We are used to seeing one compensating screw in the tail of the helicopter, driven by a gearbox, cardan shaft and hub, to compensate for the reactive moment. But Bell helicopters developed an innovative concept, replacing the tail rotor with 4 electric motors and 4 enclosed rotors. The system is called EDAT (electrically distributed anti-torque).
The system is controlled by the pilot, as in a regular helicopter with a pedal, but the propellers are not driven by rods, as with a conventional tail rotor, but by means of an electro-remote system.
The uniqueness of the system lies in the fact that each of the screws is driven by its own independent electric motor, therefore, the speed is regulated independently of each other. Electric motors drive electric generators driven by helicopter engines.
According to Bell experts, the control system is significantly safe compared to the usual compensating propeller, since when it fails, the helicopter loses control. Using electric rotors, the system will allow the pilot to safely helicopter even if three out of four rotors fail, which significantly affects the safety of flights.
Two generators operate from a shaft that goes to the tail rotor, as in the regular version of the helicopter. Even if both engines fail, the energy will be transmitted to the shaft from the screws rotating due to autorotation; accordingly, the generators will continue to operate and the helicopter will not lose control.
The electronic control system allows you to make turns with absolute accuracy, which is extremely important in hovering mode and when maneuvering at low speed. Moreover, the helicopter stably and obediently flies sideways.
The control system has been tested on a modified Bell 429 helicopter in Canadian Quebec since May 2019. We are looking forward to the results.