Amateur-built Bearhawk N22GM accident near Sevierville, Tennessee

Probable cause

Abnormal combustion in the No. 1 cylinder for reasons that could not be determined based on the available evidence, followed by the activation of the ignition system circuit breaker, which resulted in a total loss of engine power.

NTSB analysis

The pilot reported that the experimental, amateur-built airplane experienced a total loss of engine power while maneuvering at an altitude of 2,500 ft mean sea level. He activated the electronic fuel injection/ignition system emergency power switch and attempted to restart the engine, but was unsuccessful. He performed a forced landing to a field, during which the airplane sustained substantial damage to the left wing and fuselage. A review of engine and flight data recorded by the electronic flight information system revealed a sudden increase (about 240°F over 1 second) in exhaust gas temperature (EGT) in the No. 1 cylinder, consistent with abnormal combustion immediately preceded the loss of engine power. Shortly thereafter, the engine rpm began to decrease, and the electrical system load increased by about 8 amps, then decreased by about 17 amps. The engine rpm continued to decrease for the next 2.5 minutes, consistent with a windmilling propeller, before it reached 900 rpm and then decreased to 0 rpm just prior to the landing. The electronic ignition circuit breaker was found activated. The reason for the abnormal combustion and the activation of the electronic ignition circuit breaker which resulted in a total loss of engine power could not be determined based on the available information.

Text from the NTSB. Open the NTSB docket for ERA19LA139 for the full record.