NTSB Identification: SEA07FA195.
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Accident occurred Saturday, July 14, 2007 in Everett, WA
Probable Cause Approval Date: 06/30/2008
Aircraft: Yakovlev YAK-55M, registration: N55NH
Injuries: 1 Fatal.

NTSB investigators either traveled in support of this investigation or conducted a significant amount of investigative work without any travel, and used data obtained from various sources to prepare this aircraft accident report.

The day before the accident, the pilot had asked his mechanic to prepare two other airplanes for flight to a fly-in the following morning. The accident airplane had not flown in a year, nor had there been any entries in the maintenance logbooks in the last four years; it did not have a current condition inspection recorded in the logbooks. The mechanic said that he had been in the process of installing an intake oil drain kit, which drains oil from the lower 3 cylinders from a common quick drain. The mechanic said that the project was not complete, but it had progressed to the point that he had put new oil in the engine. On the morning of the accident, the pilot had to move the airplane out from the back of the hangar and install the engine cowling before flight. He flew to the airport where the fly-in was being held and landed without incident. On his return flight, as he approached the airport, he radioed the tower controller and said that his engine was running rough. Approximately two minutes later, he said that his engine had lost power, and he was going down. A witness on the ground said that he heard a loud bang and looked up to see blue-gray smoke coming from the airplane. Another witness said she saw the airplane making a low left turn, when it flipped inverted and spiraled to the ground. The airplane impacted in a residential area, approximately 15 feet behind a home. A post impact fire consumed the airplane. During an engine teardown, a cylinder was removed and significant heat distress was found on and around the main rod bearing. The main rod bearing was plastically deformed and broken; several connecting rods were bent and/or broken. Additionally, a heavy oil coating was found all along the bottom of the fuselage and most of the empennage was covered with oil. If the pilot had performed an adequate preflight before his return flight, it is likely that he would have noticed a significant loss of engine oil.

The National Transportation Safety Board determines the probable cause(s) of this accident to be:

The pilot's inadequate preflight planning and inspection that led to oil exhaustion and a catastrophic engine failure. Also causal was the pilot's attempted operation of an aircraft with known deficiencies, and the lack of a current airworthiness inspection. Contributing to the accident was the pilot's failure to maintain an adequate airspeed while maneuvering following the engine failure.

Full narrative available

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