# AD 77-13-20: Fuel Shutoff Valve

- Type: Airworthiness directive
- Status: Current
- Products: Rolls-Royce Limited, Bristol Engines Division Viper Mk. 522 and Viper Mk. 601-22
- Effective: August 1, 1977
- Superseded by: Nothing supersedes this AD
- Product type: Engine
- Amendment: 39-2945
- Registered aircraft: 6 may be affected, by airframe or engine model (OpenAirDocs)
- FAA DRS: https://drs.faa.gov/browse/excelExternalWindow/0A4B427A1B346D608625685F0052028B.0001
- DRS record last changed: May 30, 2024
- Page: https://openairdocs.org/ad/77-13-20

## The airworthiness directive

77-13-20 ROLLS ROYCE (1971), LTD: Amendment 39-2945. Applies to Bristol Viper MK. 522 and MK. 601-22 engines installed, or being held for installation, on Hawker Siddeley Model DH/BH-125 series airplanes, certificated in all categories.

Compliance is required as indicated, unless already accomplished.

To prevent interference between the engine throttle control rod and the high pressure fuel shutoff valve that could result in inability to actuate fuel shutoff, accomplish the following:

  (a) For installed engines, within the next 500 hours engine time in service after the effective date of this AD, accomplish the following in accordance with paragraph 2.A of Rolls Royce Alert Service Bulletin 73-A98 (MK. 522 engines) or 73-A13 (MK. 601-22 engines), both dated October 1975, or an FAA-approved equivalent:

  (1) Relocate the ident/data tags fitted to the fuel tube, P/N DF-21-389.

  (2) Check for adequate clearance between the fuel tube, P/N DF-21-389, and the H.P.cock control rod, P/N 25CX53-25A.

  (3) If the clearance is found not to be adequate during the inspection specified in paragraph (a)(2) of this paragraph, realign the fuel tube to provide adequate clearance.

  (b) For other engines, prior to installation on a Model DH/BH-125 airplane, ascertain the location of the ident/data tags on fuel tube P/N DF-21-389 and if it is found to be within 8 inches or less of the union nut, at the b.f.c.u. connection, remove the tags and refit to a lower position on the tube in accordance with the instructions contained in paragraph 2.B of Rolls Royce Alert Service Bulletin 73-A98 (MK. 522 engines) or 73-A13 (MK. 601-22 engines), both dated October 1975, or an FAA-approved equivalent.

NOTE: The accomplishment instructions contained in Rolls Royce Alert Service Bulletins 73-A13 and 73- A98 are identical.

This amendment becomes effective on August 1, 1977.

## Affected data sheets (2) (OpenAirDocs)

The type certificate data sheets whose models the AD names.

- [TCDS E15EU](https://openairdocs.org/tcds/E15EU) (historical): Rolls-Royce Deutschland Ltd & Co KG; names 1 of 1 models: Viper Mk. 601-22
- [TCDS E3EU](https://openairdocs.org/tcds/E3EU) (historical): Rolls-Royce Deutschland Ltd & Co KG; names 1 of 2 models: Viper Mk. 522

## 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: 6 (0 by airframe model, 6 by engine model)
- Makers: Soko 2, Aero Vodochody 1, Aerovodochody 1, Bac Jet Provost 1, Hawker Siddeley 1

Models with the most aircraft:

- [Rolls-Royce VIPER MK60122](https://openairdocs.org/engine/rolls-royce-viper-mk60122): 3 aircraft (engine model)
- [Rolls-Royce VIPER MK522](https://openairdocs.org/engine/rolls-royce-viper-mk522): 2 aircraft (engine model)
- [Rolls-Royce VIPER MK 601 series](https://openairdocs.org/engine/rolls-royce-viper-mk-601-series): 1 aircraft (engine model)

All 3 models: https://openairdocs.org/ad/77-13-20/models.md
Every aircraft: https://openairdocs.org/ad/77-13-20/aircraft.md

Its text cites no advisory circulars or STCs.

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