Airworthiness Directives; General Electric Company CF6 Series Turbofan Engines

DEPARTMENT OF TRANSPORTATION

14 CFR Part 39

[Docket No. 93-ANE-69]

Airworthiness Directives; General Electric Company CF6 Series

Turbofan Engines

AGENCY: Federal Aviation Administration, DOT.

ACTION: Notice of proposed rulemaking (NPRM).

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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 repetitive

inspections of the left compressor discharge pressure (CDP) manifold

and lower CDP tube for cracks, and if found cracked, rework or

replacement with serviceable parts. This proposal would also require

rework or replacement of the left CDP manifold, lower CDP tube, stage

14 turnbuckle, and other related CDP bleed air hardware, and inspection

of the compressor rear frame (CRF) as a terminating action to the

inspection program. This proposal is prompted by reports of cracks in

the left CDP manifold, lower CDP tube, and CRF bleed port struts, that

have resulted in inflight engine shutdowns and rejected takeoffs. The

actions specified by the proposed AD are intended to prevent cracks in

the left CDP manifold, lower CDP tube, and CRF bleed port struts, which

could result in an inflight engine shutdown, rejected takeoff, or

damage to the engine nacelle.

DATES: Comments must be received by March 14, 1993.

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-69, 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 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 93-ANE-69.'' 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-69, 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. The Federal

Aviation Administration (FAA) has received 228 reports of cracks in the

left compressor discharge pressure (CDP) manifold, lower CDP tube, and

compressor rear frame (CRF) bleed port struts. Of these 228 reports, 24

have resulted in inflight engine shutdowns, and 24 in rejected

takeoffs. The current type design hardware has been found to crack,

allowing hot air to leak into the core cowl area, resulting in false

fire warnings.

The cracks in the current type design hardware are the result of

high cycle fatigue (HCF). The excessive stress is the result of both

thermal and airframe installation loading factors. New hardware exists

which decreases operating stresses, therefore reducing the chance of

cracks due to HCF. This condition, if not corrected, may result in

cracks in the left CDP manifold, lower CDP tube, and CRF bleed port

struts, which could result in an inflight engine shutdown, rejected

takeoff, or damage to the engine nacelle.

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

50 Service Bulletin (SB) No. 75-065, Revision 1, dated March 26, 1993,

that describes procedures for rework or replacement of the left CDP

manifold, lower CDP tube, and other related CDP bleed air hardware, and

inspection of the CRF bleed port struts; GE CF6-50 SB No. 75-067, dated

March 15, 1993, that describes procedures for rework or replacement of

the stage 14 turnbuckle; and GE CF6-50 SB No. 75-064, Revision 2, dated

July 23, 1992, that describes procedures for repetitive inspections of

the left CDP manifold and lower CDP tube for cracks.

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 require repetitive inspections of the left CDP

manifold and lower CDP tube for cracks, and if found cracked, rework or

replacement with serviceable parts. This proposal would also require

rework or replacement of the left CDP manifold, lower CDP tube, stage

14 turnbuckle, and other related CDP bleed air hardware, and inspection

of the CRF as a terminating action to the inspection program. The

compliance end-date of October 31, 1996, is proposed to ensure timely

compliance. Based upon engine shop visit rates, a compliance end-date

of October 31, 1996, will ensure timely compliance while minimizing the

number of forced engine removals. The actions would be required to be

accomplished in accordance with the service bulletins described

previously.

There are approximately 2202 GE CF6-45/-50 series engines of the

affected design in the worldwide fleet. The FAA estimates that 223

engines installed on aircraft of U.S. registry would be affected by

this proposed AD, that it would take approximately 2 work hours per

engine to accomplish the proposed inspections, 32 work hours per engine

to accomplish the proposed terminating action, and that the average

labor rate is $55 per work hour. Required parts would cost

approximately $27,500 per engine. Based on these figures, the total

cost impact of the proposed AD on U.S. operators is estimated to be

$6,549,510.

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 adding the following new

airworthiness directive:

General Electric Company: Docket No. 93-ANE-69.

Applicability: General Electric Company (GE) CF6-5/-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 cracks in the left compressor discharge pressure

(CDP) manifold, lower CDP tube, and the compressor rear frame (CRF)

bleed port struts, which could result in an inflight engine

shutdown, rejected takeoff, or damage to the engine nacelle,

accomplish the following:

(a) Inspect the left CDP manifold, Part Number (P/N) 9057M84G02

and 9057M84G03, and lower CDP tube, P/N 9068M40G01, in accordance

with GE CF6-50 Service Bulletin (SB) No. 75-064, Revision 2, dated

July 23, 1992, within the next 500 hours time in service (TIS) or

150 cycles in service (CIS) after the effective date of this

airworthiness directive (AD), whichever occurs later. Thereafter,

inspect at intervals not to exceed 500 hours TIS or 150 CIS since

the last inspection, whichever occurs later.

(b) For left CDP manifolds and lower CDP tubes found cracked,

accomplish the following prior to further flight:

(1) Rework or replace the left CDP manifold, lower CDP tube, and

other related CDP bleed air hardware, and fluorescent penetrant

inspect (FPI) the CRF in accordance with GE CF6-50 SB No. 75-065,

Revision 1, dated March 26, 1993. For CRF's found cracked, either

repair in accordance with GE CF6-50 Task Number Shop Manual, GEK

50481, Chapter 72-34-01, or replace with a serviceable part.

(2) Rework or replace the stage 14 turnbuckle, P/N 1555M42P01,

in accordance with GE CF6-50 SB No. 75-067, dated March 15, 1993.

(c) Rework or replace the left CDP manifold, P/N 9057M84G02 and

9057M84G03, lower CDP tube, P/N 9068M40G01, and other related CDP

bleed air hardware, and FPI the CRF in accordance with GE CF6-50 SB

No. 75-065, Revision 1, dated March 26, 1993, at the next engine

shop visit, or by October 31, 1996, whichever occurs earlier. For

CRF's found cracked, either repair in accordance with GE CF6-50 Task

Number Shop Manual, GEK 50481, Chapter 72-34-01, or replace with a

serviceable part.

(d) Rework or replace the stage 14 turnbuckle, P/N 1555M42P01,

in accordance with GE CF6-50 SB No. 75-067, dated March 15, 1993, at

the next engine shop visit, or by October 31, 1996, whichever occurs

earlier.

(e) Rework or replacement of the left CDP manifold, lower CDP

tube, and stage 14 turnbuckle, in accordance with paragraph (b), or

paragraphs (c) and (d), as applicable, of this AD constitutes

terminating action to the repetitive inspections required in

paragraph (a) of this AD.

(f) For the purpose of this AD, an engine shop visit is defined

as the induction of an engine into a shop for maintenance involving

the separation of any major module.

(g) 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.

(h) Special flight permits may be issued in accordance with FAR

21.197 and 21.199 to operate the airplane to a location where the

requirements of this AD can be accomplished.

Issued in Burlington, Massachusetts, on December 27, 1993.

Jay J. Pardee,

Acting Manager, Engine and Propeller Directorate, Aircraft

Certification Service.

[FR Doc. 94-588 Filed 1-10-94; 8:45 am]

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