# AD 81-09-06: Bevel Gear Modules - Type: Airworthiness directive - Status: Current - Products: Airbus Helicopters AS350B, AS350C, AS350D and AS350D1 - Effective: July 23, 1981 - Published: July 16, 1981 - Issued: July 16, 1981 - Superseded by: Nothing supersedes this AD - Product type: Aircraft, Rotorcraft - Amendment: 39-4161 - Docket: 81-ASW-4 - Registered aircraft: 21 may be affected, by airframe or engine model (OpenAirDocs) - FAA DRS: https://drs.faa.gov/browse/excelExternalWindow/BBD53FA672469B8986256A4E00551B44.0001 - DRS record last changed: November 21, 2025 - Page: https://openairdocs.org/ad/81-09-06 ## The airworthiness directive 81-09-06 SOCIETE NATIONALE INDUSTRIELLE AEROSPATIALE: Amendment 39- 4161. Applies to Model AS350 series helicopters certificated in all categories which have Bevel Gear Module P/N 350A32.0300.00 or -.01 installed, except bevel gear modules which include nitrided shaft P/N 350A32.3107.23 or -.24. (Bevel Gear Module P/N 350A32.0300.02 includes nitrided shaft, P/N 350A32.3107.23 or -.24 and is exempt from this application.) Compliance required as follows, unless already accomplished: a. For bevel gear modules with 580 or more hours' time in service since new or last overhaul, comply within 20 hours time in service after the effective date of this AD, or b. For bevel gear modules with less than 580 hours' time in service since new or last overhaul on the effective date of this AD, comply prior to accumulation of 600 hours' time in service, and c. Thereafter at intervals not to exceed 300 hours' time in service. To prevent loss of mechanical drive between the bevel gear module and the epicyclic module of the main transmission gearbox, inspect the bevel gear module for wear in accordance with procedures specified in paragraph EE of Aerospatiale TELEX Service No. 05.05 (TELEX No. 22316) dated December 24, 1980, or paragraph BB of Aerospatiale TELEX Service No. 05.06 as it applies to measuring actual spline wear, or other FAA approved equivalent. If the maximum wear depth at the level of the step on the spline exceeds 1.0 mm (0.039 inch) or if the distance between two rods of 6.35 mm (.250 inch) exceeds 72.2 mm (2.84 inches), the bevel gear module must be replaced with a serviceable module before further flight. Report defects to the Chief, Aircraft Certification Staff, FAA, Europe, Africa, and Middle East Office, c/o American Embassy, Brussels, Belgium. Reporting approved by the Office of Management and Budget under OMB No. 04-R0174. Special flight permits may be issued in accordance with FAR 21.197 and FAR 21.199 to fly aircraftto a base where this AD can be accomplished. Equivalent methods of compliance with this AD must be approved by the Chief, Engineering and Manufacturing Branch, Flight Standards Division, Southwest Region, Federal Aviation Administration, P.O. Box 1689, Fort Worth, Texas 76101, or by the Chief, Aircraft Certification Staff, FAA, Europe, Africa, and Middle East Office, c/o American Embassy, Brussels, Belguim. NOTE: Aerospatiale TELEX 22316, paragraph EE, is as follows: EE. Remove main rotor mast and sun gear according to Work Cards 65 13 401 and 65 30 404. Check the wear of vertical shaft splines either by mold print, (maximum wear depth at the level of the step, 1mm (0.039 inches)) or by measurement of distance between two rods of 6.35 mm diameter. Distance between two opposite rods shall be less than 72.2 mm. If the value obtained by either one of the above methods is out of limit, return bevel gear module to an approved repair station. This AirworthinessDirective supersedes AD 81-01-05. This amendment becomes effective July 23, 1981, for all persons except those to whom it was made immediately effective by priority mail AD No. 81-09-06 dated April 23, 1981. ## Affected data sheets (1) (OpenAirDocs) The type certificate data sheets whose models the AD names. - [TCDS H9EU](https://openairdocs.org/tcds/H9EU): Airbus Helicopters; names 4 of 10 models: AS350C, AS350B, AS350D1, AS350D ## 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: 21 (21 by airframe model, 0 by engine model) - Makers: Aerospatiale 13, S N I A S 6, Eurocopter 1, Eurocopter France 1 Models with the most aircraft: - [Aerospatiale AS350B](https://openairdocs.org/model/aerospatiale-as350b): 13 aircraft (airframe model) - [S N I A S AS-350B ECUREUIL](https://openairdocs.org/model/s-n-i-a-s-as-350b-ecureuil): 5 aircraft (airframe model) - [S N I A S AS350D ASTAR](https://openairdocs.org/model/s-n-i-a-s-as350d-astar): 1 aircraft (airframe model) - [Eurocopter AS350B](https://openairdocs.org/model/eurocopter-as350b): 1 aircraft (airframe model) - [Eurocopter France AS350B](https://openairdocs.org/model/eurocopter-france-as350b): 1 aircraft (airframe model) All 5 models: https://openairdocs.org/ad/81-09-06/models.md Every aircraft: https://openairdocs.org/ad/81-09-06/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.