What happened
On Saturday, June 24, 2000, at 16:15, a Piper PA 18 A 150 Super Cub, registration F-BAYP, was performing a private flight from the Alpe d'Huez Altiport. During the takeoff roll on runway 24, the aircraft initially began to drift toward the right. Although the pilot attempted to correct the deviation, the aircraft subsequently veered to the left, exiting the runway and striking a pylon.
The investigation
The investigation focused on the aerodynamic behavior of the aircraft under the prevailing meteorological conditions, which consisted of winds from 320° to 340° at 12 to 14 knots. Investigators determined that during the initial stages of the takeoff roll, the effects of the crosswind were obscured by obstacles located to the right of the runway. Once the aircraft cleared these obstacles, the wind began to influence the flight path.
Initially, the aircraft experienced a weathercock effect, causing it to yaw to the right. The pilot applied corrective inputs to counter this movement. However, as the pilot attempted to realign the aircraft with the runway centerline using yaw corrections, the aircraft immediately rolled to the left. This secondary deviation was attributed to a combination of induced roll, the wind lifting the right wing, and overcorrection by the pilot.
Findings
- The primary cause of the excursion was the insufficient compensation for the effects of varying crosswinds.
- The pilot's attempt to correct the initial rightward drift resulted in an immediate leftward embarkation.
- The aircraft's maximum demonstrated crosswind limit is 15 knots, and the prevailing winds were near this threshold.
- The aircraft sustained heavy damage during the event.