What happened
On 2 August 2015, a Flight Design CTSW, registration G-CETF, was performing a private flight returning to Boston Aerodrome, Lincolnshire. After joining the airfield overhead at 2,000 ft, the pilot descended into the circuit for Runway 09. During the downwind leg, the pilot verified engine pressures and temperatures, noting fuel was visible in the wing root sight tubes.
Upon turning onto the final approach, the aircraft began to sink. As the pilot increased power to compensate, the engine suddenly ceased operation. An attempt to restart the engine was unsuccessful. Due to the low altitude, the pilot was unable to reach the runway and instead performed an emergency landing in an unharvested corn field short of the threshold. The impact caused the aircraft to nose over and come to rest in an inverted position. There were no injuries to the two occupants, who were able to exit the aircraft without assistance.
The investigation
The investigation examined the aircraft's fuel system and the circumstances surrounding the power loss. The Flight Design CTSW features integral fuel tanks with a design where the fuel off-take is located near the rear of the tank, without a sump to ensure the strainer remains submerged.
Following the accident, the aircraft was recovered after being righted. The pilot drained 22 litres of fuel from the system, almost all of which was contained in the right tank. This indicated a significant fuel imbalance. While an examination by insurance adjusters and repair specialists found no mechanical engine failure, the investigation considered whether the aircraft's maneuvers—specifically the sequence of turns and the application of flaps—might have caused the fuel to shift away from the off-take, leading to fuel starvation.
Findings
- The engine experienced a sudden loss of power during the final approach phase.
- The aircraft sustained extensive damage to the airframe, including the landing gear, propeller, engine covers, tailplane, and rudder.
- A significant fuel imbalance was present at the time of recovery, with nearly all remaining fuel located in the right wing tank.
- It is possible that flight maneuvers or the pitch change associated with flap selection caused the fuel level to drop below the off-take, potentially introducing air into the system.