At the rear of the
1903 Wright Flyer
one finds a pair of rudders.
The rudders are movable surfaces which are controlled by the pilot.
This slide shows what happens when the pilot deflects the
trailing edge of the rudders.
How does changing the rudder angle affect the aircraft?
As described on the inclination effects slide,
changing the angle of attack of a wing or airfoil changes
the amount of lift generated by the foil. With increased
downward deflection of the trailing edge, lift increases. The
rudders are mounted so that they will produce
forces from side to side, not up and down. With greater rudder
deflection to the right as viewed from the back of the aircraft, the
force increases to the left (as shown in this slide).
The force (lift) of the rudder is applied some distance from the aircraft
center of gravity. This creates a
torque on the aircraft and the aircraft
rotates
about its center of gravity.
If the pilot reverses the rudder deflection to the left,
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
Let's investigate how the rudder works by using a Java
simulator.
You can change the rudder setting by using the slider at the bottom.
You can also download your own copy of this applet by pushing the following button:
The program is downloaded in .zip format. You must save the file to disk and
then "Extract" the files. Click on
"Rud.html" to run the program off-line.
The Wright's initially did not think that they would need a rudder
on their aircraft since birds don't need rudders. The
1900
and
1901
aircraft were designed without rudders. But during the
glider
flights of 1901, the brothers encountered flight conditions when the
aircraft would suddenly spin out of control during maneuvers.
They included dual fixed rudders in the design of the
1902
aircraft to overcome this problem.
The test flights of 1902 initially went better than in 1901,
but in about one glide in 50 the glider would
again spin out of control on recovering from a turn at low speed. Laying
awake one night, Orville concluded that the rudders were acting as
vertical wings in which turning generated an
angle of attack
and thus
an unwanted force in the wrong direction. His solution was to
replace the twin fixed rudders with a single movable rudder.
The next morning Wilbur agreed and offered the
idea to tie the rudder deflection
into the wing warping system. Once
done, the glider worked beautifully, keeping the nose of the aircraft
pointed into the
curved
flight path. All subsequent Wright aircraft included dual, movable rudders.
The Wright's used flat plate airfoils for their rudders and deflected the
entire surface from side to side.
On modern aircraft, the rudder is a
separate piece attached to the vertical
stabilizer. The combination creates a
symmetric airfoil
and produces no lift when the rudder is aligned with the
stabilizer. Forces to the left or right then depend on the
deflection of the rudder. Modern fighter planes sometimes have two vertical
stabilizers and rudders because of the need to control the plane with
multiple, very powerful engines.
You can view a short
movie
of "Orville and Wilbur Wright" explaining how the rudder
was used to control the yaw of their aircraft. The movie file can
be saved to your computer and viewed as a Podcast on your podcast player.
