92-10-07 ROLLS-ROYCE PLC: Amendment 39-8241. Docket No. 87-ANE-05.
Applicability: Rolls-Royce plc (R-R) Viper Mk. 521, Mk. 522, and Mk. 601 turbojet engines installed on but not limited to Hawker-Siddeley HS125 and HS125-600 aircraft.
Compliance: Required as indicated, unless accomplished previously.
To prevent failure of high pressure compressor (HPC) rotor disks, causing an engine failure, accomplish the following:
(a) Remove from service HPC stage 5 and 6 rotor disks with the following part numbers (includes all Modification Standards): Viper Mk. 521: V.20492, V.20494, V.27430, V.27433, V.39638, V.39639, V.39642, V.39643, V.39677, V.39678, V.39681, V.39682, V.42057, V.42059, V.46180, V.46181, V.46182, V.46204, V.46205, and V.46206; Viper Mk. 522: V.20492, V.20494, V.27430, V.27433, V.39638, V.39639, V.39642, V.39643, V.39677, V.39678, V.39681, V.39682, V.42057, V.42059, V.46180, V.46181, V.46182, V.46204, V.46205, and V.46206; Viper Mk. 601: V.42057, V42059, V.44768,V.44769, V.44780, V.44781, V.46182, and V.46206, and replace with a serviceable part, as follows:
(1) HPC stage 5 and 6 rotor disks that have accumulated 12,500 or more cycles since new on the effective date of this AD, within the next 100 cycles in service.
(2) HPC stage 5 and 6 rotor disks that have accumulated less than 12,500 cycles since new on the effective date of this AD, at or prior to accumulating 12,600 cycles since new.
NOTES: (1) Further information pertaining to disk life limits can be obtained in Chapter 5 of the R-R Viper Mk. 521, Mk. 522, and Mk. 601 Maintenance and Shop Manuals.
(2) Reference R-R plc Service Bulletins Number 72-A154 for Viper Mk. 601, and Number 72-A372 for Viper Mk. 521 and Viper Mk. 522 engines.
(b) Special flight permits may be issued in accordance with FAR 21.197 and 21.199 to operate the airplane to a location where the requirements of this AD can be accomplished.
(c) An alternative method of compliance or adjustment of the compliance time that provides an acceptable level of safety, may be used if approved by the Manager, Engine Certification Office, FAA, Engine and Propeller Directorate. The request should be forwarded through an FAA Principal Maintenance Inspector, who may add comments and then send it to the Manager, Engine Certification Office.
NOTE: Information concerning the existence of approved alternative methods of compliance with this airworthiness directive, if any, may be obtained from the Engine Certification Office.
(d) This amendment becomes effective on September 21, 1992.