|
94-20-01
|
|||
|
Compressor Disks Category
- Engine Applicability: Pratt & Whitney (PW) JT8D-1, -1A, -1B, -7, -7A, -7B, -9, -9A, -11, -15, -15A, -17, -17A, -17R, and -17AR turbofan engines installed on but not limited to Boeing 737 and 727 series, and McDonnell Douglas DC-9 series aircraft. Compliance: Required as indicated, unless accomplished previously. To prevent fracture of the high pressure compressor (HPC) disks, that can result in uncontained release of engine fragments, inflight engine shutdown, and airframe damage, accomplish the following: (a) Within four months after the effective date of this airworthiness directive (AD), determine the fleet and sub-fleet average engine utilization rate for the 12 months of operations prior to August 17, 1994, the issue date of PW Alert Service Bulletin (ASB) No. 6038, Revision 5, in accordance with paragraph 2.A of PW ASB No. 6038, Revision 5, dated August 17, 1994. (1) For fleet or sub-fleet average utilization rates that are equal to or greater than 1,300 hours per year, and equal to or greater than 900 cycles per year, perform the following: (i) For engines or disks that are added to a fleet or subfleet after the effective date of this AD, and that were previously designated as low utilization disks in accordance with this AD, comply with the requirements of paragraph (d) of this AD. (ii) Designate all other stage 7 through 12 HPC disks as high utilization disks and comply with the requirements of paragraph (b) of this AD. (2) For fleet or sub-fleet average utilization rates that are less than 1,300 hours per year or less than 900 cycles per year, within four months after the effective date of this AD, determine the initial utilization rate for each stage 7 through 12 HPC disk in accordance with paragraph 2.B.(1) of PW ASB No. 6038, Revision 5, dated August 17, 1994. Determination of disk utilization in accordance with PW ASB No. 6038, Revision 3, dated May 8, 1992, constitutes an acceptable alternate method of compliance to paragraph (a)(2) of this AD. (i) For each HPC stage 7 through 12 disk with an initial utilization rate equal to or greater than 1,300 hours per year, and equal to or greater than 900 cycles per year, designate this disk as a high utilization disk and inspect in accordance with paragraph (c) of this AD. (ii) For each HPC stage 7 through 12 disk with an initial utilization rate less than 1,300 hours per year or less than 900 cycles per year, designate this disk as a low utilization disk and inspect in accordance with paragraph (d) of this AD. (iii) For each HPC stage 7 through 12 disk with an unknown initial utilization rate, designate this disk as a low utilization disk and inspect in accordance with paragraph (d) of this AD. NOTE: Once a disk is designated as low utilization, then it must retain this designation for the life of the disk or until recoated. (iv) For recoated or new disks, designate this disk as a high utilization disk and inspect in accordance with paragraph (c) of this AD. (b) For high average utilization fleets and sub-fleets, excluding those disks identified in paragraph (a)(1)(i) of this AD, perform the following for each HPC stage 7 through 12 disk in that fleet or sub-fleet: (1) Inspect, and recoat or replace if necessary, at the next part accessibility of the disk, in accordance with paragraph 2.D.(1)(b) and Chart A of PW ASB No. 6038, Revision 5, dated August 17, 1994. (2) Recalculate the fleet or sub-fleet average utilization rate at 12 month intervals after the previous date of utilization determination in accordance with paragraph 2.B of PW ASB No. 6038, Revision 5, dated August 17, 1994. (i) For fleet or sub-fleet average utilization rates that are equal to or greater than 1,300 hours per year, and equal to or greater than 900 cycles per year, continue to designate all stage 7 through 12 HPC disks as high utilization disks and comply with the requirements of paragraph (b) of this AD. (ii) For fleet or sub-fleet average utilization rates that are less than 1,300 hours per year or less than 900 cycles per year, within four months of compliance with paragraph (b)(2) of this AD, determine the utilization rate for each stage 7 through 12 HPC disk in accordance with paragraph 2.B.(1) of PW ASB No. 6038, Revision 5, dated August 17, 1994, as follows: (A) For each HPC stage 7 through 12 disk with a utilization rate equal to or greater than 1,300 hours per year, and equal to or greater than 900 cycles per year, designate this disk as a high utilization disk and inspect in accordance with paragraph (c) of this AD. (B) For each HPC stage 7 through 12 disk with a utilization rate less than 1,300 hours per year or less than 900 cycles per year, designate this disk as a low utilization disk and inspect in accordance with paragraph (d) of this AD. (C) For each HPC stage 7 through 12 disk with an unknown utilization rate, designate this disk as a low utilization disk and inspect in accordance with paragraph (d) of this AD. NOTE: Once a disk is designated a low utilization, then it must retain this designation for the life of the disk or until recoated. (c) For high utilization HPC stage 7 through 12 disks, perform the following: (1) Inspect, and recoat or replace if necessary, at the next part accessibility of the disk, in accordance with paragraph 2.D.(1)(b) and Chart A of PW ASB No. 6038, Revision 5, dated August 17, 1994. (2) Calculate the disk utilization rate at 12 month intervals after the previous date of utilization determination, or after installation of new or recoated disks, in accordance with paragraph 2.B.(3) of PW ASB No. 6038, Revision 5, dated August 17, 1994. (i) For HPC stage 7 through 12 disks designated as high utilization in accordance with (c)(2), comply with the requirements of paragraph (c)(1) of this AD. (ii) For HPC stage 7 through 12 disks designated as low utilization in accordance with (c)(2), comply with the requirements of paragraph (d) of this AD. (d) For low utilization HPC stage 7 through 12 disks, perform the following: (1) Determine the type of disk surface treatment for each HPC stage 7 through 12 disk in accordance with paragraph 2.E. of PW ASB No. 6038, Revision 5, dated August 17, 1994. Determination of type of disk coating in accordance with PW ASB No. 6038, Revision 3, dated May 8, 1992, constitutes an acceptable alternate method of compliance to paragraph (d)(1) of this AD. (2) Inspect, and recoat or remove from service, in accordance with paragraph 2.D.(1)(c) and Chart A of PW ASB No. 6038, Revision 5, dated August 17, 1994. (e) For HPC stage 7 through 12 disks that have been recoated in accordance with paragraphs (b)(1), (c)(1), or (d)(2) of this AD, designate these disks as high utilization and perform the following: (1) For disks installed in an engine that is part of a high utilization fleet, comply with the requirements of paragraph (b) of this AD. (2) For disks installed in an engine that is part of a low utilization fleet, comply with the requirements of paragraph (c) of this AD. (f) For the purpose of this AD, recoat of an HPC disk is defined as removal and application of new plating or coating in accordance with Sections 72-36-41, Repair 02, 72-36-42, Repair 02, 72-36-43, Repair 03, 72-36-44, Repair 03, 72-36-45, Repair 03, 72-36-46, Repair 03, as applicable, of PW JT8D Engine Manual P/N 481672. (g) For the purpose of this AD, part accessibility is defined as the removal of the disk from the engine and deblading of that disk. (h) For the purpose of this AD, a sub-fleet is defined as any individual aircraft or any portion of an operators fleet that operates in a separate and unique route structure, characterized by different flight lengths, frequencies, or geographic location. (i) 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. The request should be forwarded through an appropriate FAA Principal Maintenance Inspector, who may add comments and then send it to the Manager, Engine Certification Office. NOTE: Information concerning the existence of approved alternative methods of compliance with this airworthiness directive, if any, may be obtained from the Engine Certification Office. (j) Special flight permits may be issued in accordance with sections 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 accomplished. (k) The inspections, and replacement or recoating if necessary, shall be done in accordance with the following service document: Document No. Pages Revision Date PW ASB No. 6038 1 5 August 17, 1994 2 Original August 5, 1991 3 5 August 17, 1994 4-6 4 July 13, 1994 7-26 5 August 17, 1994 Appendix
A 27-41
5 August
17, 1994 This incorporation by reference was approved by the Director of the Federal Register in accordance with 5 U.S.C. 552(a) and 1 CFR part 51. Copies may be obtained from Pratt & Whitney, Publications Department, 400 Main Street, East Hartford, Connecticut 06108. Copies may be inspected at the 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. (l) This amendment becomes effective on November 28, 1994. 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 no. (617) 238-7137, fax (617) 238-7199.
|
|||