AD 88-03-53 ACTIVE

88-03-53 PRATT & WHITNEY: Amendment 39-6270. Final copy of telegraphic AD T88-03-53 which was issued on February 3, 1988.

Applicability: Pratt & Whitney (PW) PW4152 turbofan engines.

Compliance: Required as indicated, unless already accomplished.

To prevent the inability to reduce engine thrust that can lead to asymmetrical power and possible aircraft directional control problems, accomplish the following:

(a) For fuel metering units (FMU), Part Number (P/N) 51T217 or 53T419, with 140 operating hours or greater on the effective date of this Airworthiness Directive (AD), since new or since refurbished with new sector gears and a new or reconditioned resolver pinion gear, accomplish the following:

Remove and replace the FMU with a new or serviceable unit in accordance with the instructions in Appendix I of this AD within 10 operating hours after the effective date of this AD. (Appendix I refers to Pratt & Whitney Alert Service Bulletin Number PW4ENG A73-37, Revision 1, dated January 26, 1988, which is not reprinted in this AD.)

(b) For FMU's, P/N 51T217 or 53T419, with less than 140 operating hours on the effective date of this AD, since new or since refurbished with new sector gears and a new or reconditioned resolver pinion gear, accomplish the following:

Remove and replace the FMU with a new or serviceable unit in accordance with the instructions in Appendix I of this AD on or before accumulating 150 operating hours since new or since refurbished with new sector gears and a new or reconditioned resolver pinion gear.

(c) Thereafter, remove the FMU, P/N 51T217 or 53T419, and install a new or serviceable unit in accordance with the instructions in Appendix I of this AD at intervals not to exceed 150 FMU operating hours in service.

NOTE: PW ASB Number PW4ENG A73-37, Revision 1, dated January 26, 1988, further recommends removal and replacement of the FMU whenever the engine parameters indicate an impending hot start or excessive ground idle rotor speed (N2 in excess of 68 percent at normal bleed air extraction). FMU removal and replacement due to these operating characteristics are not mandated by this AD at this time.

(d) Aircraft may be ferried in accordance with the provisions of FAR 21.197 and 21.199 to a base where the AD can be accomplished.

(e) Upon submission of substantiating data by an owner or operator through an FAA Airworthiness Inspector, an alternate method of compliance with the requirements of this AD or adjustments to the compliance times specified in this AD may be approved by the Manager, Engine Certification Office, ANE-140, Engine and Propeller Directorate, Aircraft Certification Service, Federal Aviation Administration, 12 New England Executive Park, Burlington, Massachusetts 01803.

The FMU replacement shall be done in accordance with the instructions in Appendix I of this AD.

This amendment (39-6270, AD 88-03-53) becomes effective on September 1, 1989, as to all persons except those persons to whom it was made immediately effective by individual Telegraphic AD T88-03-53, issued February 3, 1988, which contained this amendment.