Primary finding
Probable cause
The student pilot's failure to maintain adequate main rotor rpm and the instructor's delayed remedial action.
Investigator assessment
Analysis narrative
While performing a 180-degree autorotation, the student pilot raised the collective in order to maintain the helicopter's rpms within normal parameters. At approximately 250 feet above ground level, the rotor rpm was allowed to decay to 95% at which time the helicopter began to sink. The lowest observed rpm was 85%. The certified flight instructor took control of the helicopter could not recover the helicopter prior to an impact with terrain. The helicopter landed hard and rolled onto its left side. Substantial crushing damage was sustained to the fuselage. Winds at the time of the accident were 190 degrees at 14 knots gusting to 30 knots.
Source record
Factual narrative
While performing a 180-degree autorotation, the student pilot raised the collective in order to maintain the rotor rpms within normal parameters. At approximately 250 feet above ground level, the rotor rpm was allowed to decay to 95% at which time the helicopter began to sink. The lowest observed rpm was 85%. The certified flight instructor took control of the helicopter, but could not recover prior to impact with terrain. The helicopter landed hard and rolled onto its left side. Substantial crushing damage was sustained to the fuselage. Winds at the time of the accident were 190 degrees at 14 knots gusting to 30 knots.