# AD 74-25-10: Rotor Brake Disc

- Type: Airworthiness directive
- Status: Current
- Products: Bell Helicopter Textron Canada 206A and 206B
- Effective: December 16, 1974
- Superseded by: Nothing supersedes this AD
- Product type: Aircraft, Rotorcraft
- Amendment: 39-2039
- Registered aircraft: 855 may be affected, by airframe or engine model (OpenAirDocs)
- FAA DRS: https://drs.faa.gov/browse/excelExternalWindow/3331E19A3FD77B1786256A340053EBD3.0001
- DRS record last changed: May 30, 2024
- Page: https://openairdocs.org/ad/74-25-10

## The airworthiness directive

74-25-10 BELL: Amendment 39-2039. Applies to Model 206A and 206B helicopters certificated in all categories and equipped with Rotor Brake Kit, P/N 206-706-032-1.

Compliance required within the next ten hours' time in service after the effective date of this airworthiness directive unless already accomplished.

To prevent failure of the rotor brake disc which could cause serious damage to critical components of the helicopter, accomplish the following:

a. Remove the engine to transmission driveshaft and aft coupling. (Refer to Section VI of the Maintenance and Overhaul Manual.)

b. Remove the Rotor Brake Disc Assembly P/N 4000071 or 4000071-1, attachment bolts and gasket from the coupling and discard.

c. Reinstall the coupling and driveshaft as described in the Maintenance and Overhaul Manual.

d. Disable the brake by removing the P/N 156F538-4S-0061 hose assembly between the rotor brake and firewall and capping the AN833-4C elbows with AN929-4J caps or equivalent.

e. Bell Service Bulletin No. 206-50-74-1, Revision A, dated October 29, 1974 or later FAA/DER Approved Revision, includes equivalent instructions for these procedures and lists alternate FAA approved rotor brake configurations.

f. Equivalent methods of compliance with this Airworthiness Directive must be approved by the Chief, Engineering and Manufacturing Branch, Flight Standards Division, Southwest Region, Federal Aviation Administration.

This amendment becomes effective December 16, 1974.

## Affected data sheets (1) (OpenAirDocs)

The type certificate data sheets whose models the AD names.

- [TCDS H2SW](https://openairdocs.org/tcds/H2SW): Bell Textron Canada Limited; names 2 of 12 models: 206B, 206A

## 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: 855 (855 by airframe model, 0 by engine model)
- Makers: Bell 816, Bell Helicopter Textron 29, Bell Helicopter Textron Canada 10

Models with the most aircraft:

- [Bell 206B](https://openairdocs.org/model/bell-206b): 790 aircraft (airframe model)
- [Bell Helicopter Textron 206B](https://openairdocs.org/model/bell-helicopter-textron-206b): 29 aircraft (airframe model)
- [Bell 206A](https://openairdocs.org/model/bell-206a): 23 aircraft (airframe model)
- [Bell Helicopter Textron Canada 206B](https://openairdocs.org/model/bell-helicopter-textron-canada-206b): 10 aircraft (airframe model)
- [Bell 206B II](https://openairdocs.org/model/bell-206b-ii): 3 aircraft (airframe model)

All 5 models: https://openairdocs.org/ad/74-25-10/models.md
Every aircraft: https://openairdocs.org/ad/74-25-10/aircraft.md

Its text cites no advisory circulars or STCs.

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