Game Development Reference
In-Depth Information
Figure 10-19. Straight-and-level drag profiles for the Cessna 172 Skyhawk
Keep in mind that the drag profiles shown in Figure 10-19 are for straight-and-level flight.
If the airplane was climbing or sinking, the lift would not be equal to the weight of the airplane,
and the induced drag profile would be somewhat different.
Lift over Drag Ratio
A commonly used method for characterizing the performance of airfoils and airplanes is by the
lift over drag ratio , or L/D ratio. The L/D ratio is simply the ratio of the lift coefficient (or lift
force) at a given condition to the drag ratio (or drag force).
Full-Body Aerodynamics
We've covered quite a bit of ground so far in this chapter. As you have learned, the physics of
airplanes is quite complicated. There is one more step to go until we're ready to build a flight
simulator game. The equations that model lift, drag, thrust, and gravity have to be pulled into
a single, integrated model that will be referred to as full-body aerodynamics . We'll start by
examining a force diagram for an airplane that is in a climb.
The net aerodynamic force on an airplane consists of all the lift, drag, thrust, and gravita-
tional forces acting on the plane. The basic force diagram shown in Figure 10-3 was for an
airplane traveling in straight-and-level flight. Let's examine the more general case of an airplane
that is climbing and therefore has a vertical velocity component. The force diagram for such a
flight situation is shown in Figure 10-20. For simplicity, we'll look at a two-dimensional case
where the motion of the airplane is restricted to the x-z plane.
 
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