[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]


 ========================================================================
 Proposed Rules
                                                 Federal Register
 ________________________________________________________________________
 
 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.
 
 ========================================================================
 

  Federal Register / Vol. 63, No. 237 / Thursday, December 10, 1998 / 
Proposed Rules  

[[Page 68211]]


-----------------------------------------------------------------------

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.

-----------------------------------------------------------------------

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