93-08-16 PRATT & WHITNEY: Amendment 39-8564. Docket 92-ANE-06. Supersedes AD 90-20-11, Amendment 39-6682.
Applicability: Pratt & Whitney PW4050, PW4052, PW4056, PW4060, and PW4060A model turbofan engines equipped with electronic engine control (EEC) Part Numbers 50D437, 50D821, 50D823, 51D011, and 51D012, installed on but not limited to Boeing 747 and 767 aircraft.
Compliance: Required within 30 calendar days after the effective date of this airworthiness directive (AD), unless accomplished previously.
To prevent a high pressure compressor (HPC) failure caused by excessive blade tip to airseal interference, which can result in total loss of engine thrust, accomplish the following:
(a) Incorporate the requirements of Boeing Commercial Airplanes Alert Service Bulletin (ASB) 747-73A2055, dated June 8, 1990, on PW4000 powered Boeing 747-400 aircraft, so that the minimum inflight rotational speed (rpm) of the low pressure rotor is limited to Approach Idle rpm.
(b) Incorporate the requirements of Boeing Commercial Airplanes ASB 767-73A0033, dated June 5, 1990, on PW4000 powered Boeing 767-200/-300 aircraft, so that the minimum inflight rotational speed of the low pressure rotor inflight is limited to Approach Idle rpm.
(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, 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.
(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 modification shall be done in accordance with the following Boeing service documents:
Document No.
Pages
Revision
Date
ASB 747-73A2055
1-10
Original
June 8, 1990
Total pages: 10
ASB 767-73A0033
1-12
Original
June 5, 1990
Total pages: 12
This incorporation by reference was approved previously by the Director of the Federal Register in accordance with 5 U.S.C. 552(a) and 1 CFR part 51 as of October 1, 1990 (55 FR 37316, September 11, 1990). Copies may be obtained from Boeing Commercial Airplanes, Post Office Box 3707, Seattle, WA 98124-2207. 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 on July 12, 1993.