What happened
On 3 July 2011, a Casa 1-131E Series 2000 Jungmann, registration G-RETA, was engaged in a private aerobatic practice session approximately 1.5 miles north north-west of Old Warden Aerodrome, Bedfordshire. While the pilot was executing a left-hand stall turn, the single Enma Tigre G-IV-B engine ceased operation.
Following the engine failure, the pilot verified all cockpit controls and attempted to restart the engine through various diving and yawing maneuvers. However, the aircraft was unable to reach the airfield and was outside of its gliding range. During the subsequent forced landing, the aircraft overturned, resulting in substantial damage to the airframe. The pilot, who was the sole occupant, escaped the wreckage without injury.
The investigation
The investigation focused on the sudden loss of power during the maneuver. It was determined that the engine stopped because the carburettor's limited negative g capability caused the engine to fail during the stall turn.
Furthermore, the investigators established that a restart attempt was unsuccessful due to the specific configuration of the aircraft. The G-RETA was not equipped with a starter, and the coarse pitch of the propeller prevented it from windmilling effectively to facilitate a restart.