Airworthiness Directives; Turbomeca Arriel 1 Series Turboshaft Engines

DEPARTMENT OF TRANSPORTATION

14 CFR Part 39

[Docket No. 93-ANE-78]

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 a gearbox chip detector

inspection prior to further flight, subsequent inspection at designated

intervals, and if necessary, removal of the gearbox, and also requires

modification of the gearbox if not accomplished previously. This action

would require modification to the intermediate gear that would

constitute terminating action to the repetitive chip detector

inspections. On certain engines this proposal would require immediate

modification of the intermediate gear prior to further flight. This

proposal is prompted by the availability of design improvements to the

intermediate gear. The actions specified by the proposed AD are

intended to prevent damage to the aircraft resulting from engine debris

following an uncontained engine failure.

DATES: Comments must be received by May 16, 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. 93-ANE-78, 12 New England

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

this location between 8 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 Engine Corporation, 2709 Forum Drive, Grand

Prairie, TX 75051. 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 A. 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 93-ANE-78.'' 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. 93-ANE-78, 12 New England Executive Park,

Burlington, MA 01803-5299.

Discussion

The Direction Generale de L'aviation Civile (DGAC), which is the

airworthiness authority of France, notified the Federal Aviation

Administration (FAA) that an unsafe condition may exist on Turbomeca

Arriel 1B, 1D, 1D1, 1A with TU13, and 1A1 with TU13, turboshaft

engines. The DGAC advises that they have received reports of seven

inflight engine shutdowns and three uncontained failures of the power

turbine disk. The DGAC also advises that these failures were caused by

failure of the reduction gearbox intermediate gear.

This engine model is manufactured in France and is type

certificated for operation in the United States under the provisions of

Sec. 21.29 of the Federal Aviation Regulations and the applicable

bilateral airworthiness agreement. Pursuant to this bilateral

airworthiness agreement, the DGAC 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.

On June 25, 1992, the FAA issued telegraphic airworthiness

directive (TAD) T92-13-52 to require a gearbox chip detector inspection

prior to further flight, subsequent inspection at intervals not to

exceed 5 hours time in service since the last inspection, and if

necessary, removal of the gearbox. The FAA determined after review of

the results of the investigation and analysis performed by the

manufacturer that these failures are due to high cycle fatigue that

initiates from vibration induced by gear teeth wear. Failure of the

intermediate gear can result in an overspeed condition and possible

failure of the power turbine disk. That condition, if not corrected,

can result in damage to the aircraft resulting from engine debris

following an uncontained engine failure.

On October 26, 1992, the FAA issued AD 92-24-08, Amendment 39-8413

(57 FR 54293, November 18, 1992), to supersede AD T92-13-52. That

action requires gearbox chip detector inspection at intervals not to

exceed 8 hours time in service on TU39 modified gearboxes, and requires

modification of the reduction gearbox to standard TU39, if not already

modified to standard TU39.

Since the issuance of that AD, the manufacturer has developed a

modification to the intermediate gear that will inhibit the gear teeth

wear and consequent vibration-induced high cycle fatigue.

Turbomeca has issued Service Bulletin (SB) No. 292 72 0157, Update

No. 2, dated July 30, 1993, that describes procedures for a gearbox

chip detector inspection to find evidence of metal chips that may

indicate impending gear failure, prohibits further operation of

gearboxes that have not been modified to the TU39 standard, and defines

suspect gearboxes that require rework of the gear train components to

prevent failure. Turbomeca has also issued SB No. 292 72 0169, dated

July 12, 1993, that describes procedures for modification (TU232) of

the intermediate gear.

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 92-24-08 to remove gearboxes that were

overhauled prior to June 1, 1992, within 30 days after the effective

date of this AD. Those gearboxes have intermediate gears that are prone

to gear teeth wear due to mixing of used gear train components with new

components. This proposed AD would also require immediate modification

of certain engines to the TU39 which introduces a thicker web

intermediate gear that is more resistant to HCF failure. Finally, this

proposed AD would also continue to require repetitive inspections of

the chip detector for evidence of metal chips until installation of

modification TU232 to the intermediate gear at the next overhaul or

repair of the reduction gearbox. Installation of modification TU232

would constitute terminating action to the inspection requirements of

this AD.

The FAA estimates that 270 engines installed on aircraft of U.S.

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

approximately 80 work hours per engine to accomplish the proposed

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

Turbomeca has advised the FAA that required parts would be provided at

no cost to the operator. Based on these figures, the total cost impact

of the proposed AD on U.S. operators is estimated to be $1,188,000.

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 14

CFR part 39 of the Federal Aviation Regulations 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 39-8413 (57 FR

54293, November 18, 1992) and by adding a new airworthiness directive

to read as follows:

Turbomeca: Docket No. 93-ANE-78. Supersedes AD 92-24-08, Amendment

39-8413.

Applicability: Turbomeca Arriel Model 1B, 1D, 1D1, 1A with TU13,

and 1A1 with TU13, turboshaft engines installed on but not limited

to Aerospatiale AS-350B helicopters.

Compliance: Required as indicated, unless accomplished

previously.

To prevent damage to the aircraft resulting from engine debris

following an uncontained engine failure, accomplish the following:

(a) For the following Turbomeca Arriel engine models: 1D not

modified to TU232, 1D1 not modified to TU232, 1B modified to TU39

but not modified to TU232, 1A with TU13 modified to TU39 but not

modified to TU232, and 1A1 with TU13 modified to TU39 but not

modified to TU232, accomplish the following:

(1) Except for those engines that have been inspected in

accordance with AD 92-24-08 within 8 hours time in service (TIS)

prior to the effective date of this AD, prior to further flight

remove and inspect the reduction gearbox chip detector for evidence

of metal chips in accordance with Turbomeca Service Bulletin (SB)

No. 292 72 0157, Update No. 2, dated July 30, 1993.

(2) Remove from service reduction gearbox modules that do not

meet the return to service criteria described in Turbomeca SB No.

292 72 0157, Update No. 2, dated July 30, 1993, and replace with a

serviceable part.

(3) Thereafter, at intervals not to exceed 8 hours TIS since the

last inspection, accomplish the following:

(i) Remove and inspect the reduction gearbox chip detector in

accordance with paragraph (a)(1) of this AD.

(ii) Remove from service, if necessary, the reduction gearbox

module in accordance with paragraph (a)(2) of this AD, and replace

with a serviceable part.

(4) At the next overhaul or repair of the reduction gearbox

module after the effective date of this AD, incorporate modification

TU232 in accordance with Turbomeca SB No. 292 72 0169, dated July

12, 1993. Incorporation of modification TU232 constitutes

terminating action to the inspections, and replacement, if

necessary, required in paragraphs (a)(1), (a)(2), and (a)(3) of this

AD.

(b) For the following Turbomeca Arriel engine models: 1B not

modified to TU39, 1A with TU13 not modified to TU39, and 1A1 with

TU13 not modified to TU39, prior to further flight replace reduction

gearbox module No. 5 with a reduction gearbox module No. 5 modified

to standard TU39.

(c) For the following Turbomeca Arriel engine models: 1B, 1A

with TU13, and 1A1 with TU13; with reduction gearbox modules

identified by serial numbers specified in paragraph C.(c) of

Turbomeca SB No. 292 72 0157, Update No. 2, dated July 30, 1993,

that were overhauled prior to June 1, 1992, but not overhauled

between that date and the effective date of this AD, and with less

than 200 hours TIS since overhaul, remove from service and return

for overhaul within 30 days after the effective date of this AD, in

accordance with Turbomeca Service Bulletin (SB) No. 292 72 0157,

Update No. 2, dated July 30, 1993.

(d) 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.

(e) Except for engines specified in paragraph (b) of this AD,

special flight permits may be issued in accordance with FAR 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 March 8, 1994.

Jay J. Pardee,

Manager, Engine and Propeller Directorate, Aircraft Certification

Service.

[FR Doc. 94-5942 Filed 3-14-94; 8:45 am]

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