What is an Aileron?
Of the three directions of motion, the ailerons control the roll
or bank of an airplane. These flap-like devices are located on
the trailing edge of the wings. Some planes have the ailerons
extending only half the distance of the wing whereas other planes
designed for different purposes have ailerons extending the
entire span of the wings.
Ailerons flap up and down to either make the plane roll to the
left or to the right. If you wanted to make the plane roll to the right, then
you would have to turn the control wheel to the right
causing the left aileron to go down, and the right aileron to go
up. When this happens, the right wing of the plane drops and
causes the plane to turn to the right. The turn and bank
indicator let pilots know what the current degree of roll is.
The ailerons cause the plane to roll because of the way they
deflect the air. When an aileron is down, the airflow hits the
leading edge of the wing and continues towards the trailing edge.
tends to stick to surfaces, in this
case the deflected aileron. As the airflow travels over the
aileron, it is accelerated downwards because of the relative
position of the aileron. Due to Newton's Third Law of Motion, the
force that the aileron imparts on the airflow by deflecting it
down, causes a reaction where the airflow imparts a force pushing
the aileron up. Conversely, if the aileron was deflected
upwards, then the reactive force would push the aileron down.
A similar flap-like device--the
elevator operates much
ailerons, except the elevators are located on the tail
It is important to note the different effects that each has on
the general direction of the plane.The reason lies in the
concept of torque. Torque is defined to
be the distance from the
center of mass times the force.
The center of mass, somewhere near the crossing of the wingspan
and the fuselage can be
considered as a stationary rotation
point. If the wingspan
were the x-axis and the fuselage were the y-axis, we can draw an
imaginary axis perpendicular to both these axes and label it the
z-axis. Then the force acting on the ailerons would cause the
plane to rotate along the x-z plane. Although the elevators and
ailerons shift in the same fashion, their distances from the
center of mass are on different axes, and therefore the torque
acts along different geometrical planes.