[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