What happened
On July 17, 2010, a Pilatus PC-6/B2-H2 Turbo Porter, registered F-GHVH, was performing a skydiving operation at Évora Aerodrome in Portugal. The aircraft, operated by Air 65, had just completed its ninth mission of the day, dropping eight skydivers, before approaching runway 01 for landing.
During the short final approach, the pilot experienced a sudden sensation of the aircraft sinking and then rising, as if caught in a wave. Upon touchdown on the main gear, the aircraft's tail lifted violently, causing the plane to veer 45 degrees to the right. The pilot attempted to correct the trajectory using left rudder, aft elevator, and differential braking, but the control inputs were ineffective due to the low airspeed. As the tail continued to rise, the nose pitched forward, resulting in the propeller striking the runway surface. The aircraft came to an immediate halt following the impact.
The investigation
The GPIAAF investigation examined the meteorological conditions and the aerodynamic characteristics of the aircraft. At the time of the incident, the temperature was 35 ºC, and while visibility was good, other pilots had reported localized windshear and turbulence on the final approach. Additionally, air traffic personnel observed dust devils crossing the runway near the time of the accident.
Findings
- The primary cause of the incident was the impact of meteorological phenomena on the aircraft during the landing phase.
- A sudden change in wind direction, likely a gust or windshear, acted upon the large vertical stabilizer of the aircraft, causing the tail to lift and the aircraft to yaw right.
- The aircraft's conventional landing gear configuration made it susceptible to directional instability at low speeds, where rudder effectiveness is significantly reduced.
- The pilot's use of aft elevator, while standard for headwind landings, contributed to the tail lifting further under the influence of the tailwind component.
- The aircraft sustained damage only to the propeller, and the runway surface sustained negligible scuffs.