AD 80-04-04 R1

80-04-04 R1 AVCO LYCOMING: Amendment 39-3691 as amended by Amendment 39-3881. Applies to all VO and TVO-435 series engines and to all VO, IVO, TVO and TIVO-540 series engines. To prevent possible failure of the crankshaft flange bolts perform the following, unless already accomplished: (a) Within the next 50 hours in service after effective date of this AD, engines that have accumulated 550 hours' or more time in service since new or overhaul must have the engine crankshaft flange to transmission drive coupling attaching bolt nuts checked for 15 ft.-lbs. torque measured in the tightening direction. If the torque on any attaching bolt nut is less than 15 ft.-lbs., the engine crankshaft flange and the helicopter transmission drive coupling flange must be inspected for cracks, fretting, galling, or for any metal transfer from one surface to its mating surface. Remove from service any crankshaft or drive coupling which shows such deficiencies. Prior to returning the engine to service accomplish the following: (1) Remove and discard all flange bolts. Measure all bolt holes in the crankshaft flange and repair if necessary in accordance with the requirements of AVCO Lycoming Service Instruction No. 1209B or equivalent procedure approved by Chief, Engineering & Manufacturing Branch, FAA Eastern Region. (2) Install replacement bolts in accordance with Avco Lycoming Service Instruction No. 1209B paragraph 5 or equivalent procedure approved by Chief, Engineering & Manufacturing Branch, FAA Eastern Region. Those engines which showed no such deficiencies or whose attaching bolt nut torques measured 15 ft.-lbs. may be returned to service, but the torque of the crankshaft flange attaching bolt nuts must be measured every 600 hours in service thereafter or until compliance with paragraphs (a)(1) and (a)(2) of this AD is accomplished. Amendment 39-3691 was effective February 8, 1980. This amendment 39-3881 is effective August 18, 1980.