What happened
On August 31, 2003, a Pitts S-1S, registration PH-PUP, was involved in a ground accident at Amsterdam Airport Schiphol. After landing on runway 24, the single-seat taildragger was taxiing off the runway when the tail section suddenly lifted. This caused the aircraft to capsize onto its back, after which it slid approximately 20 meters along the ground. The pilot escaped the incident uninjured, though the aircraft sustained significant damage.
The investigation
Investigators from the predecessor to the Dutch Safety Board analyzed data provided by the pilot, Schiplo airport authorities, and the Royal Netherlands Meteorological Institute (KNMI). The pilot had coordinated with air traffic control prior to departure from Lelystad, requesting the ability to choose his landing runway based on wind conditions. Shortly before landing on runway 24, the pilot was notified of a wind direction of 290 degrees at 17 knots.
During the taxi phase, the pilot had positioned the control stick backward, which deflected the elevator upward, and turned the aircraft to the right into the wind. The pilot believed a gust of wind from the rear-right caused the tail to lift. Investigators noted that while taxiing with full upward elevator is standard for tailwheel aircraft to keep the tailwheel firmly on the ground, a tailwind can catch the upward-deflected elevator and lift the tail.
Findings
- The aircraft's design as an aerobatic plane allows for large elevator deflections, making it particularly sensitive to wind forces.
- Wind measurements at the time showed fluctuating speeds and directions, suggesting a temporary tailwind component may have occurred.
- The demonstrated crosswind limit for the Pitts S-1S is 17 knots, which matched the reported wind speed at the time of the incident.
- It is possible that the upward lift from the wind caused the propeller to strike the runway, leading to engine torque-induced rotation.
- While jet blast from other aircraft was considered a potential factor, it could not be confirmed or ruled out.
- Discrepancies in wind readings between different ends of the runway were also noted as a possibility.