The Quadrotor flown on Long Island in 1956 was designed by its test pilot, D.H.Kaplan. In 1956 this radical idea was to place four rotors in the verticle position in an “H” configuration. Thrust and direction could then be changed by changing speeds between the rotors. Pitch and control is through a collective collective – ( oh my goodness is that clever!) The four engine four rotor configuration allows the pilot to avoid cyclic-pitch-control systems
Although it wasn’t developed too much further, like all test bed aircraft, what was gleaned as vital to future VSTOL aircraft.