# AD 64-11-02: Tail Rotor Pinion Gears

- Type: Airworthiness directive
- Status: Current
- Products: Siam Hiller Holdings UH-12E and UH-12E-L
- Effective: May 16, 1964
- Superseded by: Nothing supersedes this AD
- Product type: Aircraft, Rotorcraft
- Registered aircraft: 105 may be affected, by airframe or engine model (OpenAirDocs)
- FAA DRS: https://drs.faa.gov/browse/excelExternalWindow/6AC44AF938C94E1E86256A54004F0618.0001
- DRS record last changed: May 30, 2024
- Page: https://openairdocs.org/ad/64-11-02

## The airworthiness directive

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.

## Affected data sheets (1) (OpenAirDocs)

The type certificate data sheets whose models the AD names.

- [TCDS 4H11](https://openairdocs.org/tcds/4H11): Siam Hiller Holdings Inc.; names 2 of 2 models: UH-12E, UH-12E-L

## Registered aircraft it may apply to (OpenAirDocs)

Matched by airframe and engine model; the AD's applicability may narrow it by serial number, part number or equipment.

- Aircraft: 105 (105 by airframe model, 0 by engine model)
- Makers: Hiller 104, Hiller-Rogerson Helicopter 1

Models with the most aircraft:

- [Hiller UH-12E](https://openairdocs.org/model/hiller-uh-12e): 103 aircraft (airframe model)
- [Hiller UH-12E-L](https://openairdocs.org/model/hiller-uh-12e-l): 1 aircraft (airframe model)
- [Hiller-Rogerson Helicopter UH12E](https://openairdocs.org/model/hiller-rogerson-helicopter-uh12e): 1 aircraft (airframe model)

All 4 models: https://openairdocs.org/ad/64-11-02/models.md
Every aircraft: https://openairdocs.org/ad/64-11-02/aircraft.md

Its text cites no advisory circulars or STCs.

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