Why are planes turned using ailerons and not rudder?

The other answer cover the bases but let me try a slightly different explanation. When flying along straight and level, if you want to climb, you pull back on the elevators by using the yoke or stick and the aircraft climbs. Makes sense? So, let's do that same thing to turn the aircraft. read more

Instead the ailerons are used to bank the plane and then the wings and elevator turn it. The rudder is just used to correct for adverse yaw so the turn is properly balanced and not side-slipping or skidding (turning with nose or tail pointing out of the turn, respectively). read more

Rudder can turn or change the heading of a plane slightly as a secondary effect at low speed only. It is not recommended to use the rudder at high speed. An Airbus A300 crashed in New York many years back because of excessive/wrong application of the rudder in wake turbulence. The proper technique to turn an airplane is to use the ailerons. read more

Using the ailerons and bank as opposed to rudder and yaw is a much more efficient way to turn the aircraft because it is using the full lifting force of the wing to turn the aircraft. It is also a much smoother and more comfortable turn for any passengers. read more

If you are on a motorboat, you use the rudder to turn left or right, but when you talk about flying the function of rudder is mainly to keep plane in a balanced flight. The most important use of rudder is NOT to do anything positive. read more