Accident Details
The helicopter was at an altitude of 6,000 feet, flying at 70 knots, and exiting a canyon approximately 5 miles east of the airport. It was on a long final approach to runway 30.
Pre-Landing Checks and Power Loss
After completing pre-landing checks—which included verifying that warning lights were extinguished, rotor and engine tachometers and other pertinent instruments were within the green arc, and carburetor heat was outside the yellow arc—the instructor "pulled the carburetor heat up a little, and then...pushed the trim in to prepare for landing." Shortly thereafter, the engine lost power.
Autorotation and Landing
In response to the power loss, the collective control was lowered, and the instructor took control of the helicopter. The LOW RPM light illuminated and the warning horn sounded. The instructor noted that the tachometer was "in the green" and manifold pressure (MAP) was in the red arc at 25 inches. He attempted an autorotation into an open field. After flaring, the helicopter landed hard "with a slight nose right yaw." It bounced once and then rolled over onto its right side. The tail boom and tail rotor were severed during the rollover.
Post-Accident Examination
Following the accident, the engine was functionally tested and produced full power. Nothing was found that would have caused the power loss. Temperature and dew point conditions at the time were not conducive to carburetor icing.