Although only a project, the Focke Wulf Triebflügel (Thrust-wing) fighter, designed in September 1944, was a most interesting study in rotary-wing flight and embodied several radical features. The fighter was to be a tail-sitting, vertical take-off aircraft deriving its lift and thrust from three wings which rotated around the fuselage at a point approximately one-third of the fuselage length from the nose. No torque was transmitted to the fuselage from the rotating wings, since these were driven by three tip-mounted ramjets, the wings being revolved up to the ramjet operating speed by three 300kg thrust rockets.
Each ramjet was 0.68m in diameter, gave about 840kg of thrust and was developed from the experiments conducted from 1941 by Otto Pabst in Focke-Wulf’s gas dynamics department, at Bad Eilsen. Principally by the development of special fuel burners and the method of air compression, Pabst had succeeded in evolving a basic design of ramjet in which the total length was no more than 2\ times the ramjet diameter, which made the type suitable for rotary motion. Successful tests of the Pabst ramjet were made in the LFA (Brunswick) wind tunnel at speeds up to Mach 0.9.
The Triebflügel fighter was to stand vertically on the ground, supported by its four tail fins, each of which had a small outrigger wheel at its tip. The main landing load was to be taken on a single main wheel at the base of the fuselage, and during flight all wheels were enclosed by streamlined tulip-shaped pods. The pilot was accommodated conventionally in a nose cockpit with bubble hood, and the nose-mounted armament was to consist of two 30mm MK 103 cannon with 100 rounds plus two 20mm MG 151 cannon with 250 rounds.
The rotating untapered wings had a gradually decreasing pitch from root to tip in the manner of an airscrew, and no control method, apart from rpm adjustments, appears to have been intended for adjusting the wing characteristics. Control of the aircraft was by means of the control surfaces at the trailing edges of the tail fins. Thus, for flying in a horizontal path, the tail would be depressed slightly to direct part of the thrust force into a lift force.
After the war, some development of this type of VTO fighter was resumed, notably in the United States where experiments were made with aircraft using turbine-driven nose-mounted contra-rotating airscrews to counteract torque.
J.R.Smith, Antony L. Kay "German Aircraft of the Second World War", 1972
Technical data for FockeWulf Thrust-wing project
Rotating wing diameter: 11.5m, length: 9.15m, total wing area: 16.5m2, empty weight: 3200kg, ramjet and rocket fuel: 1590kg, loaded weight: 5175kg