In order to supplement the helicopter fleet of the Swiss AF, 12 Pilatus PC-6 transport aircraft were procured in 1965. All aircraft were then equipped with the Lycoming GSO-489 piston engine. 10 years later, the success of this Swiss built aircraft resulted in another procruement of 6 planes. These aircraft were then powered by the Pratt & Whitney PT A-27 turbo engine.
Additional information on the Pilatus PC-6 aircraft in use with the Swiss Air Force can be found here: