Airworthiness Directives; Turbomeca Arriel 1 Series Turboshaft Engines

DEPARTMENT OF TRANSPORTATION

14 CFR Part 39

[Docket No. 94-ANE-08]

Airworthiness Directives; Turbomeca Arriel 1 Series Turboshaft

Engines

AGENCY: Federal Aviation Administration, DOT.

ACTION: Notice of proposed rulemaking (NPRM).

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SUMMARY: This document proposes the supersedure of an existing

airworthiness directive (AD), applicable to Turbomeca Arriel 1 series

turboshaft engines, that currently requires repetitive checks for

engine rubbing noise during gas generator shutdown, and for free

rotation of the gas generator by rotating the compressor manually after

the last flight of the day. This action would continue to require these

checks, but eliminates the reference to the Turbomeca service bulletin,

allows the pilot to perform all the checks required in this proposed

rule, clarifies the inspection interval requirement for daily checks,

and specifies terminating action for the repetitive checks required by

this AD. In addition, this action would allow the check for engine

rubbing noise to be performed during engine motoring, and specifies

that the engine turbine (T4) temperature must be below 150 degrees

Centigrade when performing the check for free rotation. This proposal

is prompted by comments submitted by operators of the affected engines

in response to the existing AD and the availability of an improved

design 2nd stage nozzle guide vane. The actions specified by the

proposed AD are intended to prevent engine failure due to rubbing of

the 2nd stage turbine disk on the 2nd stage turbine nozzle guide vane,

which could result in complete engine failure and damage to the

aircraft.

DATES: Comments must be received by November 7, 1994.

ADDRESSES: Submit comments in triplicate to the Federal Aviation

Administration (FAA), New England Region, Office of the Assistant Chief

Counsel, Attention: Rules Docket No. 94-ANE-08, 12 New England

Executive Park, Burlington, MA 01803-5299. Comments may be inspected at

this location between 8:00 a.m. and 4:30 p.m., Monday through Friday,

except Federal holidays.

The service information referenced in the proposed rule may be

obtained from Turbomeca, 64511 Bordes Cedex - France. This information

may be examined at the FAA, New England Region, Office of the Assistant

Chief Counsel, 12 New England Executive Park, Burlington, MA.

FOR FURTHER INFORMATION CONTACT: Mark Rumizen, Aerospace Engineer,

Engine Certification Office, FAA, Engine and Propeller Directorate, 12

New England Executive Park, Burlington, MA 01803-5299; telephone (617)

238-7137, fax (617) 238-7199.

SUPPLEMENTARY INFORMATION:

Comments Invited

Interested persons are invited to participate in the making of the

proposed rule 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 above. All

communications received on or before the closing date for comments,

specified above, will be considered before taking action on the

proposed rule. The proposals 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 rule. All

comments submitted will be available, both before and after the closing

date for comments, in the Rules Docket for examination by interested

persons. A report summarizing each FAA-public contact concerned with

the substance of this proposal will be filed in the Rules Docket.

Commenters wishing the FAA to acknowledge receipt of their comments

submitted in response to this notice must submit a self-addressed,

stamped postcard on which the following statement is made: ``Comments

to Docket Number 94-ANE-08.'' The postcard will be date-stamped and

returned to the commenter.

Availability of NPRMs

Any person may obtain a copy of this NPRM by submitting a request

to the FAA, New England Region, Office of the Assistant Chief Counsel,

Attention: Rules Docket No. 94-ANE-08, 12 New England Executive Park,

Burlington, MA 01803-5299.

Discussion

On November 19, 1993, the Federal Aviation Administration (FAA)

issued airworthiness directive (AD) 93-23-09, Amendment 39-8745 (58 FR

63061, November 30, 1993), applicable to Turbomeca Arriel 1 series

turboshaft engines, to require repetitive checks for engine rubbing

noise during gas generator shutdown, and for free rotation of the gas

generator by rotating the compressor manually after the last flight of

the day. That action was prompted by a report of a Turbomeca Arriel 1B

engine failure, which resulted in the crash of an Aerospatiale AS350B

helicopter. That condition, if not corrected, could result in engine

failure due to rubbing of the 2nd stage turbine disk on the 2nd stage

turbine nozzle guide vane, which could result in complete engine

failure and damage to the aircraft.

Since the issuance of that AD, the FAA has received a significant

number of comments from operators of the affected engines indicating

that the performance of the checks required by this AD are within the

capabilities of the pilot. The FAA has also determined that

instructions contained in the AD are adequate for performance of

required actions, and the Turbomeca Service Bulletin (SB) No. 72 292

0181 need not be incorporated by reference. Other comments indicated

that the interval specified in the existing AD, ``after the last flight

of the day,'' is not consistent with operating and maintenance

schedules for operators who typically operate ``around the clock'' on a

24 hours per day basis, such as medevac or police operators. In

response to these comments, a ``daily'' interval has been specified for

this check.

In addition, operators reported difficulty in listening for rubbing

noises during engine shutdown, and that this check could be

accomplished during engine motoring. The FAA has also determined that

the check for free rotation must be accomplished on a cold engine due

to the variation of rotating component clearances with engine

temperature. Finally, the manufacturer has completed testing and

analysis, and has accumulated sufficient field experience to

substantiate the design of the improved 2nd stage nozzle guide vane.

This AD would require installation of modification TU 202, which

incorporates an improved 2nd stage nozzle guide vane manufactured from

a new material that is more resistant to fatigue cracking, at the next

engine overhaul after the effective date of this AD, but not later than

December 31, 1999, as terminating action for the repetitive checks.

This calendar end-date is based upon parts availability.

Turbomeca has issued SB No. 292 72 0150, dated April 10, 1992, that

specifies installing an improved design 2nd stage nozzle guide vane.

This engine model is manufactured in France and is type

certificated for operation in the United States under the provisions of

Section 21.29 of the Federal Aviation Regulations (14 CFR 21.29) and

the applicable bilateral airworthiness agreement in effect at the time

of type certification. The Direction Generale de L'Aviation Civile

(DGAC), which is the airworthiness authority for France, has kept the

FAA informed of the situation described above. The FAA has examined the

findings of the DGAC, reviewed all available information, and

determined that AD action is necessary for products of this type design

that are certificated for operation in the United States.

Since an unsafe condition has been identified that is likely to

exist or develop on other products of this same type design, the

proposed AD would supersede AD 93-23-09 to continue to require

repetitive checks for engine rubbing noise during gas generator

shutdown, and for free rotation of the gas generator by rotating the

compressor manually at a daily interval until installation of the

improved 2nd stage nozzle guide vane.

This proposed AD would allow pilots to perform all the required

checks. This action does not require special training beyond that

already incurred by pilots of the aircraft having affected engines, or

the use of tools or special measuring equipment, or reference to

technical data. Accordingly, the FAA has determined that pilots may

perform all the checks required by this proposed rule as an exception

to Sec. 43.3 of the Federal Aviation Regulations (14 CFR 43.3)

regarding the performance of maintenance.

The FAA estimates that 160 engines installed on aircraft of U.S.

registry would be affected by this proposed AD, that it would take

approximately 0.2 work hours per engine to accomplish the proposed

actions, and that the average labor rate is $55 per work hour. Required

parts would cost approximately $8,000 per engine. Based on an assumed

utilization rate and an assumed modification rate, the total cost

impact of the proposed AD on U.S. operators over the five year

compliance period is estimated to be $3,101,600.

The regulations proposed herein would not have substantial direct

effects on the States, on the relationship between the national

government and the States, or on the distribution of power and

responsibilities among the various levels of government. Therefore, in

accordance with Executive Order 12612, it is determined that this

proposal would not have sufficient federalism implications to warrant

the preparation of a Federalism Assessment.

For the reasons discussed above, I certify that this proposed

regulation (1) is not a ``significant regulatory action'' under

Executive Order 12866; (2) is not a ``significant rule'' under the DOT

Regulatory Policies and Procedures (44 FR 11034, February 26, 1979);

and (3) if promulgated, will not have a significant economic impact,

positive or negative, on a substantial number of small entities under

the criteria of the Regulatory Flexibility Act. A copy of the draft

regulatory evaluation prepared for this action is contained in the

Rules Docket. A copy of it may be obtained by contacting the Rules

Docket at the location provided under the caption ADDRESSES.

List of Subjects in 14 CFR Part 39

Air transportation, Aircraft, Aviation safety, Safety.

The Proposed Amendment

Accordingly, pursuant to the authority delegated to me by the

Administrator, the Federal Aviation Administration proposes to amend

part 39 of the Federal Aviation Regulations (14 CFR part 39) as

follows:

PART 39--AIRWORTHINESS DIRECTIVES

1. The authority citation for part 39 continues to read as follows:

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

106(g); and 14 CFR 11.89.

Sec. 39.13 [Amended]

2. Section 39.13 is amended by removing amendment 39-8745 (58 FR

63061, November 30, 1993) and by adding a new airworthiness directive

to read as follows:

Turbomeca: Docket No. 94-ANE-08. Supersedes AD 93-23-09,

Amendment 39-8745.

Applicability: Turbomeca Arriel turboshaft engines Models 1B

that do have modification TU 76 but do not have modification TU 197

or TU 202; Arriel Models 1D and 1D1 that do not have modification TU

197 or TU 202; Arriel Models 1A, 1A1, 1A2 that have had modification

TU 76 but do not have modification TU 197 or TU 202; and Arriel

Models 1C, 1C1, and 1C2 that do not have TU 197 or TU 202. These

engines are installed on but not limited to Aerospatiale Models

AS350B, SA365, and AS565 helicopters.

Compliance: Required as indicated, unless accomplished

previously.

To prevent engine failure due to rubbing of the 2nd stage

turbine disk on the 2nd stage turbine nozzle guide vane, which could

result in engine failure and damage to the aircraft, accomplish the

following:

(a) For Turbomeca Arriel turboshaft engines Models 1B that have

modification TU 76 but do not have modification TU 197 or TU 202;

and Arriel Models 1D and 1D1 that do not have modification TU 197 or

TU 202; accomplish the following:

(1) Perform a daily check for unusual engine rubbing noises

during gas generator shutdown or as engine gas generator speed

decreases after completion of engine motoring.

(2) Perform a daily check for free rotation of the gas

generator, when T4 temperature is below 150 degrees Centigrade, by

rotating the compressor manually.

(3) While checking for free rotation of the gas generator,

perform a check for engine rubbing noise.

(b) For Turbomeca Arriel turboshaft engines Models 1A, 1A1, 1A2

that have modification TU 76 but do not have modification TU 197 or

TU 202; and Arriel Models 1C, 1C1, and 1C2 that do not have

modification TU 197 or TU 202; accomplish the following:

(1) Within 50 hours time in service (TIS) after the effective

date of this AD, perform a check for unusual engine rubbing noise

during gas generator shutdown or within 5 seconds after engine

motoring.

(2) Thereafter, at intervals not to exceed 50 hours TIS since

the last check, perform a check for unusual engine rubbing noise

during gas generator shutdown or within 5 seconds after engine

motoring.

(3) Perform a daily check for free rotation of the gas generator

when T4 temperature is below 150 degrees C, by rotating the

compressor manually.

(4) While checking for free rotation of the gas generator,

perform a check for engine rubbing noise.

(c) If any engine rubbing noise is detected during the checks

required by paragraphs (a) and (b) of this AD, prior to further

flight replace gas generator module M03 with a serviceable module.

(d) Install the improved 2nd stage nozzle guide vane,

modification TU 202, at the next engine overhaul after the effective

date of this AD, but not later than December 31, 1999, in accordance

with Turbomeca Service Bulletin 292 72 0150, dated April 10, 1992.

Installation of this hardware constitutes terminating action to the

checks required by this AD.

(e) The checks required by paragraphs (a) and (b) of this AD may

be performed by the pilot holding at least a private pilot

certificate as an exception to the requirements of part 43 of the

Federal Aviation Regulations (14 CFR part 43). The checks must be

recorded in accordance with Sections 43.9 and 91.417(a)(2)(v) of the

Federal Aviation Regulations (14 CFR 43.9 and 14 CFR

91.417(a)(2)(v)), and the records must be maintained as required by

the applicable Federal Aviation Regulation.

(f) An alternative method of compliance or adjustment of the

compliance time that provides an acceptable level of safety may be

used if approved by the Manager, Engine Certification Office. The

request should be forwarded through an appropriate FAA Principal

Maintenance Inspector, who may add comments and then send it to the

Manager, Engine Certification Office.

Note: Information concerning the existence of approved

alternative methods of compliance with this airworthiness directive,

if any, may be obtained from the Engine Certification Office.

(g) Special flight permits may be issued in accordance with

sections 21.197 and 21.199 of the Federal Aviation Regulations (14

CFR 21.197 and 21.199) to operate the aircraft to a location where

the requirements of this AD can be accomplished.

Issued in Burlington, Massachusetts, on August 24, 1994.

Jay J. Pardee,

Manager, Engine and Propeller Directorate, Aircraft Certification

Service.

[FR Doc. 94-21869 Filed 9-2-94; 8:45 am]

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