Radio Aids to Navigation

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Figure shows standard symbols for the very high frequency omnidirectional radio range (VOR), a VOR collocated with distance measuring equipment (DME), and a VOR collocated with a tactical air navigation (TACAN) facility. A TACAN provides azimuth information similar to a VOR, but on an ultra high frequency (UHF) band used by military aircraft, and distance information from the DME. When the NAVAID is located on an airport, the type of facility (in this case VOR only) appears above the NAVAID box; otherwise, the appropriate symbol indicates the type of facility: VOR, VOR/DME, or collocated VOR and TACAN (VORTAC).

Note that the NAVAID box provides frequency and identification information for the Ontario VOR. The VOR frequency is 117.0 MHz, identification ONT, followed by a representation of its aural Morse code signal. The lower right corner shows a VORTAC NAVAID box. This is the Pomona VORTAC. The VOR frequency is 110.4 MHz, and the DME and TACAN channel (Ch) is 41. (Because VOR frequencies and DME channels are paired, when a pilot chooses the VOR frequency, the paired DME channel is automatically selected.) The identification of the NAVAID is POM, followed by the representation of the aural Morse code signal.

Locations were abbreviated with two letters in the early days of aviation, for instance NK was Newark. As the number of NAVAIDs and airports increased, three letter identifiers came into use. All VOR, VOR/DME, VORTAC, and many low-frequency radio beacons have three-letter identifiers.

Figure contains other standard NAVAID and flight service station communication symbols. Low- and medium-frequency NAVAIDs are shown in magenta; VOR, VOR/DME, and VORTACs are in blue. Low- and medium-frequency radio ranges have been decomissioned. Nondirectional beacons, marine beacons, and broadcast-station symbols are shown.

Heavy-line boxes indicate standard simplex FSS communication frequencies 121.5 and 122.2 MHz; simplex means one-way radio communications in which the pilot transmits and receives on the same channel. Other FSS frequencies are printed above the box —for example, 123.6 (for local airport advisories) and FSS discrete frequencies. Routine communications should be accomplished on the station’s discrete frequency. These frequencies are spread apart at individual facilities and locations to avoid frequency congestion with aircraft calling adjacent stations.

If a frequency is followed by the letter R (122.1R), the FSS has only receive capability on that frequency; therefore, the pilot transmits on 122.1 (or another designated frequency). The pilot must tune another frequency, usually the associated VOR, to receive voice communications from the FSS. This duplex communication requires the pilot to ensure that the volume is turned up on the VOR receiver. For example, in the upper right box of Fig. 11-12, the Prescott FSS has a receiver located at the Flagstaff VOR on 122.1R, noted above the NAVAID box. A pilot wishing to communicate through the VOR would tune the transmitter to 122.1 MHz, and select Flagstaff, 108.2 MHz, on the VOR receiver. An FSS can transmit on many frequencies (VORs and remote outlets, for instance). With FSS consolidation, it is important for the pilot to advise the FSS which frequency is being monitored in the airplane and the airplane’s general location. For example, “Reno Radio, Cessna four three three four echo, listening one two two point six, Ely, over.”

Note that only selected frequencies are depicted on these charts. Because en-route flight advisory service (flight watch) has a common frequency of 122.0 MHz, the frequency is not shown. Pilots calling flight watch should always include their approximate location on initial contact. Approach control and air route traffic control center frequencies are also omitted. Other frequencies are on the chart’s end panels and margins, in the Airport/Facility Directory, or are available from an FSS.

A small square in the lower right corner of the NAVAID box indicates hazardous in-flight weather advisory service (HIWAS) is available on the VOR frequency. The circled letter “T” means that a transcribed weather broadcast (TWEB) is transmitted over the VOR. An automated weather observation system and the frequency (AWOS-3 135.425) advertises the availability of this service. An underlined frequency indicates no voice communications available on that particular frequency.

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