# AD 81-04-03: Tail Rotor Drive Assembly - Type: Airworthiness directive - Status: Current - Products: Continental Copters OH-13H, OH-13E, OH-13E, OH-13H, 47, 47B, 47B3, 47D, 47D1, 47E, 47G, 47G-2 and 17 more - Effective: February 2, 1981 - Superseded by: Nothing supersedes this AD - Product type: Aircraft, Rotorcraft - Amendment: 39-4029 - Registered aircraft: 491 may be affected, by airframe or engine model (OpenAirDocs) - FAA DRS: https://drs.faa.gov/browse/excelExternalWindow/070D62ED74DBB71886256A4D0073AAE4.0001 - DRS record last changed: May 30, 2024 - Page: https://openairdocs.org/ad/81-04-03 ## The airworthiness directive 81-04-03 BELL: Amendment 39-4029. Applies to Model 47 series helicopters and military Model OH-13 series helicopters certificated in all categories which utilize tail rotor drive quill assemblies, BHT P/N 47-620-631-3, P/N 47-620-631-35, P/N 47-620-541-3, P/N 47-620-541-7, or P/N 47-620-541-9. This also includes, but is not necessarily limited to, helicopters produced under the following Type Certificates: H7SW - Texas Helicopter Corporation, U.S. Army OH-13/M74 series helicopter (BHT Model 47 series). H5SW - Tomcat Helicopters, Inc., (Continental Copters, Inc.), U.S. Army OH-13H helicopter (BHT Model 47 series). H2CE - Wilbur Isenburg (Hawkeye), U.S. Army OH-13E helicopter (BHT Model 47 series). Compliance is required within the next 600 hours' time in service after the effective date of this AD, unless already accomplished. To prevent the failure of the tail rotor drive assembly bearing and possible loss of directional control, accomplish the following: (a) Disassemble and inspect the tail rotor drive assembly (BHT P/N 47-620-631-3, P/N 47-620-631-35, P/N 47-620-541-3, P/N 47-620-541-7, or P/N 47-620-541-9) as necessary to determine the identification of the bearing at the inboard end of the transmission tail rotor drive gear, P/N 47-620-568-1. (b) If the bearing is BHT bearing P/N 47-620-929-001 or FAA-approved equivalent, reassemble and reinstall the tail rotor drive assembly as prescribed by the applicable maintenance and overhaul manuals. (c) If the bearing identified in Item (a) is any part other than BHT P/N 47-620-929-001 or FAA-approved equivalent, replace the bearing with BHT bearing, P/N 47-620-929-001, in accordance with the instructions in BHT Alert Service Bulletin No. 47-80-6, "Replacement of Bearing, P/N 47-620-605-001, with Bearing, 47-620-929-001," dated May 15, 1980. Reassemble and reinstall the tail rotor drive assembly as prescribed by the applicable maintenance and overhaul manuals. (d) Anyequivalent method of compliance with this AD must be approved by the Chief, Engineering and Manufacturing Branch, Flight Standards Division, Southwest Region, Federal Aviation Administration. The manufacturer's specifications and procedures identified and described in this directive are incorporated herein and made a part thereof pursuant to 5 U.S.C. 552(a)(1). All persons affected by this directive who have not already received these documents from the manufacturer may obtain copies upon request to Bell Helicopter Textron, Product Support Department, Post Office Box 482, Fort Worth, Texas 76101. These documents may also be examined at the Office of the Regional Counsel, Southwest Region, FAA, 4400 Blue Mound Road, Fort Worth, Texas, and at the FAA Headquarters, 800 Independence Avenue, S.W., Washington, D.C. A historical file on this AD, which includes the incorporated material in full, is maintained by the FAA at their headquarters in Washington, D.C., and at the Southwest Regional Office in Fort Worth, Texas. This amendment becomes effective February 2, 1981. ## Affected data sheets (4) (OpenAirDocs) The type certificate data sheets whose models the AD names. - [TCDS 2H3](https://openairdocs.org/tcds/2H3): Scott's-Bell 47 Inc; names 11 of 11 models: 47G-2A, 47G-3B, 47G-3, 47G-4A, 47G-5A, 47G-5, 47G-3B-2A, 47G-3B-2… - [TCDS H-1](https://openairdocs.org/tcds/H-1): Scott's-Bell 47 Inc; names 9 of 9 models: 47H-1, 47B, 47B3, 47D1, 47D, 47G-2, 47G, 47… - [TCDS 2H1](https://openairdocs.org/tcds/2H1): Scott's-Bell 47 Inc; names 4 of 4 models: 47K, 47J-2, 47J-2A, 47J - [TCDS H2GL](https://openairdocs.org/tcds/H2GL): Teryjon Aviation Inc.; names 1 of 1 models: Fast Kat I (U.S. Army OH-13S) ## 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: 491 (491 by airframe model, 0 by engine model) - Makers: Bell 477, Bell-K-Copter 3, Bell Kitz Kopters 1, Bell-Allied Helicopter 1, Bell-Carson 1, Bell-Huddleston And Wilson 1, Bell-Intermountain 1, Bell-Olympic Helicopters 1, Bell-Shippey 1, Bell-Tellijohn 1 Models with the most aircraft: - [Bell 47G-2](https://openairdocs.org/model/bell-47g-2): 87 aircraft (airframe model) - [Bell 47G-3B-1](https://openairdocs.org/model/bell-47g-3b-1): 86 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 47G-5](https://openairdocs.org/model/bell-47g-5): 40 aircraft (airframe model) - [Bell 47G-3B-2](https://openairdocs.org/model/bell-47g-3b-2): 26 aircraft (airframe model) - [Bell 47G-4A](https://openairdocs.org/model/bell-47g-4a): 20 aircraft (airframe model) - [Bell 47G-2A](https://openairdocs.org/model/bell-47g-2a): 19 aircraft (airframe model) - [Bell 47G-5A](https://openairdocs.org/model/bell-47g-5a): 19 aircraft (airframe model) - [Bell 47G-3B](https://openairdocs.org/model/bell-47g-3b): 15 aircraft (airframe model) - [Bell 47G-2A-1](https://openairdocs.org/model/bell-47g-2a-1): 13 aircraft (airframe model) - [Bell 47G-4](https://openairdocs.org/model/bell-47g-4): 13 aircraft (airframe model) - [Bell 47G3B2A](https://openairdocs.org/model/bell-47g3b2a): 7 aircraft (airframe model) - [Bell 47H-1](https://openairdocs.org/model/bell-47h-1): 6 aircraft (airframe model) - [Bell 47J](https://openairdocs.org/model/bell-47j): 6 aircraft (airframe model) - [Bell 47J-2](https://openairdocs.org/model/bell-47j-2): 6 aircraft (airframe model) - [Bell 47J-2A](https://openairdocs.org/model/bell-47j-2a): 5 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) All 36 models: https://openairdocs.org/ad/81-04-03/models.md Every aircraft: https://openairdocs.org/ad/81-04-03/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 MKC85FA189](https://openairdocs.org/ntsb/MKC85FA189), Aug 17, 1985: Bell 47G-2A (N3951U), Sedalia, MO, substantial damage --- 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.