Bell 206 N1815 accident near Walton, Kansas

Probable cause

A loss of engine power for undetermined reasons because postaccident examination of the airframe and engine revealed no anomalies.

NTSB analysis

The pilot and flight mechanic were on a maintenance flight and had entered an autorotation to check the flat-pitch rotor speed, which was satisfactory. During recovery, about 500 feet above ground level, the pilot applied the throttle but the engine did not respond. The autorotational descent continued and the pilot executed a power-off running landing to a wheat field. As the helicopter touched down, a main rotor blade struck the tail boom, separating the tail boom at its attach point. Both main rotor blades impacted terrain and the helicopter came to rest on its right side. The pilot and flight mechanic were uncertain as to whether the engine had stopped running during the autorotation recovery or whether it was only operating at idle rpm. No preimpact anomalies were discovered that would have prevented normal operation. The engine was removed and run in a test cell, and the engine met specification power. The reason for the loss of engine power could not be determined.

Text from the NTSB. Open the NTSB docket for CEN11LA356 for the full record.