What happened
On January 8, 1998, a pilot was operating an Air Création Racer 503 SL ultralight (identified 83-IA) on a cross-country flight. After noticing inconsistent engine temperature readings, the pilot decided to divert to Valence airport for an unscheduled landing. The aircraft was flying in a group of four other ultralights and was not equipped with radio communications.
As the pilot approached the airfield, they observed an AS 332 Super Puma helicopter on a landing pattern. The helicopter crossed the runway threshold at an altitude of approximately 80 meters and landed about 40 seconds later. Simultaneously, the ultralight arrived on short final, aiming for the same runway. At an altitude of roughly five meters, the 83-IA suddenly encountered a violent disturbance. The aircraft rolled sharply to the right and struck the ground approximately ten meters before the paved runway surface. The impact destroyed the airframe, though the pilot was able to exit the wreckage safely.
The investigation
The investigation focused on the interaction between the two aircraft and the atmospheric conditions at the time of the accident. Investigators reconstructed the timeline using air traffic controller records and radio communications from the helicopter.
Technical analysis examined the nature of wake turbulence produced by rotary-wing aircraft. It was established that the helicopter's rotor disk acts as a lifting surface, generating significant wingtip vortices. In the calm wind conditions present during the accident, these vortices descended toward the ground and remained concentrated. The investigation also reviewed regulatory documents regarding separation standards and pilot training manuals to determine if the risks posed by helicopter-induced turbulence were adequately addressed.