[Federal Register Volume 64, Number 13 (Thursday, January 21, 1999)]
[Rules and Regulations]
[Pages 3201-3202]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 99-1352]
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Rules and Regulations
Federal Register
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This section of the FEDERAL REGISTER contains regulatory documents
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Federal Register / Vol. 64, No. 13 / Thursday, January 21, 1999 /
Rules and Regulations
[[Page 3201]]
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DEPARTMENT OF TRANSPORTATION
Federal Aviation Administration
14 CFR Part 25
[Docket No. NM151; Special Conditions No. 25-142-SC]
Special Conditions: Boeing Model 757-300 Sudden Engine Stoppage
AGENCY: Federal Aviation Administration (FAA), DOT.
ACTION: Final special conditions.
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SUMMARY: These special conditions are issued for the Boeing Model 757-
300 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 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.
EFFECTIVE DATE: January 14, 1999.
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:
Background
On February 21, 1996, Boeing applied for an amendment to Type
Certificate No. A2NM to include the new Model 757-300 airplane, a
derivative of the Model 757-200 currently approved under Type
Certificate No. A2NM. The Model 757-300 airplane is a swept wing,
conventional tail, twin engine, turbofan powered transport. Each engine
will be capable of delivering 43,100 pounds of thrust. The airframe has
been strengthened to accommodate the increased design loads and
weights. The airplane has a seating capacity of up to 295, and a
maximum takeoff weight of 270,000 pounds (122,470 Kg).
Type Certification Basis
Under the provisions of 14 CFR 21.101, Boeing must show that the
Model 757-300 airplane meets the applicable provisions of the
regulations incorporated by reference in Type Certificate No. A2NM, or
the applicable regulations in effect on the date of application for the
change to the Model 757-300. 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. A2NM include part 25, as amended by Amendments 25-
1 through 25-45, 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
February 21, 1996; specifically part 25 as amended by Amendments 25-1
through 25-85 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 757-300 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 757-300 airplane must comply with the fuel vent
and exhaust emission requirements of part 34, effective September 10,
1990, plus any amendments in effect at the time of certification; and
the noise certification requirements of 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 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, these 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 757-300 airplane is 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 757-300 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 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 are 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 757-300 airplane.
[[Page 3202]]
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.
Discussion of Comments
Notice of proposed special conditions No. 25-98-04-SC for the
Boeing Model 757-300 airplanes was published in the Federal Register on
December 10, 1998 (63 FR 68211). No comments were received, and the
special conditions are adopted as proposed.
Applicability
As discussed above, these special conditions are applicable to the
Boeing Model 757-300. 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).
Under standard practice, the effective date of final special
conditions is 30 days after the date of publication in the Federal
Register; however, as the certification date for the Boeing Model 757-
300 is imminent, the FAA finds that good cause exists to make these
special conditions effective upon issuance.
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 Special Conditions
Accordingly, pursuant to the authority delegated to me by the
Administrator, the following special conditions are issued as part of
the type certification basis for Boeing Model 757-300 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 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:
(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.
(2) The maximum torque load, considered as ultimate, imposed by
sudden engine 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 January 14, 1999.
John J. Hickey,
Acting Manager, Transport Airplane Directorate, Aircraft Certification
Service, ANM-100.
[FR Doc. 99-1352 Filed 1-20-99; 8:45 am]
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