Incident Overview
On March 5, 2021, at approximately 08:33 local time, a serious incident occurred at Buochs Airport (LSZC) in Nidwalden, Switzerland. The aircraft, a single-engine turboprop Pilatus PC-12/47E registered as HB-FRP, was taxiing on Taxiway D when it collided with a car on a public road crossing the taxiway. The aircraft was lightly damaged, and the car sustained damage to its right side. Neither the pilot nor the car driver was injured.
Sequence of Events
The pilot, a Swiss commercial pilot employed by Pilatus Flugzeugwerke AG, was conducting a positioning flight from Buochs to Payerne under instrument flight rules. After engine start at 08:28, the pilot completed checklist items and requested taxi clearance from the aerodrome control tower at 08:30:59. Clearance was given to taxi via Taxiway D to backtrack on Runway 24.
The pilot activated the crossing signal system for the public road by pressing the radio transmit button three times on a separate frequency. The system acknowledged with a high-pitched tone. The pilot then taxied slowly eastward on Taxiway D, with all external lights on. Upon reaching the first road crossing (K1), the signal for aircraft turned green, and the pilot crossed without stopping.
At the second road crossing (K2), the aircraft triggered the signal loop, and the aircraft signal turned red for about 12 seconds before changing to green. The pilot observed vehicles stopping on the right side of the road but saw no traffic from the left. As the aircraft entered the crossing at about 20 km/h, the pilot suddenly noticed a car approaching from the left at high speed. He immediately stopped the aircraft with the power lever in idle.
The car driver, traveling at approximately 75 km/h, later stated that he saw the “Caution Aircraft” warning sign but did not notice the red traffic light until he was close to the crossing. He initiated a hard brake but could not stop in time. The right side of the car struck the spinning propeller tips of the PC-12.
After the collision, the pilot shut down the engine, informed the tower, and deactivated all systems according to the checklist. The car driver reversed and parked on the right side of the road.
Aircraft and Road Crossing Signals
The PC-12/47E HB-FRP is a low-wing, single-engine turboprop with a retractable landing gear, T-tail, length of 14.4 m, wingspan of 16.3 m, and height of 4.3 m. Its maximum takeoff weight is 4740 kg.
Taxiway D crosses a cantonal road that runs between Ennetbürgen and Stans. The crossing is controlled by signal systems with colored lights for aircraft and traffic lights for road vehicles. At the time of the incident, the crossing signal for aircraft was green, while the traffic light for the car was red. The car driver did not see the red light until late, leading to the collision.
Aftermath
The investigation by the Swiss Transportation Safety Investigation Board (STSB) found that the aircraft sustained damage only to the tips of the five propeller blades. The car suffered damage to its right side. No injuries were reported. The STSB did not assign a probable cause in its final report.