What happened
On 22 May 2020, a private pilot was conducting a local flight in an AVEKO VL-3-A microlight, registration 59DAE, near La Ferté-Bernard, France. After taking off from a private strip in Sceaux-sur-Huisne, the pilot flew a series of turns at approximately 1,500 ft. During the final sequence of turns, the aircraft's airspeed increased significantly, approaching its maximum operating speed (VNE). As the speed rose, the aircraft's pitch decreased and the bank angle increased.
During this high-speed maneuver, the right section of the horizontal tailplane—including the stabilizer and elevator—separated from the aircraft. The sudden structural failure likely caused the canopy to break and led to an uncontrollable descent. Witnesses observed the pilot deploying the reserve parachute at a low altitude, but the aircraft struck the ground shortly thereafter. The pilot was fatally injured, and the microlight was destroyed.
The investigation
The BEA examined the wreckage and flight data from the aircraft's Electronic Flight Instrument System (EFIS). Investigators found that the debris from the right horizontal tailplane was located far from the main wreckage, confirming it had detached mid-air while the aircraft was still at a significant altitude. The examination of the right elevator revealed evidence of a flutter phenomenon, characterized by intense upward and downward bending loads that caused the component to rupture.
Investigators also analyzed the stabilizer spar, finding that the rupture occurred near a layer stop in the composite structure. The investigation focused on recent modifications made to the aircraft's engine intake system, which involved replacing carburetors with an injection system. This process required disconnecting the elevator trim control cables.
Findings
- The primary cause of the accident was the mid-air rupture of the right horizontal tailplane section due to aerodynamic flutter.
- The flutter phenomenon on the right elevator was likely triggered by play in the elevator trim control linkage, which may have been introduced during the recent modification of the engine intake system.
- The increase in airspeed toward the VNE, combined with the unbalanced design of the elevator on this specific aircraft model (serial number below 100), contributed to the structural failure.
- The pilot's attention may have been diverted by interacting with ground observers during the flight.
- The pilot was returning to flight after a seven-month hiatus due to the COVID-19 pandemic and lack of usable local airstrips.