Special Conditions: Airbus Model A321neo ACF and A321neo XLR Series Airplanes; Dynamic Test Requirements for Single Occupant Oblique Seats at an Installation Angle of 49 Degrees With Airbags and 3-Point Restraint or Pretensioner Restraint Systems

<RULE> DEPARTMENT OF TRANSPORTATION <SUBAGY>Federal Aviation Administration</SUBAGY> <CFR>14 CFR Part 25</CFR> <DEPDOC>[Docket No. FAA-2024-2570; Special Conditions No. 25-875-SC]</DEPDOC> <SUBJECT>Special Conditions: Airbus Model A321neo ACF and A321neo XLR Series Airplanes; Dynamic Test Requirements for Single Occupant Oblique Seats at an Installation Angle of 49 Degrees With Airbags and 3-Point Restraint or Pretensioner Restraint Systems</SUBJECT> <HD SOURCE="HED">AGENCY:</HD> Federal Aviation Administration (FAA), DOT. <HD SOURCE="HED">ACTION:</HD> Final special conditions. <SUM> <HD SOURCE="HED">SUMMARY:</HD> These special conditions are issued for the Airbus Model A321neo ACF and A321neo XLR airplanes. These airplanes 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 a single-occupant oblique seat with an airbag and 3-point or pretensioner restraint system positioned at a 49-degree angle from the cabin centerline. 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. </SUM> <EFFDATE> <HD SOURCE="HED">DATES:</HD> Effective February 5, 2025. </EFFDATE> <FURINF> <HD SOURCE="HED">FOR FURTHER INFORMATION CONTACT:</HD> 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, WA 98198; telephone (206) 231-3209; email <E T="03">Shannon.Lennon@faa.gov</E> . </FURINF> <SUPLINF> <HD SOURCE="HED">SUPPLEMENTARY INFORMATION:</HD> <HD SOURCE="HD1">Background</HD> On April 6, 2022, Airbus SAS applied for an amendment to Type Certificate (TC) No. A28NM for the installation of a single-occupant oblique seat with an airbag and 3-point or pretensioner restraint system, positioned at a 49-degree angle from the cabin centerline in new Airbus Model A321neo ACF and A321neo XLR airplanes. Airbus Model A321neo ACF and A321neo 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 A321neo ACF is approximately 213,848 pounds, while the Airbus Model A321neo XLR has a maximum takeoff weight of approximately 222,667 pounds. <HD SOURCE="HD1">Type Certification Basis</HD> Under the provisions of 14 CFR 21.101, Airbus SAS must show that the Model A321neo ACF and A321neo 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 T="03">e.g.,</E> 14 CFR part 25) do not contain adequate or appropriate safety standards for Airbus Model A321neo ACF and A321neo 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 Model A321neo ACF and A321neo 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. <HD SOURCE="HD1">Novel or Unusual Design Features</HD> Airbus Model A321neo ACF and A321neo XLR airplanes will incorporate the following novel or unusual design feature: single-occupant oblique seats with airbag devices and 3-point restraints or a pretensioner restraint system installed at 49 degrees relative to the aircraft cabin centerline. <HD SOURCE="HD1">Discussion</HD> Title 14 of the CFR, § 25.785(d), requires that each occupant of a seat installed at an angle of more than 18 degrees relative to airplane cabin centerline, must be protected from head injury using a seatbelt and an energy-absorbing rest that supports the arms, shoulders, head, and spine, or using a seatbelt and shoulder harness designed to prevent the head from contacting any injurious object. The Airbus Model A321neo ACF and A321neo XLR airplane's single occupant oblique seat installation with airbag devices and 3-point restraint or pretensioner restraint system is novel such that the current requirements do not adequately address airbag or pretensioner devices and protection of the occupant's neck, spine, torso, and legs for seating configurations that are positioned at an angle of 49 degrees from the airplane centerline. The seating configuration installation angle is beyond the installation-design limits of current special conditions issued for seat positions at angles between 18 degrees and 45 degrees. At angles greater than 45 degrees, lateral neck bending and other injury mechanisms prevalent from a fully side-facing installation become a concern, given the addition of oblique seat properties. To address these potential injury mechanisms, these special conditions are based on FAA Policy Statement PS-AIR-25-27, “Technical Criteria for Approving Obliques Seats” as well as Policy Statement PS-ANM-25-03-R1, “Technical Criteria for Approving Side-Facing Seats.” To provide a level of safety equivalent to that afforded to the occupants of forward and aft-facing seats, new special conditions containing additional airworthiness standards for dynamic testing requirements, including both the injury criteria limits from the oblique-seat policy and the fully side-facing seat policy, are necessary. FAA-sponsored research 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 device (ATD) have identified a level of lumbar spinal tension corresponding to the no-injury impact severity. The FAA has implemented this spinal tension limit in special conditions for oblique seats. The spine tension limit selected by the FAA 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 restrain 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 upper-torso excursion. Such an 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 (a)(3) 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 t <E T="52">1</E> is reached, where t <E T="52">1</E> represents the time interval between 0 and t <E T="52">1</E> on the referenced pulse shape, as shown in AC 25.562-1B. This is an acceptable method of compliance with 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 (a) through (g) address occupant protection in consideration of the oblique-facing seats. Condition (h) addresses airbag systems. Conditions (i)(1) through (i)(3) ensure that the pretensioner system activates when intended and protects a range of occupants under various accident conditions. Cond ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━ Preview showing 10k of 30k characters. Full document text is stored and available for version comparison. ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━