Lift fan

The Republic Aviation AP-100 was a prototype VTOL 6x General Electric J85 Turbojet engined nuclear capable strike fighter concept designed by Alexander Kartveli that had 3x ducted fans in the centre of its fuselage and tail as a possible contender for the TFX Program.

[2][3][4] The Avro Canada Avrocar, commissioned by the USA, was intended to be a technology demonstrator for a supersonic VTOL aircraft.

It featured a single central fan in a circular flying wing, with engine thrust directed rearwards for forward flight.

It underwent trials between 1958 and 1961 but, due to its unstable "flying saucer" aerodynamics and lower than expected thrust, never flew out of ground effect.

The Verticraft Verticar of 1961 was a similar single-fan, directed-thrust, all-wing (or lifting body) aircraft, of conventional but very low-aspect-ratio wing planform.

In the late 1960s NASA conducted wind tunnel experiments on a series of larger aircraft designs using different numbers of fans in the wings.