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Proposed Rule

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

Document Details

Information about this document as published in the Federal Register.

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Federal Aviation Administration (FAA), DOT.


Notice of proposed amendment of special conditions.


This notice proposes amended special conditions for Boeing Model 777 series airplanes. These airplanes, manufactured by Boeing Commercial Airplanes, have novel or unusual design features associated with seats with inflatable lapbelts. Special Conditions No. 25-187-SC were issued on October 3, 2001, addressing this issue. The proposed amendment would add a new requirement that addresses the flammability of the material used to construct the inflatable lapbelt. The applicable airworthiness regulations do not contain adequate or appropriate safety standards for this design feature. The amended special conditions would 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.


Comments must be received on or before October 13, 2004.


You may send comments, identified by Docket No. NM198, using any of the following methods:

  • Mail: Federal Aviation Administration, Transport Airplane Directorate, ANM-113, Attn: Rules Docket, 1601 Lind Avenue, SW., Renton, Washington 98055-4056.
  • Fax: 1-425-227-1232, Attn: Jayson Claar.
  • Electronically:
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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.

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Comments Invited

The FAA invites interested persons to participate in this rulemaking by submitting written comments, data, or views. The most helpful comments reference a specific portion of the proposed special conditions, explain the reason for any recommended change, and include supporting data. We ask that you send us two copies of written comments.

We will file in the docket all comments we receive, as well as a report summarizing each substantive public contact with FAA personnel concerning these special conditions. The docket is available for public inspection before and after the comment closing date. If you wish to review the docket in person, go to the address in the ADDRESSES section of this preamble between 9 a.m. and 5 p.m., Monday through Friday, except Federal holidays.

We will consider all comments we receive on or before the closing date for comments. We will consider comments Start Printed Page 56962filed late if it is possible to do so without incurring expense or delay. We may change these special conditions in light of the comments we receive.

If you want the FAA to acknowledge receipt of your comments on this proposal, include with your comments a pre-addressed, stamped postcard on which the docket number appears. We will stamp the date on the postcard and mail it back to you.


On April 20, 2001, Boeing Commercial Airplanes, PO 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.


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 proposed safety standard would be added as Item 14 to existing SC 25-187-SC. Although Items 1 through 13 are standards already adopted in Special Conditions No. 25-187-SC and are not subject to further public comment, they are repeated later in this notice in order to place the additional standard in proper perspective.

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.


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.

Public Comment Period

Delivery of Model 777 airplanes with the additional flammability standard is currently scheduled for January 2006. Because a delay would significantly affect the applicant's installation and type certification of the airbag material, the public comment period is 20 days.


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.

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List of Subjects in 14 CFR Part 25

  • Aircraft
  • Aviation safety
  • Reporting and recordkeeping requirements
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Authority Citation

The authority citation for these special conditions is as follows:

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

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The Proposed Special Conditions

Accordingly, the Federal Aviation Administration proposes the following additional special condition (Item No. 14) as part of the type certification basis for the Boeing Model 777 series airplanes with inflatable lapbelts installed. (Existing special condition Items 1-13 are repeated below for clarity only.).

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). 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.

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Issued in Renton, Washington, on September 17, 2004.

Ali Bahrami,

Manager, Transport Airplane Directorate, Aircraft Certification Service.

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[FR Doc. 04-21393 Filed 9-22-04; 8:45 am]