Amateur-built ROTORWAY EXEC N614S accident near Massillon, Ohio

Probable cause

The excessive wear on the secondary shaft, from the inner bearing race, which resulted in the transmission clutch disengagement and a loss of power to the rotor system.

NTSB analysis

The pilot reported that during cruise flight the engine speed increased to a high rpm and power was no longer being transmitted to the rotor system. He initiated an autorotation to a sloping, plowed field that was soft due to recent rain. The tail struck the ground during the landing flare and the main rotor blades contacted the tailboom. Postaccident inspection of the helicopter revealed the inner race of the bearing on the secondary shaft, located above the transmission clutch, was worn into the shaft, which most likely caused the clutch to disengage. This prevented the engine power from being translated to the main rotor. The cause of the wear was undetermined, and the secondary shaft was designed by the pilot.

Text from the NTSB. Open the NTSB docket for CEN11LA305 for the full record.