What happened
On 18 September 2016, an EV-97 Teameuro．eurostar UK, registration G-GARB, was conducting a private cross-country flight from Arclid Airfield to Swansea Airport. The flight, carrying the pilot and one passenger, proceeded normally for much of the journey, with the aircraft maintaining altitudes between 2,000 and 4,150 ft amsl.
Near Builth Wells, Powys, the aircraft's flight profile changed abruptly. Radar data and eyewitness accounts indicate that after a period of level flight, the aircraft entered a steep, nose-up pitch followed by a rapid descent. Witnesses on the ground observed the aircraft in a vertical, climbing attitude before it transitioned into a nose-down, rotating, and spiralling descent. During this descent, observers noted that the left wing appeared to have folded rearwards toward the tail. The aircraft subsequently struck the ground with high vertical speed, resulting in two fatalities.
The investigation
The AAIB investigation focused on the structural integrity of the wing and the potential for aerodynamic overload. Metallurgical analysis of the left wing spar cap revealed that the failure was caused by tensile overload due to upward bending beyond the design limits. No evidence of fatigue, corrosion, or pre-existing material defects was found in the wing structure.
Investigators examined the aircraft's pitch trim mechanism, noting that the lever is positioned between the seats. Flight evaluations demonstrated that the trim lever could be moved rapidly through a large range, and accidental movement could induce significant pitch changes. The investigation also considered whether the aircraft's weight, which was estimated to be at least 21 kg above the maximum takeoff weight, contributed to the event, though the center of gravity remained within limits.
Findings
- The left wing suffered a structural failure of the lower spar cap and the upper carry-through spar due to aerodynamic loads exceeding the 4g limit load.
- The failure likely occurred during an attempt to recover from an inadvertent manoeuvre that induced a structural overload.
- The design and location of the pitch trim lever between the seats allow for the possibility of rapid, inadvertent, or abrupt trim inputs.
- The aircraft was likely operating above its maximum takeoff weight at the time of the accident.
Safety action
- Safety Recommendation 2018-001: It is recommended that the CAA, LAA, BMAA, LSA, and Evektor conduct a joint review of the pitch trim mechanism design and location on the EV-97 Teameurostar UK and amateur-built EV-97 to determine if modifications are necessary to prevent accidental or abrupt operation.