NOTE: Some airborne testing using VOTs is possible by the pilot.Īn error of ±4° should not be exceeded when testing a VOR system with a VOT. Contact the repair station for the transmission frequency and for their assistance in checking the VOR system. Some repair stations can also generate signals to test VOR receivers although not on 108.0 MHz. If an RMI is used as the indicator, the test heading should always indicate 180°. The OBS should indicate 0° showing FROM on the indicator or 180° when showing TO. Most VOTs require tuning 108.0 MHz on the VOR receiver and centering the CDI. Specific points on the airport surface are given to perform the test. These are located at numerous airports that can be identified in the Airport Facilities Directory for the area concerned. VOR receivers are operationally tested using VOR test facilities (VOT). These navigational aids are discussed separately in the following sections.įunctional accuracy of VOR equipment is critical to the safety of flight. Since the VOR indicates the aircraft’s bearing to the VOR transmitter and a co-located DME indicates how far away the station is, this relieves the pilot from having to fly over the station to know with certainty his or her location. When used with a DME, pilots can gain an exact fix on their location using the VOR and DME together. While tuned to the ILS localizer frequency, the VOR circuitry of the VOR/ILS receiver is inactive.It is common at VOR stations to combine the VOR transmitter with distance measuring equipment (DME) or a nondirectional beacon (NDB) such as an ADF transmitter and antenna. This part of the ILS is known as the localizer and is discussed below. It produces a more sensitive course deviation indication on the same instrument display as the VOR CDI display. The aircraft’s VOR receiver is used to interpret the radio signals. Īt large airports, an instrument landing system (ILS) guides the aircraft to the runway while on an instrument landing approach. When power is lost or the VOR signal is weak or interrupted, a NAV warning flag comes into view. The displayed VOR information is derived from deciphering the phase relationship between the two simultaneously transmitted signals from the VOR ground station. The pilot must steer the aircraft to the heading with the CDI centered to fly directly to or from the VOR. When chosen, the arrow is displayed in the FROM window indicating the aircraft is moving away from the VOR on the course selected. The other selectable bearing is 180° from this. One produces an arrow in the TO window of the gauge indicating that the aircraft is traveling toward the VOR station. For each location of an aircraft, the OBS can be rotated to two positions where the CDI will center. When in range of a VOR, the pilot rotates the OBS until the course deviation indicator centers. ![]() The CDI linear indicator remains essentially vertical but moves left and right across the graduations on the instrument face to show deviation from being on course. Some VORs also broadcast a voice identifier on a separate frequency that is included on the chart. The position of all VORs, TVORs, and VORTACs are marked on aeronautical charts along with the name of the station, the frequency to which an airborne receiver must be tuned to use the station, and a Morse code designation for the station. Sometimes VOR and TACAN transmitters share a location. Military has a navigational system known as TACAN that operates similarly to the VOR system. ![]() Ground VOR transmitter units are also located at airports where they are known as TVOR (terminal VOR). The Victor airway system is built around the VOR navigation system. Many of the VORs are located along airways. It consists of thousands of land-based transmitter stations, or VORs, that communicate with radio receiving equipment on board aircraft. ![]() The system was constructed after WWII and is still in use today. ![]() One of the oldest and most useful navigational aids is the VOR system.
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