Robinson Helicopter Company R44 II N754R accident near Dunlap, Illinois

Probable cause

A loss of main rotor rpm for reasons that could not be determined during postaccident examinations.

NTSB analysis

The commercial pilot stated he and the passenger were conducting a helicopter flight to observe and count geese at an altitude of 300 ft above the ground at an indicated airspeed of 60 knots. The pilot increased the collective to transition to another area when he noticed an increase in engine rpm and a decrease in rotor rpm along with the illumination of a main rotor warning light. The clutch warning light did not illuminate. The pilot initiated a downwind autorotation to a plowed field. The helicopter tipped forward on its skids, the main rotor contacted the ground, and the helicopter rolled over. Although a postaccident examination of the clutch and V-belts revealed some limited component wear, and some minor anomalies to the best tension actuator were noted, no anomalies were identified with the clutch system that would have resulted in a loss of main rotor rpm.

Text from the NTSB. Open the NTSB docket for CEN15LA198 for the full record.