00-18406. Airworthiness Directives; General Electric Company CF6-80A3 Series Turbofan Engines

AGENCY:

Federal Aviation Administration, DOT.

ACTION:

Notice of proposed rulemaking (NPRM).

SUMMARY:

This document proposes the supersedure of an existing airworthiness directive (AD), applicable to General Electric Company CF6-80A3 series turbofan engines. The existing AD currently requires initial and repetitive on-wing borescope inspections of the left hand aft engine mount link assembly for cracks, bearing migration, and, bearing race rotation, and if necessary, replacement with serviceable parts. This proposal would require initial and repetitive visual inspections of both left hand and right hand aft engine mount link assemblies for separations, cracks, and bearing race migration. Cracked or separated parts would have to be replaced prior to further flight. If spherical bearing race migration is discovered, a borescope inspection for cracks is also proposed. If no cracks are discovered by the additional borescope inspection, assemblies would have a 75-cycle grace period for remaining in service before replacement. Finally, installation of improved aft engine mount link assemblies would constitute terminating action to the inspections of this proposed AD. This proposal is prompted by a recent analysis of internal bearing friction and bearing migration and inspections which revealed migrated spherical bearing races on two CF6-80A3 series and ten CF6-80C2 series aft engine mount links. The actions specified by the proposed AD are intended to prevent aft engine mount link failure, which can result in adverse redistribution of the aft engine mount loads and possible aft engine mount system failure.

DATES:

Comments must be received by September 18, 2000.

ADDRESSES:

Submit comments to the Federal Aviation Administration (FAA), New England Region, Office of the Regional Counsel, Attention: Rules Docket No. 98-ANE-35-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 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 Rohr, Inc., 850 Lagoon Dr., Chula Vista, CA 91910-2098; telephone [phone], fax [phone]. This information may be examined at the FAA, New England Region, Office of the Regional Counsel, 12 New England Executive Park, Burlington, MA.

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 98-ANE-35-AD.” The postcard will be date stamped and returned to the commenter.

Availability of NPRMs

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. 98-ANE-35-AD, 12 New England Executive Park, Burlington, MA 01803-5299.

Discussion

On July 15, 1998, the Federal Aviation Administration (FAA) issued airworthiness directive (AD) 98-15-17, Amendment 39-10668 (63 FR 39489, July 23, 1998), applicable to General Electric Company (GE) CF6-80A3 series turbofan engines. That AD requires initial and repetitive on-wing borescope inspections of the left hand aft engine mount link assembly for cracks, bearing migration, and bearing race rotation, and, if necessary, replacement with serviceable parts. That action was prompted by a report of a fractured left hand aft engine mount link discovered during a scheduled engine removal. That condition, if not corrected, could result in aft engine mount link failure, which can result in adverse redistribution of the aft mount loads and possible aft mount system failure.

Due to the similarities between the link assembly designs, on June 28, 2000, the FAA also published a comparable rule for CF6-80C2 engine models installed on A300, A310, and MD-11 applications (AD 2000-12-08).

Recent Analysis

Since the issuance of AD 98-15-17, analysis into internal bearing friction and bearing race migration that could result in higher stress levels and reduced fatigue capability of aft engine mount links has been conducted. The analysis indicates that aft engine mount link spherical bearing race migration adversely affects link fatigue life and that right hand, as well as left hand, aft engine mount link assemblies are affected. Recent inspections also revealed migrated spherical bearing races on two CF6-80A3 series and ten CF6-80C2 series aft engine mount links. This condition, if not corrected, could result in aft engine mount link failure, which can result in adverse redistribution of the aft engine mount loads and possible aft engine mount system failure.

Service Information

The FAA has reviewed and approved the technical contents of Rohr Service Bulletin CF6-80A3-NAC-A71-064, dated April 4, 2000, that describes the aft engine mount link replacement. The FAA also has reviewed and approved the technical contents of Rohr Service Bulletin CF6-80A3-NAC-A71-061, Revision 1, dated February 22, 2000, that describes procedures for visual inspections of existing left hand and right hand aft engine mount link assemblies for separations, cracks, and spherical bearing race migration and provides rejection criteria.

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 supersede AD 98-15-17 to require initial and repetitive visual inspections of both left hand and right hand aft engine mount link assemblies for separations, cracks, and bearing race migration. If bearing race migration is discovered, this proposal would require a borescope inspection for cracks. Aft engine mount link assemblies found cracked would have to be replaced with serviceable parts prior to further flight. Aft engine mount link assemblies discovered with bearing race migration would be able to remain in service for another 75 cycles-in-service (CIS) following borescope inspection prior to replacement with serviceable parts. All left hand and right hand aft engine mount link assemblies would have to be replaced at the next engine shop visit with improved assemblies, which would constitute terminating action to the inspections. These actions would be required to be accomplished in accordance with the service bulletins described previously.

Economic Analysis

There are approximately 120 engines of the affected design in the worldwide fleet. The FAA estimates that 59 engines installed on aircraft of US registry would be affected by this proposed AD, that the cost of replacement link assemblies is approximately $9,737, that it would take approximately 2 work hours per engine to accomplish the proposed interim inspections, and that the average labor rate is $60 per work hour. Based on these figures, the total cost impact of the proposed AD over 3 years on US operators is estimated to be $588,614.

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 39-10668 (63 FR 39489, July 23, 1998) and by adding a new airworthiness directive to read as follows:

General Electric Company: Docket No. 98-ANE-35-AD. Supersedes AD 98-15-17, Amendment 39-10668.

Applicability: General Electric Company (GE) CF6-80A3 series turbofan engines, with left hand aft engine mount link assemblies, part numbers (P/Ns) 224-1608-501, 224-1608-503, or 224-1608-505 installed, or right hand aft engine mount link assemblies, P/Ns 224-1609-503, 224-1609-505, or 224-1609-507 installed. These engines are installed on but not limited to Airbus Industrie A310-200 series aircraft.

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 (d) 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 aft engine mount link failure, which can result in adverse redistribution of the aft engine mount loads and possible aft engine mount system failure, accomplish the following:

Initial Inspection

(a) Inspect aft engine mount link assemblies as follows:

Not Previously Inspected

(1) Within 400 cycles-in-service (CIS) after the effective date of this AD, if not previously inspected using Rohr Service Bulletin CF6-80A3-NAC-A71-061, Revision 1, dated February 22, 2000, or Rohr Service Bulletin CF6-80A3-NAC-A71-061, dated April 16, 1999; or

Previously Inspected

(2) Within 400 cycles-since-last-inspection (CSLI), if previously inspected using Rohr Service Bulletin CF6-80A3-NAC-A71-061, Revision 1, dated February 22, 2000, or Rohr Service Bulletin CF6-80A3-NAC-A71-061, dated April 16, 1999.

(3) Visually inspect for: separations, cracks, and spherical bearing race migration.

(4) Inspect in accordance with the Accomplishment Instructions of Rohr Service Bulletin CF6-80A3-NAC-A71-061, Revision 1, dated February 22, 2000.

Cracked or Separated Parts

(5) If a crack or separation is discovered, prior to further flight, remove the cracked or separated aft engine mount link assembly and the attaching hardware from service, and replace with serviceable parts.

Removal of Aft Engine Mount Link Assemblies With Spherical Bearing Race Migration

(6) If an aft engine mount link assembly is found with spherical bearing race migration, but no cracks or separations, prior to further flight, do either of the following:

Removal

(i) Remove the aft engine mount link assembly and the attaching hardware from service and replace with serviceable parts; or

Additional Borescope Inspection of Aft Engine Mount Link Assemblies With Spherical Bearing Race Migration

(ii) Perform an additional borescope inspection for cracks in accordance with paragraphs (2)(D)(5) and (2)(G)(5) of the Accomplishment Instructions of Rohr Service Bulletin CF6-80A3-NAC-A71-061, Revision 1, dated February 22, 2000, and perform the following:

After Additional Borescope Inspection, if Parts Are Cracked

(A) If a crack indication is discovered, prior to further flight, remove the cracked aft engine mount link assembly and the attaching hardware from service, and replace with serviceable parts.

After Additional Borescope Inspection, If Parts Are Not Cracked (Grace Period)

(B) If crack indications are not discovered, within 75 CIS after the inspection performed in accordance with paragraph (a)(6)(ii) of this AD, remove the aft engine mount link assembly from service, and replace with serviceable parts.

Attaching Hardware

(iii) Attaching hardware may be returned to service after inspection in accordance with paragraphs 2(D)(6)(a) or 2(G)(6)(a) of Rohr Service Bulletin CF6-80A3-NAC-A71-061, Revision 1, dated February 22, 2000, only if inspection of the removed link shows no cracks or separations.

Note 2:

Link attaching hardware includes the nuts, bolts and washers that secure the link.

Repetitive Inspections

(b) Thereafter, perform the actions required by paragraph (a) and associated subparagraphs at intervals not to exceed 400 CSLI.

Replacement With Improved Link Assemblies

(c) Replace aft engine mount link assemblies with improved aft engine mount link assemblies at the next engine shop visit (ESV), or prior to accumulating 29,000 engine cycles since new (CSN), whichever occurs first.

(1) Replace in accordance with the Accomplishment Instructions of Rohr Service Bulletin CF6-80A3-NAC-A71-064, dated April 4, 2000.

Left Hand Aft Engine Mount Link Assemblies

(2) Replace left hand aft engine mount link assemblies, P/Ns 224-1608-501, 224-1608-503, or 224-1608-505, with improved left hand aft engine mount link assemblies, P/Ns 224-1608-507 or 224-1608-509.

Right Hand Aft Engine Mount Link Assemblies

(3) Replace right hand aft engine mount link assemblies, P/Ns 224-1609-503, 224-1609-505, or 224-1609-507, with improved right hand aft engine mount link assemblies, P/Ns 224-1609-509 or 224-1609-511.

Terminating Action

(4) Installation of improved aft engine mount link assemblies in accordance with paragraph (c) and its subparagraphs constitutes terminating action to the inspections required by paragraphs (a) and (b) of this AD.

Alternate Methods of Compliance

(d) 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. Operators shall submit their requests through an appropriate FAA Principal Maintenance Inspector, who may add comments and then send it to the Manager, Engine Certification Office.

Note 3:

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

Ferry Flights

(e) 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 inspection requirements of this AD can be accomplished.

Issued in Burlington, Massachusetts, on July 14, 2000.

David A. Downey,

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