Airworthiness Directives; General Electric Company; CF6 Series Turbofan Engines

DEPARTMENT OF TRANSPORTATION

14 CFR Part 39

[Docket No. 93-ANE-41; Amendment 39-8907; AD 94-09-18]

Airworthiness Directives; General Electric Company; CF6 Series

Turbofan Engines

AGENCY: Federal Aviation Administration, DOT.

ACTION: Final rule.

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SUMMARY: This amendment adopts a new airworthiness directive (AD),

applicable to General Electric Company (GE) CF6-6/-45/-50 series

turbofan engines, that requires an inspection for cracks in the stage 1

high pressure turbine (HPT) disk rim bolt holes, and stage 2 HPT disk

rim and inner bolt holes; and replacement, if necessary, with

serviceable parts. This amendment is prompted by a report of an

uncontained stage 1 HPT disk failure which resulted in an aborted

takeoff. The actions specified by this AD are intended to prevent an

uncontained stage 1 or stage 2 HPT disk failure, which could result in

an inflight engine shutdown, rejected takeoff, or damage to the

aircraft.

DATES: Effective June 6, 1994.

The incorporation by reference of certain publications listed in

the regulations is approved by the Director of the Federal Register as

of June 6, 1994.

ADDRESSES: The service information referenced in this AD 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 Federal Aviation Administration

(FAA), New England Region, Office of the Assistant Chief Counsel, 12

New England Executive Park, Burlington, MA; or at the Office of the

Federal Register, 800 North Capitol Street NW., suite 700, Washington,

DC.

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: A proposal to amend part 39 of the Federal

Aviation Regulations to include an airworthiness directive (AD) that is

applicable to General Electric Company (GE) CF6-6/-45/-50 series

turbofan engines was published as a notice of proposed rulemaking

(NPRM) in the Federal Register on October 19, 1993 (58 FR 53893). That

action proposed to require an eddy current inspection for cracks in the

stage 1 high pressure turbine (HPT) disk rim bolt holes, and stage 2

HPT disk rim and inner bolt holes; and replacement, if necessary, with

serviceable parts. The inspection, and replacement, if necessary, would

be performed in accordance with GE CF6-6 Service Bulletin (SB) No. 72-

1002, dated February 12, 1993; CF6-6 SB No. 72-1003, Revision 1, dated

June 17, 1993; CF6-50 SB No. 72-1057, Revision 1, dated June 17, 1993;

and CF6-50 SB No. 72-1059, dated February 12, 1993.

Interested persons have been afforded an opportunity to participate

in the making of this amendment. Due consideration has been given to

the comments received.

One commenter supports the rule as proposed.

One commenter states that the compliance end-date of February 28,

1994, in compliance paragraph (b)(6) of the proposed rule should be

replaced by 1,000 cycles in service (CIS) after the effective date of

this AD, in order to avoid forced engine removals. The FAA concurs.

This change is consistent with the results of the failure analysis

performed by the manufacturer, and is supported by the positive

inspection results to date. This final rule has been revised

accordingly.

One commenter states that the compliance end-date of February 28,

1994, in compliance paragraph (b)(6) of the proposed rule should be

extended to one year after the effective date of this AD, in order to

avoid forced engine removals. The FAA concurs in part. The FAA agrees

that the current compliance end-date may cause forced engine removals;

however, an extension of this date alone may still cause an undue

burden on low cycle/low time operators. A cyclic definition in lieu of

a compliance end-date will help alleviate this potential problem. The

manufacturer has informed the FAA that a typical operator accumulates

approximately 1,000 CIS in one year. This change is consistent with the

results of the failure analysis performed by the manufacturer, and is

supported by the positive inspection results to date. Therefore, the

compliance end-date of February 28, 1994, in paragraph (b)(6) in the

proposed rule has been replaced in this final rule by 1,000 CIS after

the effective date of this AD.

Two commenters state that the compliance end-date of May 31, 1994,

in compliance paragraph (a)(1) and (a)(2) should be removed, and 4,500

cycles since new (CSN) should be replaced by 5,400 CSN to avoid forced

engine removals. The FAA concurs. This change is consistent with the

results of the failure analysis performed by the manufacturer, and is

supported by the positive inspection results to date. This final rule

has been revised accordingly.

Two commenters state that the compliance end-date of May 31, 1994,

in compliance paragraph (a)(3) should be replaced by 1,400 CIS after

the effective date of this AD to avoid forced engine removals. The FAA

concurs. This change is consistent with the results of the failure

analysis performed by the manufacturer, and is supported by the

positive inspection results to date. This final rule has been revised

accordingly.

Two commenters state that the compliance end-date of February 28,

1994, in compliance paragraphs (a)(4)(i) and (a)(4)(ii) should be

removed, 3,500 CSN should be replaced by 4,500 CSN, and 3,000 CSN

should be replaced by 3,500 CSN to avoid forced engine removals. The

FAA concurs in part. The FAA agrees that the current compliance end-

date may cause forced engine removals, but the proposed CSN changes are

not consistent with the results of the failure analysis performed by

the manufacturer. The results of this analysis suggest that 3,500 CSN

can be changed to 4,000 CSN; however, 3,000 CSN can not be changed.

This final rule has been revised accordingly.

Two commenters state that the compliance end-date of February 28,

1994, in compliance paragraph (a)(4)(iii) should be replaced by 1,000

CIS after the effective date of this AD, and 3,000 CSN should be

replaced by 3,500 CSN to avoid forced engine removals. The FAA concurs

in part. The FAA agrees that the current compliance end-date may cause

forced engine removals, but the proposed CSN change is not consistent

with the results of the failure analysis performed by the manufacturer.

The results of this analysis suggest that 3,000 CSN can not be changed.

This final rule has been revised accordingly.

One commenter states that the compliance end-date of May 31, 1994,

in compliance paragraphs (a)(5)(i) and (a)(5)(ii) should be removed,

and 4,500 CSN should be replaced by 6,000 CSN to avoid forced engine

removals. The FAA concurs in part. The FAA agrees that the current

compliance end-date may cause forced engine removals, but the proposed

CSN change is not consistent with the results of the failure analysis

performed by the manufacturer. The results of this analysis suggest

that 4,500 CSN can be changed to 5,400 CSN. The final rule has been

revised accordingly.

One commenter states that the compliance end-date of May 31, 1994,

in compliance paragraph (a)(5)(iii) should be replaced by 2,000 CIS

after the effective date of this AD to avoid forced engine removals.

The FAA concurs in part. The FAA agrees that the current compliance

end-date may cause forced engine removals, but the proposed CIS is not

consistent with the results of this failure analysis performed by the

manufacturer. The results of this analysis suggest that 1,400 CIS is

appropriate. This final rule has been revised accordingly.

Although no comments were received regarding compliance paragraphs

(b)(1) to (b)(5), the FAA has changed these paragraphs to be consistent

with the corresponding paragraphs in paragraph (a) of this final rule.

The economic analysis section of the proposed rule assumed that all

inspected disks would require replacement. The manufacturer has

informed the FAA that this assumption is overly conservative based on

analysis and inspection results to date, and that only approximately 2%

of the inspected disks will require replacement. The 2% figure

translates to approximately 10 disks installed on aircraft of U.S.

registry. The economic analysis section of this final rule has been

revised accordingly.

After careful review of the available data, including the comments

noted above, the FAA has determined that air safety and the public

interest require the adoption of the rule with the changes described

previously. The FAA has determined that these changes will neither

increase the economic burden on any operator nor increase the scope of

the AD.

There are approximately 650 GE CF6-6/-45/-50 series turbofan

engines of the affected design in the worldwide fleet. The FAA

estimates that 500 engines installed on aircraft of U.S. registry will

be affected by this AD, that it will take approximately 108 work hours

per engine to accomplish the required actions, and that the average

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

$77,314 per engine. Based on these figures, and assuming that 10 of the

inspected disks will require replacement, the total cost impact of the

AD on U.S. operators is estimated to be $3,743,140.

The regulations adopted herein will 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 final

rule does not have sufficient federalism implications to warrant the

preparation of a Federalism Assessment.

For the reasons discussed above, I certify that this action (1) is

not a ``significant regulatory action'' under Executive Order 12866;

(2) is not a ``significant rule'' under DOT Regulatory Policies and

Procedures (44 FR 11034, February 26, 1979); and (3) 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 final evaluation has been prepared for this action

and it is contained in the Rules Docket. A copy of it may be obtained

from the Rules Docket at the location provided under the caption

ADDRESSES.

List of Subjects in 14 CFR Part 39

Air Transportation, Aircraft, Aviation Safety, Incorporation by

reference, Safety.

Adoption of the Amendment

Accordingly, pursuant to the authority delegated to me by the

Administrator, the Federal Aviation Administration amends 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:

94-09-18 General Electric Company: Amendment 39-8907. Docket 93-ANE-

41

Applicability: General Electric Company (GE) CF6-6/ -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 an uncontained stage 1 or stage 2 high pressure

turbine (HPT) disk failure, which could result in an inflight engine

shutdown, rejected takeoff, or damage to the aircraft, accomplish

the following:

(a) Eddy current inspect (ECI) stage 1 and stage 2 HPT disks for

cracks in accordance with the Accomplishment Instructions of GE CF6-

6 Service Bulletin (SB) No. 72-1002, dated February 12, 1993, and

CF6-6 SB No. 72-1003, Revision 1, dated June 17, 1993, as follows:

(1) For GE CF6-6 series stage 1 HPT disks, Part Numbers (P/N)

9137M40P01 and 9687M39P07, with serial numbers (S/N) listed in

Appendix I or II of GE CF6-6 SB No. 72-1002, dated February 12,

1993, which have accumulated less than 2,500 cycles since new (CSN)

on the effective date of this airworthiness directive (AD), ECI the

rim bolt holes at the next engine shop visit after accumulating

2,500 CSN, but not to exceed 5,400 CSN.

(2) For GE CF6-6 series stage 1 HPT disks, P/N 9137M40P01 and

9687M39P07, with S/N listed in Appendix I or II or GE CF6-6 SB No.

72-1002, dated February 12, 1993, which have accumulated 2,500 CSN

or more, but less than 4,000 CSN on the effective date of this AD,

ECI the rim bolt holes at the next engine shop visit, but not to

exceed 5,400 CSN.

(3) For GE CF6-6 series stage 1 HPT disks, P/N 9137M40P01 and

9687M39P07, with S/N listed in Appendix I or II of GE CF6-6 SB No.

72-1002, dated February 12, 1993, which have accumulated 4,000 CSN

or more on the effective date of this AD, ECI the rim bolt holes at

the next engine shop visit, or prior to accumulating 1,400 cycles in

service (CIS) after the effective date of this AD, whichever occurs

earlier.

(4) For GE CF6-6 series stage 2 HPT disks, P/N 9084M52P02 and

9084M52P05, with

S/N listed in Appendix I or II of GE CF6-6 SB No. 72-1003, Revision

1, dated June 17, 1993, which have not accomplished the inner bolt

hole ECI prior to the effective date of this AD in accordance with

GE CF6-6 Shop Manual, GEK 9266, Chapter 72-53-04, accomplish the

following:

(i) For disks which have accumulated less than 2,000 CSN on the

effective date of this AD, ECI the rim and inner bolt holes at the

next engine shop visit after accumulating 2,000 CSN, but not to

exceed 4,000 CSN.

(ii) For disks which have accumulated 2,000 CSN or more, but

less than 3,000 CSN on the effective date of this AD, ECI the rim

and inner bolt holes at the next engine shop visit, but not to

exceed 4,000 CSN.

(iii) For disks which have accumulated 3,000 CSN or more on the

effective date of this AD, ECI the rim and inner bolt holes at the

next engine shop visit, or prior to accumulating 1,000 CIS after the

effective date of this AD, whichever occurs earlier.

(5) For GE CF6-6 series stage 2 HPT disks, P/N 9084M52P02 and

9084M52P05, with

S/N listed in Appendix I or II of GE CF6-6 SB No. 72-1003, Revision

1, dated June 17, 1993, which have accomplished the inner bolt hole

ECI prior to the effective date of this AD in accordance with GE

CF6-6 Shop Manual, GEK 9266, Chapter 72-53-04, and not found

cracked, accomplish the following:

(i) For disks which have accumulated less than 2,000 CSN on the

effective date of this AD, ECI the rim and inner bolt holes at the

next engine shop visit after accumulating 2,000 CSN, but not to

exceed 5,400 CSN.

(ii) For disks which have accumulated 2,000 CSN or more, but

less than 4,000 CSN on the effective date of this AD, ECI the rim

and inner bolt holes at the next engine shop visit, prior to

accumulating 4,500 CSN, but not to exceed 5,400 CSN.

(iii) For disks which have accumulated 4,000 CSN or more on the

effective date of this AD, ECI the rim and inner bolt holes at the

next engine shop visit, or prior to accumulating 1,400 CIS after the

effective date of this AD, whichever occurs earlier.

(6) GE CF6-6 series stage 1 HPT disks referenced in paragraphs

(a)(1), (a)(2), and (a)(3) of this AD, that have been inspected by

ECI in accordance with the procedures outlined in GE CF6-6 All

Operators Wire (AOW) 92-6-09, dated September 24, 1992, or GE CF6-6

Engine Shop Manual, GEK 9266, Chapter 72-53-03, prior to the

effective date of this AD, and whose CSN at the time of inspection

was 2,500 or more, already meet the inspection requirements of

paragraphs (a)(1), (a)(2), and (a)(3) of this AD.

(7) GE CF6-6 series stage 2 HPT disks referenced in paragraphs

(a)(4) and (a)(5) of this AD, that have been inspected by ECI in

accordance with the procedures outlined in GE CF6-6 AOW 92-6-09,

dated September 24, 1992; GE CF6-6 SB No. 72-1003, dated February

12, 1993; or GE CF6-6 Engine Shop Manual, GEK 9266, Chapter 72-53-

04, prior to the effective date of this AD, and whose CSN at the

time of inspection was 2,000 or more, already meet the inspection

requirements of paragraphs (a)(4) and (a)(5) of this AD.

(b) ECI stage 1 and stage 2 HPT disks for cracks in accordance

with the Accomplishment Instructions of GE CF6-50 SB No. 72-1057,

Revision 1, dated June 17, 1993, and CF6-50 SB No. 72-1059, dated

February 12, 1993, as follows:

(1) For GE CF6-45/-50 series stage 1 HPT disks, P/N 9283M31P02,

9283M55P04, and 9283M55P05, with S/N listed in Appendix I, II, or

III of GE CF6-50 SB No. 72-1059, dated February 12, 1993, which have

accumulated less than 2,500 CSN on the effective date of this AD,

ECI the rim bolt holes at the next engine shop visit after

accumulating 2,500 CSN, but not to exceed 5,400 CSN.

(2) For GE CF6-45/-50 series stage 1 HPT disks, P/N 9283M31P02,

9283M55P04, and 9283M55P05, with S/N listed in Appendix I, II, or

III of GE CF6-50 SB No. 72-1059, dated February 12, 1993, which have

accumulated 2,500 CSN or more, but less than 4,000 CSN on the

effective date of this AD, ECI the rim bolt holes at the next engine

shop visit, but not to exceed 5,400 CSN.

(3) For GE CF6-45/-50 series stage 1 HPT disks P/N 9283M31P02,

9283M55P04, and 9283M55P05, with S/N listed in Appendix I, II, or

III of GE CF6-50 SB No. 72-1059, dated February 12, 1993, which have

accumulated 4,000 CSN or more on the effective date of this AD, ECI

the rim bolt holes at the next engine shop visit, or prior to

accumulating 1,400 CIS after the effective date of this AD,

whichever occurs earlier.

(4) For GE CF6-45/-50 series stage 2 HPT disks, P/N 9045M35P18

and 1474M49P06, with S/N listed in the Appendix of GE CF6-50 SB No.

72-1057, Revision 1, dated June 17, 1993, which have accumulated

less than 2,000 CSN on the effective date of this AD, ECI the rim

and inner bolt holes at the next engine shop visit after

accumulating 2,000 CSN, but not to exceed 4,000 CSN.

(5) For GE CF6-45/-50 series stage 2 HPT disks, P/N 9045M35P18

and 1474M49P06, with S/N listed in the Appendix of GE CF6-50 SB No.

72-1057, Revision 1, dated June 17, 1993, which have accumulated

2,000 CSN or more, but less than 3,000 CSN on the effective date of

this AD, ECI the rim bolt holes at the next engine shop visit, but

not to exceed 4,000 CSN.

(6) For GE CF6-45/-50 series stage 2 HPT disks, P/N 9045M35P18

and 1474M49P06, with S/N listed in the Appendix of GE CF6-50 SB No.

72-1057, Revision 1, dated June 17, 1993, which have accumulated

3,000 CSN or more on the effective date of this AD, ECI the rim and

inner bolt holes at the next engine shop visit, or prior to

accumulating 1,000 CIS after the effective date of this AD,

whichever occurs earlier.

(7) GE CF6-45/-50 series stage 1 HPT disks referenced in

paragraphs (b)(1), (b)(2), and (b)(3) of this AD, that have been

inspected by ECI in accordance with the procedures outlined in GE

CF6-50 AOW 92-50-15, dated September 24, 1992, or GE CF6-50 Engine

Task Numbered Shop Manual, GEK 50481, Chapter 72-53-03, prior to the

effective date of this AD, and whose CSN at the time of inspection

was 2,500 or more, already meet the inspection requirements of

paragraphs (b)(1), (b)(2), and (b)(3) of this AD.

(8) GE CF6-45/-50 series stage 2 HPT disks referenced in

paragraphs (b)(4), (b)(5), and (b)(6) of this AD, that have been

inspected by ECI in accordance with the procedures outlined in GE

CF6-50 AOW 92-50-15, dated September 24, 1992; GE CF6-50 SB No. 72-

1057, dated February 12, 1993; or GE CF6-50 Engine Task Numbered

Shop Manual, GEK 50481, Chapter 72-53-04, prior to the effective

date of this AD, and whose CSN at the time of inspection was 2,000

or more, already meet the inspection requirements of paragraphs

(b)(4), (b)(5), and (b)(6) of this AD.

(c) Remove from service disks found cracked, and replace with

serviceable parts. Inspect replacement disks in accordance with

paragraphs (a) or (b) of this AD, if applicable.

(d) 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.

(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 14

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

the requirements of this AD can be accomplished.

(g) The inspections shall be done in accordance with the

following service bulletins:

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Document No. Pages Revision Date

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GE CF6-6 SB

No. 72-1002................................. 1-12 Original............ February 12, 1993.

Total Pages: 12.

GE CF6-6 SB

No. 72-1003................................. 1-3 1................... June 17, 1993.

4-21 Original............ February 12, 1993.

Total Pages: 21.

GE CF6-50 SB

No. 72-1057................................. 1-2 1................... June 17, 1993.

3-14 Original............ February 12, 1993.

Total Pages: 14.

GE CF6-50 SB

No. 72-1059................................. 1-17 Original............ February 12, 1993

Total Pages: 17.

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This incorporation by reference was approved by the Director of

the Federal Register in accordance with 5 U.S.C. 552(a) and 1 CFR

part 51. Copies may be obtained from General Electric Aircraft

Engines, CF6 Distribution Clerk, Room 132, 111 Merchant Street,

Cincinnati, OH 45246. Copies may be inspected at the FAA, New

England Region, Office of the Assistant Chief Counsel, 12 New

England Executive Park, Burlington, MA; or at the Office of the

Federal Register, 800 North Capitol Street NW., suite 700,

Washington, DC.

(h) This amendment becomes effective on June 6, 1994.

Issued in Burlington, Massachusetts, on April 26, 1994.

Jay J. Pardee,

Manager, Engine and Propeller Directorate, Aircraft Certification

Service.

[FR Doc. 94-10502 Filed 5-4-94; 8:45 am]

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