Part of Aircraft (4)

Part of Aircraft (4)

RUDDER

At the rear of the fuselage of most aircraft
one finds a vertical stabilizer and a rudder.
The stabilizer is a fixed wing section whose
job is to provide stability for the aircraft, to
keep it flying straight. The vertical stabilizer
prevents side-to-side, or yawing, motion of
the aircraft nose. The rudder is the small
moving section at the rear of the stabilizer
that is attached to the fixed sections by
hinges. Because the rudder moves, it varies
the amount of force generated by the tail
surface and is used to generate and control
the yawing motion of the aircraft.
The rudder is used to control the position of
the nose of the aircraft. Interestingly, it is
NOT used to turn the aircraft in flight.
Aircraft turns are caused by banking the
aircraft to one side using either ailerons or
spoilers. The banking creates an unbalanced
side force component of the large wing lift
force which causes the aircraft’s flight path to
curve. The rudder input insures that the
aircraft is properly aligned to the curved
flight path during the maneuver. Otherwise,
the aircraft would encounter additional drag
or even a possible adverse yaw condition in
which, due to increased drag from the control
surfaces, the nose would move farther off the
flight path.
The rudder works by changing the effective
shape of the airfoil of the vertical stabilizer.
As described on the shape effects slide,
changing the angle of deflection at the rear of
an airfoil will change the amount of lift
generated by the foil. With increased
deflection, the lift will increase in the opposite
direction. The rudder and vertical stabilizer
are mounted so that they will produce forces
from side to side, not up and down. The side
force (F) is applied through the center of
pressure of the vertical stabilizer which is
some distance (L) from the aircraft center of
gravity. This creates a torque
T = F * L
on the aircraft and the aircraft rotates about
its center of gravity. With greater rudder
deflection to the left as viewed from the back
of the aircraft, the force increases to the
right. If the pilot reverses the rudder
deflection to the right, the aircraft will yaw in
the opposite direction. We have chosen to
base the deflections on a view from the back
of the aircraft towards the nose, because that
is the direction in which the pilot is looking