AD 77-13-20
Applicability
| Type | Manufacturer | Model | Details |
|---|---|---|---|
| engine | Rolls-Royce Limited, Bristol Engines Division | Viper Mk. 522 | ROLLS ROYCE (1971), LTD Model Bristol Viper MK. 522 and MK. 601-22 Engines |
| engine | Rolls-Royce Limited, Bristol Engines Division | Viper Mk. 601-22 | ROLLS ROYCE (1971), LTD Model Bristol Viper MK. 522 and MK. 601-22 Engines |
Unsafe Condition
Interference between the engine throttle control rod and the high pressure fuel shutoff valve could result in inability to actuate fuel shutoff.
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Required Actions
Relocate ident/data tags on fuel tube P/N DF-21-389, check clearance between fuel tube and H.P. cock control rod P/N 25CX53-25A, and realign fuel tube if clearance is inadequate. For engines not yet installed, ensure ident/data tags are positioned more than 8 inches from the union nut at the b.f.c.u. connection or refit them to a lower position as specified.
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Compliance Time
within the next 500 hours engine time in service after the effective date of this AD
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Affected Aircraft
Rolls-Royce Limited, Bristol Engines Division Model Viper Mk. 522 and Viper Mk. 601-22 engines installed or held for installation on Hawker Siddeley Model DH/BH-125 series airplanes
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Source: Official FAA Source ↗
Retrieved: Apr 8, 2026
Rights: U.S. Government Public Domain
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