limited to 105 degrees in either direction from forward-
facing.
    e. 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 lb.
    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 
three (3) milliseconds as measured by the thoracic instrumentation 
specified in 49 CFR part 572, subpart E, filtered in accordance with 
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-

[[Page 14237]]

1609. 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: Airbus must demonstrate that the installation of seats via 
plinths or pallets meet 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 also installed, the 
airbag systems must meet the requirements in the airbag (inflatable 
restraint) special conditions applicable to the Airbus Model A321 
series airplanes.

    Issued in Des Moines, Washington, on January 11, 2021.
Suzanne Masterson,
Manager, Transport Airplane Strategic Policy Section, Policy and 
Innovation Division, Aircraft Certification Service.
[FR Doc. 2021-05307 Filed 3-12-21; 8:45 am]
BILLING CODE 4910-13-P