Amateur-built KITFOX IV N6140S accident near Escondido, California

Probable cause

A total loss of power due to an oil exhaustion induced seizure of the engine. The pilot's decision to continue flight to the original destination after becoming aware of the in-flight oil leak instead of landing at an intermediate airport to investigate the source and extent of the problem is also causal. Contributing to the accident was the pilot's reuse of the pushrod oil seal during maintenance in contradiction to the engine manufacturer's maintenance instructions.

NTSB analysis

During cruise flight the pilot observed oil trailing along the landing gear strut. He checked the engine oil pressure indicator, and confirmed it was displaying a normal oil pressure. He then altered his flight path to include areas suitable for performing a forced landing. He continued to monitor the oil pressure as he approached an airstrip. The oil pressure did not change, and he decided to continue the flight to his destination. Shortly thereafter, the oil pressure dropped to zero, and the engine lost all power. The pilot performed a forced landing; however, during the landing roll out, the airplane struck a ditch and nosed over. Inspection of the engine revealed that the number four cylinder exhaust pushrod O-ring seal had failed, which allowed the oil to exit the engine, causing the engine to seize. The pilot stated that he had removed the cylinder head 2 years prior to the accident, and reused the exhaust pushrod O-ring seal. According to the engine manufacturer's maintenance manual recommendations, all sealing rings, gaskets, securing elements, O-rings and oil seals are to be replaced at engine reassembly.

Text from the NTSB. Open the NTSB docket for WPR09LA369 for the full record.