01-27191. Airworthiness Directives; General Electric Company (GE) CF6-45 and CF6-50 Series Turbofan Engines

AGENCY:

Federal Aviation Administration, DOT.

ACTION:

Notice of proposed rulemaking (NPRM).

SUMMARY:

The Federal Aviation Administration (FAA) proposes to adopt a new airworthiness directive (AD) that is applicable to GE CF6-45 and CF6-50 series turbofan engines. This proposal would require a reduction of the cyclic life limit for certain low pressure turbine rotor (LPTR) stage 2 disks, and would require removing certain LPTR stage 2 disks from service before exceeding the new, lower cyclic life limit. In addition, the proposal would require removing from service certain LPTR stage 2 disks that currently exceed, or will exceed, the new, lower cyclic life limit according to the compliance schedule described in this proposal. This proposal is prompted by a report of a cracked LPTR stage 2 disk found during a visual inspection. The actions specified by the proposed AD are intended to prevent an uncontained engine failure and damage to the airplane, resulting from cracks in the LPTR stage 2 disk.

DATES:

Comments must be received by December 31, 2001.

ADDRESSES:

Submit comments in triplicate to the Federal Aviation Administration (FAA), New England Region, Office of the Regional Counsel, Attention: Rules Docket No. 2001-NE-33-AD, 12 New England Executive Park, Burlington, MA 01803-5299. Comments may be inspected, by appointment, at this location between 8 a.m. and 4:30 p.m., Monday through Friday, except Federal holidays. 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.

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 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 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-33-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-33-AD, 12 New England Executive Park, Burlington, MA 01803-5299.

Discussion

An LPTR stage 2 disk cracked in the forward slot area was discovered during a shop visit visual inspection. The manufacturer has determined that the crack is a result of low cycle fatigue failure. As a result, the manufacturer has reevaluated the 15,500 cycles-since-new (CSN) cyclic life limit for LPTR stage 2 disks part numbers (P/N's) 9061M22P08 and 9061M22P10, and has recalculated the cyclic life limit. This proposal would establish a new, lower cyclic life limit of 10,400 CSN for LPTR stage 2 disks P/N's 9061M22P08 and 9061M22P10 and would require removing certain LPTR stage 2 disks from service before exceeding the new, lower cyclic life limit. In addition, the proposal would require removing from service certain LPTR stage 2 disks that currently exceed, or will exceed, the new, lower cyclic life limit according to a compliance schedule based on accumulated cycles on the disk on the effective date of the AD. The compliance schedule is established on the basis of a risk analysis that the FAA has reviewed. The FAA has determined that the compliance schedule based on that risk analysis establishes an acceptable level of safety for those disks operated beyond the new life limit. The actions specified by the proposed AD are intended to prevent an uncontained engine failure and damage to the airplane, resulting from cracks in the LPTR stage 2 disk.

FAA's Determination of an Unsafe Condition and Proposed Actions

Since an unsafe condition has been identified that is likely to exist or develop on other GE CF6-45 and CF6-50 series turbofan engines of the same type design, the proposed AD would establish a new, lower cyclic life limit of 10,400 CSN for LPTR stage 2 disks P/N's 9061M22P08 and 9061M22P10 and would require removing certain LPTR stage 2 disks from service before exceeding the new, lower cyclic life limit. In addition, the proposal would require removing from service certain LPTR stage 2 disks that currently exceed, or will exceed, the new, lower cycle life limit according to a compliance schedule based on accumulated cycles on the disk on the effective date of this AD.

Economic Analysis

There are approximately 1,376 GE CF6-45 and CF6-50 series turbofan engines of the affected design in the worldwide fleet. The FAA estimates that 664 engines installed on airplanes of U.S. registry would be affected by this proposed AD. The proposed action does not impose any additional labor costs. A new disk would cost approximately $72,870 per engine. Based on these figures, and on the prorating for the usage of the disks, the cost effect of the proposed AD on U.S. operators is estimated to be $10,385,724.

Regulatory Analysis

This proposed rule 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 proposed rule.

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 Company: Docket No. 2001-NE-33-AD.

Applicability: This airworthiness directive (AD) is applicable to General Electric Company (GE) CF6-45 and CF6-50 series turbofan engines. These engines are installed on, but not limited to, Airbus Industrie A300 series, Boeing 747 series, and McDonnell Douglas DC-10 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 (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: Compliance with this AD is required as indicated, unless already done.

To prevent an uncontained engine failure and damage to the airplane, resulting from cracks in the low pressure turbine rotor (LPTR) stage 2 disk, do the following:

(a) Remove from service LPTR stage 2 disks, part numbers (P/N's) 9061M22P08 and 9061M22P10 in accordance with Table 1 as follows:

Table 1.—LPTR Stage 2 Disk Removal Schedule

If disk cycles-since-new (CSN) on the effective date of this AD are:	Then remove disk:
(1) Fewer than 5,300 CSN	Before exceeding 10,400 CSN.
(2) 5,300 CSN or more, but fewer than 10,400 CSN	Within 5,100 additional cycles-in-service from the effective date of this AD.
(3) 10,400 CSN or more	At next LPTR stage 2 disk exposure, or by 15,500 CSN, whichever occurs earlier.

(b) After the effective date of this AD, do not install any LPTR stage 2 disk, P/N 9061M22P08 or 9061M22P10, that has 10,400 or more CSN into an engine.

(c) Except for as provided in paragraph (a) of this AD, this action establishes a new, cyclic life limit of 10,400 CSN for LPTR stage 2 disk, P/N 9061M22P08 and 9061M22P10, which is published in Chapter 05-10-00 of CF6-45 and CF6-50 Engine Shop Manual, GEK 50481.

Definition

(d) For the purpose of this AD, LPTR stage 2 disk exposure is defined as disassembly and removal of the LPTR stage 2 disk from the LPTR structure, regardless of whether any blades, bolts, nuts, bolt retainers, blade retainers, blade inserts, balance weights, wear strips, or seals remain assembled to the disk.

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 must submit their request 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

(f) Special flight permits may be issued in accordance §§ 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 done.

Issued in Burlington, Massachusetts, on October 22, 2001.

Thomas Boudreau,

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