Amateur-built Lancair IV-TP N420M accident near Rio Linda, California

Probable cause

A loss of engine power for reasons that could not be determined based on available evidence.

NTSB analysis

The pilot departed on a visual flight rules cross-country flight in his turboprop-equipped experimental airplane. Onboard data indicated that, upon reaching about 6,500 ft mean sea level, about 5 minutes after takeoff, the airplane pitched down about 25° and entered an approximate 35° left bank; the engine power reduced to idle with a simultaneous decrease in fuel flow. Several seconds later, the voltage began to slowly decrease, consistent with the generator turning off. The airplane continued to descend toward the nearest airport and ultimately impacted powerlines and terrain about 1.3 nautical miles from the approach end of the runway. The pilot made no radio transmissions that indicated that he was experiencing an emergency.

Examination of the fuel system and engine revealed no mechanical malfunctions or failures, and the reason for the reduction of engine power could not be determined. The propeller was found in a low pitch position. The propeller was not equipped with a feathering pump; therefore, unless the propeller control was moved to the feather position immediately following a loss of engine power, the speed of the counterweights and the aerodynamic loads on the blades would quickly degrade to a point where feathering would become impossible. It is likely that, had the pilot immediately placed the propeller control into the feather position following the loss of engine power, significantly less drag would have been produced by the propeller and the airplane would likely have been able to reach the intended runway.

The first responders reported that the pilot stopped breathing shortly after being extricated from the wreckage. Given that the pilot diverted the airplane and initially survived the impact, it is unlikely that he experienced sudden incapacitation during the flight.

Text from the NTSB. Open the NTSB docket for WPR17FA179 for the full record.