What happened
On 27 June 2007, a Rotorway Executive 90, registration G-BUJZ, was conducting a training sortie near Takely and Andrewsfield. The flight was intended to involve general handling exercises, including an autorotation to go-around, to assist a pilot in renewing their type rating.
During the flight, the aircraft was performing a practice autorotation. While attempting to recover with power, the rotor RPM began to decrease. The instructor took control of the aircraft and prepared for a second autorotation. During this maneuver, the student pilot raised the collective while simultaneously opening the throttle at approximately 15 feet above the ground. Although the engine responded, it failed to provide sufficient power, causing the rotor RPM to continue dropping. The instructor attempted to overshoot the landing area but, realizing the RPM was still decaying, opted to land in a nearby field containing standing crops.
Shortly after the aircraft touched down, it pitched forward and rolled onto its starboard side. The impact resulted in extensive damage to the canopy, tail boom, horizontal stabilizer, main rotor shaft, and main rotor blades. The single crew member on board sustained minor injuries.
The investigation
The investigation focused on the loss of engine performance and the subsequent loss of rotor RPM. The instructor noted that they had encountered similar low rotor RPM situations in this specific aircraft type previously. Following the accident, the maintenance organization conducted an inspection of the engine; however, they were unable to find any evidence of a mechanical cause for a loss of power.