What happened
On 2 June 2014, a Piper PA-18-150 Super Cub, registration G-OOMF, was conducting a tailwheel differences training flight near Wellesbourne Mountford Airfield in Warwickshire. During the fourth circuit of the flight, while the aircraft was on the base leg and the pilot was reducing engine power, the engine RPM dropped rapidly.
The instructor took control of the aircraft after identifying symptoms of fuel starvation. Although the student confirmed the fuel selector was in the correct position, the instructor found that engine power could only be maintained by oscillating the throttle between idle and full forward. Realising the airfield could not be reached, the instructor declared a MAYDAY and identified a nearby field containing standing crops as the only viable landing site.
Upon touchdown, the standing crop became entangled in the aircraft's main landing gear. This caused the aircraft to lose stability and tip onto its back. Both occupants of the aircraft escaped without injury.
The investigation
The investigation focused on the sudden loss of engine power and the subsequent landing. The instructor reported that the mixture control was found in the fully lean position following the accident.
Investigators noted that the student pilot, who possessed over 350 flying hours, was primarily accustomed to flying a Robin DR400. In that aircraft, the carburettor heat control operates in a manner very similar to the mixture control on the Piper PA-18-150 Super Cub. The investigation established that the student had inadvertently set the mixture control to lean instead of adjusting the carburettor heat while reducing power on the base leg.
Findings
- The engine power loss was caused by the student pilot accidentally leaning the fuel mixture.
- The aircraft sustained damage to the propeller, wings, wing struts, tailplane, and canopy.
- The aircraft overturned because the standing crop in the landing field became entangled in the main landing gear.