In the flight control system of F/A-18, where is the servo-loop closed? I mean which of these two scenarios happen: 1-The position of the actuator and servo-valve ram are sent to the flight control computer and the servo-loop is closed there in the software, 2-the servo-loop is closed near actuator that means the actuator has an interface that receives a command and compares it with the actual position. If the second scenario is what happens, the interface is digital or analog?
1 Answer
Ram position feedback is sent back to the relevant channel in one of the two flight control computers via wire carrying an analogue signal. If it is a leading edge flap, aileron or rudder it is done twice. The big surfaces (Trailing Edge Flap and Horizontal Stab) are quad redundant. The signal is processed on a printed circuit board inside the box. There is negative feedback occurring via an operational amplifier type circuit.