Solving the Problems of Flight
Any aircraft design has to solve three critical problems: lift - generating an upward force greater than the weight of the plane; thrust - propelling the plane forward; and control - stabilizing and directing the plane’s flight. Any number of approaches can achieve these results, but natural selection eliminated the early designs that failed to meet the requirements of efficiency, reliability, and durability. The design rapidly evolved into the familiar, basic configuration that virtually all airplanes share.
The elevator (I) produces pitch (up-down movement of the nose), for longitudinal control. Ailerons (J) produce roll (rotation of the wings), for lateral control.
The rudder (K) produces yaw (right and left movement), for directional control. These movements in combination turn the aircraft.