00-26141. Airworthiness Directives; General Electric Company (GE) CF-645 and CF6-50 Series Turbofan Engines

AGENCY:

Federal Aviation Administration, DOT.

ACTION:

Notice of proposed rulemaking (NPRM).

SUMMARY:

This document proposes to revise an existing airworthiness directive (AD), applicable to certain GE turbofan engines. That AD currently requires initial and repetitive inspections of high pressure compressor (HPC) rear shafts and installation of a certain rear shaft flange bolt configuration. This action would add additional HPC rear shaft part numbers for reworked rear shafts to the AD. This proposal is prompted by the need to ensure that the additional HPC rear shafts listed in this proposed rule receive the same inspections as part numbers covered by the current amendment. The actions specified by the proposed AD are intended to detect and replace cracked HPC rear shafts, which, if not replaced, could lead to an uncontained engine failure.

DATES:

Comments must be received by November 16, 2000.

ADDRESSES:

Submit comments to the Federal Aviation Administration (FAA), New England Region, Office of the Regional Counsel, Attention: Rules Docket No. 90-ANE-25-AD, 12 New England Executive Park, Burlington, MA 01803-5299. Comments may also be sent via the Internet using the following address: “[e-mail]”. Comments sent via the Internet must contain the docket number in the subject line. 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 Company, Technical Publications Department, 1 Neumann Way, Cincinnati, OH 45215. This information may be examined at the FAA, New England Region, Office of the Regional 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:

Karen Curtis, Aerospace Engineer, Engine Certification Office, FAA, Engine and Propeller Directorate, 12 New England Executive Park, Burlington, MA 01803-5299; telephone: [phone]; fax: [phone].

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 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 90-ANE-25-AD.” The postcard will be date stamped and returned to the commenter.

Availability of NPRM's

Any person may obtain a copy of this NPRM by submitting a request to the FAA, New England Region, Office of the Regional Counsel, Attention: Rules Docket No. 90-ANE-25-AD, 12 New England Executive Park, Burlington, MA 01803-5299.

Discussion

On March 18, 1991, the FAA issued AD 91-10-03, Amendment 39-6956 (56 FR 19920, May 1, 1991), applicable to GE CF6-45 and CF6-50 turbofan engines, to require initial and repetitive inspections of HPC rear shafts and installation of a certain rear shaft flange bolt. That action was prompted by reports of 35 HPC rear shafts found cracked in the bolt hole area. The inspection requirements of that AD were intended to detect and replace cracked HPC rear shafts to prevent an HPC rear shaft fracture, which could result in an uncontained engine failure. On April 4, 1995, the FAA issued AD 91-10-03 Revision 1, Amendment 39-9186 (60 FR 1879, May 13, 1995), applicable to GE CF6-45 and CF6-50 series turbofan engines. That action was prompted by an FAA determination that the Parts Manufacturer Approval (PMA) Production Approval Listing, Supplement No. 27, authorizes the use of Valley-Todeco (VT) bolts, part number (P/N) VCD0016, as an alternate to GE bolts, P/N 1375M69P01. The VT bolt is identical in design to the GE bolt and the amendment adds the VT bolt to the applicability. That amendment also clarifies that engines with one or more PMA bolts, P/N VCD0016 installed, must accomplish the inspection requirements of the original AD, and allow the installation of PMA bolts as alternates to the GE bolts. That AD Revision requires initial and repetitive inspections to detect and replace cracked HPC rear shafts to prevent an HPC rear shaft fracture, which could result in an uncontained engine failure.

New Information

Since that revision to the AD was issued, the FAA has become aware of HPC rear shaft rework P/N's that have been issued by the manufacturer that are not listed in AD 91-10-03, Revision 1 but should be inspected.

Proposed Actions

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 revise AD 91-10-03 Revision 1 to add HPC rear shaft rework P/N's to the AD. The actions would be required to be accomplished in accordance with the SB's described previously.

Economic Impact

There are about 1,730 engines of the affected design in the worldwide fleet. The FAA estimates that 469 engines installed on aircraft of U.S. registry would be affected by this proposed AD, that it would take about 2 work hours per engine to accomplish the proposed actions, and that the average labor rate is $60 per work hour. Required labor would cost about $120.00 per engine. Based on these figures, the total labor cost impact of the proposed AD on U.S. operators is estimated to be $56,280.

Regulatory Impact

This proposal does not have federalism implications, as defined in Executive Order 13132, because it would not have a substantial direct effect 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. Accordingly, the FAA has not consulted with state authorities prior to publication of this proposal.

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. 106(g), 40113, 44701.

§ 39.13

[Amended]

2. Section 39.13 is amended by removing Amendment 39-9186 (60 FR 18729, April 13, 1995), and by adding a new airworthiness directive (AD), to read as follows:

General Electric Company: Docket No. 90-ANE-25-AD. Revises AD 91-10-03, Revision 1, Amendment 39-9186.

Applicability: General Electric Company (GE) CF6-45 and CF6-50 series turbofan engines installed on, but not limited to, McDonnell Douglas DC-10 series, Boeing 747 series, and Airbus A300 series airplanes.

Note 1:

This airworthiness directive (AD) applies to each engine identified in the preceding applicability provision, regardless of whether it has been modified, altered, or repaired in the area subject to the requirements of this AD. For engines that have been modified, altered, or repaired so that the performance of the requirements of this AD is affected, the owner/operator must request approval for an alternative method of compliance in accordance with paragraph (e) of this AD. The request should include an assessment of the effect of the modification, alteration, or repair on the unsafe condition addressed by this AD; and, if the unsafe condition has not been eliminated, the request should include specific proposed actions to address it.

Compliance: Required as indicated, unless accomplished previously. To prevent a high pressure compressor (HPC) rear shaft fracture, which could result in an uncontained engine failure and/or in-flight engine shutdown, accomplish the following:

(a) Fluorescent-penetrant inspect HPC rear shafts having the part numbers (P/N's) in Table 1 below, in accordance with the Accomplishment Instructions of GE Service Bulletin (SB) No. 72-958, Revision 1, dated October 18, 1990 as follows:

Table 1

9127M58P03	9079M63P12	9079M63P15	9079M63P16
9079M63P17	9079M63P18	9079M63P19	1999M25P01
1999M25P02	1999M25P03	1999M25P04	1999M25P05
1999M25P06	1999M25P07

(1) For HPC rear shafts currently installed with hook bolts, P/N 9012M99G10, 9114M95G07, and 9114M95G10, inspect in accordance with the following schedule:

(i) For shafts that have not been previously inspected and have 10,000 cycles since new (CSN) or more on the effective date of this AD, inspect within the next 1,500 cycles in service (CIS) after the effective date of this AD.

(ii) For shafts that have not been previously inspected and have fewer than 10,000 CSN on the effective date of this AD, inspect within the next 2,500 CIS from the effective date of this AD, or before accumulating 7,500 CSN, whichever occurs later. However, no shaft may exceed 11,500 CSN before inspection.

(iii) For shafts that have been previously inspected and have 3,000 cycles since last inspection (CSLI) or fewer on the effective date of this AD, inspect within 4,500 CSLI, or before accumulating 7,500 CSN, whichever occurs later.

(iv) For shafts that have been previously inspected and have greater than 3,000 CSLI on the effective date of this AD, inspect within the next 1,500 CIS from the effective date of this AD, or before accumulating 7,500 CSN, whichever occurs later.

(v) Remove from service HPC rear shaft hook bolts identified in (a)(1) of this AD after any inspection performed in accordance with paragraph (a)(1) of this AD and replace with new tapered turn-around bolts, P/N 1375M69P01 or VCD0016.

(2) For HPC rear shafts installed with turn-around bolts, P/N 9249M54P01, or tapered turn-around bolts, P/N 1375M69P01 or VCD0016, inspect in accordance with the following schedule:

(i) For shafts that have not been previously inspected and have 6,500 CSN or more on the effective date of this AD, inspect within the next 2,500 CIS after the effective date of this AD.

(ii) For shafts that have not been previously inspected and have fewer than 6,500 CSN on the effective date of this AD, inspect before accumulating 9,000 CSN.

(iii) For shafts that have been previously inspected and have 3,500 CSLI or fewer on the effective date of this AD, inspect within 6,000 CSLI, or before accumulating 9,000 CSN, whichever occurs later.

(iv) For shafts that have been previously inspected and have more than 3,500 CSLI on the effective date of this AD, inspect within the next 2,500 CIS after the effective date of this AD, or before accumulating 9,000 CSN, whichever occurs later.

(v) Remove from service HPC rear shaft turn-around bolts identified in paragraph (a)(2) of this AD after any inspection performed in accordance with paragraph (a)(3) of this AD and replace with new tapered turn-around bolts, P/N 1375M69P01 or VCD0016.

Note 2.

Information concerning the tapered turn-around bolt noted in paragraph (a) of this proposed AD can be found in GE SB No. 72-877.

(b) Remove from service, prior to further flight, any shafts found cracked at inspection.

(c) Thereafter, for shafts that have been inspected in accordance with paragraph (a) of this AD, reinspect in accordance with the Accomplishment Instructions of GE SB No. 72-958, Revision 1, dated October 18, 1990, at intervals not to exceed 6,000 CSLI.

(d) Compliance with paragraph (a) of AD 91-10-03, Revision 1 satisfies the corresponding requirements of paragraph (a) of this AD. For the purposes of this AD, the inspection cycle interval must be measured from the last HPC rear shaft bolt hole inspection, regardless of any rear shaft rework and re-identifying after inspection.

Alternative Methods of Compliance

(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 (ECO). Operators shall submit their request through an appropriate FAA Principal Maintenance Inspector, who may add comments and then send it to the Manager, ECO.

Note 3:

Information concerning the existence of approved alternative methods of compliance with this airworthiness directive, if any, may be obtained from the Manager, ECO.

Special Flight Permits

(f) Special flight permits may be issued in accordance with §§ 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 October 5, 2000.

David A. Downey,

Assistant Manager, Engine and Propeller Directorate, Aircraft Certification Service.