NTSB Identification: ERA11LA156
14 CFR Part 91: General Aviation
Accident occurred Wednesday, February 23, 2011 in Clarksville, FL
Probable Cause Approval Date: 11/17/2011
Aircraft: CESSNA 172G, registration: N3740L
Injuries: 2 Uninjured.
NTSB investigators may not have traveled in support of this investigation and used data provided by various sources to prepare this aircraft accident report.
According to the pilot, prior to conducting low level power line inspection flights, he filled both fuel tanks. During the flight, the pilot noted the right fuel tank guage showed about 3/4 full, and the left guage showed about 1/4 full. He was not concerned because he knew he had sufficient fuel due to timing. About 2 hours, 45 minutes of flight time after refueling, the engine lost power. The pilot's attempts to restart the engine by switching fuel tanks and applying carburetor heat were unsuccessful. The airplane descended into trees, coming to rest nose-down in a near-vertical attitude. The following day, the pilot and an FAA inspector saw fuel leaking from the right wing fuel cap vent, but not from the left.
A postaccident engine test revealed that, with fuel in both tanks, the engine would start and operate with fuel selected from the left tank and both tanks, but not from the right tank. Additional examination revealed that a small steel ball from the right supply side of the fuel selector had migrated to the gascolator. The steel ball would have normally been able to push against a spring-loaded larger steel ball, which then would have been displaced away from an orifice to allow fuel to flow. The airplane's owner and a friend, who were not certificated mechanics, had previously performed maintenance on the fuel selector, which likely dislodged the small steel ball. The dislodged small steel ball would normally have prevented fuel flow from the right tank immediately. However, the right tank did supply fuel to the engine for about 10 subsequent hours of airplane operation, likely because the larger steel ball had been temporarily jammed into an open position due to debris found in the fuel selector.
The National Transportation Safety Board determines the probable cause(s) of this accident to be: A loss of engine power due to fuel starvation as a result of the owner's improper maintenance of the fuel selector valve, which resulted in a lack of fuel supply from the right fuel tank. Full narrative available
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