Incident Overview
A student pilot was conducting takeoffs and landings in the traffic pattern when the low rotor RPM warning horn activated. The student attempted to extinguish the warning by manipulating the throttle and collective but was unsuccessful. Subsequently, the student entered an autorotation. During the autorotation, the student did not verify the main rotor RPM using the rotor tachometer.
Touchdown and Rollover
The helicopter touched down approximately one-quarter mile southeast of the airport in a soft field. The skids dug into the soft soil, causing the helicopter to roll over.
Post-Incident Inspection
A Federal Aviation Administration (FAA) inspector examined the aircraft and engine, which included an engine start and static run-up. The engine started normally and was exercised throughout its normal power range. No anomalies were found with the engine operation.
Maintenance History
Maintenance records revealed a history of false low rotor RPM warning horn activations in the helicopter dating back nine months. Each time pilots reported the warning horn discrepancy, maintenance personnel replaced a system component and returned the helicopter to service. However, the problem persisted despite these component changes.
Pilot Training
Certified flight instructors (CFIs) stated that they had trained students, including the accident pilot, on how to cope with the nuisance warning horn activations.