What happened
On July 27, 2008, at approximately 20:00, an Ultralair Weedhopper AX3 ultralight aircraft, identified as 40-HK, crashed near the Tosse ultralight airfield in France. The aircraft was being operated by its owner for a post-maintenance test flight. According to an eyewitness, the aircraft reached an altitude of approximately 500 feet in level flight shortly after takeoff. Suddenly, the aircraft rolled sharply to the left, entered a descent, and collided with the ground. The impact resulted in the death of the pilot and the total destruction of the aircraft.
The investigation
The investigation focused on the aircraft's condition following recent maintenance work. The pilot had recently replaced the wing fabric (consisting of left and right sleeves) to prepare for a banner-towing season. Because the new fabric was slightly smaller than the original, the pilot had removed the plastic end caps from several upper wing reinforcement tubes to allow the fabric sleeves to be closed over the structure. These end caps were later recovered from the hangar where the maintenance had been performed. Additionally, investigators found that one of the right-wing strut ends was not properly secured to the wing at the time of the flight.
Findings
Investigators determined that the primary cause of the accident was the pilot's decision to proceed with the flight despite known inadequate maintenance. The removal of the reinforcement tube end caps and the unattached wing strut likely created an aerodynamic asymmetry in lift that rendered the aircraft uncontrollable. The investigation also noted that the pilot was under financial pressure to begin a banner-towing contract and had been warned by a peer regarding the risks of flying the aircraft in its modified state.