This amendment supersedes an existing airworthiness directive (AD), applicable to certain Pratt & Whitney (PW) JT8D series turbofan engines, that currently requires initial and repetitive inspections of certain front compressor fan hubs and shotpeening of the forward and aft rim to web radius. This amendment requires a reduction in the initial inspection interval for front compressor fan hubs installed in all positions of all applicable aircraft, establish a compliance end- date, and clarify the wording of the compliance requirements. This amendment is prompted by a report of a front compressor fan hub fracture installed in a Boeing 737 aircraft that resulted in the release of fan blades and portions of the hub outer rim. The actions specified by this AD are intended to prevent fracture of the front compressor fan hub, which can result in an uncontained engine failure and damage to the aircraft. DATES: Effective July 21, 1995.
The incorporation by reference of certainpublications listed in the regulations is approved by the Director of the Federal Register as of July 21, 1995. ADDRESSES: The service information referenced in this AD may be obtained from Pratt & Whitney, Technical Publications Department, M/S 132-30, 400 Main Street, East Hartford, CT, 06108. This information may be examined at the Federal Aviation Administration (FAA), New England Region, Office of the Assistant Chief 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: Mark A. Rumizen, Aerospace Engineer, Engine Certification Office, FAA, Engine and Propeller Directorate, 12 New England Executive Park, Burlington, MA, 01803-5299; telephone (617) 238-7137, fax (617) 238-7199. SUPPLEMENTARY INFORMATION: A proposal to amend part 39 of the Federal Aviation Regulations (14 CFR part 39) by superseding AD 93-14-14, Amendment 39-8638 (58 FR 39644, July26, 1993) which is applicable to PW JT8D series turbofan engines, was published in the Federal Register on November 21, 1994 (59 FR 59973). That action proposed to reduce the initial inspection interval to require front compressor fan hubs installed in all positions of all applicable aircraft be inspected at the next shop visit, and to establish a compliance end date of December 31, 1999, or 6000 total part cycles (TPC) after the effective date of this AD for the initial inspection. That action also proposed to clarify the wording of paragraph (b)(4) to emphasize that the repetitive inspection is required at the next opportunity when the front compressor fan hub is accessible at the detail level in the shop only after accumulating 2500 additional cycles in service (CIS) since the last inspection. The actions would be required to be accomplished in accordance with Pratt & Whitney (PW) Alert Service Bulletin (ASB) No. A6104, Revision 3, dated June 16, 1994.
Interested persons havebeen afforded an opportunity to participate in the making of this amendment. Due consideration has been given to the comments received.
One commenter states that the reporting requirements of the AD be removed. The FAA does not concur. This corrective action program was based on a risk analysis that assumed a frequency of inspection relative to fleet usage. The reporting requirements of the AD allow this frequency of inspections to be monitored to ensure it is consistent with the assumptions, thereby confirming that the corrective action program is appropriate for maintaining the forecasted risk level.
One commenter supports the amendment as proposed.
After careful review of the available data, including the comments noted above, the FAA has determined that air safety and the public interest require the adoption of the rule as proposed.
There are approximately 2165 engines of the affected design in the worldwide fleet. The FAA estimates that 1475 engines installed on aircraft of U.S. registry and 690 domestic uninstalled engines will be affected by this AD, that it will take approximately 12 work hours per engine to accomplish the required actions, and that the average labor rate is $55 per work hour. Based on these figures, the total cost impact of the AD on U.S. operators is estimated to be $1,428,900.
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.
For the reasons discussed above, I certify that this action (1) is not a "significant regulatory action" under Executive Order 12866; (2) is not a "significant rule" under DOT Regulatory Policies and Procedures (44 FR 11034, February 26, 1979); and (3) 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 final evaluation has been prepared for this action and it is contained in the Rules Docket. A copy of it 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. App. 1354(a), 1421 and 1423; 49 U.S.C. 106(g); and 14 CFR 11.89. 39.13 - [AMENDED]
2. Section 39.13 is amended byremoving Amendment 39-8638 (58 FR 39644, July 26, 1993) and by adding a new airworthiness directive, Amendment 39-9227, to read as follows: