Ailerons are often seen to have push-pull rod and cable-pulley mechanism both but rudder are mostly operated by cable. Even though Push-pull rod requires less maintenance, more reliable, rudder are constantly are operated through cable. If weight can be the issue why not ailerons or elevator be operated by cable.
I want to know different aspect of using cable in rudder different than above.
Speaking as a private pilot and not as an airframe engineer, I would suggest that the answer lies in the angle between the cockpit and the control surfaces. It's a straight shot back through the fuselage from the rudder pedals to the rudder and from the control yoke to the elevons in the empennage (tail section), which allows the use of cables without the need for (too many) pulley wheels to operate them around corners. Such would be needed should the ailerons be operated by cables because the tension would have to be transmitted first from the cockpit out laterally along the wing and then make a turn backward in order to achieve the leverage needed for up/down movement of the control surfaces against the onrushing airflow. The flaps may be a different story since they're placed nearer the fuselage and somewhat behind the front seats.
Pulley wheels would be just one more thing that might break and would impart frictional wear and tear on the cables over time. Or the cable could simply slip out from its groove around the pulley wheel and get jammed in the works. Speaking as a pilot, thanks but no thanks to any possibility of that happening.
All that said, I'm not familiar with the pros and cons of cables vs. pushrods except that:
- I see more occasion for mechanical wear and tear using pushrods than I do using cables;
- One never need worry about a cable getting bent out of shape.
Ergo, use cables wherever that choice presents itself, provided you don't need too many pulley wheels to make them work.
All these subtle considerations accumulate with experience over time, resulting in aircraft with long and clean safety records. That's why I would think twice before flying an experimental aircraft except as a test pilot with good life insurance. Stepping into one of those, you throw a lot of that accumulated experience out the window to try something new and perhaps fatefully different. Famous case in point: John Denver in his Long EZ. I suspect that as he turned around in his seat to switch the fuel valve from the empty tank to the full tank, his opposite foot involuntarily pushed down on the rudder pedal, sending him into a tailspin. As I understand it, he'd have had to unbuckle his seat harness to reach the fuel valve, which is not where you want to be when you're trying to recover from a tailspin.
Rudders are almost exclusively cable operated. This is because cables provide the simplest, lightest, and most reliable rudder control system you can install.
for ailerons or elevator ,a lot of pulleys are necessary for routing the cables, the control system tends to develop more resistance in the control stick, making it feel "heavy on the controls."
the use of push-pull tubes and rods than cables for controlling both the elevators and the ailerons results in a very light efficient installation, especially in low wing aircraft.
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