Game Development Reference
and starboard wings. This lift differential, separated by the distance between the ailer‐
ons, creates a torque that rolls the aircraft. To roll the aircraft to the port side (the pilot's
left), the starboard aileron would be deflected in a downward direction while the port
aileron would be deflected in an upward direction relative to the pilot. Likewise, the
opposite deflections of the ailerons would induce a roll to the starboard side. In a real
aircraft, the pilot controls the ailerons by moving the flight stick to either the left or
Elevators, the tail “wings,” are used to control the pitch of the aircraft. (Elevators can be
flaps, as shown in Figure 15-2 , or the entire tail wing can rotate as on the Lockheed
Martin F-16.) When the elevators are deflected such that their trailing edge goes down
with respect to the pilot, a nose-down pitch rotation will be induced; that is, the tail of
the aircraft will tend to rise relative to its nose, and the aircraft will dive. In an actual
aircraft, the pilot achieves this by pushing the flight stick forward. When elevators are
deflected such that their tailing edge goes up, a nose-up pitch rotation will be induced.
Elevators are very important for trimming (adjusting the pitch of ) the aircraft. Generally,
the aircraft's center of gravity is located above the mean quarter-chord line of the aircraft
wings such that the center of gravity is in line with the main lift force. However, as we
explained earlier, the lift force does not always pass through the quarter-chord point.
Further, the aircraft's center of gravity may very well change during flight—for example,
as fuel is burned off and when ordnance is released. By controlling the elevators, the
pilot is able to adjust the attitude of the aircraft such that all of the forces balance and
the aircraft flies at the desired orientation (pitch angle).
Finally, the rudder is used to control yaw. The pilot uses foot pedals to control the rudder;
pushing the left (port) pedal yaws left and pushing the right pedals yaws right (star‐
board). The rudder is useful for fine-tuning the alignment of the aircraft for approach
on landing or when sighting up a target. Typically, large rudder action tends to also
induce roll motion that must be compensated for by proper use of the ailerons.
In some cases the rudder consists of a flap on the trailing edge of the vertical tail, while
in other cases there is no rudder flap and the entire vertical tail rotates. In both cases,
the vertical tail, which also provides directional stability, will usually have a symmetric
airfoil shape; that is, its mean camber line will be coincident with its chord line. When
the aircraft is flying straight and level, the tail will not generate lift since it is symmetric
and its attack angle will be 0. However, if the plane sideslips (yaws relative to its flight
direction), then the tail will be at an angle of attack and will generate lift, tending to
push the plane back to its original orientation.