78-17-08: Fifteenth Stage Compressor Disks

78-17-08 PRATT & WHITNEY AIRCRAFT: Amendment 39-3288. Applies to all Pratt & Whitney Aircraft JT9D-3, -3A, -7, -7A, -7AH, -7H, -7F, -7J, -20, and -20B turbofan engines containing fifteenth stage compressor disk, P/N 672915 or P/N 658615. Compliance required as indicated, unless already accomplished. To preclude failures of fifteenth stage compressor disks due to low cycle fatigue cracking, inspect disks in accordance with the procedures specified in Pratt & Whitney Aircraft Alert Service Bulletin 4908, dated August 7, 1978, or later revision approved by the Chief, Engineering and Manufacturing Branch, Federal Aviation Administration, New England Region, as specified below: (a) For disks with 6500 or more cycles in service, on the effective date of this AD, inspect within the next 100 cycles in service. (b) For disks having less than 6500 cycles in service, on the effective date of this AD, inspect prior to reaching 6600 cycles. (c) Reinspect the disks in paragraphs (a) and (b) in accordance with the following schedule: 1. Disks inspected by the Rim Access Ultrasonic Inspection method must be reinspected within the next 600 cycles and every 600 cycles in service thereafter. 2. Disks inspected by the HPC Central Cavity Access or the Detail Access Eddy Current Inspection method must be reinspected within the next 1600 cycles and every 1600 cycles thereafter. If any crack indications are found, the disk must be removed from service prior to further flight. In no case shall the established life limit of the disk be exceeded. Upon request of the operator, an equivalent method of compliance with the requirements of this AD may be approved by the Chief, Engineering and Manufacturing Branch, Federal Aviation Administration, New England Region. Upon request of the operator, an FAA maintenance inspector, subject to prior approval of the Chief, Engineering and Manufacturing Branch, New England Region, may adjust the repetitive inspection interval specified in this AD to permit compliance at an established inspection period of the operator if the request contains substantiating data to justify the increase for that operator. The manufacturer's specifications and procedures identified and described in this directive are incorporated herein and made a part hereof pursuant to 5 U.S.C. 552(a)(1). All persons affected by this directive, who have not already received these documents from the manufacturer, may obtain copies upon request to Pratt & Whitney Aircraft, Division of United Technologies Corporation, 400 Main Street, East Hartford, Connecticut 06108. These documents may also be examined at the Federal Aviation Administration, New England Region 12 New England Executive Park, Burlington, Massachusetts, and at FAA Headquarters, 800 Independence Avenue, S.W., Washington, D.C. A historical file on this AD, which includes the incorporated material in full, is maintained by the FAA at its Headquarters in Washington, D.C., and the New England Region. This amendment becomes effective September 1, 1978.