Flight Details
The pilot completed an uneventful one-hour flight in a Cessna 172E equipped with a Continental O-300-D engine. After topping off the fuel tanks, the pilot departed on a second one-hour flight. Both flights were maintenance checks following the replacement of all six cylinder piston rings and the re-honing of all six cylinders.
Accident Sequence
While on final approach to Runway 25, the pilot encountered "very rough turbulence" as he reduced power. The engine then lost power. Believing he could not reach the runway, the pilot executed a 180-degree course reversal and performed an off-airport landing in soft terrain covered by high grass. During the landing roll, the aircraft's nose gear collapsed.
Post-Crash Examination
On-site examination revealed fuel present in the aircraft's fuel system immediately after the forced landing. Subsequent post-crash examination found no evidence of mechanical malfunction in the engine, ignition, air delivery, or fuel system. The only discrepancy noted was the non-functionality of the right wing gas cap vent, which was required under FAA Airworthiness Directive 79-10-14R. Examination showed that the rubber gasket would not unseat and allowed normal venting. The left fuel tank vent was examined and found to function satisfactorily. The engine was test run with a new carburetor and then with the reassembled original carburetor; both tests yielded satisfactory results. The fuel system was examined, and no blockages were found in any lines, nor were any particulates found in the fuel filters.