The Federal Aviation Administration (FAA) has received a report of a fractured left hand aft mount link discovered during a scheduled engine removal of a General Electric Company (GE) CF6-80A3 series turbofan engine. Failure analysis revealed a fatigue type fracture with no metallurgical anomalies and no geometric discrepancies in the area of the crack origin. Over the course of the investigation of the cracked left hand aft mount link assembly and the review of other link assemblies returned from service, two conditions were noted that individually could be considered benign but when combined could result in higher stress levels and the reduced fatigue capability of link assemblies. The first condition is the incorrect orientation of the entry slots of the spherical bearing assembly and the second condition is high friction between the bearing and the race resulting from contamination between faying bearing surfaces. This condition, if not corrected, could result in left hand aft mount link failure, which can result in adverse redistribution of the aft mount loads and possible aft mount system failure.
On May 20, 1998, the Direction Generale de L'Aviation Civile (DGAC), the airworthiness authority of France, issued AD 98-205-260(B), applicable to Airbus A310 aircraft, addressing this unsafe condition by requiring initial and repetitive on-wing borescope inspections of the left hand aft mount link assembly for cracks, bearing migration, and bearing race rotation, and, if necessary, replacement with serviceable parts. On June 3, 1998, the Transport Airplane Directorate (TAD) of the FAA issued AD 98-12-24, also applicable to Airbus A310 aircraft, requiring a one-time on-wing borescope inspection for cracks and bearing migration. The Engine and Propeller Directorate has consulted with the DGAC and the TAD and has determined that it is necessary to issue this AD applicable to GE CF6-80A3 series engines mandating repetitive borescopeinspections in order to assure the continued airworthiness of the aft mount links.
The FAA has reviewed and approved the technical contents of Rohr Alert Service Bulletin (ASB) No. CF6-80A3-NAC-A71-060, dated January 30, 1998, that describes procedures for borescope inspections of the left hand aft mount link for cracks, bearing migration, and bearing race rotation.
Since an unsafe condition has been identified that is likely to exist or develop on other engines of the same type design, this AD is being issued to prevent left hand aft mount link failure. This AD requires initial and repetitive on-wing borescope inspections of the left hand aft mount link assembly for cracks, bearing migration, and bearing race rotation, and, if necessary, replacement with serviceable parts. The investigation is ongoing, and further rulemaking may be necessary that may require additional piece-part inspections or the installation of a modified left hand aft mount link assembly that would terminate the repetitive inspections required by this AD. The actions are required to be accomplished in accordance with the ASB described previously.
Since a situation exists that requires the immediate adoption of this regulation, it is found that notice and opportunity for prior public comment hereon are impracticable, and that good cause exists for making this amendment effective in less than 30 days. Comments Invited
Although this action is in the form of a final rule that involves requirements affecting flight safety and, thus, was not preceded by notice and an opportunity for public comment, comments are invited on this rule. Interested persons are invited to comment on this 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 under the caption "ADDRESSES." All communications received on or before the closing date for comments will be considered, and this rule may be amended in light of the comments received. Factual information that supports the commenter's ideas and suggestions is extremely helpful in evaluating the effectiveness of the AD action and determining whether additional rulemaking action would be needed.
Comments are specifically invited on the overall regulatory, economic, environmental, and energy aspects of the rule that might suggest a need to modify the 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 that summarizes each FAA-public contact concerned with the substance of this AD 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.
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.
The FAA has determined that this regulation is an emergency regulation that must be issued immediately to correct an unsafe condition in aircraft, and is not a "significant regulatory action" under Executive Order 12866. It has been determined further that this action involves an emergency regulation under DOT Regulatory Policies and Procedures (44 FR 11034, February 26, 1979). If it is determined that this emergency regulation otherwise would be significant under DOT Regulatory Policies and Procedures, a final regulatory evaluation will be prepared and placed in the Rules Docket. A copy of it, if filed, 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 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: