Summary
On 10 June 1969 at 1055 hours local time, a Pilatus Turbo-Porter PC6/B1A-H2, registered HB-FDP, suffered an accident upon landing at Buochs airfield. The aircraft, operated by Pilatus Flugzeugwerke AG for a demonstration flight, nosed over after touchdown, resulting in the destruction of the propeller and turbine. Both the pilot and passenger were uninjured.
Investigation
The accident was reported by Pilatus AG to the Swiss Federal Air Office on the same day. The investigation was conducted by the Bureau for Aircraft Accident Investigation, with the investigator taking witness statements on 3 July 1969 at Buochs. No cantonal authorities participated.
Elements
Pilot
The pilot, an Austrian national born in 1943, held a valid private pilot's license with extensions for towing flights and a commercial pilot's license. He had logged 530 total flying hours with 1040 landings, including 200 hours and 250 landings on the Pilatus Porter. In the preceding three months, he flew 60 hours with 150 landings, of which 8 hours and 30 landings were on the accident aircraft type. His license was current, and no previous incidents were recorded.
Passenger
The passenger, a French national born in 1914, sat in the right seat and was not involved in controlling the aircraft. He was participating in the demonstration flight for an aviation magazine.
Aircraft
The accident aircraft was a Pilatus Turbo-Porter PC6/B1A-H2 (HB-FDP), built in 1968, owned and operated by Pilatus Flugzeugwerke AG. It was equipped with a Pratt & Whitney PT6 A-20 turboprop engine and a Hartzell T10178 broad-blade propeller. The aircraft had recently been fitted with this new propeller and Good Year dual-piston brakes, which provided increased effectiveness compared to previous single-piston brakes. The aircraft had 335 total operating hours at the time. Weight and balance were within limits.
Weather
Weather was clear with 1/8 cloud cover at 8000 meters, wind from 070 degrees at 3 knots, visibility 10 kilometers, and QNH 1016 hPa.
Terrain
The accident occurred on runway 07 at Buochs airfield.
Organization
The flight was a demonstration of the newly equipped Turbo-Porter as part of Pilatus Flugzeugwerke AG operations.
Accident Sequence
On 10 June 1969 at 0940, the pilot and passenger took off for a demonstration flight. After about 15 minutes, the pilot flew a tight turn onto active runway 07. He applied full aft trim and extended landing flaps to 38 degrees. The aircraft executed a short and steep final approach. At 1055, it touched down 100 meters past the threshold, level with the runway vehicle, initially on the main landing gear. It briefly lifted off again before settling into a three-point landing. During or immediately after touchdown, the pilot engaged reverse thrust. Immediately after the second touchdown in a three-point attitude, the tail rose, causing the propeller to strike the ground.
Damage
The occupants were uninjured. The propeller and turbine engine were completely destroyed. Runway surface damage was minor (scrape marks).
Discussion
The pilot held valid licenses and was qualified for the demonstration flight, but this was his first flight with the broad-blade propeller and the new dual-piston brakes. The aircraft was airworthy and certified for flight, though the prototype propeller had not yet been submitted for Swiss certification; however, Fairchild-Hiller had conducted tests and an FAA certificate existed. The pilot's actions of full aft trim and full flaps were in accordance with the flight manual. The pilot stated he was unaware that the aircraft touched down twice, but a witness confirmed the bounce. The pilot reported inadvertently applying the brakes and reverse after the second touchdown. The new brakes were significantly more effective than those he had previously used.
Conclusion
The accident was caused by careless landing technique, with the pilot not fully accounting for the aircraft's more effective brakes.