I have little doubt in my mind that the most neglected art form in aviation must surely be rudder control. By that I do not mean that most pilots do not know how to use the rudder at all, but rather that very few pilots fully appreciate the significance of proper rudder usage. I always enjoy flying with a pilot that trained on taildraggers, because these pilots are very aware of the rudder and properly appreciate that, when flying a taildragger, incorrect rudder use will almost certainly cause the aircraft to crash on take off or landing. There is no if, but, or maybe. In a taildragger, use the rudder correctly or crash the aircraft. Unfortunately for newer pilots most training establishments these days have fleets of aircraft with tricycle undercarriages and this does little to impress upon students the importance of learning how to properly use this vital control.
An example of when the rudder is unnecessarily neglected is when flying in mild turbulence. In any turbulence at all, there will be a degree of fluctuation in angle of attack on each main wing. This fluctuation will not necessarily be equal on each wing so, as the angle of attack briefly increases on either wing, there will be an increase in drag on that wing. This of course will cause the nose to yaw from side to side even though the pilot is attempting to fly the aircraft in a straight line. Most pilots, leisure and professional, that I have flown with tend to ignore this general "scalloping" of the nose and merely concentrate on keeping the wings level using aileron alone. This is wrong. The rudder must be seen as an accessory control to the ailerons and must be used at all times. If you apply right aileron, apply right rudder. If you apply left aileron, apply left rudder. In other words, apply rudder in the same direction as the turn, at the same time as the aileron is being applied. The rudder is not there to be used only for the take off and the landing; it is one of the flying controls and must be used at all times, in conjunction with the ailerons. To this end, many general aviation aircraft actually have interlinked controls whereby the rudder is connected to the ailerons via springs. This is so that, when aileron is applied, rudder is automatically applied in the same direction, at the same time. The connection via springs is so that this can be over-ridden as in the case of take off and landing, where a crossed control situation may be required.
Let us re-cap on just why it is necessary to apply rudder simultaneously with aileron. When the control column is moved to the right, the right hand aileron moves up whilst the left hand aileron moves down. If we look at the left hand aileron, it can then be seen that the chord line has moved. Remember, the chord line is an imaginary line joining the leading edge of the wing to the trailing edge. In this case, the trailing edge of the wing has in effect moved downwards, increasing the effective angle of the chord line to the relative airflow.
Since angle of attack is a function of chord line and relative airflow it can be seen, in this case, that the angle of attack has been effectively increased on the left hand wing. This causes the lift to increase on that wing. With any increase in lift we know that we always get an increase in drag therefore, because the left hand aileron has been deflected downwards, there is an increase in drag on that wing. This is the force that would cause the aircraft to roll right but yaw left, due to the increase in drag on the left hand wing. This is called adverse aileron yaw. It is precisely because of this force that rudder needs to be applied simultaneously with any aileron input. In other words, the rudder is used merely to prevent the nose of the aircraft from yawing the opposite direction to the turn required. Therefore, in normal flight, the rudder could be referred to as a "yaw preventer" rather than a rudder. The amount of rudder input varies with the amount of aileron input.
Practically, if you sit in an aircraft, you will have the control yoke sitting just above your knees. If you imagine that there are two rods, one extending upwards from your right knee to the right hand side of the yoke and one extending upwards from your left knee to the left hand side of the yoke, as you move the control yoke to the right, so the rod would automatically cause you to apply right rudder and vice versa. The more the yoke movement, the more rudder would be applied. If you imagine this to be the case, you should have no problem perfecting the art of correct rudder control.
In a longer type aircraft, like a Cherokee Six, incorrect rudder control will result in the tail of the aircraft moving significantly from side to side which is quite uncomfortable for passengers sitting in the rear. Initially, flying with correct rudder inputs is quite tiresome but if you always concentrate on correct rudder use, it eventually becomes second nature. Keep the ball in the middle!
