P.Grosz, G.Haddow, P.Shiemer Austro-Hungarian Army Aircraft of World War One

Fruba Fighter

  By the time he designed the Fruba Fighter in late 1918, Ingenieur Julius Kolin could look back on a productive aeronautical career that had begun in Professor Knoller's aero laboratory in 1911. As Knoller's assistant, Kolin played an important part in constructing the first Knoller prototype (30.05) at Thone & Fiala. In 1915, Kolin became the production supervisor of the Knoller biplanes at Aviatik. In 1916, he rejoined Knoller to work in the new propeller test facility at Fischamend. It was here that Kolin designed and tested the wooden rotors for the PKZ 2 helicopter. And here he met Sigmund Jaray, a prewar furniture manufacturer, who had the task of fabricating the helicopter rotors.
  In 1918, Kolin designed a high-performance fighter which was to be built in Jaray's aircraft repair facility known as the Flugzeug Reparatur und Bau Anstalt (Fruba - aircraft repair and manufacturing facility) that had been established in late 1916. As aerodynamic consultant to Julius von Berg, Kolin was well apprised of latest Aviatik rotary-engined fighters, which may account for the similarity of the Fruba fighter to Aviatik designs. Kolin had in mind
  to build a vertical take-off aircraft, capable of hanging in the air and shooting upwards. I replaced the then inferior steel and steel tubing of the structural components by high-strength veneer and veneer tubing. This was possible owing to the high skill of Jaray personnel in handling wood. The end result was an aircraft of 540 kg (1191 lb) weight fully loaded and a propeller thrust of 650 kg (1433 lb) using a 150 hp Le Rhone(St) rotary engine.
  The Fruba fighter, completed in late 1918, fell victim to the Armistice and, according to Kolin, was never properly tested.