# AD 75-22-21: Main Gear Boxes

- Type: Airworthiness directive
- Status: Current
- Products: Airbus Helicopters SA.316B Alouette III
- Effective: October 30, 1975
- Superseded by: Nothing supersedes this AD
- Product type: Aircraft, Rotorcraft
- Amendment: 39-2393
- Registered aircraft: 4 may be affected, by airframe or engine model (OpenAirDocs)
- FAA DRS: https://drs.faa.gov/browse/excelExternalWindow/4043517E3F47AD8C86256A33006FB7F5.0001
- DRS record last changed: May 30, 2024
- Page: https://openairdocs.org/ad/75-22-21

## The airworthiness directive

75-22-21 SOCIETE NATIONALE INDUSTRIELLE AEROSPATIALE: (S.N.I.A.S., formerly SUD AVIATION). Amendment 39-2393. Applies to Model SA316B Alouette III helicopters, certificated in all categories, incorporating main rotor transmission gearbox (MGB), Serial Number 9,999 or lower, P/N 3160S.62.00.000.10 through .12 incorporating Modification AM1212, or P/N 3160S.62.00.000.13 or .14.

Compliance is required as indicated, unless already accomplished.

To prevent possible failure of the main gearbox, accomplish the following:

  (a) Within the next 10 hours' time in service after the effective date of this AD, install a temporary operating limitations placard on the instrument panel in full view of the pilot reading as follows: "Operate in accordance with the limitations specified in the Alouette III SE.3160 Helicopter Flight Manual. Limitations or performance specified in Appendix 2 of that manual are not applicable to this helicopter."

  (b) Within the next 450 hours' time inservice after the effective date of this AD, replace the MGB with a serviceable MGB having a part number specified in Subparagraph 1C of Alouette Service Bulletin No. 01.34 dated June 24, 1974, or an FAA-approved equivalent.

  (c) After complying with paragraph (b) of this AD, the placard required by paragraph (a) may be removed.

This amendment becomes effective October 30, 1975.

## Affected data sheets (1) (OpenAirDocs)

The type certificate data sheets whose models the AD names.

- [TCDS H1IN](https://openairdocs.org/tcds/H1IN): Airbus Helicopters; names 1 of 5 models: SA.316B Alouette III

## 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: 4 (4 by airframe model, 0 by engine model)
- Makers: Aerospatiale 2, Sud 2

Models with the most aircraft:

- [Sud SA316B ALOUETTE III](https://openairdocs.org/model/sud-sa316b-alouette-iii): 2 aircraft (airframe model)
- [Aerospatiale SA316B ALOUETTE III](https://openairdocs.org/model/aerospatiale-sa316b-alouette-iii): 2 aircraft (airframe model)

All 2 models: https://openairdocs.org/ad/75-22-21/models.md
Every aircraft: https://openairdocs.org/ad/75-22-21/aircraft.md

Its text cites no advisory circulars or STCs.

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