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3.3. SHAPING THE WINGS 23
Specifying Flaps and Slats
The right half of the Control Geometry’s Controls tab is labeled Flap Specs, and it is used to set
up the aircraft’s flaps and slats.
Let’s walk through the settings here.
Slats change the lift characteristics of a wing. They allow a higher angle of attack for the wing,
resulting in a lower stall speed. Two slats can be set up for each aircraft. Using the parameters seen
in Figure 3.16, you can set the type of slat—either true slats or Krueger flaps. (Note that Krueger
flaps are not technically slats. They deploy by hinging forward from the wing instead of sliding
from the top of the wing’s leading edge like slats do.)
Figure 3.16: The “slat type” and “increase in stall angle” settings
Next to the “slat type” control is the “increase in stall angle from leading edge device deployment”
parameter, seen in Figure 3.16. Slats work by allowing the wing to go to a higher angle of
attack without stalling—that is, without losing lift. Slats in the real world allow the wing to gain
up to eight degrees of angle of attack without stalling.
Figure 3.17: The flap type and size settings
Like slats, flaps alter a wing’s lift characteristics. They allow the wing to generate a given
amount of lift at a lower speed, resulting in the aircraft stalling at a lower speed. Two flaps can
be set up for each aircraft. Using the parameters shown in Figure 3.17, you can set the type of
flap, chosen from a large number of options. Each type of flap has unique lift, drag, and moment
characteristics, as described in the dark gray box below the flap type setting. Four types of flaps
available in X-Plane are illustrated in Figure 3.18.
To the right of the flap type setting are the two parameters controlling the size of the flaps.
Just like when setting up ailerons, rudders, and elevators, you must specify the flap size on both
the root side and the tip side. These are set as a decimal part of whatever wing section the flap is
placed on.
Beneath the flap type and size settings are the parameters that control the aerodynamic coefficients
for each flap, as seen in Figure 3.19. Plane Maker will automatically calculate the coefficients