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22 3. SHAPING THE BODY OF AN AIRCRAFT
In the Controls tab, a number of possible control surfaces can be created, from ailerons to
elevators to rudders to speedbrakes to flaps. Each of these works in a similar way. The left half of
the window, in the box labeled Control Sizes, sets up ailerons, elevators, rudders, roll spoilers, drag
rudders, and speedbrakes. The right half of the window, labeled Flap Specs, sets up flaps and slats
only.
Specifying Ailerons, Elevators, and Other Surfaces
The right half of the Control Geometry’s “Controls” tab is labeled Control Sizes, and it is used for
all control surfaces except the flaps and slats.
Figure 3.15 shows the parameters to specify a single control surface (namely, an aileron). There
are four input fields here. On the far left is the control surface’s root-side width, as a decimal part
of the chord length of the wing section it is placed on. Thus, if this root width were set at 0.50 and
it were used in a wing whose root was 5 feet wide, the control surface would have a width of 2.5
feet on the side closest to the fuselage.
Figure 3.15: A single, representative control surface specification
To the right of the root width is the tip width, also specified as a decimal part of the wing it
is placed on. So, if the tip width were set at 0.1 and it were used on a wing whose tip was 10 feet
wide, the control surface would have a width of 1 foot on the side farthest from the fuselage.
These two parameters, root and tip width, function identically on all the control surfaces available.
To the right of the two size parameters are the fields controlling how far the surface can move,
measured in degrees. For instance, in the aileron of Figure 3.15 these are, from left to right, how
far up the aileron can deflect and how far down it can deflect.
Specifications for ailerons, elevators, and rudders all follow this same pattern: parameters for
the root and tip width, followed by parameters for the maximum deflections. The roll spoilers and
drag rudder are exceptions to this pattern. They move one at a time, and they only move upward.
For this reason, they have only one parameter for maximum deflection.
Additionally, the speedbrake may have two maximum deflections: one for normal, in-flight operation,
and one for ground use. Unlike the other control surface types, speedbrakes don’t have to
be mounted to a wing—they can also be mounted directly on the fuselage (or anywhere else, for
that matter). For information on doing this, see the section “Adding Body-Mounted Speedbrakes”
below.
At the bottom of the Control Sizes box is the “control surface type” setting, which modifies how
effective the surfaces are in X-Plane. Surfaces which are “corrugated with gaps” are least effective.