NGX rudder deflection

[Not_Boeing_Not_Going 1]

thank you all very much for these useful and interesting topics, i hope to see the PMDG 777 flight controls drop down because this is give you interesting feel of realism although it is not a very important thing to be simulated!.

[davierosoft 13]

In 737, indeed, cables control directly the hydraulic actuators but with a computer that intermediates the direct motion of the control depending on the airspeed. In other words, as speed increases, the maximum possible deflection is reduced to protect the structure and against overcontrol. When the HYD is out, the mechanism does not assist with power, defelction computer is out and gives direct deflection control this time fully proportional with control movement, feel mechanism on the feel and center unit does not artificially create any feel because it cannot anymore (also HYD actuated) and you are dealing with the real forces now anyway . Oh, and there is also mach trim to prevent mach ducking based on pitot like sensors on the vertical stabiliser and a computer just for that.

The 737 elevators work 99% similar to the 737-100 elevator.

There is no electrical computer acting on the feel force, there is a "computer" but it is fully hydromechanical and it only change the centering spring lenght by adding or removing forces, if hydraulic will be lost, the pressure drops and the forces will be released.

For the actuator, it is near the elevators, it works in normal conditions preventing that control column acts directl on the surface, but, when in manual reversion mechanical stops inside the PCU will move the surface like it is on a cessna (more force is required). The "freedom" is +-1° of column movement.

Other planes works different, the cables ends to the input quadrant and all is then moved by pressure, no pressure, no movement.

In the 737 without a cable cut or a jam or other strange not normal reasons, the surface will always move with the column, same (limited by the 1 or 2° of freedom) as the column, this giving no way to change the surface usage, ailerons will always work, and will be never used like flaps, something that FBW planes or fully hyd planes are able to do as there is no mechanical link. The same planes will need a RAT or ADG in case of a complete power failure and/or they will need some mechanical backups... 737 doesn't need a rat, it can still fly with battery power only.

The logic of using cables still on full FBW planes is to give a "last chance" to land the plane in case of a very bad day. the stabilizer can be used to pitch the plane, rudder and engines to roll and steer. All of them are redundant systems that engineers and laws requires for a safe aircraft.