01-5496. Airworthiness Directives; General Electric Co. CF6-80C2 Turbofan Engines

AGENCY:

Federal Aviation Administration, DOT.

ACTION:

Notice of proposed rulemaking (NPRM).

SUMMARY:

This document proposes the adoption of a new airworthiness directive (AD) that is applicable to General Electric Company (GE) CF6-80C2 turbofan engines with certain stage 1 high pressure turbine (HPT) rotor disks installed. This proposal would require initial and repetitive inspections of certain HPT rotor disks for cracks in the bottom of the dovetail slot. This proposed AD is prompted by a report of an uncontained failure of an engine during a high-power ground run for maintenance. The actions specified by this proposed AD are intended to detect cracks in the bottoms of the dovetail slots that could propagate to failure of the disk and cause an uncontained engine failure.

DATES:

Comments must be received by April 11, 2001.

ADDRESSES:

Submit comments to the Federal Aviation Administration (FAA), New England Region, Office of the Regional Counsel, Attention: Rules Docket No. 2001-NE-05-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.

The service information referenced in this AD may be obtained from General Electric Company via Lockheed Martin Technology Services, 10525 Chester Road, Suite C, Cincinnati, Ohio 45215, telephone [phone], fax [phone]. This information may be examined at the Federal Aviation Administration (FAA), New England Region, Office of the Regional Counsel, 12 New England Executive Park, Burlington, MA.

FOR FURTHER INFORMATION CONTACT:

Ann Mollica, 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 action 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 action must submit a self-addressed, stamped postcard on which the following statement is made: “Comments to Docket Number 2001-NE-05-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. 2001-NE-05-AD, 12 New England Executive Park, Burlington, MA 01803-5299.

Discussion

On September 22, 2000, a Boeing 767-2B7(ER), equipped with GE CF6-80C2B2 model engines, experienced an uncontained failure of the stage 1 HPT rotor disk during a high-power ground run for maintenance. The investigation of the failure has indicated that the stage 1 HPT rotor disk separation was the result of a crack that initiated in the aft corner radius of the bottom of a dovetail slot. The FFA had received two additional reports of stage 1 HPT rotor disks that were found to have cracks in the aft corner radius of the bottom of the dovetail slots. The cracks were found during shop visits in 1996 and 1999. In both cases, the cracks initiated from handling type damage to the aft corner radius of the bottoms of the dovetail slots. The actions specified by this proposed AD are intended to detect cracks in the bottoms of the dovetail slots that could propagate to failure of the disk and cause an uncontained engine failure.

Manufacturer's Service Information

The FAA has reviewed and approved the technical contents of GE alert service bulletin (ASB) CF6-80C2 72-A1026, dated January 17, 2001, that describes procedures for fluorescent penetrant, visual and eddy current inspections of the bottoms of the dovetail slots.

Differences Between the Manufacturer's Service Information and This AD

Although the GE ASB CF6-80C2 72-A1026, dated January 17, 2001, only requires a one-time inspection, the FAA has determined that repetitive inspections are required to achieve an acceptable level of safety.

Determination of an Unsafe Condition

Since an unsafe condition has been identified that is likely to exist or develop on other GE CF6-80C2 engines of the same type design, this AD is being proposed to detect cracks in the bottoms of the dovetail slots that could propagate to failure of the disk and cause an uncontained engine failure. For stage 1 HPT rotor disks with greater than 1,500 cycles-since-new (CSN), this proposed AD would require an initial inspection at the next shop visit before accumulating 3,500 cycles-in-service (CIS) after the effective date of this AD. For disks with 1,500 CSN or fewer on the effective date of this AD, this proposed AD would require an initial inspection at the next shop visit before accumulating 5,000 CSN. This proposed AD would also require repetitive inspections at piece-part opportunity, and if cracked, replacement with a serviceable disk. The actions would be done in accordance the service bulletin described previously.

Economic Impact

There are approximately 2,954 engines of the affected design in the worldwide fleet. The FAA estimates that 637 engines installed on aircraft of U.S. registry would be affected by this proposed AD. The FAA estimates that it would take approximately 3 work hours per engine to accomplish the proposed actions, and the average labor rate is $60 per work hour. Required parts would cost approximately $283,480 per engine. The FAA also estimates that approximately 191 engines per year will have shop visits, and that of those 191 engines, approximately two disks per year will have to be replaced. Based on these figures, the total cost impact of the proposed AD on U.S. operators is estimated to be $601,340 per year.

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 adding the following new airworthiness directive:

General Electric Co.: Docket 2001-NE-05-AD.

Applicability: This airworthiness directive (AD) is applicable to General Electric Company (GE) CF6-80C2 series turbofan engines with stage 1 high pressure turbine (HPT) rotor disks, part numbers (P/N's) 1531M84G02, 1531M84G06, 1531M84G08, 1531M84G10, 9392M23G10, 9392M23G12, 9392M23G21, and 1862M23G01 installed. These engines are installed on, but not limited to Airbus Industrie A300 and A310 series, Boeing 747 and 767 series, and McDonnell Douglas MD-11 series airplanes.

Note 1:

This 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 (f) of this AD. The request should include an assessment of the effect of the modification, alternation, 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: Compliance with this AD is required as indicated below, unless already done.

To detect cracks in the bottoms of the dovetail slots that could propagate to failure of the disk and cause an uncontained engine failure, perform the following inspections:

(a) Inspect the stage 1 HPT rotor disk in accordance with 3.A(1) through 3.C.(10)(i) of the Accomplishment Instructions of GE alert service bulletin (ASB) CF6-80C2 72-A1026, dated January 17, 2001, and Table 1 of this AD, and replace if necessary, as follows:

Table 1.—Compliance Times for Stage 1 HPT Disk Inspections

Stage 1 HPT rotor disk cycles-since-new (CSN) on the effective date of this AD	Initial inspection	Repetitive inspection
(1) 1,500 CSN or fewer	At the next engine shop visit (ESV) after the effective date of this AD, but not to exceed 5,000 CSN	At each piece-part exposure.
(2) More than 1,500 CSN	At the next ESV after the effective date of this AD, but not to exceed 3,500 cycles-in-service (CIS) after the effective date of this AD	At each piece-part exposure.
(3) Any number of CSN if the disk has been inspected using CF6-80C2 72-A1024, dated October 13, 2000, before the effective date of this AD	At the next ESV after the effective date of this AD	At each piece-part exposure.

(b) After the effective date of this AD, do not install any stage 1 HPT rotor disk with greater than zero CSN until it has been inspected in accordance with 3.A.(1) through 3.C.(10)(i) of the Accomplishment Instructions of GE ASB CF6-80C2 72-A1026, dated January 17, 2001.

(c) Thereafter, inspect the disk at each piece-part exposure, and replace if necessary.

Definitions

(d) The following definitions apply for this AD:

(1) Piece-part exposure means the stage 1 HPT rotor disk is considered completely disassembled as follows:

(i) When done in accordance with the disassembly instructions in the engine manufacturer's Engine Manual, AND

(ii) the disk has accumulated more than 100 CIS since the last piece-part opportunity inspection, if the disk was not damaged or related to the cause for its removal from the engine.

(2) An ESV is defined as the induction of an engine into a shop where the separation of a major engine flange will occur after the effective date of this AD. The following actions, either separately or in combination, are not considered ESV's for the purpose of this AD.

(i) Induction of an engine into a shop solely for removal of the upper compressor stator case for airfoil maintenance.

(ii) Induction of an engine into a shop solely for the module level inspection of the high pressure compressor rotor 3-9 spool.

Reporting Requirements

(e) Report the following information on all disks that equal or exceed the reject criteria of GE ASB CF6-80C2 72-A1026, within 5 calendar days of the inspection, to the Manager, Engine Certification Office. Reporting requirements have been approved by the Office of Management and Budget and assigned OMB control number 2120-0056.

(1) Engine model in which the stage 1 HPT rotor disk was installed, AND

(2) Disk P/N, AND

(3) Disk serial number, AND

(4) CSN on the disk, AND

(5) Cycles-since-last-inspection, AND

(6) Date and location of the inspection

Alternative Methods of Compliance

(f) 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 requests through an appropriate FAA Principal Maintenance Inspector, who may add comments and then send it to the Manager, ECO.

Note 2:

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

Special Flight Permits

(g) 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 February 27, 2001.

David A. Downey,

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