NATO and the German Armed Forces required an aircraft that was able to take off from unprepared airfields to undertake close air support missions. It had to be able to fly at extreme-low-altitude in order to prevent attacks of anti-aircraft weapons and radar detection.
The VAK 191B was designed with short wings and a minor extension so it would provide its pilots a tolerable flight and bear aerodynamically difficult extreme-low-altitude-flights.
The first prototype flew in late 1971, the transfer of vertical flight in horizontal and vice versa as well as turning off and on the lift-engines was achieved on October 1972 in Manching, Bavaria, at a speed of 400 km/h.
All three VAK 191B experimental aircraft completed a total of 91 flights that lasted all together 12 hours
