AD 64-11-02

64-11-02 HILLER: Amdt. 730 Part 507 Federal Register May 16, 1964. Applies to All Model UH-12E Helicopters.

Compliance required as indicated.

A number of failures of the tail rotor pinion gear have been experienced. These failures have been experienced with several different gear heat treat lots and on helicopters both with and without rotor brakes installed. To preclude any additional failures, accomplish the following:

(a) Replace tail rotor pinion gears identified as Hiller P/N 23522 or P/N 23634 with a tail rotor pinion gear P/N 23634-3 as follows:

(1) Gears with less than 50 hours total time in service on the effective date of this AD shall be replaced prior to the accumulation of 100 hours' total time in service.

(2) Gears with 50 hours or more total time in service on the effective date of this AD shall be replaced within the next 50 hours' time in service.

(b) Tail rotor pinion gears identified as P/N 23634-3 are satisfactory for unlimitedservice life.

NOTE: An "-A" following P/N 23634 should be disregarded inasmuch as this is a gear vendor's marking and not part of the Hiller part number.

(Hiller Service Information Letter No. 3036 "C" covers this same subject.)

This supersedes AD 63-26-02.

This directive effective May 16, 1964.