# AD 90-01-11: Tail Rotor Gearbox Bearing Set

- Type: Airworthiness directive
- Status: Current
- Products: Bell Helicopter Textron 204B
- Effective: February 1, 1990
- Superseded by: Nothing supersedes this AD
- Product type: Aircraft, Rotorcraft
- Amendment: 39-6450
- Docket: 89-ASW-50
- Registered aircraft: 7 may be affected, by airframe or engine model (OpenAirDocs)
- FAA DRS: https://drs.faa.gov/browse/excelExternalWindow/D794CF0372C1679C86256A4D0071A1D1.0001
- DRS record last changed: May 30, 2024
- Page: https://openairdocs.org/ad/90-01-11

## The airworthiness directive

90-01-11 BELL HELICOPTER TEXTRON, INC.: Amendment 39-6450. Docket No. 89-ASW-50.

Applicability: Bell Helicopter Textron, Inc., Model 204B helicopters, certificated in any category, with tail rotor gearbox duplex bearing sets, P/N 204-040-424-001, with serial numbers (S/N's) 1 thru 182, MB183 thru MB382, MB442, MB486, MB513, MB518, MB519, MB524, MB530, MB531, MB544, MB545, MB548, MB549, MB551, MB553, MB554, MB561, MB659, MB743, MB744, MB760 thru MB769 and MB927 thru MB936, installed in tail rotor gearbox output quill, P/N 204-040-012-009.

Compliance: Required as indicated, unless already accomplished.

To prevent failure of the tail rotor duplex bearing which could result in loss of tail rotor control and subsequent loss of the helicopter, accomplish the following:

  (a) Within the next 100 hours' time in service after the effective date of this AD, remove the tail rotor gearbox duplex bearing set, P/N 204-040-424-001, from service and replace with a serviceablepart before further flight.

  (b) In accordance with FAR Sections 21.197 and 21.199, the helicopter may be flown to a base where the requirements of this AD may be accomplished.

  (c) An alternate method of compliance or adjustment of the compliance time which provides an acceptable level of safety may be used when approved by the Manager, Rotorcraft Certification Office, ASW-170, Rotorcraft Directorate, FAA, Southwest Region, Fort Worth, Texas.

This amendment (39-6450, AD 90-01-11) becomes effective on February 1, 1990.

## Affected data sheets (1) (OpenAirDocs)

The type certificate data sheets whose models the AD names.

- [TCDS H1SW](https://openairdocs.org/tcds/H1SW): Bell Textron Inc.; names 1 of 5 models: 204B

## 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: 7 (7 by airframe model, 0 by engine model)
- Makers: Bell 7

Models with the most aircraft:

- [Bell 204-B](https://openairdocs.org/model/bell-204-b): 7 aircraft (airframe model)

All 1 models: https://openairdocs.org/ad/90-01-11/models.md
Every aircraft: https://openairdocs.org/ad/90-01-11/aircraft.md

Its text cites no advisory circulars or STCs.

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