What happened
The flight was conducted to administer a Certified Flight Instructor (CFI) practical test for the pilot-in-command. The examining FAA inspector had no prior experience flying this specific make and model but possessed 1,816 total hours, primarily in Bell 47 and 206 helicopters. The initial portion of the check ride proceeded normally until it was interrupted by police activity.
During the subsequent phase, the examiner chopped the engine power to simulate an emergency while the aircraft was climbing through approximately 285 feet above ground level at a speed of 42 knots. The pilot-in-command reported that as he lowered the collective pitch, the tachometer needles split, indicating a loss of rotor RPM. He attempted to recover by putting the helicopter into a dive and gradually increasing throttle, but was unable to synchronize the engine and rotor speeds.
The helicopter subsequently struck the ground on the heel of the left skid and rolled over. There was no evidence of pre-impact mechanical malfunction or failure.
The investigation
Investigation of the wreckage revealed no pre-impact malfunctions or failures that would have impaired normal operation. The accident sequence was analyzed against the aircraft's 269C Height/Velocity diagram, which defines safe operating envelopes for helicopter operations at low altitudes and specific airspeeds.
Findings
The examiner chopped the power while the helicopter was operating close to the minimum limits of the height-velocity diagram for the given speed and altitude. This maneuver placed the aircraft in a region where sufficient rotor inertia might not be maintained to autorotate safely if engine power is lost, leading to the loss of rotor RPM and subsequent impact.
Safety message
Pilots must strictly adhere to the helicopter's Height/Velocity diagram during operations. Maneuvers that place the aircraft within the dead zone or near its boundaries, particularly during training or simulated emergencies, carry a high risk of power-off stall and ground impact.