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7.2. USING X-PLANE’S NAVIGATION MAPS 75
lope transmitter, which provides vertical guidance to the runway. The glideslope beacon functions
similarly to the localizer, sending out two tones that have the same frequency, but different modulations.
The difference is that the glideslope tells the plane that it is either too high or too low
for its distance from the runway. The pilot uses this information to push the craft’s nose up or
down as needed. The ILS will allow a pilot to fly on instruments only to a point that is a half mile
from the end of the runway at 200 feet (depending on the category of the ILS) above the ground.
If the runway cannot be clearly seen at that point the pilot is prevented from executing a normal
landing. If this happens, the pilot in real life is required to fly a “missed approach” and climb back
to altitude in order to try again or go somewhere else.
7.1.2.4 GPS Navigation
The Global Positioning System was first created for the US military and introduced to the public in
the early 1990s. This system consists of a series of satellites orbiting the Earth which continuously
send out signals telling their orbital location and the time the signal was sent. A GPS receiver can
tune in to the signals they send out and note the time it took for the signal to travel from the
satellite to the receiver for several different satellites at once. Since the speed at which the signals
travel is known, it is a simple matter of arithmetic to determine how far from each satellite the
receiver is. Triangulation (or, rather, quadrangulation) is than used to determine exactly where the
receiver is with respect to the surface of the Earth. In an aircraft, this information is compared with
the onboard database to determine how far it is to the next airport, navigational aid (NAVAID),
waypoint, or whatever. The concept is simple, but the math is not. GPS systems have turned the
world of aviation on its head, allowing everyday pilots to navigate around with levels of accuracy
that were unimaginable 20 years ago.
There are several types of GPS radios available, and about 11 of these have been modeled in
X-Plane. While the intricate workings of the various GPS radios are complex, the basic principals
are pretty consistent. If you want to navigate from one location to another just launch X-Plane,
open the aircraft of your choice, then press the “Direct To” key on the GPS radio (sometimes shown
as the symbol −→D ) and enter the airport ID you’d like to navigate to. On the Garmin 430, entry
is performed using the control knob on the bottom right of the unit. Use the outer knob to select
which character of the identifier to modify, the use the inner knob to scroll through the characters
(see the section “A Note on Radio Tuning” for more information on using the knobs).
The databases in these radios are not limited simply to the identifiers of the airports you may
wish to fly to. You can enter the IDs for any VOR or NDB station you’d like, or the name of any
waypoint or fix you’d like to go to.
7.2 Using X-Plane’s Navigation Maps
X-Plane’s navigation maps come in a few different varieties, each of which is useful for a different
situation. These navigation maps are found in the Local Map window, which is launched from the
Location menu. This window is divided into five tabs, corresponding to the five different maps
available: Hi-Speed, Low Enroute, High Enroute, Sectional, and Textured. Note that a discussion
of the elements of these maps (the ILS, VOR, and NDB beacons) can be found above, in the section
“Modern Means of Navigation.”
The Hi-Speed map gives maximum speed. It is useful for scrolling around the map quickly,
changing NAVAIDS quickly, or, if the “Draw Cockpit on Second Monitor” option is checked in the
Rendering Options screen, using the map drawn on one monitor while flying in the cockpit drawn