AD 93-10-51

93-10-51 PRATT & WHITNEY CANADA: Amendment 39-8604. Docket 93-ANE-33.

Applicability: Pratt & Whitney Canada (P&WC) auxiliary power unit (APU) Model PW901A, Part No. 3910001, installed on but not limited to Boeing Model 747-400 aircraft.

Compliance: Required as indicated, unless accomplished previously.

To prevent APU gear failure, which can result in smoke contamination of aircraft passenger cabins, accomplish the following:

(a) Within 10 APU hours, or 5 days after the effective date of this airworthiness directive (AD), whichever occurs first, in accordance with P&WC Alert Service Bulletin No. A16159R1, dated May 12, 1993:

(1) Disassemble the APU load gearbox and remove the scavenge pump oil strainer element, Part No. (P/N) 3107647-01; and

(2) Reassemble APU load gearbox, reinstalling the existing chip detector, P/N 3910098-01, and adapter, P/N 3910242-01.

(b) Within 10 APU operating hours, or 5 days after the effective date of this AD, whichever occurs first:

(1) Inspect the APU load gearbox and accessory gear box magnetic chip detectors in accordance with the appropriate aircraft maintenance manual; and

(2) Thereafter, inspect the chip detectors at intervals not to exceed 150 APU operating hours since the last inspection.

(c) 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, New York Aircraft 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, New York Aircraft Certification Office. NOTE: Information concerning the existence of approved alternative methods of compliance with this airworthiness directive, if any, may be obtained from the New York Aircraft Certification Office.

(d) Special flight permits may be issued in accordance with FAR 21.197 and 21.199 to operate the airplane to a location where the requirements of this AD can be accomplished.

(e) The removal and inspections shall be done in accordance with the following alert service bulletin:

Document No. Pages Date PWC No. A16159R1 1-4 May 12, 1993 Total pages: 4.

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 Canada, 1000 Marie-Victorin, Longueil, Quebec, Canada J4G 1A1. 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.

(f) This amendment becomes effective August 10, 1993, to all persons except those persons to whom it was made immediately effective by telegraphic AD T93-10-51, issued May 20, 1993, which contained the requirements of this amendment.