[Federal Register Volume 64, Number 97 (Thursday, May 20, 1999)]
[Proposed Rules]
[Pages 27478-27480]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 99-12609]


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DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 25

[Docket No. NM157; Notice No. 25-99-05-SC]


Special Conditions: Boeing Model 767-400ER Sudden Engine Stoppage

AGENCY: Federal Aviation Administration (FAA), DOT.

ACTION: Proposed special conditions.

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SUMMARY: This document proposes special conditions for the Boeing Model 
767-400ER airplane. This airplane will have a novel or unusual design 
feature associated with sudden engine stoppage. The applicable 
airworthiness regulations do not contain adequate or appropriate safety 
standards for this design feature. These proposed special conditions 
contain the additional safety standards that the Administrator 
considers necessary to establish a level of safety equivalent to that 
established by the existing airworthiness standards.

DATES: Comments must be received on or before July 6, 1999.

ADDRESSES: Comments on this proposal may be mailed in duplicate to: 
Federal Aviation Administration, Office of the Regional Counsel, 
Attention: Rules Docket (ANM-7), Docket No. NM157, 1601 Lind Avenue SW, 
Renton, Washington, 98055-4056, or delivered in duplicate to the Office 
of the Regional Counsel at the above address. Comments must be marked: 
NM157. Comments may be inspected in the Rules Docket weekdays, except 
Federal holidays, between 7:30 a.m. and 4 p.m.

FOR FURTHER INFORMATION CONTACT: Joe Jacobsen, FAA, Standardization 
Branch, ANM-113, Transport Airplane Directorate, Aircraft Certification 
Service, 1601 Lind Avenue SW., Renton, Washington, 98055-4056; 
telephone (425) 227-2011; facsimile (425) 227-1149.

SUPPLEMENTARY INFORMATION:

Comments Invited

    Interested persons are invited to participate in the making of 
these proposed 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 received 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 notice must include with those 
comments a self-addressed, stamped postcard on which the following 
statement is made: ``Comments to NM157.'' The postcard will be date 
stamped and returned to the commenter.

Background

    On January 14, 1997, Boeing Commercial Airplane Group applied for 
an amendment to Type Certificate No. A1NM to include the new Model 767-
400ER airplane, a derivative of the Model 767-200/-300 series 
airplanes. The Model 767-400ER airplane is a swept-wing, conventional-
tail, twin-

[[Page 27479]]

engine, turbofan-powered transport. The airframe has been strengthened 
to accommodate the increased design loads and weights. The airplane has 
a seating capacity of up to 375, and a maximum takeoff weight of 
450,000 pounds (204,120 Kg). Each engine will be capable of delivering 
62,000 pounds of thrust. The flight controls are unchanged beyond those 
changes deemed necessary to accommodate the stretched configuration.

Type Certification Basis

    Under the provisions of 14 CFR Sec. 21.101, Boeing must show that 
the Model 767-400ER airplane meets the applicable provisions of the 
regulations incorporated by reference in Type Certificate No. A1NM, or 
the applicable regulations in effect on the date of application for the 
change to the Model 767-400ER. 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. A1NM include 14 CFR part 25, as 
amended by Amendments 25-1 through 25-45 with a few exceptions, and 
certain other later amended sections of part 25 that are not relevant 
to these special conditions. In addition, Boeing has chosen to comply 
with the applicable regulations in effect on January 14, 1997; 
specifically part 25 as amended by Amendments 25-1 through 25-89 and 
certain other earlier amended sections of part 25 that are not relevant 
to these special conditions. Three exemptions have been granted. These 
special conditions form an additional part of the type certification 
basis.
    If the Administrator finds that the applicable airworthiness 
regulations (i.e., part 25, as amended) do not contain adequate or 
appropriate safety standards for the Boeing Model 767-400ER airplane 
because of a novel or unusual design feature, special conditions are 
prescribed under the provisions of Sec. 21.16.
    In addition to the applicable airworthiness regulations and special 
conditions, the Model 767-400ER airplane must comply with the fuel vent 
and exhaust emission requirements of 14 CFR part 34, effective 
September 10, 1990, plus any amendments in effect at the time of 
certification; and the noise certification requirements of 14 CFR part 
36, effective December 1, 1969, as amended by Amendment 36-1 through 
the amendment in effect at the time of certification.
    Special conditions, as appropriate, are issued in accordance with 
14 CFR Sec. 11.49 after public notice, as required by Secs. 11.28 and 
11.29(b), and become part of the type certification basis in accordance 
with 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 engine proposed for the Boeing Model 767-400ER airplane will 
incorporate the unusual design feature of a high-bypass ratio fan jet 
engine that will not seize and produce transient torque loads in the 
same manner that is envisioned by current Sec. 25.361(b)(1) related to 
``sudden engine stoppage.''

Discussion

    For the engine proposed for the Model 767-400ER airplanes, the 
limit engine torque load imposed by sudden engine stoppage due to 
malfunction or structural failure (such as compressor jamming) has been 
a specific requirement for transport category airplanes since 1957. The 
size, configuration, and failure modes of jet engines has changed 
considerably from those envisioned in 14 CFR Sec. 25.361(b) when the 
engine seizure requirement was first adopted. Engines have grown much 
larger and are now designed with large bypass fans capable of producing 
much higher torque loads if they become jammed.
    Relative to the engine configuration that existed when the rule was 
developed in 1957, the present generation of engines are sufficiently 
different and novel to justify issuance of a special condition to 
establish appropriate design standards. The latest generation of jet 
engines is capable of producing engine seizure torque loads that are 
significantly higher than previous generations of engines.
    The FAA is developing a new regulation and a new advisory circular 
that will provide more comprehensive criteria for treating engine 
torque loads resulting from sudden engine stoppage. In the meantime, a 
special condition is needed to establish appropriate criteria for the 
Boeing Model 767-400ER airplane.

Limit Engine Torque Loads for Sudden Engine Stoppage

    In order to maintain the level of safety envisioned by 
Sec. 25.361(b), more comprehensive criteria are needed for the new 
generation of high bypass engines. These special conditions distinguish 
between the more common seizure events and those rare seizure events 
resulting from structural failures in the engine. For these more rare 
but severe seizure events, the criteria would allow some deformation in 
the engine supporting structure (ultimate load design) in order to 
absorb the higher energy associated with the high bypass engines, while 
at the same time protecting the adjacent primary structure in the wing 
and fuselage by applying a higher factor of safety to the maximum 
torque load imposed by sudden engine stoppage due to a structural 
failure.

Applicability

    As discussed above, these special conditions are applicable to the 
Boeing Model 767-400ER. 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, these special conditions 
would apply to that model as well under the provisions of 
Sec. 21.101(a)(1).

Conclusion

    This action affects only certain novel or unusual design features 
on one model series of airplanes. It is not a rule of general 
applicability, and it affects only the applicant who applied to the FAA 
for approval of these features on the airplane.

List of Subjects in 14 CFR Part 25

    Aircraft, Aviation safety, Reporting and recordkeeping 
requirements.

    The authority citation for these 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 (FAA) proposes the 
following special conditions as part of the type certification basis 
for Boeing Model 767-400ER airplanes.
    1. Engine Torque Loads. In lieu of compliance with Sec. 25.361(b), 
compliance with the following special condition is proposed:
    (a) For turbine engine and auxiliary power unit installations, the 
mounts and local supporting structure must be designed to withstand 
each of the following:
    (1) The maximum torque load, considered as limit, imposed by:

[[Page 27480]]

    (i) sudden deceleration of the engine due to a malfunction that 
could result in a temporary loss of power or thrust capability, and 
that could cause a shutdown due to vibrations; and
    (ii) the maximum acceleration of the engine and auxiliary power 
unit.
    (2) The maximum torque load, considered as ultimate, imposed by 
sudden engine or auxiliary power unit stoppage due to a structural 
failure, including fan blade failure.
    (3) The load condition defined in paragraph (a)(2) of this section 
is also assumed to act on adjacent airframe structure, such as the wing 
and fuselage. This load condition is multiplied by a factor of 1.25 to 
obtain ultimate loads when the load is applied to the adjacent wing and 
fuselage supporting structure.

    Issued in Renton, Washington, on May 7, 1999.
John J. Hickey,
Acting Manager, Transport Airplane Directorate, Aircraft Certification 
Service, ANM-100.
[FR Doc. 99-12609 Filed 5-19-99; 8:45 am]
BILLING CODE 4910-13-P