Airworthiness Directives; General Electric Company CF6 Series Turbofan Engines

DEPARTMENT OF TRANSPORTATION

14 CFR Part 39

[Docket No. 94-ANE-11]

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 notice proposes the supersedure of an existing

airworthiness directive (AD), applicable to General Electric Company

(GE) CF6-45/-50/-80A series turbofan engines, that currently requires a

one-time ultrasonic and eddy current inspection of the high pressure

compressor rotor (HPCR) stage 3-9 spool for cracks. This action would

retain the inspection requirements of the current AD, but would

accelerate the inspection schedule, and introduce a repetitive

inspection requirement. This proposal is prompted by a review of the

inspection results to date, which indicate that the crack occurrence

rate is higher than initially projected. The actions specified by the

proposed AD are intended to prevent an uncontained HPCR stage 3-9 spool

failure, which could result in damage to the aircraft.

DATES: Comments must be received by June 2, 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-11, 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 94-ANE-11.'' 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-11, 12 New England Executive Park,

Burlington, MA 01803-5299.

Discussion

On October 25, 1991, the Federal Aviation Administration (FAA)

issued airworthiness directive (AD) 91-20-01, Amendment 39-8035 (56 FR

55230), to require a one-time ultrasonic and eddy current inspection of

the high pressure compressor rotor (HPCR) stage 3-9 spool for cracks.

That action was prompted by two reports of spools found cracked in

service. That condition, if not corrected, could result in an

uncontained HPCR stage 3-9 spool failure, which could result in damage

to the aircraft.

Since the issuance of that AD, the FAA has received reports of five

additional spools found cracked in service. Investigation indicates

that the cracks initiated in sub-surface origins in the stage 9 bore

region of the spool. These cracks form from metallurgical anomalies

that result from reduced forging work associated with the sixteen inch

billet material used in the manufacture of certain HPCR stage 3-9

spools.

Based on the investigation findings, and the higher than projected

crack occurrence rates, the FAA has determined that the inspection

schedule in the current AD should be accelerated, and a repetitive

inspection requirement be implemented.

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

50 Service Bulletin (SB) No. 72-1000, Revision 2, dated September 9,

1993, and GE CF6-80A SB No. 72-583, Revision 4, dated September 15,

1993, which describe procedures for the ultrasonic and eddy current

inspection of the HPCR stage 3-9 spool.

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 91-20-01, would retain the one-time

ultrasonic and eddy current inspection of the HPCR stage 3-9 spool for

cracks as required in the current AD, but would accelerate the

inspection schedule, and introduce a repetitive ultrasonic and eddy

current inspection requirement.

There are approximately 462 GE CF6-45/-50/-80A series engines of

the affected design in the worldwide fleet. The FAA estimates that 67

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

proposed AD, that it would take approximately 584 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 $127,412 per

engine. Based on these figures, and assuming that 3 of the inspected

spools will require replacement, the total cost impact of the proposed

AD on U.S. operators is estimated to be $2,534,276.

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 ``major rule'' under Executive Order 12291;

(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 39-8035 (56 FR

55230; October 25, 1991) and by adding a new airworthiness directive to

read as follows:

General Electric Company: Docket No. 94-ANE-11. Supersedes AD 91-20-

01, Amendment 39-8035.

Applicability: General Electric Company (GE) CF6-45/-50/-80A

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

A300 and A310 series, Boeing 747 and 767 series, and McDonnell

Douglas DC-10 series aircraft.

Compliance: Required as indicated, unless accomplished

previously.

To prevent an uncontained high pressure compressor rotor (HPCR)

stage 3-9 spool failure, which could result in damage to the

aircraft, accomplish the following:

(a) Eddy current and ultrasonic inspect GE CF6-45/-50 HPCR stage

3-9 spools, Part Number (P/N) 9136M89G02, 9136M89G03, 9136M89G06,

9136M89G08, 9253M85G01, 9253M85G02, 9273M14G01, and 9331M29G01, with

serial numbers (S/N) listed in Table 2 of GE CF6-50 Service Bulletin

(SB) No. 72-1000, Revision 2, dated September 9, 1993, as follows:

(1) For spools that have not been previously inspected in

accordance with GE CF6-50 SB No. 72-888, Original, Revision 1,

Revision 2, Revision 3, or Revision 4, or GE CF6-50 SB No. 72-1000,

Original, Revision 1, or Revision 2, inspect in accordance with

paragraph 2.C of GE CF6-50 SB No. 72-1000, Revision 2, dated

September 9, 1993, at the next engine shop visit, or by 30 days

after the effective date of this AD, whichever occurs earlier.

(2) For spools that have been inspected in accordance with GE

CF6-50 SB No. 72-888, Original, Revision 1, or Revision 2, inspect

in accordance with paragraph 2.D of GE CF6-50 SB No. 72-1000,

Revision 2, dated September 9, 1993, at the next engine shop visit,

or by December 31, 1994, whichever occurs earlier.

(3) For spools that have been inspected in accordance with GE

CF6-50 SB No. 72-888, Original, Revision 1, or Revision 2, and GE

CF6-50 SB No. 72-1008, Original, inspect in accordance with

paragraph 2.D of GE CF6-50 SB No. 72-1000, Revision 2, dated

September 9, 1993, at the next piece-part exposure, or within 3,500

cycles in service (CIS) since inspected in accordance with GE CF6-50

SB No. 72-1008, Original, whichever occurs earlier.

(4) For spools that have been inspected in accordance with GE

CF6-50 SB No. 72-888, Revision 3, or Revision 4, or GE CF6-50 SB No.

72-1000, Original, Revision 1, or Revision 2, inspect in accordance

with paragraph 2.D of GE CF6-50 SB No. 72-1000, Revision 2, dated

September 9, 1993, at the next piece-part exposure, or within 3,500

CIS since inspected in accordance with, GE CF6-50 SB No. 72-888,

Revision 3, or Revision 4, or GE CF6-50 SB No. 72-1000, Original,

Revision 1, or Revision 2, whichever occurs earlier.

(b) Thereafter, for spools that have been inspected in

accordance with paragraph (a) of this AD, reinspect in accordance

with paragraph 2.D of GE CF6-50 SB No. 72-1000, Revision 2, dated

September 9, 1993, at intervals not to exceed 3,500 CIS since the

last inspection.

(c) Eddy current and ultrasonic inspect GE CF6-80A HPCR 3-9

spool, P/N 9136M89G10, with S/N's listed in Table 2 of GE CF6-80A SB

No. 72-583, Revision 4, dated September 15, 1993, as follows:

(1) For spools that have not been previously inspected in

accordance with GE CF6-80A SB No. 72-500, Original, Revision 1,

Revision 2, Revision 3, or Revision 4, or GE CF6-80A SB No. 72-583,

Original, Revision 1, Revision 2, Revision 3, or Revision 4, inspect

in accordance with paragraph 2.C of GE CF6-80A SB No. 72-583,

Revision 4, dated September 15, 1993, at the next engine shop visit,

or by 30 days after the effective date of this AD, whichever occurs

earlier.

(2) For spools that have been previously inspected in accordance

with GE CF6-80A SB No. 72-500, Revision 3, or Revision 4, or GE CF6-

80A SB No. 72-583, Original, Revision 1, Revision 2, Revision 3, or

Revision 4, inspect in accordance with paragraph 2.D of GE CF6-80A

SB No. 72-583, Revision 4, dated September 15, 1993, at the next

piece-part exposure, or within 3,500 CIS since inspected in

accordance with GE CF6-80A SB No. 72-500, Revision 3, or Revision 4,

or GE CF6-80A SB No. 72-583, Original, Revision 1, Revision 2,

Revision 3, or Revision 4, whichever occurs earlier.

(d) Thereafter, for spools that have been inspected in

accordance with paragraph (c) of this AD, reinspect in accordance

with paragraph 2.D of GE CF6-80A SB No. 72-583, Revision 4, dated

September 15, 1993, at intervals not to exceed 3,500 CIS since the

last inspection.

(e) Remove from service prior to further flight HPCR stage 3-9

spools that meet or exceed the reject criteria established in

Section 2.C and 2.D, as applicable, of GE CF6-50 SB No. 72-1000,

Revision 2, dated September 9, 1993, and GE CF6-80A SB No. 72-583,

Revision 4, dated September 15, 1993, as appropriate.

(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 flange.

(g) For the purpose of this AD, piece-part exposure is defined

as disassembly and removal of the stage 3-9 spool from the HPCR

rotor.

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

compliance time, which provides an acceptable level of safety, may

be used when 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 alternate

methods of compliance with this airworthiness directive, if any, may

be obtained from the Engine Certification Office.

(i) Special flight permits may be issued, in accordance with 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 April 26, 1994.

Jay J. Pardee,

Manager, Engine and Propeller Directorate, Aircraft Certification

Service.

[FR Doc. 94-10503 Filed 5-2-94; 8:45 am]

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