Bell 206 N820H accident near Pahokee, Florida

Probable cause

A loss of main rotor rpm for reasons that could not be determined, which resulted in an autorotation and a subsequent hard landing and rollover.

NTSB analysis

The pilot had been performing low-altitude agricultural operations for about two hours when he heard an aural “chirp” with no associated caution panel lights. After scanning the instruments, he observed nothing abnormal, then immediately the low rotor rpm horn sounded, and the helicopter started to lose altitude as the rotor speed decayed. He briefly observed a red engine light on the instrument panel, and initiated an autorotation from an altitude about 50 ft above the ground and airspeed of about 35 knots. The helicopter landed hard on uneven terrain and rolled over; a post-crash fire ensued. The pilot and passenger egressed without injury.

Although examination of the engine and its recovered components revealed no evidence of preaccident mechanical anomalies, the extent of the impact and thermal damage precluded a thorough examination, and the reason for the loss of rotor rpm could not be determined based on the available information.

Text from the NTSB. Open the NTSB docket for ERA21LA126 for the full record.