Airliner flight control questions
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Airliner flight control questions
Hello,
Im here asking about flight controls of a non fly by wire airliner (767, 747, 737 etc)
Ok so I know the basic concept, yoke rudder pedal etc to control rod through artificial feel system to servo hydraulic actuator which moves the surface.
But first, how does the artificial feel system work. Is it a computer or a mechanical system? And what data does it take to do its thing (which vaguely I know its to outcome forces on the surface and for the pilots to feel it)
And what is the control rod made of? Simple metal rod, cable etc.
I would appreciate images of the items stated (control rod, artificial feel system and the servo actuator)
Thanks guys
Im here asking about flight controls of a non fly by wire airliner (767, 747, 737 etc)
Ok so I know the basic concept, yoke rudder pedal etc to control rod through artificial feel system to servo hydraulic actuator which moves the surface.
But first, how does the artificial feel system work. Is it a computer or a mechanical system? And what data does it take to do its thing (which vaguely I know its to outcome forces on the surface and for the pilots to feel it)
And what is the control rod made of? Simple metal rod, cable etc.
I would appreciate images of the items stated (control rod, artificial feel system and the servo actuator)
Thanks guys
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737
Elevator feel is provided by the elevator feel computer. Inputs of airspeed (from the elevator pitot
system) and stabilizer position (center of gravity) enable the computer to simulate aerodynamic
forces. Feel is transmitted to the control columns by the elevator feel and centering unit. The feel
computer utilizes system A or B pressure to operate the feel system. Whichever system is providing
higher pressure is the only one utilized by the feel computer.
If either system A or B fails, the computer senses the imbalance, and the FEEL DIFF PRESS Light
illuminates when the flaps are up, The light also illuminates if one of the elevator feel pitot systems
fails or a frozen pitot probe results in a difference in elevator feel computer output pressures. The
feel system operates normally with only one hydraulic system operating.
Elevator feel is provided by the elevator feel computer. Inputs of airspeed (from the elevator pitot
system) and stabilizer position (center of gravity) enable the computer to simulate aerodynamic
forces. Feel is transmitted to the control columns by the elevator feel and centering unit. The feel
computer utilizes system A or B pressure to operate the feel system. Whichever system is providing
higher pressure is the only one utilized by the feel computer.
If either system A or B fails, the computer senses the imbalance, and the FEEL DIFF PRESS Light
illuminates when the flaps are up, The light also illuminates if one of the elevator feel pitot systems
fails or a frozen pitot probe results in a difference in elevator feel computer output pressures. The
feel system operates normally with only one hydraulic system operating.
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Artificial feel
The simple old system basically inducted pitot pressure into a bellows that mechanically moved a control rod to limit the allowable movement of the flight control system.
Some systems use output data off the ADC and have electro-mechanical devices to limit flight control movement.
In the modern jet, a flight control computer receives DADC data used for limiting movement. Sorry no pics, most control rods would be made of an aluminum alloy.
Some systems use output data off the ADC and have electro-mechanical devices to limit flight control movement.
In the modern jet, a flight control computer receives DADC data used for limiting movement. Sorry no pics, most control rods would be made of an aluminum alloy.
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On the 737/757/767 the artificial feel system of both the ailerons and the rudder consist of an input which moves a roller up a cam. The shape of the cam allows the roller to move in either direction i.e left/right or up/down depending on the direction of the input. The roller is held in the centre and 'neutral' position of the cam by spring force. The input you make into the control system moves the roller out of the neutral position in the cam and follows the cam profile-this is all against the force of the spring which provides the feel. So the feel comes from the cam profile and spring force.
The artificial feel system for the elevator is a little more complex. Basically there is a elevator feel computer system which provides feel to the control column mechanically. Now, this computer is purely mechanical. It has inputs from typically two hydraulic systems, pitot and static air pressure in pneumatic form not electronic, and a position input from the stabiliser which is also mechanical and not electrical.
Hope that makes sense!
The artificial feel system for the elevator is a little more complex. Basically there is a elevator feel computer system which provides feel to the control column mechanically. Now, this computer is purely mechanical. It has inputs from typically two hydraulic systems, pitot and static air pressure in pneumatic form not electronic, and a position input from the stabiliser which is also mechanical and not electrical.
Hope that makes sense!
