57-16-01 DOUGLAS: Applies to All DC-4 and C-54 Series Aircraft. \n\n\tCompliance required as indicated. \n\n\tAccidents have occurred due to the collapse of the nose gear shock strut, P/N 8066 and 8066A. Investigation reveals that some failures have occurred in the steel piston tube, P/N 8066-4, as a result of corrosion and repeated loading over an extended period of time, while others have failed from fatigue only. Initial fractures may occur on the outside of the tube adjacent to the top edges of the nose gear fork, P/N 8066A-60, or on the inside of the tube in the vicinity of the top of the internal reinforcing sleeve. Because of this, the following must be accomplished: \n\n\t1.\tInspect as soon as practical but not later than October 1, 1956, unless equivalent inspection conducted within the last landing gear overhaul, all nose gear piston tubes, P/N 8066-4, both on the inside and on the outside diameters, for evidence of fatigue and/or excessive corrosion in the vicinity of theedges of the internal reinforcing ring and spacer tube or liner and in the vicinity of the top edge of the external sleeve, for evidence of cracks. \n\n\t2.\tIf cracks are found the part must be replaced. (Certain parts can be reworked in accordance with Douglas Service Bulletins. Such parts may be continued in service after rework provided the repetitive inspections limitations contained in the Service Bulletin are adhered to.) \n\n\t3.\tAny corrosion found to exist must be removed and the part provided with adequate corrosion protection. \n\n\t4.\tParts found to be satisfactory and not reworked per Douglas Service Bulletins may be continued in service until January 1, 1958, and then must be reworked per Douglas Service Bulletin No. 111. \n\n\t(Douglas Service Bulletin DC-4 No. 111 dated April 19, 1956, and revised November 6, 1956, covers this same subject, and outlines methods of inspections with the limitations on each as well as permanent rework instructions. Service Bulletin DC-4 No. 111, Addendum No. 1 dated November 6, 1956, covers Operations Limitations on unreworked nose gear struts as well as struts reworked per Service Bulletin DC-4 No. 111, reissued October 3, 1956.) \n\n\tThis supersedes AD 56-12-01.