AD 77-21-05

77-21-05 ROLLS ROYCE AERO, LTD: Amendment 39-3055. Applies to Dart Engines Series 527, 528, 529, 531, 532, 533, 534, 535, 536, 550, 542-4, 542-10, and 543-10 that have modification 1425 incorporated and are installed on, but not necessarily limited to, Nihon YS-11, Convair 600 and 640, Handley Page Herald, Fokker F27, Fairchild F27, Grumman Gulfstream I, and Hawker Siddeley 748 series.

Compliance is required as indicated.

To prevent overheating and failure of high pressure turbine discs, accomplish the following:

(a) Within the next 500 hours engine time in service after the effective date of this AD and thereafter at intervals not to exceed 1500 hours engine time in service, inspect the flame tube bridge pieces for cracking of the support legs in accordance with the instructions contained in paragraph 4.C of Rolls Royce Dart Service Bulletin Da 72-420, dated October 1975 (hereinafter referred to as the Bulletin), or an equivalent approved by the Chief, Aircraft Certification Staff, Europe, Africa, and Middle East Region, FAA, c/o American Embassy, APO New York, NY 09667 (hereinafter referred to as FAA-approved equivalent).

(b) If, during an inspection required by this AD, flame tube bridge piece cracking is detected, replace the affected part with a serviceable part before further flight (except that the aircraft may be flown in accordance with FAR 21.197 and 21.199 to a base where the work can be performed), and continue to inspect in accordance with either paragraphs (c) or (d) of this AD, as applicable.

(c) If, during an inspection required by paragraph (a) of this AD, flame tube bridge piece leg cracking is found, establish a repetitive inspection interval for all engines in the fleet in accordance with paragraph 4.A.(3)(b) of the Bulletin or an FAA-approved equivalent and continue to inspect the fleet in accordance with paragraph (a) of this AD within the fleet repetitive inspection interval established under this paragraph.

(d) If, during a repetitive inspection conducted in accordance with this paragraph or paragraph (c) of this AD, a cracked bridge piece leg of any flame tube in the fleet is found, establish a further reduced repetitive inspection interval for all engines in the fleet in accordance with paragraph 4.B.(3) of the Bulletin or an FAA- approved equivalent and continue to inspect the fleet in accordance with paragraph (a) of this AD within the fleet repetitive inspection interval established under this paragraph.

This amendment becomes effective November 11, 1977.