AD 92-10-07
Applicability
| Type | Manufacturer | Model | Details |
|---|---|---|---|
| engine | Rolls-Royce Limited, Bristol Engines Division | Viper Mk. 521 | ROLLS-ROYCE PLC Models Viper Mk. 521, Mk. 522, and Mk. 601 Engines |
| engine | Rolls-Royce Limited, Bristol Engines Division | Viper Mk. 522 | ROLLS-ROYCE PLC Models Viper Mk. 521, Mk. 522, and Mk. 601 Engines |
| engine | Rolls-Royce Limited, Bristol Engines Division | Viper Mk. 601-22 | ROLLS-ROYCE PLC Models Viper Mk. 521, Mk. 522, and Mk. 601 Engines |
Unsafe Condition
Failure of high pressure compressor (HPC) rotor disks, causing an engine failure.
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Required Actions
Remove from service HPC stage 5 and 6 rotor disks with specified part numbers and replace with serviceable parts. For disks with 12,500 or more cycles since new as of the effective date, comply within the next 100 cycles. For those with less than 12,500 cycles, comply at or prior to 12,600 cycles since new.
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Compliance Time
Within the next 100 cycles in service (for disks with 12,500+ cycles since new as of effective date) or at or prior to 12,600 cycles since new (for disks with less than 12,500 cycles).
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Affected Aircraft
Rolls-Royce plc Viper Mk. 521, Mk. 522, and Mk. 601 turbojet engines installed on but not limited to Hawker-Siddeley HS125 and HS125-600 aircraft.
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Source: Official FAA Source ↗
Retrieved: Apr 8, 2026
Rights: U.S. Government Public Domain
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