Dehavilland BEAVER L-20A (DHC-2) N4957 accident near Port Alsworth, Alaska

Probable cause

A partial loss of engine power for reasons that could not be determined.

NTSB analysis

The pilot and five passengers departed from a remote lake in the float-equipped airplane. The pilot reported that, shortly after takeoff, he felt the manifold pressure decrease, and he advanced the propeller and throttle controls. The engine initially responded with an increase in rpm and manifold pressure but subsequently lost total power. The pilot performed a forced landing into a heavily wooded area, and the airplane sustained substantial damage to the fuselage and wings.

A postaccident examination of the engine revealed no evidence of preimpact mechanical malfunctions or failures that would have precluded normal engine operation. Passengers reported that the pilot made an aggressive steep turn at low altitude with no change in engine noise from takeoff to impact with terrain. Based on available evidence, it is likely that the engine sustained a partial loss of engine power for reasons that could not be determined.

Text from the NTSB. Open the NTSB docket for ANC24LA049 for the full record.