NTSB Identification: SEA05FA097.
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Accident occurred Monday, May 09, 2005 in Lowell, ID
Probable Cause Approval Date: 09/13/2005
Aircraft: Piper PA-28-235, registration: N8805W
Injuries: 1 Serious.

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.

While in cruise flight, the aircraft's engine began to lose power, resulting in the pilot being unable to maintain his assigned altitude. Eventually the engine quit, and the pilot was forced to attempt a controlled crash in heavily forested mountainous terrain. A post-accident inspection determined that the number four exhaust valve had stuck in the fully open position, and that there was a build-up of valve guide material on the valve stem. An inspection of the aircraft logs revealed that the valve guides and stems had not been inspected in accordance with Lycoming Mandatory Service Bulletin 388C (not mandatory for aircraft operating under part 91) at the recommended 400 hour interval. It was also determined that the engine had been displaying symptoms typical of intermittent valve sticking (rough running for a few seconds immediately after start-up) prior to the accident flight and a number of other prior flights. The pilot, who was unaware that the rough running was possibly associated with sticking valves, had not taken the aircraft to an Airframe and Powerplant mechanic to determine the reason for the symptom.

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

The number four exhaust valve sticking in the open position during cruise flight. Factors include the pilot's failure to have an Airframe and Powerplant mechanic look at the engine after it had run rough immediately after start-up prior to this and a number of other flights, and no suitable terrain and a dense forest in the area where the loss of engine power occurred.

Full narrative available

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