[Federal Register Volume 63, Number 237 (Thursday, December 10, 1998)]
[Proposed Rules]
[Pages 68211-68212]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 98-32821]
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Proposed Rules
Federal Register
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This section of the FEDERAL REGISTER contains notices to the public of
the proposed issuance of rules and regulations. The purpose of these
notices is to give interested persons an opportunity to participate in
the rule making prior to the adoption of the final rules.
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Federal Register / Vol. 63, No. 237 / Thursday, December 10, 1998 /
Proposed Rules
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DEPARTMENT OF TRANSPORTATION
Federal Aviation Administration
14 CFR Part 25
[Docket No. NM151; Notice No. 25-98-04-SC]
Special Conditions: Boeing Model 757-300 Sudden Engine Stoppage
AGENCY: Federal Aviation Administration (FAA), DOT.
ACTION: Notice of proposed special conditions.
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SUMMARY: This notice proposes special conditions 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 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 January 11, 1999.
ADDRESSES: Comments on this proposal may be mailed in duplicate to:
Federal Aviation Administration, Regional Counsel, Attn: Rules Docket
(ANM-7), Docket No. NM151, 1601 Lind Avenue SW., Renton, Washington,
98055-4056, or delivered in duplicate to the Regional Counsel at the
above address. Comments must be marked: NM151. 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: 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 NM151.'' The postcard will be date
stamped and returned to the commenter.
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 proposed 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 proposed special
conditions. Three exemptions have been granted. The special conditions
that may be developed as a result of this notice will 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, the special conditions would also apply to the
other model under the provisions of Sec. 21.101(a)(1).
[[Page 68212]]
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.
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 proposed special conditions
would 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 proposed 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 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, the 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
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 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 December 3, 1998.
John W. McGraw,
Acting Manager, Transport Airplane Directorate, Aircraft Certification
Service, ANM-100.
[FR Doc. 98-32821 Filed 12-9-98; 8:45 am]
BILLING CODE 4910-13-M
