What happened
On September 21, 2013, a private pilot conducted a local flight departing from the Marville ULM platform. Approximately ten minutes after takeoff, witnesses observed the Michel Colomban MC15E flying at a low altitude of about 30 meters. The aircraft was noted to be flying at a low airspeed with a high pitch attitude.
As the aircraft passed over the threshold of runway 12 right, it entered a right-hand turn toward runway 12 left. During this maneuver, the aircraft banked sharply to the right and lost altitude abruptly. The aircraft struck the ground between the thresholds of the left runways, and a fire subsequently broke out. The pilot was killed, and the aircraft was destroyed.
The investigation
The investigation focused on the aircraft's recent modifications and the weight configuration during the flight. The PH-THE had recently undergone a conversion from twin thermal engines to an electric propulsion system using Lithium Polymer (LiPo) batteries.
Investigators examined the aircraft's weight and balance. While the original MC15E design allowed for a maximum takeoff mass of 170 kg, the new electric motor and battery setup increased the empty weight to approximately 110 kg, which theoretically limited the allowable pilot weight to 60 kg. At the time of the accident, the pilot's weight was estimated at 80 kg.
Witnesses also noted that the aircraft appeared to struggle for airspeed immediately after takeoff, appearing to be "hanging on the propeller" with a high pitch attitude. The investigation also looked into the battery performance, noting that power delivery in electric motors decreases as the battery discharges.