# AD 77-13-02: Brake Control

- Type: Airworthiness directive
- Status: Current
- Products: Textron BH.125 Series 400A, BH.125 Series 600A, DH.125 Series 1A, DH.125 Series 1A-522, DH.125 Series 1A/R-522, DH.125 Series 1A/S-522, DH.125 Series 3A, DH.125 Series 3A/R, DH.125 Series 3A/RA and DH.125 Series 400A
- Effective: July 20, 1977
- Superseded by: Nothing supersedes this AD
- Product type: Aircraft, Large airplane
- Amendment: 39-2926
- Registered aircraft: 4 may be affected, by airframe or engine model (OpenAirDocs)
- FAA DRS: https://drs.faa.gov/browse/excelExternalWindow/20E45076C8B7126D862569A50064B0FB.0001
- DRS record last changed: January 21, 2026
- Page: https://openairdocs.org/ad/77-13-02

## The airworthiness directive

77-13-02 HAWKER SIDDELEY AVIATION, LTD: Amendment 39-2926. Applies to Model DH/BH-125 airplanes, all series, certificated in all categories.

Compliance is required as indicated.

To prevent the failure of the knife edges of the brake control valve, P/N AC. 61520, and the possible complete loss of braking on one side of the airplane with no advance warning to the flight crew, accomplish the following:

  (a) Comply with paragraph (b) or (c) of this AD as follows, and, thereafter, continue to comply with paragraph (b) or (c) of this AD at intervals not to exceed 4,500 landings since last compliance:

  (1) For airplanes having brake control valve knife edges that have accumulated less than 4,300 landings on the effective date of this AD, compliance is required prior to the accumulation of 4,500 landings.

  (2) For airplanes having brake control valve knife edges that have accumulated 4,300 or more landings, but less than 5,900 landings, on the effective date ofthis AD, compliance is required prior to the accumulation of an additional 200 landings.

  (3) For airplanes having brake control valve knife edges that have accumulated 5,900 or more landings on the effective date of this AD, compliance is required prior to the accumulation of 6,100 landings or an additional 100 landings whichever occurs later.

  (4) For airplanes for which no records exist that indicate the number of landings the brake control valve knife edges have accumulated, compliance is required prior to the accumulation of 100 landings after the effective date of this AD.

  (b) Replace the knife edges with new parts, P/Ns ACO. 34629, ACO. 34630, and ACO. 36133, in accordance with Paragraph A, of Section 2, titled "Accomplishment Instructions," of Hawker Siddeley Aviation, Ltd. Service Bulletin 32-166, dated January 27, 1976, or an FAA- approved equivalent.

  (c) Replace the brake control valve, P/N AC. 61520, with a valve of the same part number that incorporates knife edges having part numbers specified in paragraph (b) of this AD in accordance with Paragraph B, of Section 2, titled "Accomplishment Instructions," of Hawker Siddeley Aviation, Ltd. Service Bulletin 32- 166, dated January 27, 1976, or an FAA-approved equivalent.

This amendment becomes effective July 20, 1977.

## Affected data sheets (1) (OpenAirDocs)

The type certificate data sheets whose models the AD names.

- [TCDS A3EU](https://openairdocs.org/tcds/A3EU): Textron Aviation Inc.; names 10 of 50 models: DH.125 Series 1A/R-522, BH.125 Series 400A, BH.125 Series 600A, DH.125 Series 400A, DH.125 Series 3A/R, DH.125 Series 1A, DH.125 Series 1A-522, DH.125 Series 3A…

## 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: Hawker Siddeley 4

Models with the most aircraft:

- [Hawker Siddeley BH.125-400A](https://openairdocs.org/model/hawker-siddeley-bh-125-400a): 2 aircraft (airframe model)
- [Hawker Siddeley DH.125-3A/RA](https://openairdocs.org/model/hawker-siddeley-dh-125-3a-ra): 2 aircraft (airframe model)

All 2 models: https://openairdocs.org/ad/77-13-02/models.md
Every aircraft: https://openairdocs.org/ad/77-13-02/aircraft.md

Its text cites no advisory circulars or STCs.

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