Why do planes have dual controls?

Question

Why do planes have dual controls?

Answer 1

Andy B posted "Also in airliners each control yolk can be disconnected from each other and will control only one side of the control surfaces...for instance the Captains side, when disconnected, will control the left aileron and left side of the elevator."

say what?? please explain......first I ever heard of this.

I find this hard to believe.

Answer 2

Not just so the co-pilot can take over without changing seats, but to have a packup set in case something breaks.

Answer 3

Not all airplanes have dual controls.  For example older Beachcraft Bonanzas have a "throw over" control yolk, meaning the controls can be thrown over to the other pilot.  

Aircraft used in flight instruction are required to have dual controls.

The statement about a redundant set of controls in case something breaks is not true, the controls are all hooked to one set of cables that control the surfaces.  Airliners have two redundant sets of control wires running above and below the passenger cabin so if one is broken or damaged the other set can control the airplane.  Also in airliners each control yolk can be disconnected from each other and will control only one  side of the control surfaces...for instance the Captains side, when disconnected, will control the left aileron and left side of the elevator.

Answer 4

To permit flight instruction and relief pilot operations.

Answer 5

It is not very easy to switch seats in flight and it is even harder to pull over to switch drivers.

Even my wife can keep the plane from slamming into something when I have to scratch an itch or grab a beer (JK).