Hiller-copter

Stanley Hiller became interested in helicopter designs in his mid teens, and during his experiments decided that counterrotating rotors showed more promise than a single rotor with tail rotor. It would eliminate the torque reaction, making the machine easier to fly and cutting down on vibration. Though he had no formal engineering education, he built his own prototype machines and in 1944 he demonstrated this device in a San Francisco street. It performed well, flying forwards, backwards, sideways and in tight circles.

 With financing from Henry Kaiser he started manufacturing helicopters commercially. Though the counterrotating blade concept seemed to be an ideal solution the company's first commercial success was in 1950 with the conventional UH-12.