What are those unusual white cone structures found in fields, and how are they connected to aviation? They are referred to as VOR (Very High Frequency Omni-Directional Range) stations. VOR stations have been in operation since the 1930s and have seen extensive use since the 1970s, yet to those unfamiliar with them, they may seem completely alien.
The VOR radio navigation system consists of two parts: receivers, which are mounted on the majority of aircraft, and grounded components, known as stations.
VORs aided pilots in their global navigation long before global positioning systems (GPS) were commercially accessible.
Although many VORs are going out of service due to their age, they continue to serve a crucial purpose in aviation. The existing VOR infrastructure is gradually being adapted to serve as a backup navigation system in case of GPS outages.
VOR Meaning in Aviation?
The primary objective is to facilitate short-range navigation for aircraft. The VOR stations on the ground send out signals that planes with VOR receivers pick up. These signals act as beacons, allowing pilots to accurately identify their position with respect to the station and stay on course.
To further aid pilots in their navigation, VOR can be used in tandem with other navigation technologies. One such case is with the Distance Measuring Equipment (DME), which when used together helps pilots in knowing the course and distance to/from the station.
As a result of technological advancements, some aviation authorities throughout the world are gradually phasing out VORs, although thousands of them are still in use. With these stations, pilots can have an easy time during cross-country flights, instrument approaches, or those moments when they go off course and need to quickly determine their aircraft’s location.
What Does VOR Do?
VOR stations primarily transmit a three-letter identification via Morse code. The stations are aligned with magnetic north and use their beams for radial navigation VOR. They broadcast 360 radials in all directions. Operating within the very high frequency (VHF) band, from 108.0 MHz to 117.95 MHz, these stations allow aircraft equipped with receivers to determine their position and stay on course. VOR radio navigation offers an accuracy of approximately one degree and serve as key reference points for flights across the country.
Features and Components of VOR
The VOR radio navigation system consists of the ground components and the airplane components. Communication between the ground and aircraft components is initiated by the ground component.
Active Antenna and VHF
The aircraft is equipped with a VOR antenna, a flight deck instrument (e.g., a Horizontal Situation Indicator or a Course Deviation Indicator) that shows the course information, and a VOR frequency selector (e.g., a Garmin GNC 355 or a Bendix/King KNS 80).
Alternatively, portable VOR transceivers can be used. A number of separate VOR systems are installed on some general aviation and cargo aircraft. Modern decks often have both GPS and its radio navigation VOR. allowing pilots the option to switch between the two whenever necessary.
Morse Code Identifier
For identifying purposes, every 30-60 seconds, each VOR station broadcasts a distinct three-letter identifier in Morse code. This helps pilots determine the specific VOR station from which a signal is emanating.
Distance Measuring Equipment (DME)
To determine the distance from an aircraft to a big VOR station, DME is often used with UHF transponders, which are receivers and transmitters, on the ground, and UHF interrogators, which are transmitters and receivers, on board the plane.
The DME measures what is known as the “slant distance.” This is the horizontal length between the transmitter (station) and the receiver. For example, an aircraft flying horizontally one nautical mile (nm) from the VOR station would display the same reading as a plane flying vertically one nautical mile distant (around 6,000 feet). However, there is a small cone of confusion over the DME station.
A VOR station is designated as VOR-DME when it employs DME. However, the use of solo DMEs on sectional charts is becoming more common as VORs are being phased out. For instance, GOG (Goodsprings DME) can be used by sophisticated navigation systems for airline and sometimes business aircraft.
How Does VOR Work?
As mentioned before, the operating frequency range of a VOR is 108.0 MHz to 117.95 MHz. The VORs point towards magnetic north and give out 360 radials from their respective stations. The system transmits a master signal, also referred to as the reference phase, that remains constant and a variable signal (variable phase) that changes over time.
In flight, the VOR antenna—often mounted on the tail of an aircraft—receives this signal and transmits it to the cockpit receiver. The bearing from the station is determined by comparing the VOR’s master and variable signals, which the VOR receiver on the aircraft uses.
This bearing represents the radial that the airplane is now riding. All this bearing data is then shown via the HSI (horizontal situation indicator). This allows the pilot to align the flight course with the target airway by evaluating their current location and path variation.
Although most VOR stations are connected to DME, some are linked to TACAN (Tactical Air Navigation. Stations that have DME installed in them provide pilots with the ability to see how far away the station is at a glance using cockpit readouts. Pilots can utilise these features more effectively with a thorough understanding of VOR navigation.
Conclusion
For many years, VOR has been an essential part of aviation navigation, giving pilots precise and dependable directions. Despite the advancements made possible by satellite-based navigation systems like GPS, VOR radio navigation continues to play a crucial role in aviation safety and efficiency by providing redundancy.
However, to stay relevant in the evolving aviation industry, VOR will need to integrate with emerging technologies and fulfil its role as a dependable backup system.
For the foreseeable future, it will continue to be an indispensable tool for pilots, air traffic controllers, and aviation authorities, ensuring the skies remain safe and accessible for all.