AD 74-12-08

74-12-08 AIRESEARCH MANUFACTURING COMPANY of ARIZONA: Amendment 39-1862. Applies to Model TSCP700-5 Auxiliary Power Units installed in, but not limited to, Airbus Industries Model A300B aircraft certificated in all categories.

Compliance required as indicated.

(a) For APU's with less than 1500 operating cycles on the effective date of this AD, inspect, prior to any further in-flight operation, unless already accomplished, the fuel control differential pressure regulator housing, P/N 977320-1 or -2, for minimum dimensions and cracks per paragraphs 2.B.(2) and (3) of AiResearch Alert Service Bulletin 969900-49-A3644, dated May 14, 1974, or later FAA-approved revisions. Re-work parts, if necessary, per paragraph 2.B.(4).

Housings which meet the prescribed minimum dimensions, or which are reworked to meet these dimensions per paragraph 2.B.(4) shall be re-identified as P/N 977320-4. Housings not meeting these dimensional requirements shall be rendered unserviceable and replaced with serviceable P/N 977320-4 housings. Housings which meet inspection and dimensional requirements may be continued in service up to a maximum of 1500 operating cycles.

Note: For the purpose of this AD, an APU operating cycle is any operation consisting of a start and shut-down. The number of cycles may be determined by actual count, or, subject to acceptance by the assigned FAA Maintenance Inspector, may be calculated by dividing the fuel control assembly time in service by the operator's fleet average APU operating time per APU operating cycle.

(b) For all APU's with 1,500 or more operating cycles in service on the effective date of this AD, inspect per (a), above, prior to further in-flight operation, unless already accomplished, and, in addition thereto, and prior to further in-flight operation, modify the fuel control assembly per (c), below.

(c) Before exceeding 1500 operational cycles in service, inspect the fuel control differential pressure regulator body per paragraph 2.B.(2) and modify the fuel control assembly in accordance with paragraph 2.C. of AiResearch Service Bulletin 969900-49-A3644, dated May 14, 1974, or later FAA-approved revisions. Re-identify fuel control assembly per paragraph 2.D. of the referenced service bulletin.

(d) Within 3000 operating cycles in service after the accomplishment of paragraph (c), above, and at intervals not to exceed 3000 operating cycles in service thereafter, perform the inspections as defined in paragraph 2.B.(2) of AiResearch Service Bulletin 969900-49-A3644, dated May 14, 1974, or later FAA-approved revisions.

(e) The inspections prescribed in paragraph (d), above, may be discontinued when the fuel control differential pressure regulator P/N 977320-4 is replaced with a housing, P/N 977656-1.

(f) Equivalent procedures may be approved by the Chief, Aircraft Engineering Division, FAA Western Region, upon submission of adequate substantiation data.

This amendment becomes effective June 10, 1974.