A cockpit instrument called VOR, an in-cockpit instrument typically visible as a CDI, HSI, or RMI, lets aviators obtain azimuth information. Operating between 108.0 MHz and 117.95 MHz, the beacon emits 360 radials oriented to magnetic north so aircraft can pinpoint bearing. During each transmission the signal has two phases - reference and variable - and a VOR receiver compares the difference between these phases to determine the aircraft's bearing from the station.
Aircrew rotate the frequency selector to lock onto the chosen station, then use that bearing to fly point-to-point along established airways between VORs. Low-altitude stations serve up to 40 nautical miles below 18,000 feet while high-altitude stations reach 130 nautical miles to flight level 450, and terminal VOR covers 25 nautical miles up to 12,000 feet. A published VOR approach gives accurate guidance by following specific selected radials.
Expert behind this article
Jim Goodrich
Jim Goodrich is a pilot, aviation expert and founder of Tsunami Air.
What is a VOR receiver in an airplane?
A VOR receiver in an airplane receives signals from nearby VOR ground stations, determines the aircraft's bearing from the station, and compares the difference between the VOR's variable and reference phase.
In the cockpit the receiver is the box that decodes the pair of 30 Hz signals broadcast by a ground station on a designated very-high-frequency channel. The antenna on the tail transfers the signal to that receiver, which detects the phase offset between the AM reference and the FM variable, determines which radial the aircraft is on, and indicates whether flying that track takes the aircraft towards (TO) or away from (FROM) the station. A course deviation indicator, horizontal situation indicator or radio magnetic indicator is driven by the receiver so the pilot sees the bearing referenced to magnetic north and the needle deflection needed to stay on course. When a VOR/DME pair is selected the same box also assures automatic DME selection, presenting both azimuth and distance information from the common source.
The receiver works line-of-sight - reliable signals are received at distances up to 199 NM when the aircraft is high enough - and in light aircraft the installation is identical: the same antenna, receiver and indicator give the same TO/FROM and radial data, letting any aircraft with a receiver remain on course. Before departure the unit can be checked for accuracy with the VOT test signal or a radiated test signal from an appropriately rated radio repair station. When two receivers are installed they can be cross-checked against each other and must match within a 4 degree tolerance.
The VOR antenna is a piloting tool that constitutes the aircraft's link to the ground-based VOR network. Through this link the VOR radio allows continuous communication, letting me identify my radial. Because the VOR instrument strengthens piloting fundamentals, its stable output gives reassurance.
Jim GoodrichPilot, Airplane Broker and Founder of Tsunami Air
How does VOR work in aviation?
VOR is a navigation system that operates in the 108.0 MHz-117.95 MHz band. From each ground station the equipment transmits two signals simultaneously: a 30 Hz reference phase signal sent in all directions and a 30 Hz rotating azimuth signal that sweeps 360 degrees at 30 revolutions per second. The first signal is an amplitude-modulated carrier while the second is carried on a frequency-modulated subcarrier. A receiver in the cockpit compares the phase difference between the stationary master signal and the rotating variable signal. The resulting phase offset drives the needle, so the instrument shows azimuth information relative to magnetic north. Each distinct phase difference is known as a radial.
Low-altitude VOR operates below 18,000 feet (5,486.4 meters) and has a range of 40 nautical miles (74.08 kilometers) whereas high-altitude VOR works up to about 130 miles (212.96 kilometers) at flight levels up to FL450 (45,000 feet or 13,716 meters). Terminal VOR works near airports. The signals provide common checkpoints and support low-altitude Victor Airways, high-altitude Jet Routes, departure procedures, and non-precision approaches. Because range varies proportionally to the altitude of the receiving equipment, pilots track radials from one station to the next, achieving point-to-point navigation along airways. A dual-receiver check - tuning two receivers to the same station and confirming both match within a 4 degree tolerance - is used to verify equipment accuracy before departure. Although many airports now replace VOR approaches with RNAV (GNSS) approaches, the FAA VOR Minimum Operational Network ensures VOR remains a trusted backup if GPS fails.
How to use a VOR in aviation
To use a VOR in aviation follow the instructions given below.
- Twist the OBS knob until the needle is centered and the white triangle appears next to the TO designator
- Tune in the frequency for the desired station as found on the map
- Turn up the volume and check that the identifier matches with that on the map
- Use the OBS to place the radial you want to fly inbound on the reciprocal course index
- Set VOR frequency and confirm the identifier before approach
To use a VOR, first check that the VOR is not indicating an OFF flag. Tune in the frequency for the desired station as found on the map and then turn up the volume and check that the identifier matches. It is important to identify the station to guarantee you are not tracking the wrong station. The CDI needle will deflect in the direction you need to turn to get to the station, so consistent instrument scanning and course corrections are required. The VOR radial an aircraft is on depends upon the position of the OBS: turn the OBS knob until the CDI needle centers, the reciprocal course index now displays the radial you are crossing. To fly away from the station, center the needle with a FROM indication; procedure includes intercepting and flying specific radial away from station.
Ground-based radio signals guide aircraft along the 360 electronic courses the VOR station provides. VOR approach, a non-precision instrument approach, requires reviewing the approach plate, setting the VOR frequency and confirming the identifier. Steps include preparation, descent, final descent and landing, maintain published altitudes until reaching final approach fix or Minimum Descent Altitude, and follow published descent gradient from the approach chart. VOR approach includes initial approach fix, final approach fix and missed approach point while briefing includes tracking initial approach fix using CDI and maintaining course alignment using CDI guidance. GPS integration can be used with the VOR approach, but VORTAC can still be used by general aviation pilots relying solely on ground-based radio signals.
I utilize the VOR as a dependable instrument for exact guidance. My first exposure was during instrument practice, when I set the proper frequency and recognized the facility with the Morse command identifier. I practiced distinguishing between TO and FROM signals, and I performed tracking workouts until the procedure required substantial attention.
Jim GoodrichPilot, Airplane Broker and Founder of Tsunami Air
What is VOR radial in aviation?
A VOR radial is a magnetic bearing extending from a VOR/VORTAC/TACAN station. It is the line on the ground emanating or radiating outwards, like spokes of a wheel, and it is always FROM the station. Every VOR emits 360 radials, numbered 001 to 360 degrees, each representing a specific magnetic direction away from the station. For example, the radial pointing north is the 360 radial, the radial pointing east is the 090 radial, the radial pointing south is the 180 radial, and the radial pointing west is the 270 radial.
This line of position is called the VOR radial, and it is always related to magnetic direction from the radio aid. Bearing is the radial that the aircraft is currently on, and it is displayed on instruments like the CDI and HSI for precise flying. The OBS knob allows the pilot to select VOR radials by placing them above the course index or below the reciprocal course index, enabling the pilot to intercept and track a specific radial. If you are flying toward a VOR on the 180 degree course, you are actually flying on the 360 degree radial, because the radial is always FROM the station, not toward it.
Radials are standard in IFR and VFR navigation worldwide, and pilots use them to fly directly to or from a VOR station, to track routes, and to maintain position. A VOR radial combined with DME distance allows a one-station position fix, making it a strong tool for en-route navigation. Understanding that radial is a variant of bearing, but always FROM the station, helps pilots interpret the VOR indicator correctly and maintain situational awareness.
A VOR radial is a magnetic heading that expands outbound from the facility, giving one of 360 straight-line routes through the atmosphere. I choose one of these 360 radials, adjust the VOR radio, and steer the aircraft to connect that particular course of magnetic heading. This capacity to recognize and pursue a radius keeps me continuously aware of my angled association to the land base, making the radial the mainstay of the VOR network.
Jim GoodrichPilot, Airplane Broker and Founder of Tsunami Air
Where is the aircraft located in relation to the VOR?
The aircraft itself bears a small VOR antenna, usually located on the tail, therefore the instrument is physically aboard the airplane. The ground station is far from the airport, and as the aircraft moves farther away from VOR the signal sensitivity increases. DME collocates with VOR and gives distance from VOR station, so pilot knows nautical miles, not only bearing.
How to read VOR in aviation?
To read VOR, first tune the ground transmitter. Voice identification follows, but the VOR identifier is transmitted in Morse code. Second, turn the omnibearing selector (OBS) knob. The three elements of the instrument are the OBS itself, the CDI, and the TO/FROM indicator. Continue rotating until the CDI needle centers; the number that now sits on top of the display is the radial you are on. Third, track the selected course. The ground transmitter produces 360 electronic courses, the CDI indicates direction left or right until you intercept the chosen radial. Fly the heading displayed beside the OBS. Finally, manage the COP when transitioning to the next VOR route segment. Before the COP, navigate using the previous VOR. After the COP, switch to the new VOR and repeat the tuning, OBS setting, and identification routine. A published COP is accompanied by mileage from the nearest VOR. COPs are established by procedure designers based on distance between VORs, signal strength, and terrain. Although GPS units automate the execution of COPs, pilots must still understand COPs for partial-panel or equipment failures.
To read a VOR, I first put the wanted path on the Omni Bearing Selector, so the core of the device comprised the chosen radial. The chosen radial is my planned route to or from the facility, and the TO/FROM annunciator showed my location relative to the VOR ground facility. While traveling through a wide ravine, I was required to intercept a particular radial incoming to a VOR, so I faced the intercept direction. I remember concentrating intently on the Course Deviation Indicator, because the CDI needle traveled from a full-scale deviate to a centered placement as I moved onto the intercept bearing.
Jim GoodrichPilot, Airplane Broker and Founder of Tsunami Air
