[Federal Register Volume 60, Number 145 (Friday, July 28, 1995)]
[Proposed Rules]
[Pages 38771-38773]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 95-18591]



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DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 33

[Docket No. 95-ANE-42; Notice No. SC-95-04-NE]


Special Conditions: Allison Engine Company Model 250-C40 
Turboshaft Engine

agency: Federal Aviation Administration (FAA), DOT.

action: Notice of proposed special conditions.

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summary: This notice proposes special conditions for the Allison Engine 
Company Model 250-C40 turboshaft engine. This engine will have novel or 
unique engine ratings that are not defined by the applicable 
airworthiness regulations. This notice proposes the safety standards 
for those novel or unique ratings that the Administrator considers 
necessary to establish a level of safety equivalent to that established 
by the airworthiness standards of part 33 of the Federal Aviation 
Regulations (FAR).

dates: Comments must be submitted on or before August 28, 1995.

addresses: Comments on this proposal may be submitted in triplicate to: 
Federal Aviation Administration (FAA), New England Region, Office of 
the Assistant Chief Counsel, Attn: Rules Docket No. 95-ANE-42, 12 New 
England Executive Park, Burlington, Massachusetts 01803-5299. Comments 
must be marked: Docket No. 95-ANE-42. Comments may be inspected at this 
location between 8:00 a.m. and 4:30 p.m., Monday through Friday, except 
Federal holidays.

for further information contact: Chung Hsieh, Engine and Propeller 
Standards Staff, ANE-110, Engine and Propeller Directorate, Aircraft 
Certification Service, FAA, New England Region, 12 New England 
Executive Park, Burlington, Massachusetts 01803-5229; (617) 238-7115; 
Fax (617) 238-7199.

SUPPLEMENTARY INFORMATION:

Comments Invited

    Interested persons are invited to participate in the making of the 
proposed special conditions by submitting such written data, views, or 
arguments as they may desire. Communications should identify the Rules 
Docket number and be submitted in triplicate to the address specified 
under ADDRESSES. All communications received on or before the closing 
date for comments, specified under DATES, will be considered by the 
Administrator before taking action on the proposal. The proposal 
contained in this notice may be changed in light of the comments 
received.
    Comments are specifically invited on the overall regulatory, 
economic, environmental, and energy aspects of the proposed special 
conditions. 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 proposal will be filed in 
the docket.
    Commenters wishing the FAA to acknowledge receipt of their comments 
submitted in response to this notice must submit with those comments a 
self-addressed, stamped postcard on which the following statement is 
made: ``Comments to Docket No. 95-ANE-42'' The postcard will be dated 
stamped and returned to the commenter.

Background

    On May 11, 1993, the Allison Engine Company (AE) applied for an 
amendment to type certificate E1GL to include a new model 250-C40 
turboshaft engine. On March 30, 1995, the Allison Engine Company 
applied for 30-second one engine inoperative (OEI) and 2-minute OEI 
ratings for the engine. The AE Model 250-C40 turboshaft engine will be 
rated at 30-Second OEI, 2-Minute OEI, 30-Minute OEI, Continuous OEI, 
Takeoff, and Maximum Continuous ratings.
    The applicable airworthiness requirements do not contain 30-Second 
OEI and 2-Minute OEI rating definitions, and do not contain adequate or 
appropriate safety standards for the type certification of these new 
and unusual engine ratings.

Type Certification Basis

    Under the provisions of section 21.17(a) of the FAR, Allison Engine 
Company must show that the AE Model 

[[Page 38772]]
250-C40 turboshaft engine meets the requirements of the applicable 
regulations in effect on the date of the application. The applicable 
regulations for this engine is FAR part 33, effective February 1, 1965, 
as amended by Amendments 33-1 through 33-4.
    The Administrator finds that the applicable airworthiness 
regulations in 33, as amended, do not contain adequate or appropriate 
safety standards for the AE Model 250-C40 turboshaft engine because of 
the new and unique engine ratings. Therefore, the Administrator 
proposes special conditions under the provisions of section 21.16 to 
establish a level of safety equivalent to that established in the 
regulations.
    Special conditions, as appropriate, are issued in accordance with 
section 11.49 of the FAR after public notice and opportunity for 
comment, as required by sections 11.28 and 11.29(b), and become part of 
the type certification basis in accordance with section 21.17(a)(2).
Conclusion

    This action affects only certain novel or unusual design features 
on one model engine. It is not a rule of general applicability and 
affects only the manufacturer who applied to the FAA for approval of 
these features on the engine.

List of Subjects in 14 CFR Part 33

    Air transportation, Aircraft, Aviation safety, Safety.

    The authority citations for these special conditions is as follows:

    Authority: 49 U.S.C. App. 1354(a), 1421, 1423; 49 U.S.C. 106(g).

The Proposed Special Conditions

    Accordingly, the Federal Aviation Administration (FAA) proposes the 
following special conditions as part of the type certification basis 
for the Allison Engine Company (AE) Model 250-C40 turboshaft engine:


Sec. 33.7  Engine ratings and operating limitations.

    In addition to the requirements of section 33.7, the following 
ratings are defined as:
    (a) Rated 30-Second One-Engine-Inoperative (OEI) Power: The 
approved brake horsepower developed statically in standard atmosphere 
at sea level, or at a specified altitude and temperature, for continued 
one-flight operation after the failure of one engine in multi-engine 
rotorcraft, limited to three periods of use, no greater than 30 seconds 
each, at rotor shaft rotation speed and gas temperature established for 
this rating by part 33 or this special condition.
    (b) Rated 2-Minute OEI Power: The approved brake horsepower, 
developed statically in standard atmosphere at sea level, or at a 
specified altitude and temperature, for continued one-flight operation, 
after failure of one engine in multi-engine rotorcraft, limited to 
three periods of use, of up to two minutes each, at rotor shaft 
rotation speed and gas temperature established for this rating by part 
33 or this special condition.


Sec. 33.4  Instructions for continued airworthiness.

    In addition to the requirements of section 33.4, the mandatory 
inspection and maintenance actions required following the use of the 
30-Second or 2-Minute OEI rating, must be included in the airworthiness 
limitations section of the appropriate engine manuals.


Sec. 33.27  Turbine, compressor, fan, and turbo-supercharger rotors.

    In addition to the requirements of section 33.27, the following 
additional test requirements must be considered under 33.27(c)(2). For 
30-Second and 2-Minute OEI conditions, test for a period of 5 minutes--
    (a) At 100 percent of the highest speed that would result from 
failure of the most critical component of each turbine and compressor 
or system in a representative installation of the engine when operating 
at 30-Second and 2-Minute OEI rating conditions.
    (b) The test speed must take into account minimum material 
properties, maximum operating temperature, and the most adverse 
dimensional tolerances.
    (c) Following the test, rotor growth and distress beyond 
dimensional limits for an overspeed condition is permitted for 30-
Second and 2-Minute OEI rating only, provided the structural integrity 
of the rotor is maintained, as shown by a procedure acceptable to the 
Administrator.


Sec. 33.29  Instrument connection.

    In addition to the requirements of section 33.29, the engine must 
provide for a means:
    (a) To indicate when the engine is at either 30-Second or 2-Minute 
OEI-rated power level; and
    (b) To determine the elapsed time of operation at 2-Minute OEI and 
30-Second OEI rated power levels.


Sec. 33.67  Fuel system.

    In addition to the requirements of section 33.67, the engine must 
provide for a means for automatic availability and automatic control of 
the 30-second OEI power; and engine test runs must be performed to 
demonstrate automatic switching to a 30-Second OEI rating condition.


Sec. 33.83  Vibration test.

    In addition to the requirements of section 33.83, the following 
additional test requirements must be considered under 33.83(a):
    For 30-Second and 2-Minute OEI rating conditions, the vibration 
survey shall cover the ranges of power, and both the physical and 
corrected rotational speeds for each rotor system, corresponding to 
operations throughout the range of ambient conditions in the declared 
flight envelope, from the minimum rotor speed up to 103 percent of the 
maximum rotor speed permitted for 2-Minute OEI rating, and up to 100 
percent of the maximum rotor speed permitted for 30-Second OEI rating 
speed. If there is any indication of a stress peak arising at high 
physical or corrected rotational speeds, the surveys shall be extended 
in order to quantify the phenomenon and to ensure compliance with the 
requirements of section 33.63.


Sec. 33.85  Calibration tests.

    In addition to the requirements of section 33.85, tests performed 
at the 30-Second and 2-Minute OEI ratings, during the applicable 
endurance test prescribed in section 33.87, may be used to show 
compliance with the requirements of section 33.85.


Sec. 33.87  Endurance test.

    In addition to the requirements of section 33.87, an engine test 
must be conducted four times, using the following test sequence, for a 
total of not less than 120 minutes:
    (a) Takeoff Power--three minutes at rated takeoff power.
    (b) 30-Second OEI power--thirty seconds at rated 30-Second OEI 
power.
    (c) 2-Minute OEI power--two minutes at rated 2-Minute OEI power.
    (d) 30-Minute OEI, Continuous OEI, or Maximum Continuous power--
five minutes at rated 30-Minute OEI power, or rated Continuous OEI 
power, or rated Maximum Continuous power, whichever is greatest, except 
that during the first test sequence this period shall be 65 minutes.
    (e) 50 percent takeoff power--one minute at 50 percent takeoff 
power.
    (f) 30-second OEI power--thirty seconds at rated 30-Second OEI 
power.
    (g) 2-minute OEI power--two minutes at rated 2-Minute OEI power.
    (h) Idle power--one minute at Idle power.

[[Page 38773]]



Sec. 33.88  Engine overtemperature test.

    In addition to the requirements of section 33.88, the following 
must be performed:
    (a) For engines that do not provide a means for temperature 
limiting; conduct a test for a period of five minutes at the maximum 
permissible power-on RPM, with the gas temperature at least 75 degrees 
Fahrenheit higher than the 30-Second OEI rating operating temperature 
limit.
    (b) For engines that provide a means for temperature limiting; 
conduct a test for a period of four minutes at the maximum permissible 
power-on RPM, with the gas temperature at least 35 degrees Fahrenheit 
higher than the 30-Second OEI rating operating temperature limit.
    (c) A separate test engine may be used for each test.
    (d) Following the test, rotor assembly growth and distress beyond 
serviceable limits for an overtemperature condition is permitted, 
provided the structural integrity of the rotor assembly is maintained, 
as shown by a procedure that is acceptable to the Administrator.


Sec. 33.93  Teardown inspection.

    In addition to the requirements of section 33.93, this special 
condition requires that the engine be completely disassembled after 
completing the additional testing of section 33.87. The engine may 
exhibit deterioration in excess of that permitted in section 33.93(b), 
and may include some engine parts and components that may be unsuitable 
for further use. It must be shown by procedures approved by the 
Administrator that the structural integrity of the engine, including 
mounts, cases, bearing supports, shafts and rotors, is maintained.

    Issued in Burlington, Massachusetts, on July 20, 1995.
Robert E. Guyotte,
Acting Manager, Engine & Propeller Directorate, Aircraft Certification 
Service.
[FR Doc. 95-18591 Filed 7-27-95; 8:45 am]
BILLING CODE 4910-13-M