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Very High Frequency Omni-directional Range (VOR)

The VOR station transmits two signals: one is constant in all directions and the other varies the phase relative to the first signal. The VOR receiver senses the phase difference between the two frequencies and the difference identifies 360 different directions or "radials" from the VOR. The aircraft is on one, and only one, radial from the station. The system does not provide distance information.

When the appropriate VOR frequency is entered into a navigation radio, the VOR indicator connected to that radio is used to find where the aircraft is relative to the VOR station. The vertical needle on the VOR indicator is called a Course Deviation Indicator (CDI) and shows whether the aircraft is right or left of the chosen course. A "To/From/Off" indicator indicates whether the aircraft is on the "to" or "from" side. If the aircraft is "abeam the station," an "off" indication is given. To fly toward the station, the Omni Bearing Selector (OBS) is turned until the CDI is centered with a "to" indication. The pilot then flies that heading. To find out where the aircraft is located from that station, center the needle with a "from" indication. If a radial is dialed into the VOR indicator, the CDI will be right or left of the center and either a "to" or a "from" indication will be seen. The heading of the aircraft does not matter.