A VOR (VHF Omnidirectional Range) instrument tells you where your aircraft is relative to a ground-based radio station by displaying three key pieces of information: the course you’ve selected, how far off that course you are, and whether that course points toward or away from the station. Learning to read these three elements together is the core skill of VOR navigation.
The Three Parts of the VOR Display
Every VOR indicator has three components you need to watch simultaneously. The Omni Bearing Selector (OBS) is the knob you rotate to choose a course, displayed as a compass heading at the top of the instrument (0 to 360 degrees). The Course Deviation Indicator (CDI) is the vertical needle in the center of the instrument that swings left or right to show whether you’re off course. The TO/FROM flag is a small indicator that reads either “TO,” “FROM,” or displays a red flag when the signal is unusable.
The CDI needle works on a fixed scale. Full deflection to one side means you are 10 degrees or more off the selected course. Most instruments have five dots on each side of center, so each dot represents 2 degrees of deviation. A centered needle means you’re right on the selected course. This is far less sensitive than an ILS localizer, where full deflection is only 2.5 degrees, so keep in mind that even a small CDI movement on a VOR represents a meaningful position error.
How the TO/FROM Flag Works
The TO/FROM flag answers a simple question: if you flew the course shown on the OBS, would you be heading toward the station or away from it? This has nothing to do with your actual heading. It’s based purely on your position relative to the station and the course you’ve dialed in.
Here’s a concrete example. Say you’re north of a VOR station and you set the OBS to 180. The flag reads TO, because a course of 180 (due south) would take you toward the station. Now rotate the OBS to 360 without moving the airplane. The flag flips to FROM, because a course of 360 (due north) would take you away from the station. Your position hasn’t changed. Only the selected course changed, and the flag updated to match.
If the flag shows a red “NAV” warning, a barber pole, or “OFF” instead of TO or FROM, the signal is unreliable, you’re roughly 90 degrees from the selected course, or you’re directly over the station. Don’t navigate off a flagged indication.
Finding Which Radial You’re On
Radials always radiate outward from the station, like spokes on a wheel, and they’re named by their magnetic bearing from the station. The 090 radial goes east from the station. The 270 radial goes west. To figure out which radial you’re currently on, rotate the OBS until the CDI needle centers with a FROM indication. The number at the top of the course index is your radial.
This is worth repeating because it trips up many students: center the needle with FROM to find your radial. If you center it with TO instead, the number on top tells you the course to fly toward the station, which is the reciprocal of your radial, not the radial itself. Both are useful, but they answer different questions.
Flying Toward and Away From a Station
To fly directly to a VOR, rotate the OBS until the CDI centers with a TO indication. The course shown is your inbound heading. Turn to that heading, keep the needle centered, and you’ll track straight to the station.
To fly outbound on a specific radial, dial that radial into the OBS. You should see a FROM flag and the CDI will deflect toward the direction you need to turn to intercept the radial. Once the needle centers, turn to the heading shown and fly it outbound. The key principle: when flying away from a station, you want FROM. When flying toward it, you want TO.
If you’re told to fly inbound on a specific radial, place that radial number on the bottom of the course index (which means its reciprocal is on top). You’ll see a TO flag, and the CDI deflects toward the direction you need to turn. This keeps the needle “sensing” correctly.
Reverse Sensing and How to Avoid It
Reverse sensing is the most common source of confusion with a VOR. It happens when your heading is roughly opposite to the course you’ve selected on the OBS. In this situation, the CDI needle deflects in the “wrong” direction: if you’re left of course, the needle points right, and correcting toward the needle takes you further off course instead of back on track.
For example, say you’ve dialed in a course of 090 with a FROM flag, but you’re actually flying a heading of 270 (the opposite direction). The TO/FROM flag might still show FROM even though you’re flying toward the station, and the CDI will sense in reverse. Correcting toward the needle will steer you further off your intended path.
The fix is straightforward. When flying outbound from a station, always set the OBS to match your heading (FROM flag). When flying inbound, set the OBS to your inbound course (TO flag). If your heading and your selected course are in the same general hemisphere of the compass, the needle will sense correctly: deflect right means turn right, deflect left means turn left.
Before You Navigate: Tuning and Identifying
Before reading the instrument, you need to confirm you’re receiving the right station. Tune the VOR frequency on your navigation radio, then listen to the Morse code identifier. Every VOR broadcasts a unique Morse code sequence, and it’s printed on your chart next to the frequency. If you can’t hear the identifier, the signal is unreliable and shouldn’t be used for navigation. Stations undergoing maintenance may transmit a signal without the identifier, which means the VOR data could be inaccurate.
For IFR (instrument flight rules) operations, your VOR receiver must be checked within the past 30 days. A ground-based test signal or designated airport checkpoint allows a maximum error of plus or minus 4 degrees. An airborne checkpoint allows plus or minus 6 degrees. If you have dual VOR systems, you can check them against each other by tuning both to the same station. The two indicated bearings must agree within 4 degrees.
Finding Your Position With Two VORs
A single VOR tells you which radial you’re on, but that only narrows your position to a line extending from the station. To pinpoint your location, tune a second VOR on your other navigation radio and identify that radial too. Your position is where the two radials cross on the chart. This is called a cross-fix, and it’s one of the most practical uses of VOR navigation beyond simple station tracking.
For this to work well, the two radials should cross at a reasonable angle, ideally between 45 and 135 degrees. If they cross at a very shallow angle, a small CDI error translates into a large position error along one of the radials.
VOR Availability Going Forward
The FAA is gradually reducing the number of VOR stations in the continental United States through its VOR Minimum Operational Network (MON) program. GPS has become the primary means of navigation for most aircraft, so many VORs are being decommissioned. The remaining network is designed so that any aircraft experiencing a GPS failure can navigate to an airport with a suitable instrument approach within 100 nautical miles using VOR alone. The surviving stations are also getting expanded service volumes, with usable signals starting at 5,000 feet above ground level, to support longer station-to-station routes with fewer facilities. VOR navigation remains a required skill and a critical backup, but the infrastructure is shrinking to match its evolving role.