twinrotor

Twinrotor refers to a type of helicopter configuration that utilizes two main rotors. These rotors are typically mounted side-by-side, one behind the other, or in a coaxial arrangement. The primary purpose of a twinrotor system is to counteract the torque generated by a single main rotor, which would otherwise cause the helicopter fuselage to spin in the opposite direction.

In a side-by-side configuration, known as a tandem rotor system, two large rotors are mounted at the front and rear of the fuselage. Each rotor spins in the opposite direction of the other, thus canceling out their torques. This arrangement provides excellent longitudinal stability and a large center of gravity range, making it suitable for heavy-lift helicopters.

Another common twinrotor arrangement is the coaxial rotor system, where two main rotors are mounted on the same mast, one above the other, each rotating in opposite directions. This configuration is mechanically complex but offers a compact footprint and good maneuverability. It is often found on smaller helicopters and some advanced military designs.

Less common is the intermeshing rotor system, where two rotors are mounted close together at an angle, with their blades intermeshing without colliding. This also cancels out torque and provides a stable platform. The German Flettner Fl 282 Kolibri is a notable example of this type.

The twinrotor design, in its various forms, offers advantages in terms of lift capacity, stability, and maneuverability compared to single-rotor helicopters, though often at the cost of increased mechanical complexity and power requirements.