[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]


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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.

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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