[Federal Register Volume 63, Number 107 (Thursday, June 4, 1998)] [Proposed Rules] [Pages 30423-30425] From the Federal Register Online via the Government Publishing Office [www.gpo.gov] [FR Doc No: 98-14882] ======================================================================= ----------------------------------------------------------------------- DEPARTMENT OF TRANSPORTATION Federal Aviation Administration 14 CFR Part 25 [Docket No. NM148; Notice No. 25-98-03-SC] Special Conditions: Boeing Model 777 Series Airplanes; Seats With Articulating Seat Backs AGENCY: Federal Aviation Administration (FAA), DOT. ACTION: Notice of proposed special conditions. ----------------------------------------------------------------------- SUMMARY: This notice proposes special conditions for Boeing Model 777 series airplanes. These airplanes will have novel and unusual design features associated with seats with articulating seat backs. The applicable regulations do not contain adequate or appropriate safety standards for this design feature. The proposed special conditions contain the additional safety standards that the Administrator considers necessary to establish a level of safety equivalent to that provided by the existing airworthiness standards. DATES: Comments must be received on or before July 20, 1998. ADDRESSES: Comments on this proposal may be mailed in duplicate to: Federal Aviation Administration, Office of the Regional Counsel, Attn: Rules Docket (ANM-7), Docket No. NM148, 1601 Lind Avenue SW, Renton, Washington, 98055-4506; or delivered in duplicate to the Office of the Regional Counsel at the above address. Comments must be marked: Docket No. NM148. Comments may be inspected in the Rules Docket weekdays, except Federal holidays, between 7:30 a.m. and 4:00 p.m. FOR FURTHER INFORMATION CONTACT: Jeff Gardlin, Propulsion, Mechanical Systems, and Crashworthiness Branch, ANM-112, Transport Airplane Directorate, Aircraft Certification Service, FAA, 1601 Lind Avenue SW., Renton, Washington 98055-4056; telephone (206) 227-2136; facsimile (425) 227-1149. SUPPLEMENTARY INFORMATION: Comments Invited Interested persons are invited to participate in the making of these special conditions by submitting such written data, views, or arguments as they may desire. Communications should identify the regulatory docket or notice number and be submitted in duplicate to the address specified above. All communications received on or before the closing date for comments will be considered by the Administrator. The proposals described in this notice may be changed in light of the comments received. All comments submitted will be available in the Rules Docket for examination by interested persons, both before and after the closing date for comments. A report summarizing each substantive public contact with FAA personnel concerning this rulemaking will be filed in the docket. Persons wishing the FAA to acknowledge receipt of their comments submitted in response to this request must submit with those comments a self-addressed, stamped postcard on which the following statement is made: ``Comments to Docket No. NM148.'' The postcard will be date stamped and returned to the commenter. Background On April 15, 1998, the Boeing Company applied for a change to Type Certificate No. T00001SE to include Model 777 series airplanes equipped with seats with articulating seat backs (seats that have a portion of the seat back that moves under inertia loads). Sicma Aero Seat, a Boeing supplier, has designed a seat for installation on a Boeing 777- 300 airplane with an articulating seat back that is designed to rotate forward under a prescribed inertial load. The prescribed inertial load is slightly below the 16g test condition of Sec. 25.562. The inertial load causes the seat back mounted video monitor and headrest assembly to partially separate from the seat back and pivot forward. The goal of the design is to reduce the mass of the upper seat back subject to impact, thereby reducing the Head Injury Criteria (HIC) measurement and enhancing passenger safety. Section 25.562 specifies that dynamic tests must be conducted for each seat type installed in the airplane. The pass/fail criteria for these seats include structural as well as human tolerance criteria. In particular, the regulations require that persons not suffer serious head injury under the conditions specified in the tests, and that a HIC measurement of not more than 1000 units be recorded, should contact with the cabin interior occur. While the test conditions described in this section are specific, it is the intent of the requirement that an adequate level of head injury protection be provided for crash severities up to and including that specified. The FAA has established guidance, known as ``simplified HIC certification,'' which provides a simplified procedure for demonstrating compliance with the HIC requirements of Sec. 25.562(c)(5). This procedure provides test conditions that meet the intent of the requirements, without causing excessive testing to be performed. The typical seat back has three areas that are considered head strike zones within the +/-10 degree yaw range of impact orientation. The procedure describes two different tests that address these three head strike zones for the majority of cases. Because Sec. 25.562 and FAA guidance do not adequately address seats with articulating seat backs, the FAA recognizes that appropriate pass/fail [[Page 30424]] criteria need to be developed that do fully address the safety concerns specific to occupants of these seats. Type Certification Basis Under the provisions of 14 CFR Sec. 21.101, Boeing must show that Model 777 airplanes equipped with seats with articulating seat backs comply with the regulations in the U.S. type certification basis established for the Model 777 airplane. The U.S. type certification basis for the Model 777 is established in accordance with 14 CFR Secs. 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., 14 CFR 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 14 CFR Sec. 21.16 to establish a level of safety equivalent to that established in the regulations. 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 14 CFR Part 34 and the noise certification requirements of 14 CFR Part 36. Special conditions, as appropriate, are issued in accordance with 14 CFR Sec. 11.49 after public notice, as required by 14 CFR Secs. 11.28 and 11.29(b), and become part of the type certification basis in accordance with 14 CFR Sec. 21.101(b)(2). 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, the special conditions would also apply to the other model under the provisions of Sec. 21.101(a)(1). Novel or Unusual Design Features The Boeing Company is proposing installing seats with articulating seat backs on a Boeing Model 777-300 airplane. The articulating seat back is designed to rotate forward under a prescribed inertial load. The prescribed inertial load is slightly below the 16g test condition specified in Sec. 25.562. The inertial load causes the seat back mounted video monitor and headrest assembly to partially separate from the seat back and pivot forward. The goal of the design is to reduce the mass of the upper seat back subject to impact, thereby reducing the HIC and enhancing passenger safety. The Federal Aviation Regulations (FAR) state the performance criteria for head injury protection in objective terms. Further guidance in addressing head injury protection for the majority of cases is described in the above mentioned Transport Airplane Directorate memorandum. However, none of these criteria are adequate to address the specific issues raised concerning seats with articulating seat backs. The FAA has therefore determined that, in addition to the requirements of 14 CFR part 25, special conditions are needed to address requirements particular to installation of seats with articulating seat backs. Accordingly, in addition to the passenger injury criteria specified in 14 CFR Secs. 25.562 and 25.785, these special conditions are proposed for the Boeing Model 777 series airplanes equipped with seats with articulating seat backs. Note that HIC, which is addressed in this proposed special condition, does not address occupant injury due to contact with sharp edges or protrusions. Damage to the anthropomorphic test device (ATD) will be used as part of the evaluation of protrusions and sharp edges in demonstrating compliance with Sec. 25.785(b). Other conditions may be developed, as needed, based on further FAA review and discussions with the manufacturer and civil aviation authorities. Discussion The seat with the articulating seat back is a new and complex design that warrants additional requirements to ensure an equivalent level of safety to that provided by the regulations. This seat reduces the effective mass that an occupant contacts during a high inertial load, thereby increasing the amount of head injury protection. However, additional considerations are necessary to ensure that the articulating seat back design does not introduce other hazards to occupants. If the articulating seat back fails to break away at the designed inertial load, the seat back may remain rigid, resulting in a significantly higher head injury than allowed for in the regulations. To ensure that the occupant does not contact a rigid seat back, the seat back must break away each time the designed break away inertial load is encountered. In addition, it is important to evaluate the articulating seat back at lower values than the designed break away inertial load. During a lower inertial load (e.g., 10g), the occupant may contact the seat. Since the seat will not break away prior to the occupant contacting the seat during this lower inertial load, the occupant may receive a more severe head injury than during an event occurring at the designed break away inertial load. The intent of the regulations is that the occupant is protected from head injury for crash severities up to and including that specified. When the articulating seat back breaks away, the video monitor pivots and moves forward, leaving a rectangular opening in the seat back. This opening could pose an entrapment hazard to the person seated behind the seat. During any testing for certification, the head must not become entrapped. In addition, the head must not become entrapped in any other foreseeable operating conditions for the range of occupants. The articulating seat back may have protrusions and/or recessed areas (i.e., bottom lip of the seat back opening) that pose a head injury hazard to the occupant during emergency conditions. As stated in Sec. 25.562(c)(5), the head impact for a seat occupant cannot exceed a HIC of 1,000 units. The ``simplified HIC certification'' procedure is commonly used to demonstrate compliance with Sec. 25.562(c)(5). Due to the non-standard articulating seat back configuration, the ``simplified HIC certification'' procedure alone may not be sufficient for demonstrating compliance with Sec. 25.562(c)(5). The ATD must come in contact with these protrusions or recessed areas of the seat back opening during testing. If the ATD does not contact these areas using the ``simplified HIC certification'' procedure, additional testing will be required to demonstrate compliance with Sec. 25.562(c)(5). The first delivery of a Model 777-300 airplane with these additional novel or unusual design features is currently scheduled for October of 1998, with the certification program scheduled to begin in May. Because a delay would significantly affect the applicant's testing, installation, and type certification of these seats, the public comment period is 30 days. Applicability As discussed above, these special conditions are applicable to the Model 777 series airplanes. Should Boeing apply at a later date for a change to the type certificate to include another model incorporating the same novel or unusual design feature, the special conditions would apply to that model as well under the provisions of 14 CFR Sec. 21.101(a)(1). [[Page 30425]] 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 the manufacturer who applied to the FAA for approval of these features on the airplane. List of subjects in 14 CFR Part 25 Air transportation, Aircraft, Aviation safety, Safety. The authority citation for these proposed special conditions is as follows: Authority: 49 U.S.C. 106(g), 40113, 44701, 44702, 44704. The Proposed Special Conditions Accordingly, the Federal Aviation Administration proposes the following special conditions as part of the type certification basis for the Boeing Model 777 series airplanes equipped with seats with articulating seat backs: 1. The articulating seat back must reliably break away at the designed inertial load. 2. The seat must provide an equivalent level of head injury protection under the maximum inertia loading conditions under which the articulating seat back will not break away. The HIC value must not exceed 1,000 units at any time prior to break away. 3. The head must not become entrapped in the seat back opening created by the articulating seat back, during any testing conducted to demonstrate compliance with Secs. 25.562 and 25.785(b), and these special conditions. The head must also not become entrapped in the seat back opening during any other foreseeable operating or crash conditions. 4. The HIC must not exceed 1,000 units for any obvious protrusions or recessed areas of the seat back opening (i.e., bottom lip of the seat back opening). The anthropomorphic test device (ATD) must come in contact with these protrusions or recessed areas of the seat back opening. 5. It must be shown that the additional breakaway features of the articulating seat back do not pose an entrapment hazard to the occupant of a seat having these features and impacted from the rear. Issued in Renton, Washington, on May 27, 1998. John J. Hickey, Acting Manager, Transport Airplane Directorate, Aircraft Certification Service, ANM-100. [FR Doc. 98-14882 Filed 6-3-98; 8:45 am] BILLING CODE 4910-13-P