Flybarless

From RC Helicopter Wiki

Generally referring to a two-bladed rotor system that does not have a flybar to help stabilize it. Helicopter rotor systems having more than two blades are all flybarless. Since the flybar is absent, a flybarless rotor system usually needs a series of additional gyros and an additional mixer (sometimes called a virtual flybar) to help stabilize the head and make it flyable. While it is possible to fly a flybarless head without these extra gyros and mixers, it is very difficult. The benefit of a flybarless two-bladed head is increased maneuverability and lower rotating mass, which means more power to the rotors. Flybarless rotor heads with more than two blades are very useful for scale models.