There’s an old saying that’s as true today as it always has been - if it isn’t broken, don’t fix it. And aviation has embraced that idea and taken it to heart, which is probably why it’s still using technology that most industries would regard as being archaic to help aircraft to know where they are and guide them to where they need to be.
VOR (Very High-Frequency Omni-Directional Range) was developed in the United States in the latter half of the nineteen thirties and was first used in nineteen forty-seven. A short wave aircraft navigational system that operates in the VHF (Very High Frequency) range, VOR is the main radio system that aircraft all over the world use in order to help them to navigate.
In layman’s terms, VOR is a “line of sight” transponder system that sends out a radio signal that includes its beacon's unique morse code or voice recording identifier, and other information that an aircraft with a VOR receiver can then use to plot its magnetic bearing and location.
Designed as a system that aircraft and pilots can use to help them stay on course and follow their flight plan, by the end of the twentieth century there were more than three thousand VOR beacons in constant operation around the world and more than a third of them were located in America,
VOR signals help pilots to navigate using either air highways (which use an altitude of eighteen thousand feet or less), more commonly know in the United States as Victor Airways, or jet routes (which are used above eighteen thousand feet), and any pilot with a VOR receiver can tune into the successive beacons, which then act as a marker to help them stay on course.
Even though it should have retired and bought a condo in Florida a decade ago, VOR is still working hard to keep the planes in the air and make sure that they get to where they’re going.
Are VORs Still Used?
Even though it’s old, VOR is still in use today and it is still being used by pilots and aircraft all over the world. Having said that, like all things it has had its moment in the sun, which in VOR’s case was far longer than its original designers ever dreamed it would be, and is now regarded as being obsolete, and is, rather sadly, coming to the end of its operational life.
In order to give aircraft and their operating companies the opportunity to update and upgrade the navigational systems that their aircraft use, the worldwide VOR system is gradually being phased out, and slowly decommissioned. In the last two decades, more than two thousand VOR beacons have been taken out of service, and of the three thousand that were in daily use at the beginning of the millennium, only nine hundred remain.
While VOR was an effective navigational aid for more than seventy years, it wasn’t and isn’t as accurate as the GPS (Global Positioning System) software that most modern aircraft, and ATC’s (Air Traffic Control) use, and like all of the greatest pioneers of aviation, VOR was eventually left behind by its more advanced and easier to use replacement.
Do Airliners Use VOR?
Yes and no. While every airliner used to use VOR as its main navigational system, almost every civilian airliner in the world now uses some form of FMS (Flight Management System) which uses a combination of available information to plot a plane’s position and help it to stay on course.
FMS systems aren’t solely reliant on a single guidance system and use multiple streams of information to help an aircraft and its pilots to maintain their designated flight path and course. If an aircraft has GPS installed, the FMS will usually default to using it as the main source of navigational information, but they can, and do, also use the VOR array and its beacons and the signals they provide.
The FMS system is why almost every airliner in operational use around the world still has at least one VOR receiver in its cockpit, as it adheres to, and incorporates the idea of multiple redundancy. If for some reason, an aircraft’s GPS system failed, the FMS could then switch to VOR and would keep the airliner flying and guide it to its eventual destination.
How Do You Read A VOR Receiver?
That depends on which type of VOR receiver an aircraft is using. Smaller aircraft typically use an OBI (Omni-Bearing Indicator) which allows a pilot to tune into the VOR signal and get a fix on it, and navigate according to the clarity and volume of that signal.
If the pilot begins to go off course, the signal will begin to fade and if it does it means that the pilot is drifting off course. The only way to stay in course with an OBI is by making sure that the VOR signal remains loud and clear.
An RMI (Radio Magnetic Indicator) presents the VOR signal to the pilot on a rotating card and the plane as a triangle on said card. By adjusting the triangle’s position on the bearing presented on the rotating card (which is shown on screen), the pilot can adjust the course of the plane being flown and lock on to the signal and bearing that the VOR is sending.
HSI (Horizontal Signal Indicator) and RNAV (Area Navigation) systems work in conjunction with the onboard computer of an airplane to present the pilot with the data that the VOR beacon is sending in a much more user friendly and easy to understand way.
Pilots can then use that information to stay on the beacon trajectory, or if they need to, to adjust the course of the airplane in order to correctly follow the information that it provides.
How Does VOR Operate?
Despite its age, VOR is surprisingly sophisticated. Set up as an array of global beacons, VOR sends out a repeating phased horizontal signal that’s broadcast by a shortwave antenna and rotates around thirty times a second. It sounds complicated because believe it or not, the science and engineering that makes VOR work really is. Complicated that is.
In the simplest terms, a VOR beacon works like this. An antenna sends out a signal that is composed of either morse code or a voice recording that contains its position and any other relevant navigational information.
A pilot can then tune into, and lock onto, this signal using an onboard VOR receiver to get a “fix” on his position and use that signal to alter or adjust the course of the aircraft if needed. By “tuning” into successive VOR transmissions and signals, a pilot can use them to navigate between the point of departure, and the eventual destination, of an aircraft.
How Far Can A VOR Reach?
As it’s a short wave transmission system, a VOR signal has a surprisingly small range, which is why the system relies, and relied, on multiple worldwide beacons in order to work. Pilots and navigational software tune into and jump between a series of successive beacons in an array in order to make sure that the VOR signal, and information, that they receive is constantly updated.
Every VOR beacon in the global array has an effective signal distance of somewhere in the region of two hundred miles, which can be slightly increased or decreased, depending on the power of the VOR receiver in an aircraft.