What happened
On August 22, 2014, at approximately 10:00 local time, a Humbert ultralight aircraft, identified as 05-KU, was conducting a local flight from Gap Tallard aerodrome as part of a paid sightseeing flight. The aircraft was carrying a pilot and one passenger.
After roughly 3-and-a-half minutes of flight, the pilot joined the base leg of the traffic pattern for runway 21L, an unpaved strip, at an altitude of approximately 2,600 ft. As the aircraft transitioned to the final approach at a speed of about 90 km/h, the aircraft experienced a sudden, uncommanded pitch-up. The pilot attempted to correct the nose-up attitude by applying full forward elevator input, but the control response was ineffective.
As the pitch-up continued, the airspeed dropped rapidly to 60 km/h, leading the aircraft into a right-hand spin. Despite the pilot applying full left rudder, the aircraft completed two and a half turns in a spin before striking vegetation and colliding with the ground. The impact resulted in the destruction of the aircraft.
The investigation
Investigators examined the aircraft's control surfaces, including the elevator and other flight controls, but found no mechanical malfunctions that could have contributed to the event. The aircraft's weight and balance were within the manufacturer's specified limits.
Technical analysis confirmed that the aircraft was not equipped with a stall warning system. The stall speed for this model at its maximum takeoff weight of 450 kg is 60 km/h. The pilot, an experienced instructor with 1,500 total flight hours (including 360 hours on this type), stated that engine power remained unchanged during the initial pitch-up maneuver.