03/31/2008. Remarks by Walter van Tilborg: "The PK X-1 is a two-seater with a 180 hp Franklin 60440-C4 engine, and was designed by Lt.Col. Paul Kjølseth mainly to test a collective and cyclic pitch rotor system that was patented by him in 1956. The PK X-1 was built by the Luftforsvarets Forsyningskommando (Air Force Supply Command) at Kjeller near Oslo.

First flown in May 1955, the performance of the helicopter was never recorded, but the dimensions are: rotor diameter 30 ft 4.56 in (9.26 m), length 25 ft 7.09 in (7.80 m), and height 8 ft 3.61 in (2.53 m). The PK X-1 and the later PK X-2 were the first, and so far only indigenous helicopter designs in Norway. The
PK X-1 is now preserved at the Forsvarets flysamling (Armed Forces Aircraft Collection) at Cardmoen AFB, Norway.