# AD 52-28-04: Tail Rotor Pinion Shaft

- Type: Airworthiness directive
- Status: Current
- Products: Scotts-Bell 47 47B, 47B3, 47D and 47D1
- Superseded by: Nothing supersedes this AD
- Product type: Aircraft, Rotorcraft
- Registered aircraft: 54 may be affected, by airframe or engine model (OpenAirDocs)
- FAA DRS: https://drs.faa.gov/browse/excelExternalWindow/3F0FD5FC8B5C6B4686256A34004EE335.0001
- DRS record last changed: May 30, 2024
- Page: https://openairdocs.org/ad/52-28-04

## The airworthiness directive

52-28-04 BELL: Applies to Models 47B, 47B3, 47D and 47D1 Helicopters (Prior to Serial Number 477).

Compliance required as soon as possible, but not later than January 10, 1953.

Magnetically inspect tail rotor pinion shaft, P/N 30-613-361, for damage and for cracks originating the keyway or fillet area. Replace shaft immediately if worn, damaged, cracked or if it does not pass the magnetic inspection satisfactorily. If the shaft passes the above inspections satisfactorily, or if a new shaft is being installed, accomplish the following prior to assembly: Place shaft in a lathe which is equipped with a grinding attachment. Use a 1/8-inch grinding wheel to increase the width of the recess at each side of bearing boss and grind a 0.030 to 0.040 inch radius at bottom of recesses. Reworked diameters of the shaft at the recesses at each side of the bearing boss are acceptable down to 0.763 inch and 0.604 inch respectively. These minimums must not be exceeded. Width of recesses are not to exceed 0.140 inch. There must not be any signs of the old radii or scratches.

(Bell Mandatory Service Bulletin No. 84, Revision B, dated April 29, 1953, covers the same subject.)

## Affected data sheets (1) (OpenAirDocs)

The type certificate data sheets whose models the AD names.

- [TCDS H-1](https://openairdocs.org/tcds/H-1): Scott's-Bell 47 Inc; names 4 of 9 models: 47B, 47B3, 47D1, 47D

## 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: 54 (54 by airframe model, 0 by engine model)
- Makers: Bell 52, Bell Kitz Kopters 1, Bell-Allied Helicopter 1

Models with the most aircraft:

- [Bell 47D1](https://openairdocs.org/model/bell-47d1): 47 aircraft (airframe model)
- [Bell 47D](https://openairdocs.org/model/bell-47d): 4 aircraft (airframe model)
- [Bell 47B](https://openairdocs.org/model/bell-47b): 1 aircraft (airframe model)
- [Bell Kitz Kopters 47D1](https://openairdocs.org/model/bell-kitz-kopters-47d1): 1 aircraft (airframe model)
- [Bell-Allied Helicopter 47D1](https://openairdocs.org/model/bell-allied-helicopter-47d1): 1 aircraft (airframe model)

All 5 models: https://openairdocs.org/ad/52-28-04/models.md
Every aircraft: https://openairdocs.org/ad/52-28-04/aircraft.md

Its text cites no advisory circulars or STCs.

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