What happened
On 23 July 2009, a VPM M16 Tandem Trainer gyroplane, registration G-IJMC, was conducting a private local flight along the River Thames. During an attempt to climb from 600 ft to 800 ft, the pilot observed that the engine speed failed to rise above 4,000 rpm. While the pilot managed to briefly increase the speed to 4,200 rpm via the throttle, the aircraft subsequently suffered a total loss of engine power.
After observing the runway at Chiltern Park, the pilot decided to attempt a landing at the airfield, which was approximately 4 km away. However, a second loss of power occurred, prompting the pilot to declare a PAN-PAN call to RAF Benson. The pilot then initiated a forced descent into a nearby field.
As the aircraft approached the landing site, the pilot noted the field had a significant downward slope in the direction of the approach. During the landing sequence, a combination of an untimely wind gust, the downward slope of the terrain, and the pilot's flare technique caused the aircraft to strike the ground heavily. The impact broke the nosewheel, and a rotor blade struck the sloping ground. The aircraft then rolled onto its side, resulting in extensive damage to the airframe and rotor.
The investigation
The investigation focused on the mechanical failure of the Subaru EA81 piston engine. While no coolant was found at the accident site, a detailed inspection of the engine revealed that the head gasket around one of the cylinders had failed. This failure was accompanied by a breach in the cylinder wall, which led to the loss of coolant, subsequent overheating, and the eventual loss of engine power.