57-16-02: Rudder Tab Push-Pull Tube

57-16-02 DOUGLAS: Applies to All DC-7 Series Aircraft Prior to Fuselage No. 697. \n\n\tCompliance required as indicated. \n\n\tAn operator recently experienced a failure in the threaded area of the forward end of the rudder tab push-pull tube P/N 3483231, which resulted in a declared emergency and unscheduled landing due to loss of rudder control. Investigation reveals that tubes reamed to accommodate the end fittings are unsatisfactory. Also, it has been determined that many rudder tab push tube assemblies, P/N's 3593396, 3593396-501, as well as 3483231, have been reamed in order to accommodate the end fittings. \n\n\tOn all aircraft on which the above-mentioned assemblies have 5,000 hours of operation or more an inspection must be conducted within the next 300-hour operation, unless already accomplished, to determine whether the rods have been reamed and for signs of failure of the tube and end fittings. All assemblies found cracked and those reamed in excess of the limits outlined in Douglas Service Bulletin DC-7 No. 181 reissued February 8, 1957, must be replaced. 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\tAll assemblies not cracked and are not reamed in excess of the limits specified in the Douglas Service Bulletin must be visually reinspected at periods not to exceed 300 hours of operation until they are replaced with new push-pull tube assembly, P/N 3593396, which have been manufactured without resorting to reaming. \n\n\t(Douglas Service Bulletin DC-7 No. 68, reissued February 8, 1957, describes the modifications required to install P/N 3593396 on those aircraft that presently incorporate P/N 3483231.) \n\n\tThis supersedes AD 56-24-3.