What happened
On November 8, 2008, a trainee pilot was conducting solo circuit training in an Aero AT-3, registration F-GNMT, at Toussus-le-Noble aerodrome. During the second takeoff attempt of the session, the pilot began extending the flaps. At that moment, the aircraft suddenly veered to the left, and the pilot was unable to maintain the intended trajectory. To mitigate the impact of the excursion, the pilot reduced engine power and applied the brakes. The aircraft subsequently left the left side of the runway and came to a stop in the grass. There were no injuries and no damage to the aircraft.
The investigation
The investigation focused on the meteorological conditions and the pilot's decision-making process. Air traffic control records indicated that wind speeds had increased significantly during the flight session. While the initial takeoff featured winds from 180° at 14 knots with gusts up to 21 knots, subsequent reports showed sustained winds from 190° at 16 knots. The aircraft's flight manual specifies a maximum demonstrated crosswind component of 11.7 knots for takeoff and landing.
Investigators also noted that the instructor, who was providing a local flight lesson in a separate aircraft, had lowered the radio volume and was not monitoring the trainee's specific radio communications during the maneuver. The trainee pilot had been authorized to fly approximately 40 minutes prior, with instructions to shorten the flight if the wind intensified.
Findings
- The primary cause of the excursion was the decision to proceed with takeoff and continue flight operations despite excessive crosswind components.
- The wind conditions exceeded the maximum demonstrated crosswind limits specified in the aircraft's flight manual.
- The pilot was unable to maintain directional control during the flap extension phase due to the lateral force of the wind.