AD 75-07-10

75-07-10 AIRESEARCH MANUFACTURING COMPANY of ARIZONA: Amendment 39-2144 as amended by Amendment 39-2189. Applies to AiResearch TFE731-2 and -3 series engines.

Compliance required as indicated.

To detect, prevent and correct wear of the transfer gearbox vertical bevel gear bearing support which can result in failure of the accessory drive and contamination of the engine lubrication system, accomplish the following:

(A) Within the next 25 hours time in service after receipt of this Airworthiness Directive, unless previously accomplished, and at intervals not to exceed 50 hours time in service thereafter, inspect the lower shoulder of transfer gearbox vertical bearing support for wear and replacements as required per AiResearch Service Bulletin TFE731-72-3019, dated February 27, 1975, or later FAA-approved revisions.

(B) The inspections required by paragraph (A) above, are not required if the engine is equipped with a transfer gearbox assembly, P/N 3070093-3, designated as Series I, Change 2 or Series 3, and may be discontinued on engines equipped with Series I Transfer Gearbox Assemblies when the bearing support, P/N 3070217-1, is replaced with an improved bearing support, P/N 3070217-3, per AiResearch Service Bulletin TFE731-72-3020, dated February 27, 1975, or later FAA-approved revisions. Bearing supports, P/N 3070217-1, which are removed from service shall be rendered unserviceable.

(C) Equivalent procedures may be approved by the Chief, Aircraft Engineering Division, FAA Western Region, upon submission of adequate substantiating data.

(D) Aircraft may be flown to a base for performance of maintenance required by this AD per FAR's 21.197 and 21.199.

Amendment 39-2144 became effective April 3, 1975, for all persons except those to whom it was made effective by airmail letters dated February 28, 1975.

This amendment 39-2189 becomes effective May 1, 1975.