What happened
On April 11, 2016, a private flight involving a Pilatus PC-12/47E, registration HB-FWM, experienced a runway excursion during landing at St. Gallen-Altenrhein Airport (LSZR). The aircraft, operated by Calanda Wings AG, was arriving from Schwäbisch Hall-Hessenthal, Germany, with a pilot and one passenger on board.
During the landing roll with flaps set to 40°, the left main tire burst. This sudden failure caused the aircraft to veer left, momentarily leaving the paved runway surface. The pilot managed to maneuver the aircraft back onto the runway, eventually coming to a stop approximately 700 meters past the runway threshold. The incident resulted in minor injuries to one person and light damage to the aircraft.
The investigation
Investigators analyzed flight data recorder information, which revealed that the aircraft made a smooth touchdown at approximately 73 KIAS. Data showed that as the aircraft decelerated, it began to deviate left at a speed of 20 KIAS. The investigation examined the aircraft's braking system, noting that on this model, brakes are actuated by applying pressure with the balls of the feet against the upper edge of the rudder pedals. This design lacks a system to prevent the wheels from locking during brake application.
Physical inspection of the aircraft revealed a burst left tire, abrasions on the right tire, and a dent on the edge of the left flap, caused by contact with a runway light. The investigation also reviewed the pilot's technique and the possibility of unintended brake application during the touchdown phase.
Findings
Analysis of the tire damage and visible brake marks on the runway suggests that the wheel brakes were likely applied lightly during touchdown. Because the landing was smooth, the tires were dragging across the pavement unnoticed by the pilot. When the left tire burst, the resulting increase in rolling resistance on the left side caused the aircraft to veer off the runway. The investigation concluded that the incident was due to operational factors rather than mechanical failure.