Early Sikorsky FBW development
Sikorsky with its SHADOW XS-76 demonstrator helicopter extensively evaluated helicopter FBW controls. At that time we concentrated on the types of controllers and did little evaluating more complex control laws. The Shadow aircraft had an electric side arm controller, electric conventional pedals and an electric back driven collective in the front cockpit. The copilot’s station had an electric sidearm controller. The pilots station had conventional mechanical controls that could override and shut off the FBW control system.
Two sidearm controllers were evaluated. One ridged stick and one with limited compliance similar the F-16. Configurations evaluated included: 4 axis, pitch ,roll, yaw and collective on the side arm controller, 3 plus 1, pitch roll and Yaw on the side arm controller and a conventional collective. The collect was back driven and would move up and down with input from the side arm controller. A lemon squeezed type switch on the collective would disable the collective function on the side arm controller. Lastly we evaluated a conventional configuration, pitch and roll on the side arm controller, yaw pedals and a conventional collective that was moved up and down.
The co-pilots side arm controller was typically a 4 axis controller and was used to assist the front seat pilot through some maneuvers. This was extensively used when military pilots and dignitaries were provided with a front seat demonstration flights.