74-16-01 GENERAL DYNAMICS: Amendment 39-1904 as amended by Amendment 39-3206. Applies to General Dynamics Model 340 and 440 series airplanes, certificated in all categories, including those modified for turbo-propeller power.
Compliance required as indicated.
To prevent loss of structural integrity of the frame, due to longitudinal cracks in the stringer or beltframe at the beltframe attach points, accomplish the following:
(a) For airplanes with more than 52,000 hours time in service as of the effective date of this AD, perform an initial inspection of the stringer to frame attachments per (g)(1), within 300 hours additional time in service, unless already accomplished within the last 4,700 hours time in service, in addition:
(1) Aircraft certificated at a maximum gross weight of 55,000 pounds or less, and without a main deck cargo door, within 5,000 hours time in service from the initial inspection, inspect per paragraph (g)(2), and thereafter:
(i) Within 5,000 hours time in service from the inspection accomplished per paragraph (g)(2), and thereafter at intervals not to exceed 5,000 hours time in service from the last inspection, inspect per paragraph (g)(3); and,
(ii) Within 7,500 hours time in service from the inspection accomplished per paragraph (g)(2), and thereafter at intervals not to exceed 7,500 hours time in service from the last inspection, inspect per paragraph (g)(4).
(2) Aircraft with a main deck cargo door and aircraft certificated at a maximum gross weight of more than 55,000 pounds, within 5,000 hours time in service from the initial inspection and thereafter at intervals not to exceed 5,000 hours time in service from the last inspection, inspect per paragraph (g)(2).
(b) For airplanes with more than 42,000 hours time in service, up to and including 52,000 hours time in service as of the effective date of this AD, perform an initial inspection of the stringer to frame attachments per (g)(1), within 1,500 hours additional time in service, unless already accomplished within the last 3,500 hours time in service, and reinspect in accordance with paragraph (a)(1) or (a)(2).
(c) For airplanes with more than 35,000 hours' time in service up to and including 42,000 hours' time in service as of the effective date of this A.D., perform an initial inspection of the stringer to frame attachments per (g)(1), below, within the next 3,000 hours' time in service, unless already accomplished within the last 4,500 hours' time in service, and thereafter perform the inspection described in (g)(2), below, at intervals not to exceed 7,500 hours' additional time in service. See (f), below, for reduction in repetitive inspection interval.
(d) For airplanes with more than 25,000 hours' time in service up to and including 35,000 hours' time in service as of the effective date of this A.D., perform an initial inspection of the stringer to frame attachment per (g)(1), below, within the next 3,000 hours' time in service, unless already accomplished within the last 7,000 hours' time in service, and thereafter perform the inspection described in (g)(2), below, at intervals not to exceed 10,000 hours' time in service. See (f), below, for reduction in repetitive inspection interval.
(e) For those airplanes with less than 25,000 hours' time in service on the effective date of this A.D., and have not previously been inspected for cracks, perform the initial inspection described in (g)(1), below, within 3,000 hours' additional time in service after accumulating 25,000 hours' time in service. Repetitive inspections must be performed per (g)(2), below, at the intervals required by (a) through (d), above. For those aircraft which have been previously inspected for cracks per (g)(1), below, accomplish the repetitive inspections per (g)(2), below, at the intervals required by (a) through (d), above. The first inspection per (g)(2) must be accomplished before accumulating 28,000 hours' total time in service or 10,000 additional flight hours from the inspection per (g)(1), whichever occurs later.
(f) The second inspection, for airplanes affected by paragraphs (c) and (d), above, will be within the 7,500 or 10,000 hours' time in service as specified; however, for subsequent inspections, the interval will be based upon the airplane time in service at the time of the last inspection rather than the total time in service which results in the airplane reaching the next category. If the last inspection was accomplished when the airplane had more than 42,000 hours' time in service, all subsequent inspections must be at intervals not to exceed 5,000 hours' additional time in service.
(g) (1) Perform a close, visual, above the floor level, inspection of the stringers and beltframes for evidence of cracks at all stringer to beltframe attach points between stations 140 and 889.
(2) Perform a close visual inspection of all stringer to frame attachment (above and below floor level) for evidence of cracks between stations 140 and 889.
(3) Perform a close visual inspection of all stringer to frame attachment for evidence of cracks below the floor between stations 681 and 889.
(4) Perform a close visual inspection of all stringer to frame attachment for evidence of cracks between stations 140 and 889 above the floor and between stations 140 and 681 below the floor.
(5) If cracks are found in any of these inspections, repair in accordance with applicable structural repair manual prior to further flight.
(h) Equivalent inspections and repairs may be approved by the Chief, Aircraft Engineering Division, upon the submission of adequate substantiating data.
(i) This A.D. may be amended to modify the repetitive inspection intervals if substantiating data is presented to the Chief, Aircraft Engineering Division, FAA Western Region.
(j) If cracks are found as a result of the inspections performed in compliance with this A.D., report the findings to the Chief, Aircraft Engineering Division, FAA Western Region, P.O. Box 92007, Worldway Postal Center, Los Angeles, California 90009. (Reporting approved by the Bureau of Budget under BOB No. 04-R-0174.)
Identify part number, total hours' time in service on the part and time in service since last inspection; number, size and location of crack(s); total time on the aircraft, serial number of the aircraft.
(k) Airplanes may be flown to a base for the accomplishment of maintenance required by this A.D. per FAR's 21.197 and 21.199.
Amendment 39-1904 became effective on August 2, 1974.
This amendment 39-3206 becomes effective May 4, 1978.