Beech A36 N18403 accident near Mcalester, Oklahoma

Probable cause

A total loss of engine power for reasons that could not be determined because postaccident examination of the engine did not reveal any evidence of mechanical malfunctions or failures that would have precluded normal operation.

NTSB analysis

The private pilot stated that the flight originated with full fuel tanks. About 8 minutes after takeoff, he noticed fuel leaking from the left fuel tank cap for a short period. The pilot continued the flight, switching fuel tanks every 25 minutes. The flight continued uneventfully until the engine lost total power while the airplane was entering the downwind leg to land. The pilot switched fuel tanks and attempted to restart the engine to no avail. The pilot performed a forced landing in a field; the airplane touched down hard and contacted a hay bale, which resulted in substantial damage to the wings and compromised the fuel system. Postaccident examination of the main fuel tank caps revealed the O-rings were cracked. Maintenance records showed that the O-rings were replaced about 17 months before the accident. Although it is unknown how much fuel leaked from the fuel cap during the flight, the pilot reported that, about 50 minutes before the accident, both fuel tanks were indicating about 3/4 full; thus, it is doubtful that enough fuel would have leaked to result in fuel exhaustion. A postaccident engine test run was conducted with the fuselage strapped down on a trailer; an alternate fuel system was rigged to both the left and right fuel inlet lines at the fuselage. The engine started without hesitation and ran smoothly up to 1,500 rpm using the left fuel tank inlet. The test was repeated using the right fuel tank inlet, and the engine performed in the same manner. The rpm was not increased any higher due to the security of the fuselage during the test. Postaccident examination of the engine did not reveal evidence of preimpact malfunctions or failures that would have precluded normal operation; thus, the reason for the loss of engine power could not be determined.

Text from the NTSB. Open the NTSB docket for CEN17LA357 for the full record.