Both designs used the principle of counter-rotating side-by-side intermeshing rotors, as the means to solve the problem of torque compensation, normally countered in single–rotor helicopters by a tail rotor, fenestron, NOTAR, or vented blower exhaust.
The two helicopter designs employed the concept of counter-rotating side-by-side intermeshing rotors to compensate for torque, a problem commonly addressed in single-rotor helicopters with the aid of a tail rotor, fenestron, NOTAR, or vented exhaust system.