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Federal Register / Vol. 86, No. 49 / Tuesday, March 16, 2021 / Proposed Rules
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 Boeing Model 737800 airplane 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 applicant apply for a supplemental type certificate to modify any other model included on the same type certificate 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, the Boeing Model 737800
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 11.38, and they become part of the type certification basis under 21.101.

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Novel or Unusual Design Features The Boeing Model 737800 airplane will incorporate the following novel or unusual design features:
Airbags mounted to structure to prevent head injury.
Discussion Haeco proposes to install structuremounted airbags instead of inflatable lap belts as a means to protect each occupant from serious injury in the event of an emergency landing, as required by 25.562c5, on 737800
airplanes.
Such use of airbags to provide injury protection for the occupant is a novel or unusual feature for this airplane model, and the applicable airworthiness regulations do not contain adequate or appropriate airworthiness standards for these design features. Therefore, special conditions are needed to address requirements particular to installation of airbags in this manner.
Special conditions exist for airbags installed on seat belts, known as inflatable lap belts, which have been installed on transport airplane passenger seats. Structure-mounted airbags, although a novel design, were first introduced on Jetstream Aircraft Limited Model 4100 series airplanes, which resulted in issuance of Special Conditions 25ANM127 on May 14,
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1997. These special conditions supplemented 14 CFR part 25 and, more specifically, 25.562 and 25.785.
The structure-mounted airbag, similar to the inflatable lap belt, is designed to limit occupant forward excursion in the event of an emergency landing. These airbags will reduce the potential for serious injury, including reducing the head-injury criterion measurement defined in part 25. However, structuremounted airbags function similarly as automotive airbags, where the airbag deploys from furniture located in front of the passenger, relative to the airplanes direction of flight, forming a barrier between the structure and occupant. Also, unlike the inflatable lap belt, the structure-mounted airbag does not move with the occupant. To account for out-of-position and brace-position occupants, the airbag is designed to conform to the curvature of the exposed structure in the head-strike zone.
Because the airbag system is essentially a single-use device, it could deploy under crash conditions that are not sufficiently so severe as to require the injury protection the airbag system provides. Because an actual crash is frequently composed of a series of impacts before the airplane comes to rest, a larger impact following the initial impact could render the airbag system unavailable. This potential situation does not exist with standard upper-torso restraints, which tend to provide continuous protection regardless of impact severity, or number of impacts, in a crash event. Therefore, the airbag system installation should be such that it provides protection, when it is required, by not expending its protection when it is not required. If the airbag deployment threshold is unnecessarily low, the airbag would need to continue to provide protection when an impact requiring protection occurs.
These proposed special conditions are based upon Special Conditions 25605
SC for the Boeing Model 7879
airplanes equipped with B/E Aerospace Super-Diamond model business-class passenger seats and associated furniture.
Additionally, the special conditions address protection of the occupants neck and spine for the structuremounted airbag deployment. When using the HIC15 head-injury method for airbag impacts calculated in accordance with 49 CFR 571.208 the neck and spine limits are included as part of the allowance. These additional conditions are based on special conditions issued previously on oblique seats. The proposed special conditions contain the additional safety standards that the Administrator considers necessary to
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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 737800 airplane as modified by Haeco. Should Haeco 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, these special conditions would apply to that model as well.
Conclusion This action affects only a certain novel or unusual design features on one model of airplane. 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. 106f, 106g, 40113, 44701, 44702, 44704.

The Proposed Special Conditions Accordingly, the Federal Aviation Administration FAA proposes the following special conditions as part of the type certification basis for Boeing Model 737800 airplanes, as modified by Haeco Cabin Solutions:
1. The applicant must demonstrate by test that the structure-mounted airbag will deploy and provide protection under crash conditions where it is necessary to prevent serious injury to a 50th percentile occupant, as specified in 25.562. The means of protection must provide a consistent approach to energy absorption for a range of occupants, from a two-year-old child to a 95th percentile male. In addition, the following situations should be considered:
The seat occupant is holding an infant.
The seat occupant is a child in a child restraint device.
The seat occupant is a child not using a child restraint device.
The seat occupant is a pregnant woman.
a. Head-Injury Criteria Compliance with 25.562c5 is required, except that, if the ATD has no apparent contact with the seat/structure but has contact with an airbag, a head-

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