AD 94-09-18

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.

Final rule.

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 ofthis 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 priorto 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, 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 and inner 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, orGE 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 servicebulletins:

Document No.
Pages
Revision
Date
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.

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.

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.

39.13 - [AMENDED]

2. Section 39.13 is amended by adding the following new airworthiness directive: