Accident Overview
On April 1, 2013, at 1220 central daylight time, a Cessna model 172 airplane, registration N8033B, was substantially damaged during a forced landing following a loss of engine power shortly after takeoff from Three Castles Airpark (4D1) in Wonewoc, Wisconsin. The commercial pilot was not injured. The flight was conducted under Part 91 without a flight plan in day visual meteorological conditions.
Flight History
The flight originated at Park Falls Municipal Airport (KPKF) in Park River, Wisconsin, at 1030, destined for St Louis Metro-East Airport (3K6) in St. Jacob, Illinois. The pilot intended to make one fuel stop but had not selected the airport due to ample fuel. During cruise on the right wing fuel tank, the engine began running rough. After applying carburetor heat, the pilot made a precautionary landing at 4D1. Post-landing, he visually inspected the engine but found no issues. He heard a "whoosh" sound and a "crinkle" from the metal fuel tank when loosening the right fuel cap, which he attributed to a pressure differential from a rapid descent on a single tank. The left tank contained about 2 gallons; the right about 10. Believing the venting issue resolved by removing the cap, he restarted the engine with the fuel selector on both tanks, performed a run-up, and departed.
Accident Sequence
Shortly after takeoff at about 300 feet, the engine roughened. At 200 feet, it lost complete power as the pilot attempted to return. During the forced landing into a seasonal marsh, the left wing struck a tree.
Postaccident Examination
A Federal Aviation Administration Airworthiness Inspector found the external fuel tank vent line on the left wing strut obstructed by foreign material, likely insect debris. The cross-tank vent line was also obstructed. The engine responded to cockpit controls during a test run. After the run, a "whoosh" sound was heard when loosening the right fuel cap. Testing revealed a restriction in the flapper-valve assembly, preventing free air passage. No foreign material was noted around the valve seat, but the rubber flap remained engaged to its metal seat under pressure. The restriction lessened with repeated pressure and suction.
Probable Cause
Not provided in the source.