Focke - Wulf Triebflügel The Focke - Wulf " Triebflügel ( " Triebfluegel " if the ü - umlaut is not used ) , or Triebflügeljäger " , literally meaning " thrust - wing fighter " , was a German concept for an aircraft designed in 1944 , during the final phase of World War II as a defence against the ever - increasing Allied bombing raids on central Germany . It was a Vertical Take - Off and Landing tailsitter interceptor design for local defense of important factories or areas which had small or no airfields . The " Triebflügel " had only reached wind - tunnel testing when the Allied forces reached the production facilities . No complete prototype was ever built . Design . The design was particularly unusual . It had no wings , and all lift and thrust were provided by a rotor / propeller assembly 1 / 3 of the way down the side of the craft ( roughly halfway between cockpit and tailplane ) . When the plane was sitting on its tail in the vertical position , the rotors would have functioned similarly to a helicopter . When flying horizontally , they would function more like a giant propeller . The three rotor blades were mounted on a ring assembly supported by bearings , allowing free rotation around the fuselage . At the end of each was a ramjet . To start the rotors spinning , simple rockets would have been used . As the speed increased , the flow of air would be sufficient for the ramjets to work and the rockets would expire . The pitch of the blades could be varied with the effect of changing the speed and the lift produced . There was no reaction torque to cause a counter rotation of the fuselage since the rotor blades were driven at their tips by the ramjets . Fuel was carried in the fuselage tanks , and was piped through the centre support ring and along the rotors to the jets . A cruciform empennage at the rear of the fuselage comprised four tailplanes , fitted with moving ailerons that would also have functioned as combined rudders and elevators . The tailplane would have provided a means for the pilot to control a tendency of the fuselage to rotate in the same direction as the rotor caused by the friction of the rotor ring , as well as controlling flight in pitch , roll and yaw . A single large and sprung wheel in the extreme end of the fuselage provided the main undercarriage . Four small castoring wheels on extensible struts were placed at the end of each tailplane to steady the aircraft on the ground and allow it to be moved . The main and outrigger wheels were covered by streamlined clamshell doors when in flight . When taking off , the rotors would be angled to give lift as with a helicopter or , more accurately , a gyrodyne . Once the aircraft had attained sufficient altitude it could be angled into level flight . This required a slight nose - up pitch to provide some downward thrust as well as primarily forward thrust . Consequently , the four cannon s in the forward fuselage would have been angled slightly downward in relation to the centre line of the fuselage . The rotors provided the only significant lift in horizontal flight . To land , the craft had to slow its speed and pitch the fuselage until the craft was vertical . Power could then be reduced and it would descend until the landing gear rested on the ground . This would have been a tricky and probably dangerous maneuver given that the pilot would be seated facing upward and the ground would be behind his head at this stage . Unlike some other tailsitter aircraft , the pilot ' s seat was fixed in the direction for forward flight . The spinning rotor would also obscure rear vision . This design was unique among 20th - century VTOL craft , and other German concept craft . However , some early design studies for the Rotary Rocket Roton spacecraft in the 1990s showed a free - spinning rotor with tip - driven rotors providing lift . In the 1950s , the USA built prototype tailsitter aircraft ( the Lockheed XFV , and Convair XFY Pogo ) , but these were powered by conventional turboprops , with nose - mounted contra - rotating propellers to counter torque . They also used conventional wings for lift , though their cruciform tails with integral landing gear were broadly comparable to the " Triebflügel " .