Incident Overview
A pilot reported that while en route to Fernandina Beach, Florida, an auto re-lite master caution indication appeared on the annunciator panel. The pilot diverted to Deland Airport for a precautionary landing.
Approach and System Indications
During the approach, an electronic control unit (ECU) failure indication was observed. The pilot cycled the ECU switch from auto to manual twice, after which the engine began to overspeed. The pilot then rolled the throttle back twice and received a "fuel flow fix" voice warning. The engine started making loud "bangs" resembling a compressor stall.
Attempted Landing
The pilot stated he tried to maintain forward airspeed to clear trees. After clearing the trees and power lines, a voice warning "low rotor" activated. During the descent to land, the pilot increased collective to arrest the descent. The "low rotor" warning light illuminated again, and the helicopter landed hard. The main rotor blades contacted the tail boom and severed it from the airframe.
FADEC Procedures and Operational Notes
According to the FADEC malfunction procedures, occasional electronic transients may produce a false ECU fail indication. If the ECU fail indication persists after two reset attempts, the switch should be placed in MANUAL, and the twistgrip used to manually control Np/Nr at 100%. An operational note states that occasional RPM transients between 90% and 106.4% are allowable as long as maximum or minimum RPM limits are not exceeded, and the pilot is advised to land as soon as practical.
Post-Accident Inspection
Inspection of the engine and engine accessories revealed no evidence of pre-impact part failures.