# AD 56-20-03: Tail Rotor Hub Bolts

- Type: Airworthiness directive
- Status: Current
- Products: Scotts-Bell 47 47B, 47B3, 47D, 47D1, 47G, 47G-2 and 47H-1
- Superseded by: Nothing supersedes this AD
- Product type: Aircraft, Rotorcraft
- Registered aircraft: 212 may be affected, by airframe or engine model (OpenAirDocs)
- FAA DRS: https://drs.faa.gov/browse/excelExternalWindow/39FAF019ED1992B886256A34004F90EB.0001
- DRS record last changed: May 30, 2024
- Page: https://openairdocs.org/ad/56-20-03

## The airworthiness directive

56-20-03 BELL: Applies to All Models 47B, 47B3, 47D, 47D1, 47G, 47G2 and 47H1.

Compliance required as soon as possible but not later than October 20, 1956.

Failure of the tail rotor hub retention bolts P/N 47-641-052-1 has occurred in service. The probable cause of the bolt failures experienced to date has not been determined and this problem is currently being investigated. At the conclusion of this investigation Bell anticipates supplying a newly designed hub retention bolt as a replacement for the present bolts. In the interim it is mandatory that a service life of 300 hours be established for the subject bolt. At this time it is necessary to remove the two tail rotor retention bolts and replace them with new retention bolts of the same part number.

(Bell Mandatory Service Bulletin No. 112 dated August 8, 1956, covers this 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 7 of 9 models: 47H-1, 47B, 47B3, 47D1, 47D, 47G-2, 47G

## 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: 212 (212 by airframe model, 0 by engine model)
- Makers: Bell 200, Bell-K-Copter 3, Bell Kitz Kopters 1, Bell-Allied Helicopter 1, Bell-Carson 1, Bell-Olympic Helicopters 1, Bell-Shippey 1, Bell-Tellijohn 1, Bell-Transworld Helicopter Cor 1, Bell-Yehnert 1

Models with the most aircraft:

- [Bell 47G-2](https://openairdocs.org/model/bell-47g-2): 87 aircraft (airframe model)
- [Bell 47G](https://openairdocs.org/model/bell-47g): 55 aircraft (airframe model)
- [Bell 47D1](https://openairdocs.org/model/bell-47d1): 47 aircraft (airframe model)
- [Bell 47H-1](https://openairdocs.org/model/bell-47h-1): 6 aircraft (airframe model)
- [Bell 47D](https://openairdocs.org/model/bell-47d): 4 aircraft (airframe model)
- [Bell-K-Copter 47G](https://openairdocs.org/model/bell-k-copter-47g): 2 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)
- [Bell-Shippey BELL 47G](https://openairdocs.org/model/bell-shippey-bell-47g): 1 aircraft (airframe model)
- [Bell-Carson 47G](https://openairdocs.org/model/bell-carson-47g): 1 aircraft (airframe model)
- [Bell-Tellijohn 47G-2](https://openairdocs.org/model/bell-tellijohn-47g-2): 1 aircraft (airframe model)
- [Bell-K-Copter 47G-2](https://openairdocs.org/model/bell-k-copter-47g-2): 1 aircraft (airframe model)
- [Bell-Transworld Helicopter Cor 47G-2](https://openairdocs.org/model/bell-transworld-helicopter-cor-47g-2): 1 aircraft (airframe model)
- [Bell-Olympic Helicopters 47G2](https://openairdocs.org/model/bell-olympic-helicopters-47g2): 1 aircraft (airframe model)
- [Bell-Yehnert 47G-2](https://openairdocs.org/model/bell-yehnert-47g-2): 1 aircraft (airframe model)
- [Continental Copters 47G](https://openairdocs.org/model/continental-copters-47g): 1 aircraft (airframe model)

All 17 models: https://openairdocs.org/ad/56-20-03/models.md
Every aircraft: https://openairdocs.org/ad/56-20-03/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.