Accident Sequence
The flight instructor reported that during a second traffic pattern, the helicopter climbed to approximately 1,000 feet AGL with the intention of practicing an autorotation entry and glide followed by a power recovery and go-around at about 200–300 feet AGL. Both pilots were at the controls on final approach. After lowering the collective, the engine rpm dropped directly to zero. The instructor took control while the student attempted an engine restart. The instructor could not recall any further events until after the impact.
Witness Observations
According to a witness, the helicopter struck the runway hard, causing both landing skids to split laterally. The helicopter then rolled onto its left side, and a fire ensued.
Weight and Balance
Prior to the flight, the student and flight instructor performed weight and balance calculations, indicating a helicopter weight of 1,859.6 pounds. The density altitude at the time was calculated to be 7,162 feet. The Pilot's Flight Manual (PFM) performance figure 5-3 (gross weight versus density altitude diagram) specified that, for the given density altitude, the maximum weight to maintain the autorotation characteristics shown in performance figure 5-2 (height/velocity diagram) was 1,600 pounds.
Engine Examination
An examination of the helicopter's engine and systems revealed no anomalies.