What happened
On the evening of April 22, 2001, a Buse'Air 150 microlight, identified as 89-IR, was conducting a cross-country flight near Lasson, France. While in cruise flight, witnesses on the ground observed the aircraft suddenly bank to the left and pitch toward the ground. The impact resulted in the total destruction of the aircraft and the deaths of two occupants, the pilot and a passenger.
At the time of the accident, weather conditions were favorable, with visibility exceeding 10 km and light winds. Although the aircraft's airspeed indicator was found stuck at 230 km/h—exceeding the manufacturer's maximum speed (VNE) of 220 km/h—investigators determined that the speed at the moment of the structural failure was not definitively known and could not be attributed to overspeeding.
The investigation
Investigators recovered the main wreckage in a concentrated area, but a search along the flight path revealed several pieces of the wing's leading edge scattered at distances of 60, 115, and 150 meters from the main site. The distribution of these components was characteristic of an in-flight structural breakup. Examination of the engine and propeller showed no malfunctions prior to the impact.
Detailed analysis of the wing components focused on the interface between the adhesive and the leading edge material. The leading edge was constructed of a glass fiber composite with a polyester resin matrix. Investigators examined the surfaces of the spars and the leading edges to determine the nature of the separation.
Findings
- The investigation established that the separation of the leading edges was caused by an adhesive failure at the interface between the adhesive and the structural components.
- The fracture was identified as an "adhesion failure," meaning the bond between the adhesive and the material was insufficient, rather than a failure of the composite material itself.
- Evidence showed that the adhesive had not been applied across the entire surface of the spar.
- Similar manufacturing defects, involving improper bonding, were discovered on the rudder and elevator, which remained intact during the flight.
- The structural integrity of the wing spars and the leading edge material remained undamaged, confirming that the failure originated solely from poor assembly quality.