Double rotor
In helicopters, a double rotor refers to the use of two main rotors , usually of the same size , in which their torque ( yaw moment ) is balanced out by turning in opposite directions . The coupling of the two rotors via their gears or transmission shafts ensures synchronous running in all operating states. A distinction is made in the construction:
- Tandem configuration : The rotors are arranged one behind the other in the direction of flight, with the rear of the two rotor levels usually higher than the front.
- Transverse rotors : The rotors are arranged next to each other, mostly on arms
- Flettner double rotor : rotor axes diverging by a small angle
- Coaxial rotor : rotors arranged one above the other on an axis
Double rotors are also arranged in the transverse axis on some VTOL and convertible aircraft , analogous to the helicopters with side rotors, for example on the Bell Boeing V-22 . When transitioning to level flight, they serve as propellers .