Hi folks got a couple of questions about the B737 flight control system:
The aileron control system as far as I know consists of the two control columns, of an aileron trim, of two aileron power control units and of a single dual powered aileron attached to the outboard portion of each wing. Movement of the yokes, which are interconnected through a cable system and a bus control drum, is transferred through a set of wires and push pull rods to the two power control units which then, that's where it gets cloudy, forward the inputs to the aileron. If I am not mistaken each power control unit consists of a set of pistons horizontally placed and basically transfers the hydraulic pressure from the associated hydraulic system to the aileron. Now my question is: how? Is it connected directly to the aileron through a hydraulic actuator or it operates a sort of pully, cable, push-pull rod sytem in turn connected to the aileron? the only thing that I know is that the piston is secured to the structure of the wing while the housing, as a pressure is routed to either side of the piston depending on the direction of the yoke movement, slides back and forth moving the aileron. Somewhere in the wiring between the control columns and the PCU there is a Feel control unit which I assume, please correct me if I am wrong, consists of a spring system that creates a sort of artificially induced resistance to the displacement of the yoke, giving the pilot the feeling of aerodynamic load. The trim, I believe somehow increases or decreases the tension of the spring. Is that correct? besides, what is the function of the balance panel, where is it located, how does it interact with the aileron, I know it is normally held down by the pressure over the wing acting upon it, but somehow that pressure is disrupted when the aileron is deflected, still wondering which way the balance panel moves? One last question: in the event of a dual hydraulic system failure the system automatically shifts into a manual mode and the aileron is operated manually through the balance tab, mechanically connected to the yokes, is the reversion process initiated automatically by a sort of pressure switch in the PCU or there is a switch?
Thanks for your willingness