Special Conditions: Boeing Model 777 Series Airplanes; Seats With Inflatable Lapbelts

AGENCY:

Federal Aviation Administration (FAA), DOT.

ACTION:

Final special conditions.

SUMMARY:

These amended special conditions are issued to Boeing Commercial Airplanes for the Model 777 series airplanes. These airplanes have a novel or unusual design feature associated with seats with inflatable lapbelts. Special Conditions No. 25-187-SC were issued on October 3, 2001, addressing this issue. Boeing subsequently applied to amend the special conditions to add a new requirement that addresses the flammability of the material used to construct the inflatable lapbelt. The applicable airworthiness regulations, including those contained in Special Conditions No. 25-187-SC, do not contain adequate or appropriate safety standards for this design feature. The amended special conditions contain the additional safety standards that the Administrator considers necessary to establish an appropriate level of safety considering the safety benefits associated with the inflatable lapbelt.

DATES:

Effective October 29, 2004.

FOR FURTHER INFORMATION CONTACT:

Jayson Claar, FAA, Airframe and Cabin Safety Branch, ANM-115, Transport Airplane Directorate, Aircraft Certification Service, 1601 Lind Avenue SW., Renton, Washington, 98055-4056; telephone (425) 227-2194.

SUPPLEMENTARY INFORMATION:

Background

On April 20, 2001, Boeing Commercial Airplanes, P.O. Box 3707, Seattle, Washington 98124, applied for a type certificate design change to install inflatable lapbelts for head injury protection on certain seats in Boeing Model 777 series airplanes. The Model 777 series airplane is a swept-wing, conventional-tail, twin-engine, turbofan-powered transport. The inflatable lapbelt is designed to limit occupant forward excursion in the event of an accident. This will reduce the potential for head injury, as determined by the Head Injury Criteria (HIC) measurement. The inflatable lapbelt behaves similarly to an automotive airbag, but in this case the airbag is integrated into the lapbelt, and inflates away from the seated occupant. While airbags are now standard in the automotive industry, the use of an inflatable lapbelt is novel for commercial aviation.

Because the existing airworthiness standards of 14 CFR part 25 do not address inflatable lapbelts, the FAA developed special conditions to address this design feature. Special Conditions No. 25-187-SC were issued to Boeing Commercial Airplanes on October 3, 2001, and published in the Federal Register on October 12, 2001 (66 FR 52017).

On February 26, 2004, The Boeing Company requested that the FAA amend SC No. 25-187-SC to address flammability of the airbag material. During the development of the inflatable lapbelt the manufacturer was unable to develop a fabric that would meet the inflation requirements for the bag and the flammability requirements of Part I(a)(1)(i) of appendix F to part 25. The fabrics that were developed that meet the flammability requirement did not produce acceptable deployment characteristics. However, the manufacturer was able to develop a fabric the meets the less stringent flammability requirements of Part I(a)(1)(iv) of appendix F to part 25 and has acceptable deployment characteristics.

Discussion

Part I of appendix F to part 25 specifies the flammability requirements for interior materials and components. There is no reference to inflatable restraint systems in appendix F because such devices did not exist at the time the flammability requirements were written. The existing requirements are based on both material types, as well as use, and have been specified in light of the state-of-the-art of materials available to perform a given function. In the absence of a specific reference, the default requirement would be for the type of material used to construct the inflatable restraint, which is a fabric in this case. However, in writing a special condition, the FAA must also consider the use of the material, and whether the default requirement is appropriate. In this case, the specialized function of the inflatable restraint means that highly specialized materials are needed. The standard normally applied to fabrics is a 12-second vertical ignition test. However, materials that meet this standard do not perform adequately as inflatable restraints. Since the safety benefit of the inflatable restraint is very significant, the flammability standard appropriate for these devices should not screen out suitable materials, thereby effectively eliminating use of inflatable restraints. The FAA will need to establish a balance between the safety benefit of the inflatable restraint and its flammability performance. At this time, the 2.5-inch per minute horizontal test is considered to provide that balance. As the state-of-the-art in materials progresses (which is expected), the FAA may change this standard in subsequent special conditions to account for improved materials.

The additional safety standard is added as Item 14 to existing SC 25-187-SC. Items 1 through 13 are standards already adopted in Special Conditions No. 25-187-SC.

Type Certification Basis

Under the provisions of § 21.101, Boeing Commercial Airplanes must show that the Model 777 series airplanes, as changed, continue to meet the applicable provisions of the regulations incorporated by reference in Type Certificate No. T00001SE, or the applicable regulations in effect on the date of application for the change. The regulations incorporated by reference in the type certificate are commonly referred to as the “original type certification basis.” The regulations incorporated by reference in Type Certificate No. T00001SE are as follows: Amendments 25-1 through 25-82 for the Model 777-200, and amendments 25-1 through 25-86 with exceptions for the Model 777-300. The U.S. type certification basis for the Model 777 is established in accordance with §§ 21.29 and 21.17 and the type certification application date. The U.S. type certification basis is listed in Type Certificate Data Sheet No. T00001SE.

If the Administrator finds that the applicable airworthiness regulations (i.e., part 25 as amended) do not contain adequate or appropriate safety standards for Boeing Model 777 series airplanes because of a novel or unusual design feature, special conditions are prescribed under the provisions of § 21.16.

In addition to the applicable airworthiness regulations and special conditions, the Boeing Model 777 must comply with the fuel vent and exhaust emission requirements of part 34 and the noise certification requirements of part 36.

Special conditions, as defined in § 11.19, are issued in accordance with § 11.38 and become part of the type certification basis in accordance with § 21.101.

Applicability

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 or similar novel or unusual design feature, the special conditions would also apply to the other model under the provisions of § 21.101.

Discussion of Comments

Notice of proposed amendment of Special Conditions No. 25-187-SC was published in the Federal Register on September 23, 2004 as Notice 25-04-03-SC (69 FR 56961). We received one comment.

Comment: The commenter states that the special conditions should address the Model 747, A340, and A380 airplanes as well. As written the special conditions give the Model 777 a marketing advantage over these other airplanes that are used in similar markets. The Model 747, A340, and A380 should have the ability to take advantage of this functionality until a suitable material is found that addresses the functionality of the system as well as the 12-second vertical burn requirements.

FAA Reply: The special conditions are not a rule of general applicability and therefore cannot be applied to other airplanes such as the Model 747, A340, and A380. However, should an applicant apply for certification of an airplane with the same or similar design of inflatable lapbelts, we would consider that request for a less stringent flammability requirement for the inflatable bag fabric as well. We would consider the state-of-the-art inflatable bag fabric at that time.

Under standard practice, the effective date of final or amended special conditions would be 30 days after the date of publication in the Federal Register. However, because delivery of the affected airplanes with this additional novel or unusual design feature is imminent, and because a delay would significantly affect the applicant's installation and type certification of the lapbelt, the FAA finds that good cause exists for making these amended special conditions effective upon issuance.

Conclusion

This action affects only certain novel or unusual design features on the Boeing Model 777 series airplanes. It is not a rule of general applicability, and it affects only Model 777 series airplanes listed on Type Certificate Data Sheet T00001SE.

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(g), 40113, 44701, 44702, 44704.

The Amended Special Conditions

Accordingly, pursuant to the authority delegated to me by the Administrator, the following amended special conditions are issued as part of the type certification basis for the Boeing Model 777 series airplanes with inflatable lapbelts installed.

1. Seats With Inflatable Lapbelts. It must be shown that the inflatable lapbelt will deploy and provide protection under crash conditions where it is necessary to prevent serious head injury. The means of protection must take into consideration a range of stature from a two-year-old child to a ninety-fifth percentile male. The inflatable lapbelt must provide a consistent approach to energy absorption throughout that range. In addition, the following situations must be considered:

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 child not using a child restraint device.

d. The seat occupant is a pregnant woman.

2. The inflatable lapbelt must provide adequate protection for each occupant regardless of the number of occupants of the seat assembly, considering that unoccupied seats may have active seatbelts.

3. The design must prevent the inflatable lapbelt from being either incorrectly buckled or incorrectly installed such that the inflatable lapbelt would not properly deploy. Alternatively, it must be shown that such deployment is not hazardous to the occupant and will provide the required head injury protection.

4. It must be shown that the inflatable lapbelt system is not susceptible to inadvertent deployment as a result of wear and tear, or inertial loads resulting from in-flight or ground maneuvers (including gusts and hard landings), likely to be experienced in service.

5. Deployment of the inflatable lapbelt must not introduce injury mechanisms to the seated occupant, or result in injuries that could impede rapid egress. This assessment should include an occupant who is in the brace position when it deploys and an occupant whose belt is loosely fastened.

6. It must be shown that an inadvertent deployment that could cause injury to a standing or sitting person is improbable.

7. It must be shown that inadvertent deployment of the inflatable lapbelt during the most critical part of the flight will either not cause a hazard to the airplane or is extremely improbable.

8. It must be shown that the inflatable lapbelt will not impede rapid egress of occupants 10 seconds after its deployment.

9. The system must be protected from lightning and HIRF. The threats specified in Special Condition No. 25-ANM-78 are incorporated by reference for the purpose of measuring lightning and HIRF protection. For the purposes of complying with HIRF requirements, the inflatable lapbelt system is considered a “critical system” if its deployment could have a hazardous effect on the airplane; otherwise it is considered an “essential” system.

10. The inflatable lapbelt must function properly after loss of normal aircraft electrical power, and after a transverse separation of the fuselage at the most critical location. A separation at the location of the lapbelt does not have to be considered.

11. It must be shown that the inflatable lapbelt will not release hazardous quantities of gas or particulate matter into the cabin.

12. The inflatable lapbelt installation must be protected from the effects of fire such that no hazard to occupants will result.

13. There must be a means for a crewmember to verify the integrity of the inflatable lapbelt activation system prior to each flight or it must be demonstrated to reliably operate between inspection intervals.

14. The inflatable material may not have an average burn rate of greater than 2.5 inches/minute when tested using the horizontal flammability test as defined in 14 CFR part 25, appendix F, part I, paragraph (b)(5).