Airworthiness Directives; General Electric Company CF6 Series Turbofan Engines

SUMMARY: This document proposes the adoption of a new airworthiness

directive (AD) that is applicable to General Electric Company (GE) CF6-

45/-50 series turbofan engines. This proposal would require a reduction

of the low cycle fatigue (LCF) retirement lives for certain high

pressure turbine rotor (HPTR) stage 2 disks, and would provide a

drawdown schedule for those affected parts with reduced LCF retirement

lives. This proposal is prompted by the results of a refined life

analysis performed by the manufacturer which revealed minimum

calculated LCF lives significantly lower than published LCF retirement

lives. The actions specified by the proposed AD are intended to prevent

a LCF failure of the HPTR stage 2 disk, which could result in an

uncontained engine failure and damage to the aircraft.

DATES: Comments must be received by February 21, 1995.

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-37, 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 General Electric Aircraft Engines, CF6 Distribution

Clerk, Room 132, 111 Merchant Street, Cincinnati, OH 45246. 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: Robert J. Ganley, Aerospace Engineer,

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

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

238-7138; 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-37.'' 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-37, 12 New England Executive Park,

Burlington, MA 01803-5299.

Discussion

This proposed airworthiness directive (AD) is applicable to General

Electric Company (GE) CF6-45/-50 series turbofan engines. A study

performed by the manufacturer using updated life analyses for the high

pressure turbine rotor (HPTR) stage 2 disk has revealed minimum

calculated low cycle fatigue (LCF) lives which are significantly lower

than published LCF retirement lives. This condition, if not corrected,

could result in a LCF failure of the HPTR stage 2 disk, which could

result in an uncontained engine failure and damage to the aircraft.

The FAA has reviewed and approved the technical contents of GE CF6-

50 Service Bulletin (SB) No. 72-1069, dated September 12, 1994, that

describes a reduction in the published LCF retirement lives for

affected HPTR stage 2 disks, and an FAA-approved rework procedure for

the affected disks to increase the FAA-approved LCF retirement life to

8,750 or 9,700 cycles since new (CSN), depending on the CSN of the disk

when the rework is performed.

Since an unsafe condition has been identified that is likely to

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

proposed AD would require a reduction of the published LCF retirement

lives for certain HPTR stage 2 disks, and would provide a drawdown

schedule for those affected disks with reduced LCF retirement lives. If

the FAA-approved rework is accomplished, the LCF retirement life may be

increased to 8,750 or 9,700 cycles, depending on the CSN of the disk

when the rework is performed. The actions would be required to be

accomplished in accordance with the service bulletin described

previously.

The FAA estimates that 280 engines installed on aircraft of U.S.

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

approximately 194 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 $16,383 per engine. Based on these

figures, the total cost impact of the proposed AD on U.S. operators is

estimated to be $7,574,840.

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 adding the following new

airworthiness directive:

General Electric Company: Docket No. 94-ANE-37.

Applicability: General Electric Company (GE) CF6-45/-50 series

turbofan engines installed on but not limited to Airbus A300 series,

Boeing 747 series, and McDonnell Douglas DC-10 series aircraft.

Compliance: Required as indicated, unless accomplished

previously.

To prevent a low cycle fatigue (LCF) failure of the high

pressure turbine rotor (HPTR) stage 2 disk, which could result in an

uncontained engine failure and damage to the aircraft, accomplish

the following:

(a) Remove from service HPTR stage 2 disks Part Numbers (P/N)

1474M49P04, 1474M49P05, 1474M49P06, 9045M35P15, 9045M35P17, and

9045M35P18, in accordance with the following:

(1) For disks that have accumulated less than 3,500 cycles since

new (CSN) on the effective date of this airworthiness directive

(AD), remove disk from service prior to accumulating 7,080 CSN.

(2) For disks that have accumulated 3,500 CSN or more, but less

than 7,080 CSN on the effective date of this AD, remove disk from

service prior to accumulating 7,080 CSN, or prior to accumulating

3,100 cycles in service (CIS) after the effective date of this AD,

whichever occurs later, but not to exceed 9,700 CSN.

(3) For disks which have accumulated 7,080 CSN or more on the

effective date of this AD, remove disk from service at the next

piece-part exposure, but not to exceed 9,700 CSN.

(b) Remove from service HPTR stage 2 disks P/N 9264M58P01,

9264M58P02, and 9264M58P03 prior to accumulating 7,080 CSN.

(c) This AD establishes the following new LCF retirement lives

which will be published in Chapter 5 of the CF6-50 Engine Task

Numbered Shop Manual, GEK 50481: 7,080 cycles for HPTR stage 2 disk

P/N 1474M49P04, 1474M49P05, 1474M49P06, 9045M35P15, 9045M35P17,

9045M35P18, 9264M58P01, 9264M58P02, and 9264M58P03.

(d) GE CF6-50 Service Bulletin (SB) No. 72-1069, dated September

12, 1994, describes an FAA-approved rework procedure for the

affected disks. Accomplishment of this rework increases the FAA-

approved LCF retirement life to 8,750 or 9,700 cycles, depending on

the CSN of the disk when the rework is performed.

(e) 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.

(f) 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 December 14, 1994.

Kirk E. Gustafson,

Acting Manager, Engine and Propeller Directorate, Aircraft

Certification Service.

[FR Doc. 94-31181 Filed 12-19-94; 8:45 am]

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