Effects of Primary Flight Controls

Chapter 4.3

Adverse Yaw

Applicability:

Mainly this effect is seen on slow aircraft and large wingspanned aircraft.

Gliders show a strong adverse yaw due to their large wingspan. School aircraft have negligable adverse yaw.

Adverse Yaw

Explanation:

Adverse Yaw is produced by the deflection of the ailerons. It appears at the entry and exit of turns. The cause is the increase in drag on the upgoing wing due to the downward deflection of it’s aileron.

The effect produced is a YAW opposite to the direction of the turn. This yaw effect remains constant until the ailerons have been returned to neutral.

Adverse Yaw

Countermeasure:

The adverse yaw shall be compensated at the entry of the turn by a preventive application of the rudder.

The coordination of the flight control is executed using the ball of the Turn Coordinator. The deflection intensity of the rudder depends upon the amount of deflection of the ailerons.

Dihedral Effect

During a turn in flight, the outer tip of the wing travels along the longest course. This brings about a higher airspeed on that wingtip area which results in a slight increase in lift. This generates a momentum around the roll axis, which increases the lateral bank of the aircraft. To counteract this, add a minimum of aileron in the opposite direction of the turn to stabilize it. This effect is particularly noticeable in gliders.

Summary

The adverse yaw and the induced roll are compensated by a conscious control of the airplane using the PRIMARY FLIGHT CONTROLS in the three axis.

Knowledge of the type and magnitude of disturbances makes it possible to apply countermeasures before they manifest.