Special Conditions: Turbomeca Model Arriel 2S1 Turboshaft Engine

SUMMARY: These special conditions are issued for the Turbomeca Model

Arriel 2S1 turboshaft engine. This engine will have novel or unique

engine ratings that are not defined by the applicable airworthiness

regulations. These special conditions contain the additional safety

standards which 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).

EFFECTIVE DATE: May 15, 1996.

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:

Background

On February 25, 1994, Turbomeca applied for an amendment to type

certificate E19EU to include a new Model Arriel 2S1 turboshaft engine.

The Model Arriel 2S1 turboshaft engine will be rated at 30-Second and

2-Minute one engine inoperative (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 21.101 of the Federal Aviation

Regulations (FAR), Turbomeca must show that the Model Arriel 2S1

turboshaft engine meets the applicable provisions of the regulations as

referenced in Type Certificate No. E19EU or the applicable regulations

in effect on the date of the application. The regulations incorporated

by reference in Type Certificate No. E19EU are Section 21.29 and part

33, effective February 1, 1965, as amended by Amendments 33-1 through

33-5, Turbomeca, however, has elected, under section 21.17, to comply

with Amendments 33-1 through 33-14. The FAA has determined that the use

of the airworthiness standards as amended by the later amendments for

type certification of this derivative engine will enhance safety and

therefore accepts the Turbomeca's proposal.

The Administrator finds that the applicable airworthiness

regulations in part 33, as amended, do not contain adequate or

appropriate safety standards for the Turbomeca Model Arriel 2S1

turboshaft engine because of the new and unique engine ratings.

Therefore, the Administrator prescribes 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 21.101(b)(2).

Discussion of Comments

Interested persons have been afforded the opportunity to

participate in the making of these special conditions. No comments were

received on the special conditions as proposed. However, comments

addressing numerous issues were received in response to proposed

special conditions for a similar engine program, Allison Engine Company

(AE) Model 250 turboshaft engine. These comments were discussed in

Notice No. SC-95-04-NE published in the Federal Register on November

27, 1995 (FR 60 58204). As a result of those comments, changes to the

proposals and for clarification in certain sections of the special

conditions were made. The FAA has determined that those changes made to

the special conditions for AE Model 250 engine are also applicable to

Turbomeca Arriel Model 2S1 engine and therefore they are adopted in

this Final special conditions. In addition, some editorial changes have

also been made to section 33.27 of this Final special condition for

clarification.

After careful review of the available data, the FAA determined that

air safety and the public interest require the adoption of the special

conditions with the changes described previously.

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.

PART 33--[AMENDED]

The authority citation for these special conditions continues to

read 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 the Turbomeca Model 2S1 turboshaft

engine:

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. 33.7 Engine Ratings and Operating Limitations.

In addition to the requirements of section 33.7, the following

ratings are defined as:

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(a) Rated 30-Second one engine inoperative (OEI) power: The

approved brake horsepower developed under static conditions at

specified altitudes and temperatures within the operating limitations

established for the engine under part 33 and this special conditions,

for continued one-flight operation after the failure of one engine in

multi-engine rotorcraft, limited to three periods of use, no longer

than 30 seconds each, in any one flight, and followed by mandatory

inspection and prescribed maintenance action.

(b) Rated 2-Minute OEI power: The approved brake horsepower,

developed under static conditions at specified altitudes and

temperatures, within the operating limitations established for the

engine under part 33 and this special conditions, for continued one-

flight operation after the failure of one engine in multi-engine

rotorcraft, limited to three periods of use, of no longer than 2

minutes each in any one flight, and followed by mandatory inspection

and prescribed maintenance action.

Sec. 33.27 Turbine, Compressor, Fan, and Turbo-supercharger Rotors.

For 2-minute and 30-second OEI ratings, in addition to the

requirements of section 33.27(b), turbine and compressor rotors must

have sufficient strength to withstand the conditions specified in one

of the following tests for the most critically stressed rotor component

of each turbine and compressor including integral drum rotors and

centrifugal compressor, as determined by analysis or other acceptable

means. The selection of the test from the following paragraph (a) or

(b) of this section is determined by the speed defined in paragraph

(a)(2) or (b)(2), whichever is higher.

(a) Test for a period of two and one-half minutes--

(1) At its maximum operating temperature except as provided in

paragraph 33.27(c)(2)(iv); and

(2) At the highest speed determined, in accordance with section

33.27(c)(2) (i) through (iv).

(3) This test may be performed using a separate test vehicle as

desired.

(b) Test for a period of 5 minutes--

(1) At its maximum operating temperature except as provided in

paragraph 33.27(c)(2)(iv); and

(2) 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, and

(3) The test speed must take into account minimum material

properties, maximum operating temperature, and the most adverse

dimensional tolerances.

(4) This test may be performed using a separate test vehicle as

desired.

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

have a provision for a means to:

(a) Alert the pilot when the engine is at the 30-Second OEI and a

2-Minute OEI power levels;

(b) Determine, in a positive manner, that the engine has been

operated at each rating; and

(c) Determine the elapsed time of operation of each rating.

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 functioning of both of these means.

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 the highest

physical or corrected rotational speeds, the surveys shall be extended

sufficiently to reveal the maximum stress values present except that

the extension needs not cover more than a further 2 percent beyond

those speed.

Sec. 33.85 Calibration Test.

In addition to the requirements of section 33.85, tests performed

at the 30-Second and 2-Minute OEI ratings, during the applicable

additional endurance test prescribed in section 33.87 as amended by

these special conditions, 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.

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

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additional testing of section 33.87. The engine must comply with

section 33.93(a), but it 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 April 3, 1996.

James C. Jones,

Acting Manager, Engine & Propeller Directorate, Aircraft Certification

Service.

[FR Doc. 96-9252 Filed 4-12-96; 8:45 am]

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