What happened
On June 10, 1969, a Pilatus Turbo-Porter HB-FDP, operated by Pilatus Flugzeugwerke AG, was conducting a demonstration flight at Buochs airfield. The flight included the pilot and a passenger, a journalist attending the flight to write a report for a French aviation magazine.
During the approach to runway 07, the pilot executed an exceptionally steep and short final approach. The aircraft initially touched down on its main landing gear approximately 100 meters past the threshold. Following this initial contact, the aircraft briefly lifted again before performing a three-point landing. During the landing sequence, the pilot engaged the reverse thrust. Immediately after the second touchdown in the three-point position, the tail of the aircraft lifted, causing the propeller to strike the ground.
The investigation
The investigation examined the aircraft's recent modifications and the pilot's handling of the landing. The HB-FDP had recently been equipped with a new Hartzell wide-chord propeller, which provided enhanced performance and stronger reverse thrust capabilities. Additionally, the aircraft had been upgraded with Goodyear dual-piston brakes, which offered significantly more braking power than the previous single-piston version.
Investigators reviewed the pilot's qualifications and flight experience. While the pilot was fully licensed and experienced in the aircraft type, this was his first flight operating with the new propeller configuration and the upgraded braking system. The investigation also confirmed that the aircraft's weight and balance were within limits and that the pilot had correctly configured the flaps and trim for a light load.
Findings
- The two occupants remained uninjured during the event.
- The engine and propeller sustained total destruction due to the ground strike.
- The primary cause of the accident was careless landing technique, specifically the pilot's failure to account for the increased effectiveness of the new braking system and the altered handling characteristics of the new propeller.