What happened
On July 25, 2012, a Rans Coyote S6 ultralight, identified as 59-DCJ, was performing a training flight at the Merville Calost aerodrome. The flight, which involved an instructor and a student, began with a takeoff from an unpaved runway for the purpose of circuit training. Shortly after the initial climb reached approximately 300 feet, the engine suddenly stopped. The instructor took control of the aircraft to perform an emergency landing in a nearby field. During this maneuver, the student managed to restart the engine, allowing the instructor to continue the flight at a low altitude to complete the circuit and return to the runway. After handing control back to the student, the engine failed a second time during the final approach. Believing there was insufficient altitude to attempt another restart but enough to reach the runway, the instructor allowed the student to continue the landing. The student, experiencing significant stress, initiated the flare too high. This resulted in a hard landing where the aircraft struck the runway and bounced several times, causing the landing gear to break and the aircraft to come to a halt on the runway.
The investigation
The investigation focused on the cause of the dual engine failures and the circumstances leading to the landing error. Investigators examined the fuel system of the BMW R1100 engine, noting that the student, who is also an aircraft mechanic, identified the system as being susceptible to "vapor lock." This phenomenon occurs when fuel boils in the fuel lines due to high temperatures. On the day of the accident, the aircraft had remained stationary with the engine idling for approximately 15 minutes due to heavy airfield traffic. The ambient temperature was 27°C, creating conditions highly conducive to fuel vaporization. The investigation also reviewed the crew's decision-making process during the second engine failure and the subsequent landing execution.