What happened
On Saturday, July 10, 1999, an Aquilair Swing ultralight, identified as 43-DA, was involved in an accident near Monistrol-sur-Loire during a training flight. The flight sequence began when the instructor noticed engine misfires and observed deformation in the manual fuel pump, leading to the conclusion that the fuel tank vent was blocked. To address the issue, the instructor performed an emergency landing in a nearby alfalfa field, which resulted in no damage to the aircraft.
Following repairs, the instructor decided to move the aircraft to an adjacent field, which he believed offered better conditions for a subsequent takeoff. The instructor took the controls in the front seat while the student occupied the rear seat. During the takeoff roll, the uneven and sloped terrain caused the aircraft to veer to the right. As the aircraft became airborne, the right landing gear struck a fence wire running along the edge of the field. This impact caused the instructor to lose control, leading to a crash on the ground. The accident resulted in one injury (the instructor) and the destruction of the aircraft.
The investigation
The investigation focused on the circumstances surrounding the takeoff attempt and the environmental factors present at the site. Investigators examined the terrain conditions, the mechanical state of the aircraft following the initial engine issue, and the takeoff trajectory. Meteorological data recorded at the site indicated a southwest wind of 5 to 15 knots, visibility greater than 10 km, and temperatures of 19 °C.