AD 64-21-04

64-21-04 FAIRCHILD: Amdt. 814 Part 507 Federal Register September 11, 1964. Applies to Model F-27 Aircraft, Serial Numbers 1 through 97, and 99.

Compliance required as indicated.

There have been cracks found in the rib caps and stringers in the vertical stabilizer where the rib at water line 201.575 attaches to the hat and zee section stringers. To preclude the condition from developing in other such aircraft, accomplish the following:

(a) On aircraft with less than 1,000 hours' time in service on the effective date of this AD, comply with (c) prior to the accumulation 1,050 hours' time in service, unless already accomplished within the last 200 hours' time in service, and thereafter at intervals not to exceed 200 hours' time in service from the last inspection.

(b) On aircraft with 1,000 or more hours' time in service on the effective date of this AD, comply with (c) within the next 50 hours' time in service after the effective date of this AD, unless already accomplished within the last 150 hours' time in service, and at intervals thereafter not to exceed 200 hours' time in service from the last inspection.

(c) Inspect for cracks in the skin, rib and stringers on both sides of the vertical stabilizer along and directly adjacent to water line 201.575, from the trailing edge of the stabilizer, forward, to the auxiliary spar (located directly aft of the stabilizer leading edges). Use X-ray or dye penetrant in conjunction with at least a 10-power glass, or FAA-approved equivalent inspection. If cracks are found accomplish (d).

(d) Repair cracked parts in accordance with an FAA-approved repair or replace cracked parts with a part of the same part number or an FAA approved equivalent before further flight except that a ferry flight may be made in accordance with the provisions of CAR 1.76.

(e) The repetitive inspection intervals specified in (a) and (b) may be increased from 200 hours' time in service to 800 hours' time in service from the last inspection on aircraft that are modified in accordance with Fairchild Service Bulletin No. 55-4 dated March 1, 1963, or an FAA approved equivalent.

(f) Upon request of the operator, an FAA maintenance inspector, subject to prior approval of the Chief, Engineering and Manufacturing Branch, FAA Eastern Region, may adjust the repetitive inspection intervals specified in this AD to permit compliance at an established inspection period of the operator if the request contains substantiating data to justify the increase for such operator.

(Fairchild Service Bulletins 55-4 dated March 1, 1963, and 55-5 dated March 1, 1963, cover this subject.) This supersedes AD 63-10-2. This directive effective September 12, 1964.