HPC Disk Failure

Category - Engine
Effective Date - 09/08/1995
Recurring - No
Supersedes - N/A
Superseded by - 95-26-03
Amendment 39-9345.
Docket 95-ANE-40

Applicability: Pratt and Whitney (PW) Model JT8D-9A turbofan engines identified by the following Serial Numbers: 656953, 656981, 657299, 657308, 657607, 657608, 657612, 666862 666868, 666906, 666912, 666915, 666948, 666955, 666957, 666967, 666973, 666987, 667136, 667137, 667143, 667154, and 667165. These engines are installed on but not limited to Boeing 727 and 737 series, and McDonnell Douglas DC-9 series aircraft.

Note: 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 use the authority provided in paragraph (d) to request approval from the Federal Aviation Administration (FAA). This approval may address either no action, if the current configuration eliminates the unsafe condition, or different actions necessary to address the unsafe condition described in this AD. Such a request should include an assessment of the effect of the changed configuration on the unsafe condition addressed by this AD. In no case does the presence of any modification, alteration, or repair remove any engine from the applicability of this AD.

Compliance: Required as indicated, unless accomplished previously.

To prevent an uncontained high pressure compressor (HPC) disk failure and damage to the aircraft, accomplish the following:

(a) For engines that contain any 7th through 12th stage HPC disk that has accumulated 2,900 or more cycles in service (CIS) on the effective date of this AD since HPC disk inspection performed by Turk Hava Yollari (THY), visually inspect each 7th through 12th stage HPC disk within 10 days, or 100 CIS after the effective date of this AD, whichever occurs first, for evidence of corrosion pitting and cracks in accordance with PW JT8D Engine Manual, Part Number (P/N) 481672, Section 72-36-41 through -46, as applicable. Pay particular attention to the inspection of the bolt holes, and shielding holes, as applicable. Replace all corroded or cracked disks with a serviceable part prior to further flight.

(b) For engines that contain any 7th through 12th stage HPC disk that has accumulated less than 2,900 CIS on the effective date of this AD since HPC disk inspection performed by THY, visually inspect each 7th through 12th stage HPC disk prior to the accumulation of 3,000 CIS since HPC inspection performed by THY for evidence of corrosion pitting and cracks in accordance with PW JT8D Engine Manual, P/N 481672, Section 72-36-41 through -46, as applicable. Pay particular attention to the inspection of the bolt holes, and shielding holes, as applicable. Replace all corroded or cracked disks with a serviceable part prior to further flight.

(c) No AD action is required for those engines that contain 7th through 12th stage HPC disks that were all inspected by an FAA approved repair station after the last 7th through 12th stage HPC disk inspection performed by THY.

(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. 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.

(e) 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.

(f) This amendment becomes effective September 8, 1995, to all persons except those persons to whom it was made immediately effective by telegraphic AD T95-15-51, issued July 10, 1995, which contained the requirements of this amendment.

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.