VOR

Updated at: 2025-12-01 10:42
navigation
A VHF Omnidirectional Range (VOR) is a ground-based radio navigation aid that provides aircraft with magnetic bearing information to or from a specific station, enabling accurate en 6route navigation and instrument procedures in almost all weather conditions.<\/b>

1. Definition of VOR

A VHF Omnidirectional Range (VOR) is a short‑range radio navigation system operating in the Very High Frequency (VHF) band, typically between 108.00 MHz and 117.95 MHz. It transmits azimuth (direction) information that allows an aircraft receiver to determine its magnetic bearing relative to the VOR ground station.
VOR is a type of nonsatellite, groundbased navigation aid. The signal pattern forms 360 discrete bearings, known as radials, each corresponding to a magnetic direction from the station (for example, the 090 radial lies due east of the station).
In simple terms, when tuned and identified correctly, a VOR receiver in the cockpit tells the pilot which radial the aircraft is currently on and whether flying a selected course will take the aircraft toward or away from the station.

2. Purpose of VOR in aviation

The primary purpose of VHF Omnidirectional Range is to provide reliable, all‑direction course guidance for aircraft operating under Instrument Flight Rules (IFR) and Visual Flight Rules (VFR). VORs form part of the traditional radio navigation infrastructure that supports airways, terminal procedures, and approaches.
Key purposes include:
  • En‑route navigation: Defining airways and reporting points for safe, structured traffic flows.
  • Terminal navigation: Providing course guidance for Standard Instrument Departures SIDs and Standard Terminal Arrival Routes STARs .
  • Approach procedures: Supporting non‑precision instrument approaches to runways, sometimes in combination with Distance Measuring Equipment (DME).
  • Position fixing: Allowing pilots to determine their position using one or more VOR stations, especially when Global Navigation Satellite System (GNSS) is unavailable or not used.
  • Redundancy and backup: Offering an independent navigation source alongside satellite‑based systems such as Global Positioning System (GPS).
For student pilots, VORs are often the first radio navigation aids learned in detail because they illustrate fundamental concepts of radials, courses, and tracking, which also apply to more advanced systems.

3. Use of VOR in aviation

3.1 Basic VOR components and indications

A typical aircraft VOR installation includes:
  • VOR receiver: Electronic unit that tunes the station frequency and processes the signal.
  • VOR indicator: Often a Course Deviation Indicator (CDI) or Horizontal Situation Indicator (HSI) that displays course and deviation.
  • OBS (Omni Bearing Selector): Knob used to select the desired course or radial.
  • TO/FROM flag: Shows whether the selected course will take the aircraft toward or away from the station.
  • NAV flag: Warns of unreliable or absent signal.
The CDI needle shows lateral deviation from the selected course. When centered, the aircraft is on the selected course line to or from the station, within the system accuracy limits. Full‑scale deflection usually represents 10° off course for a conventional VOR indicator.

3.2 Tuning and identifying a VOR

Correct use of any VOR begins with tuning the correct frequency and positively identifying the station. Identification uses a three‑letter Morse code identifier and sometimes a spoken station name. Listening to the ident confirms that the receiver is tuned to the intended station and that the signal is reliable.
If the Morse code ident is missing or distorted, the station should be considered unreliable, and navigation using that VOR should be avoided, even if the indicator appears to function.

3.3 Tracking to and from a VOR

To use a VOR for basic navigation, a pilot typically selects a desired course to or from the station and then corrects heading to keep the CDI needle centered. This process is known as tracking. Small heading corrections are made into the needle to counteract wind drift and maintain the intended ground track.
A common technique is to choose a course that corresponds to the desired ground track, then apply a wind correction angle determined by observing CDI movement over time. If the needle drifts off center, the pilot adjusts the heading slightly toward the needle until it remains stable.

3.4 Intersections and cross‑bearing fixes

Two or more VOR stations can be used to determine an aircraft’s position by plotting the intersecting radials. This method is called a cross‑bearing or cross‑fix. It is commonly used to identify airways intersections, holding fixes, and reporting points.
In practice, the pilot tunes and identifies each VOR in turn, notes the radial on which the aircraft lies, and then uses a chart or navigation display to locate the intersection of those radials. Modern avionics can perform this automatically, but the underlying principle is the same.

3.5 VOR, VOR/DME, and VORTAC

There are several related types of VOR installations:
  • VOR: Provides azimuth (direction) information only.
  • VOR/DME: Combines VOR with Distance Measuring Equipment (DME), giving both bearing and slant‑range distance to the station.
  • VORTAC: A combined VOR and Tactical Air Navigation (TACAN) facility, serving both civil and military users. Civil aircraft use the VOR and DME functions.
When distance information is available, pilots can determine precise position using a single station by combining radial and DME distance (for example, "on the 270 radial at 15 DME"). This is especially useful for holding patterns and stepdown fixes on approaches.

4. Operational considerations for VOR use

4.1 Line‑of‑sight and coverage

VOR operates in the VHF band, which is essentially line‑of‑sight. Coverage depends on altitude, terrain, and the station’s power. At low altitude or behind terrain, the signal may be weak or unavailable. Charts often show a VOR’s service volume, indicating the altitude and distance range for reliable use.
Student pilots should understand that a VOR that works well at cruise altitude may not be usable near the surface, particularly in hilly or mountainous areas. Loss of signal or fluctuating indications near coverage limits is normal and should be anticipated.

4.2 Accuracy and limitations

VOR systems are generally accurate to within ±4°. This is sufficient for airway navigation and non‑precision approaches but less precise than modern satellite navigation. Errors can arise from station calibration, airborne equipment, or site effects such as reflections from nearby terrain or structures.
Pilots should avoid over 6controlling in response to small CDI movements and instead aim to keep deviations within practical limits, typically one dot (about 26) during en 6route flight and tighter during approaches as required by procedures and regulations.

4.3 Station passage and cone of confusion

When an aircraft passes directly over a VOR station, the signal geometry causes rapid changes in the indicated radial and may momentarily produce unreliable indications. This area is called the cone of confusion. The TO/FROM flag may switch and the CDI may fluctuate.
Procedures that use station passage, such as certain holding patterns and approaches, assume that pilots understand this limitation and rely on timing, DME, or other cues rather than expecting stable CDI indications exactly overhead the station.

4.4 Reverse sensing and course selection

Reverse sensing occurs when the pilot selects a course on the OBS that does not match the intended direction of travel relative to the station. In this situation, flying toward the CDI needle can actually take the aircraft away from the desired course line.
To avoid reverse sensing with a conventional CDI, the selected course should usually match the direction of travel along the desired track. For example, when tracking inbound on the 270 radial (which is a 090° course to the station), the OBS should be set to 090°, not 270°.

4.5 Checks, monitoring, and redundancy

Operational practice requires that VOR equipment be checked periodically. In some jurisdictions, specific checks and tolerances are mandated before using VOR as a primary navigation source for IFR. Typical checks include comparing indications at known checkpoints, cross‑checking between two independent receivers, or comparing with other navigation sources.
In flight, pilots should continuously monitor the Morse ident and compare VOR indications with other available navigation information, such as GPS, visual references, or other navaids, to detect any anomalies early.

5. Practical examples for student pilots

The following short examples illustrate common VOR uses in basic training. They are simplified and do not replace official procedures or instructor guidance.

5.1 Tracking inbound to a VOR

A student pilot wishes to fly to a nearby VOR located northwest of the aircraft’s position. After tuning and identifying the station, the pilot rotates the OBS until the CDI centers with a TO indication and notes the course, for example 320°. The pilot then turns the aircraft to a heading close to 320° and adjusts for wind to keep the CDI centered, thus tracking directly toward the VOR.

5.2 Intercepting an airway defined by a VOR radial

An airway is defined as the 180 radial of a VOR. The aircraft is east of the radial and needs to join the airway northbound. The pilot selects 360° on the OBS (the inbound course to the station along the 180 radial), observes the CDI deflected to the left, and chooses an intercept heading, for example 330°. As the CDI moves toward center, the pilot reduces the intercept angle and then tracks the 360° course, remaining on the airway.

5.3 Using VOR/DME for position reporting

On a cross‑country flight, the pilot is required to report position to air traffic control. The aircraft is using a VOR/DME station. The CDI shows the aircraft on the 045 radial and the DME reads 22 nautical miles. The pilot can report position as "22 DME on the 045 radial" of the named VOR, giving controllers an accurate fix.

5.4 Holding over a VOR

In a basic holding pattern using a VOR, the fix is usually the station itself or a specified radial and distance. The pilot uses the OBS to track the inbound course to the fix, times the outbound leg, and uses the CDI to re‑intercept the inbound course. Understanding station passage, cone of confusion, and wind correction is essential for accurate holding.
For student pilots, mastering VHF Omnidirectional Range techniques builds a solid foundation in instrument navigation, supports safe cross‑country flying, and provides an effective backup to satellite‑based navigation systems.