# AD 53-01-01: Gearbox Mounting Sleeve

- Type: Airworthiness directive
- Status: Current
- Products: Scotts-Bell 47 47D1
- Superseded by: Nothing supersedes this AD
- Product type: Aircraft, Rotorcraft
- Registered aircraft: 49 may be affected, by airframe or engine model (OpenAirDocs)
- FAA DRS: https://drs.faa.gov/browse/excelExternalWindow/D7C39718484C37BC86256A34004EE579.0001
- DRS record last changed: May 30, 2024
- Page: https://openairdocs.org/ad/53-01-01

## The airworthiness directive

53-01-01 BELL: Applies to Model 47D1 Helicopters, Serial Numbers 477 to 625, Inclusive.

Compliance required at next 300-hour teardown inspection but not later than February 28, 1953.

In order to improve the method of mounting the tail rotor gearbox assembly and to avoid the possibility of distorting the S10R bearing when tightening the existing clamp, install sleeve P/N 47-640-058-1 on assembly 47-640-044-3. Clamping ring P/N 47-644-197-1 and clamp P/N 47-640-046-1 are replaced by the riveted sleeve.

(Mandatory Service Bulletin No. 90, Revision B, dated December 8, 1952, covers this same subject. Service Bulletin No. 90, Revision A, also covers the same subject but Revision B simplifies the installation and completes the parts called out.)

## 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 1 of 9 models: 47D1

## 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: 49 (49 by airframe model, 0 by engine model)
- Makers: Bell 47, 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 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 3 models: https://openairdocs.org/ad/53-01-01/models.md
Every aircraft: https://openairdocs.org/ad/53-01-01/aircraft.md

Its text cites no advisory circulars or STCs.

---
OpenAirDocs.org is an independent research project of [Contrail Labs](https://contraillabs.com/). It is not affiliated with the FAA or the NTSB. Source documents are U.S. government works in the public domain.