When any of our flight controls are deflected into the airflow, the strength of the force created depends on three factors:
The surface area is determined by the aircraft designers and is out of our control. The angle at which the control is deflected is determined by how far we deflect the cockpit controls (control column or rudder pedals). The third factor, the speed of the airflow over the control surface, has two influences – our airspeed and our power setting.
The higher your airspeed, the more effective the controls will be. Any movement of a control surface will result in more air being deflected since the air is flowing over the control at a higher rate. As there is more airflow over the control surface, there is more resistance to the deflection of the controls. To the pilot, the controls will feel firmer and more effective.
At lower airspeed, there is less resistance to control movements and a greater deflection is required to achieve the same rate of pitch, roll or yaw. To the pilot, the controls will feel less effective.
In single engine propeller aircraft, the air forced backwards by the propeller increases the airflow over the elevator and rudder.
At lower speeds and high power settings (such as in a climb), the difference in airflow over the elevator and rudder compared to the ailerons can be substantial. The pilot will notice the elevator and rudder being firm and effective while the ailerons are less effective.