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50 CHAPTER 5. FLIGHT IN X-PLANE
The precipitation slider sets the level of precipitation. Depending on the temperature around
the airplane and in the clouds where it is formed, this will be in the form of rain, hail, or snow.
The thunderstorms slider adjusts the tendency for convective activity. The weather radar map
in the lower-right of the window shows where the cells are forming. Flying into these cells results
in heavy precipitation and extreme turbulence. The turbulence is great enough that in reality,
airplanes can fly into thunderstorms in one piece and come out in many smaller pieces.
Taking helicopters into these icing and thunderstorm situations is interesting because their very
high wing-loading on their rotor and the fact that the rotor is free teetering causes them to have
a pretty smooth ride in turbulence. They are still not indestructible, though, and they are subject
to icing on their blades just like an airplane.
The turblnc (turbulence) slider automatically sets all the sliders in the center of the screen
that control the wind and turbulence. Drag this slider down to the left and hold it there for a few
seconds to set all of the wind and turbulence to zero for a smooth flight.
Next, in the bottom left corner of the window, the temperature at the nearest airport and
the barometric pressure (air pressure) at sea level can be set. Keep in mind that the “standard
atmosphere” is 59 ◦ F (15 ◦ C) and 29.92 inches mercury (1013 millibars).
The middle column of this window controls three wind layers. Each layer has an altitude, wind
speed, shear speed, shear direction, and turbulence associated with it. X-Plane will use the high,
middle, and low altitude settings to interpolate between the layers. The circles to the right of each
altitude setting change the direction from which the wind is coming. Click and drag near the edge
of the circle and the wind will come from the direction that you let go of the mouse button (for
instance, for wind moving from the south to the north, click the very bottom of the circle and
release the mouse button there).
Enter the thermal tops, thermal coverage, and thermal climb rate in the upper right of
this window. These controls are mainly used when flying gliders. In addition to thermals, X-Plane
also runs air up and down the terrain as wind blows into mountains, simulating the effects that real
glider pilots have to keep in mind and try to take advantage of. Try setting the wind at 30 knots
or better at a right angle to a mountain range and running along the upwind side of the mountain
range in a glider—you should be able to stay aloft on the climbing air if you stay pretty low. Drift
to the downwind side of the mountain, though, and an unstoppable descent is assured!
The runway conditions drop-down box is found on the right side of the window, directly
beneath the thermals controls. Conditions can be set to clean and dry, damp, or wet, and wet
and damp conditions can be either patchy or uniform. At low enough temperatures, as in real life,
a wet runway will become an icy one. This control is automatically modified when increasing the
amount of precipitation.
Beneath the runway conditions is the wave height and wave direction for bodies of water.
Changing the wave height, in feet, will also modify the wave length and speed.
Finally, beneath the runway conditions is a visual representation of the weather X-Plane generated
based on your parameters. Clicking the Regenerate weather now button will cause X-Plane
to generate a new weather system with those same parameters.
5.4.1.2 Setting Randomly-Generated, Realistic Weather
By far the simplest way of generating weather is to use weather that you exercise only a small degree
of control over. In this case, X-Plane creates a weather system with some amount of uncertainty in
it, allowing you some control over the features of the weather system without bogging you down in
the details.