57-16-03 DOUGLAS: Applies to All Model DC-7 Series Aircraft Prior to Fuselage No. 697. \n\n\tCompliance required as indicated. \n\n\tNumerous cases have been reported wherein fatigue failures have occurred in the elevator control tab pushrod assembly, P/N 4499117. Investigation reveals that tubes reamed to accommodate the end fittings are unsatisfactory. Also, it has been determined that P/N 4499117 as well as other assemblies, P/N's 2357984, 3593467, and 4335618, have been reamed to permit installation of the end fittings. \n\n\tUnless already accomplished, inspect all the above assemblies within the next 300 hours for fatigue cracks or reaming. Unless disassembled x-ray is believed to be the only reliable means of verifying whether the tubes have been reamed in excess of the limits specified by Douglas. \n\n\tIf cracks are found or reaming exceeds the limits specified in Douglas Service Bulletin DC-7 No. 181 reissued February 8, 1957, the part must be replaced. \n\n\tAll parts reamed within tolerances specified in the Douglas Service Bulletin must be visually reinspected for fatigue cracks at intervals not to exceed 300 hours. When P/N's 4335618 and 4499117 as well as any P/N 3593467, which have been reamed, are replaced with P/N 359347 now manufactured by controlling the swaging of the tube instead of reaming to permit installation of the end fittings, the repeated inspection may be discontinued. \n\n\t(Douglas Service Bulletin DC-7 No. 132 revised November 13, 1956, covers the installation of P/N 3593467 and the associated changes required to make the installation on aircraft originally incorporating P/N 4335618 or P/N 4499117.) \n\n\tThis supersedes AD 56-24-04.