What happened
On March 31, 2015, an instructor and a student were conducting a training session involving circuit patterns and precision landings at the Belleville Villié-Morgon aerodrome. The aircraft, an Air Création Skypper ultralight (identified as 69-ABU), was performing its second circuit. As the aircraft approached the runway threshold on final approach, at an estimated altitude of 100 meters and low airspeed, the pilot lost control. The aircraft entered a series of violent oscillations before colliding with the ground.
An eyewitness observed the aircraft performing significant yaw and roll movements. The instructor was at the controls, seemingly performing a sideslip exercise. During the maneuver, the control bar moved forward to its limit while the engine was at idle. This was followed by a sharp pitch-up, a sudden pitch-down, and a right-hand spin that transitioned into a "tumbling" motion. The aircraft performed approximately four to five pitch oscillations before impact. The collision resulted in two injuries and the total destruction of the aircraft.
The investigation
The investigation focused on the aerodynamic behavior of the aircraft and the environmental conditions at the time of the accident. Investigators examined the wreckage and found that all structural failures were the result of sudden, heavy loading, consistent with either negative G-loading or the ground impact. No mechanical anomalies were found prior to the accident.
Meteorological data indicated a wind from the west to northwest at 6 knots, with gusts up to 20 knots and associated turbulence. The investigation also noted that while the instructor was proficient in English, the student's level of comprehension was sometimes insufficient for the flight briefings and verbal exchanges.
Findings
- The primary cause was the execution of a sideslip demonstration at low speed and low altitude within turbulent atmospheric conditions, which triggered a wing stall.
- The resulting stall led to an immediate spin, causing the carriage to tilt and initiating the tumbling phenomenon.
- The aircraft's manual explicitly warns against stalls during climbs or sudden power reductions, noting that once a tumbling motion begins, the only remaining safety measure is the deployment of the emergency parachute.