Primary finding
Probable cause
A partial loss of engine power for undetermined reasons.
Investigator assessment
Analysis narrative
According to the instructor, the student pilot was making a practice autorotation to be followed by a powered recovery in preparation for his taking the private pilot practical test. When power was added, only 2500 rpm (instead of 3050 rpm) were attained. The helicopter slid approximately 2 feet on a rain-soaked field. The skid toes dug into the soft ground, stopping forward movement and causing the fuselage to shift forward. The main rotor blades contacted and severed the tail rotor driveshaft. In addition the tail rotor gearbox, tailboom, and a main rotor blade were damaged. Postaccident examination of the engine and powertrain revealed no anomalies that would have prevented the engine from producing full power.
Source record
Factual narrative
According to the instructor, the student pilot was making a practice autorotation to be followed by a powered recovery in preparation for his taking the private pilot practical test. When power was added, only 2500 rpm (revolutions per minute) instead of 3050 rpm was attained. A forced landing ensued and the helicopter slid approximately 2 feet on a rain-soaked field. The skid toes dug into the soft ground, stopping forward movement and causing the fuselage to shift forward. The main rotor blades contacted and severed the tail rotor driveshaft. In addition, the the tail rotor gearbox, tailboom, and a main rotor blade were damaged. Post-accident examination of the engine and power train revealed no anomalies that would have prevented the engine from producing full power.