Airworthiness Directive 98-26-07
one-timeAirworthiness Directives; Rolls-Royce Limited, Bristol Engines Division, Viper Models Mk.521 and Mk.522 Turbojet Engines
What this AD requires
This amendment adopts a new airworthiness directive (AD), applicable to Rolls-Royce Limited, Bristol Engines Division, (R-R) Viper Models Mk.521 and Mk.522 turbojet engines, that requires replacement of certain high pressure (HP) fuel pumps with an improved design which is more tolerant of reduced lubricity fuel caused by water contamination. This amendment is prompted by reports of HP fuel pump drive shaft failures resulting in in-flight engine shutdowns. These failures have been attributed to the reduced lubricity properties of fuel which is contaminated by water. The actions specified by this AD are intended to prevent HP fuel pump failures, which can result in an in-flight engine shutdown.
Which aircraft AD 98-26-07 applies to
Applies only when the specified high pressure (HP) fuel pump part numbers are installed: Model Mk.521 engines with P/N MGBB.167 or MGBB.134; Model Mk 522 engines with P/N MGBB.137, MGBB.145, MGBB.168, or MGBB.169. Installed on but not limited to Raytheon (formerly British Aerospace, Hawker Siddeley) Model DH.125 series and BH.125 series 400A airplanes.
Whether AD 98-26-07 actually applies to your aircraft (by serial and installed parts) and whether it’s already complied with comes from that aircraft’s records.
How AD compliance is recorded
A valid compliance record (14 CFR 43.9) states:
Tailplate reads a tail number’s logbooks and matches every applicable AD — including this one — to its compliance evidence, with recurring next-due dates computed.
Look up a tail number →Read the full directive (Federal Register)Applicability is derived from the FAA directive corpus and is advisory, not a legal airworthiness determination. Compliance is established only from an aircraft’s actual records.