# AD 90-10-05: Tail Rotor Gearbox - Type: Airworthiness directive - Status: Current - Products: Bell Helicopter Textron TH-1L, UH-1E, UH-1L, UH-1F, UH-1B, TH-1L, UH-1E, UH-1L, UH-1A, UH-1B, UH-1H, TH-1L and 8 more - Effective: June 5, 1990 - Superseded by: Nothing supersedes this AD - Product type: Aircraft, Rotorcraft - Amendment: 39-6596 - Docket: 89-ASW-52 - Registered aircraft: 369 may be affected, by airframe or engine model (OpenAirDocs) - FAA DRS: https://drs.faa.gov/browse/excelExternalWindow/E980741E73C0ED7B86256A4D004E0EC5.0001 - DRS record last changed: May 30, 2024 - Page: https://openairdocs.org/ad/90-10-05 ## The airworthiness directive 90-10-05 CALIFORNIA DEPARTMENT OF FORESTRY; GARLICK HELICOPTERS; HAWKINS AND POWERS AVIATION, INC.; HERCULES; INTERNATIONAL HELICOPTERS, INC.; OFFSHORE CONSTRUCTION; OREGON HELICOPTERS; PILOT PERSONNEL INTERNATIONAL, INC.; SMITH HELICOPTERS; SOUTHERN AERO CORPORATION; SOUTHWEST FLORIDA AVIATION; AND WEST COAST FABRICATIONS (these helicopters were manufactured by Bell Helicopter Textron, Inc under military contract): Amendment 39-6596. Docket No 89-ASW-52. Applicability: Model UH-1A, UH-1B, UH-1E, UH-1F, UH-1H, UH-1L, and TH-1L helicopters, certificated in any category. 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, determine if the tail rotor gearbox duplex bearing sets, P/N 204-040-424-001, havingthe following serial numbers are installed in the tail rotor gearbox output quill, P/N 204-040-012-009: Serial Numbers 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 MB927 thru MB936 If a part with any of the listed serial numbers is installed, replace with a serviceable part 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 that provides an equivalent 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 (39-6596, AD 90-10-05) becomes effective on June 5, 1990. ## Affected data sheets (2) (OpenAirDocs) The type certificate data sheets whose models the AD names. - [TCDS H2NM](https://openairdocs.org/tcds/H2NM): California Department of Forestry; names 1 of 1 models: UH-1F - [TCDS H3SO](https://openairdocs.org/tcds/H3SO): Richards Heavylift Helo Inc.; names 1 of 4 models: UH-1A ## 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: 369 (369 by airframe model, 0 by engine model) - Makers: Bell 340, Williams Helicopter 7, Northwest Rotorcraft 6, Bell Helicopter 3, Southwest Florida 3, Hawkins & Powers 2, Richards Heavylift Helo 2, Rotorcraft Development 2, Bell-Colonial 1, Bell-Sw Florida Avn 1 Models with the most aircraft: - [Bell UH-1H](https://openairdocs.org/model/bell-uh-1h): 291 aircraft (airframe model) - [Bell UH-1B](https://openairdocs.org/model/bell-uh-1b): 42 aircraft (airframe model) - [Bell UH-1E](https://openairdocs.org/model/bell-uh-1e): 6 aircraft (airframe model) - [Northwest Rotorcraft UH-1H](https://openairdocs.org/model/northwest-rotorcraft-uh-1h): 6 aircraft (airframe model) - [Williams Helicopter UH-1H](https://openairdocs.org/model/williams-helicopter-uh-1h): 6 aircraft (airframe model) - [Southwest Florida UH-1H](https://openairdocs.org/model/southwest-florida-uh-1h): 3 aircraft (airframe model) - [Bell Helicopter UH-1H (205)](https://openairdocs.org/model/bell-helicopter-uh-1h-205): 3 aircraft (airframe model) - [Richards Heavylift Helo UH-1H](https://openairdocs.org/model/richards-heavylift-helo-uh-1h): 2 aircraft (airframe model) - [Hawkins & Powers UH-1B](https://openairdocs.org/model/hawkins-powers-uh-1b): 2 aircraft (airframe model) - [Rotorcraft Development UH-1H](https://openairdocs.org/model/rotorcraft-development-uh-1h): 2 aircraft (airframe model) - [Bell UH-1L](https://openairdocs.org/model/bell-uh-1l): 1 aircraft (airframe model) - [Bell-Colonial UH-1B](https://openairdocs.org/model/bell-colonial-uh-1b): 1 aircraft (airframe model) - [Bell-Sw Florida Avn UH-1B](https://openairdocs.org/model/bell-sw-florida-avn-uh-1b): 1 aircraft (airframe model) - [Precision Helicopters UH-1H](https://openairdocs.org/model/precision-helicopters-uh-1h): 1 aircraft (airframe model) - [Williams Helicopter UH-1B](https://openairdocs.org/model/williams-helicopter-uh-1b): 1 aircraft (airframe model) - [Williams Helicopter Corp/Oas UH-1E](https://openairdocs.org/model/williams-helicopter-corp-oas-uh-1e): 1 aircraft (airframe model) All 16 models: https://openairdocs.org/ad/90-10-05/models.md Every aircraft: https://openairdocs.org/ad/90-10-05/aircraft.md Its text cites no advisory circulars or STCs. ## NTSB investigations that cite this AD (1) From the NTSB's public API. Aircraft are matched to registry aircraft by N-number and event date, checked against the reported serial number, make and model; the registry's history has gaps, so older matches can be wrong. Compare the reported make and model. - [NTSB WPR22LA084](https://openairdocs.org/ntsb/WPR22LA084), Jan 23, 2022: Bell UH-1E (N333XL), Gustine, CA, substantial damage. Probable cause: Failure of the 90° gearbox due to the lack of lubricating oil, which resulted in a loss of rotational drive to the tail rotor and a subsequent loss of control of the helicopter. --- 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.