# AD 77-16-07: Main Rotor Gearbox

- Type: Airworthiness directive
- Status: Current
- Products: Airbus Helicopters Deutschland BO-105A and BO-105C
- Effective: September 6, 1977
- Superseded by: Nothing supersedes this AD
- Product type: Aircraft, Rotorcraft
- Amendment: 39-3001
- Registered aircraft: 4 may be affected, by airframe or engine model (OpenAirDocs)
- FAA DRS: https://drs.faa.gov/browse/excelExternalWindow/DB15A9B0F3A785DD86256A3A006E6802.0001
- DRS record last changed: May 30, 2024
- Page: https://openairdocs.org/ad/77-16-07

## The airworthiness directive

77-16-07 MESSERSCHMITT-BOLKOW-BLOHM (MBB). Amendment 39-3001. Applies to Model BO-105A and BO-105C helicopters which incorporate main rotor gearbox oil pumps, P/N's 7631 955 112 or 7631 955 115, having Serial Numbers up to and including 229. Compliance is required as indicated, unless already accomplished. To prevent excessive wear of the sun gear in the planet gear carrier of the main rotor gearbox, accomplish the following: (a) Within the next 100 hours time in service after the effective date of this AD, modify the main rotor gearbox oil pump as follows: (1) For pumps, P/N 7631 955 115, install a stronger compression spring in accordance with MBB Service Bulletin No. 10-16, dated July 28, 1975, or an FAA-approved equivalent. (2) For pumps, P/N 7631 955 112, replace the pump plunger in accordance with MBB Service Bulletin No. 10-20, dated May 25, 1976, or an FAA-approved equivalent and install a stronger compression spring in accordance with MBB Service Bulletin No. 10-16, dated July 28, 1975, or an FAA-approved equivalent. (b) Within the next 10 hours time in service after the effective date of this AD and thereafter at intervals not to exceed 10 hours time in service since the last inspection, inspect the main rotor gearbox magnetic chip detector plug for the presence of metallic particles. If metallic particles are found, comply with the relevant instructions specified in section 10-1-2 of the MBB BO-105 Maintenance and Overhaul Manual, or an FAA-approved equivalent. (c) An equivalent means of compliance with the requirements in paragraph (b) of the AD, including the initial compliance time and the repetitive inspection interval, may be used in lieu thereof when approved by the Chief, Aircraft Certification Staff, AEU-100, Europe, Africa, and Middle East Region, Federal Aviation Administration, c/o American Embassy, Brussels, Belgium, Tel. 513.38.30. This amendment becomes effective September 6, 1977.

## Affected data sheets (1) (OpenAirDocs)

The type certificate data sheets whose models the AD names.

- [TCDS H3EU](https://openairdocs.org/tcds/H3EU): Airbus Helicopters Deutschland GmbH (AHD); names 2 of 5 models: BO-105C, BO-105A

## 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: Messerschmitt-Boelkow-Blohm-Gm 4

Models with the most aircraft:

- [Messerschmitt-Boelkow-Blohm-Gm BO-105C](https://openairdocs.org/model/messerschmitt-boelkow-blohm-gm-bo-105c): 4 aircraft (airframe model)

All 1 models: https://openairdocs.org/ad/77-16-07/models.md
Every aircraft: https://openairdocs.org/ad/77-16-07/aircraft.md

Its text cites no advisory circulars or STCs.

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