What happened
On 31 March 2012, a Rotorsport UK MTOsport, registration G-CGGL, was performing a training exercise at Kirkbride Airfield in Cumbria. The flight was being conducted by an instructor and a student, both of whom were wearing protective helmets and safety harnesses.
Following engine start, the pilot noted that the aircraft remained on the ground longer than usual, with the engine temperature appearing higher than normal, though still within safe operating limits. During the takeoff roll on Runway 05, the aircraft initially appeared to be performing normally. However, shortly after lifting off from the ground, the gyroplane experienced a sudden loss of engine power. The pilot managed to bring the aircraft back down onto the remaining portion of the runway, but was unable to decelerate sufficiently to prevent the aircraft from exiting the runway and colliding with the perimeter fence.
While the aircraft pod sustained moderate damage to the airframe, engine, rotors, and propeller, there were no injuries to the two occupants.
The investigation
Investigators examined the engine and fuel systems to determine the cause of the power loss. During the inspection, the spark plugs for cylinder 4 were found to be wet with fuel, which indicated that they had failed to fire.
Technical discussions during the investigation considered the possibility of vapour lock within the fuel lines. It was noted that the combination of a relatively warm ambient temperature and the use of winter-grade MOGAS fuel could have created conditions suitable for such an occurrence. However, investigators noted that this factor alone would not explain why the spark plugs in cylinder 4 were found to be wet with fuel.