Page 147 - Planning and Design of Airports

116 Airp o r t Pl anning

FIGURE 3-10 VOR beacon on the airfi eld at Ronald Reagan Washington
National Airport.

slant distance between the aircraft and a particular VOR station. Since
it is the air distance in nautical miles that is measured, the receiving
equipment in an aircraft flying at 35,000 ft directly over the DME sta-
tion would read 5.8 nm.
An en route air navigation aid which best suited the tactical needs
of the military was developed by the Navy in the early 1950s. This aid
is known as TACAN, which stands for tactical air navigation. This aid
combines azimuth and distance measuring into one unit instead of two
and is operated in the ultra-high-frequency band. As a compromise
between civilian and military requirements, the FAA replaced the DME

100° TO/FROM indicator
showing TO

CDI needle swung
OBS knob turns the 3 dots left, meaning
compass card, here you are 6° right of
set to 100 the 280 radial

FIGURE 3-11 Omnibearing selector.