NTSB Identification: NYC08LA137
14 CFR Part 91: General Aviation
Accident occurred Thursday, March 13, 2008 in Middlesboro, KY
Probable Cause Approval Date: 11/25/2008
Aircraft: CESSNA 150F, registration: N6651F
Injuries: 1 Serious.
NTSB investigators may not have traveled in support of this investigation and used data provided by various sources to prepare this aircraft accident report.
During a period of 6 months, a major engine overhaul and annual inspection was being performed on the pilot's airplane. The work was being performed by the pilot's friend, who was an airframe and powerplant mechanic with an inspector authorization. The accident flight was the first flight after the work was completed. About 10 minutes after departure, the engine began vibrating and lost all power during cruise flight. The major overhaul had included the installation of new cylinders. Proper installation of the new cylinders required that the exhaust valve rocker arms have a small orifice to allow oil to pass and lubricate the valves. The intake valve rocker arms did not have an orifice. Examination of the accident engine revealed that the No. 1 cylinder intake valve was stuck open, and exhibited features consistent with oil starvation. Further examination revealed that the No. 1 cylinder had an intake rocker arm (no orifices) on both the intake and exhaust valves. The No. 3 cylinder had an exhaust valve rocker arm (with orifice) on both the intake and exhaust valves. Review of a make and model engine overhaul manual revealed a caution, noting that the exhaust valve rocker arms have an orifice. Further examination of the cylinder did not reveal any additional mechanical anomalies.
The National Transportation Safety Board determines the probable cause(s) of this accident to be: The mechanic's improper maintenance installation of the No. 1 cylinder rocker arms which led to oil starvation and a loss of engine power. Full narrative available
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