Incident Summary
A private pilot, accompanied by two passengers, was flying one of two wheel-equipped airplanes en route to a remote beach site. The route of flight was over ocean waters, flanked by steep vertical cliffs extending to the water's edge. After passing the last suitable landing site, an airport about 12 miles north, the accident pilot reported to the pilot of the second airplane that he had a severe engine oil leak and was returning to the airport. The pilot reported that once the oil stopped leaking, about 3 miles from the airport, the engine began to vibrate so violently that he thought the engine would be torn from its mounts, and he shut off the engine. He turned the airplane in an attempt to glide to the nearest beach but could not reach it, forcing him to ditch the airplane about 300 yards from shore. When the airplane's main landing gear wheels touched the water, it nosed over abruptly, and the cabin rapidly filled with water. The pilot struggled to free himself and the passengers from their seat belts while upside-down and submerged in cold ocean water. After freeing himself, he swam to the rear of the airplane, kicked out one of the aft windows, swam to the surface, and summoned help. Rescue personnel discovered the two passengers still restrained within their seats.
Postaccident Examination
A postaccident examination of the engine revealed that a hex head plug located at the front of the engine, in front of the propeller governor idler gear shaft, was missing. This allowed engine oil under pressure to flow overboard. Additionally, the propeller governor idler gear shaft setscrew was loose, and the idler gear shaft was missing. There was no evidence that the hex head plug had been safety wired as required at the last engine overhaul, which had occurred 299.6 service hours prior to the accident.
Background
According to the pilot/owner, he and a friend assembled the overhauled components of the accident engine in the pilot/owner's home-based shop. He stated that all work was accomplished in accordance with Textron Lycoming technical data. The pilot/owner did not possess an aviation mechanic's certificate. The pilot/owner reported that his friend, who owned and operated an aircraft maintenance facility, was supervising his work during the engine overhaul. A review of the engine logbooks revealed that the overhaul was certified by the pilot/owner's friend, who also possessed inspector authority (IA).