What happened
On 16 May 1998, a 7/8 scale replica SE5A, registration G-BKER, was conducting aerobatic practice for an upcoming display at approximately 1,000 feet agl near North Branchal, Renfrewshire. During the flight, the pilot executed a vigorous left-hand wingover manoeuvre, immediately followed by the initiation of a loop.
As the aircraft reached the top of the loop, the pilot reduced the throttle. At this point of low airspeed, the engine faltered and ceased operation. The pilot noted that previous experience indicated a minimum airspeed of 90 kt was necessary to attempt an in-flight restart. Due to insufficient altitude to attempt such a procedure, the pilot focused on selecting a landing site and preparing an approach into a nearby field.
The chosen landing site featured a steep slope rising toward the west. Given the northeast wind direction, the pilot opted to land up the slope, which necessitated flying with a significant tailwind component. While the initial touchdown appeared successful, a subsequent inspection of the aircraft identified minor damage to the front fuselage.
The investigation
Following the incident, the pilot inspected the aircraft and found that approximately 8 gallons of fuel remained in the tanks. The engine was capable of turning over normally, and investigators confirmed that the fuel filters and vents were unobstructed. The pilot's assessment suggested that the engine failure was likely linked to the preceding manoeuvre.
Findings
- The engine failure was likely caused by momentary fuel starvation following the wingover manoeuvre, which had involved a period of negative g-force.
- The low airspeed experienced at the apex of the loop prevented the engine from maintaining a windmilling state, leading to the stoppage.