How To Do A VOR Check Before Your Next IFR Flight

If you plan to use a VOR receiver for navigation under instrument flight rules, 14 CFR 91.171 requires that the receiver be operationally checked within the preceding 30 days. There are five approved ways to satisfy the check, each with its own error tolerance, and every check must be logged with four specific items: date, place, bearing error, and signature. Miss the window and the receiver is not legal for IFR - even if the rest of the airplane is.

What the VOR check rule actually requires

The requirement lives in 14 CFR 91.171. In plain language: if you are operating under IFR and intend to use a VOR receiver for navigation, that receiver must have been operationally checked within the preceding 30 days of the flight.

Read that carefully. It is not “every 30 calendar days” or “the first of the month.” It is the preceding 30 days counted backward from the flight you are about to fly. If today is August 8, 2026, your check needs to have happened on or after roughly July 8. Miss it by one day and, legally, that receiver is unavailable to you for IFR.

The rule also does not apply to VFR. Under visual flight rules you can use a VOR freely with no 30-day check. The requirement is purely an instrument one - because in the clouds that needle may be the only thing keeping you off the terrain, and the FAA wants assurance it’s telling the truth.

Why this matters for pilots

The pilots who get caught are usually the ones who fly a mix of VFR and IFR and aren’t in the airplane every day. Instrument currency is good, the approaches and holds are logged, the annual is signed - and then the flight launches on an actual IFR clearance with a VOR that no one has checked in six weeks. The airplane is legal. The receiver isn’t. The 30-day check is the quiet variable that’s easy to forget and expensive to ignore.

What are the five ways to do a VOR check?

“Check your VOR” sounds like one task, but the regulation gives you five methods. Here’s how each works.

1. VOT (VOR Test Facility)

A VOT is a ground transmitter, usually on an airport, that broadcasts one specific signal in every direction. Tune the published VOT frequency and center the needle. Set 360 and center it, and you should see a FROM indication. Set 180 and center it, and you should see a TO indication.

The classic memory aid is “Cessna 180 TO” - 180, TO. Allowable error: ±4 degrees. VOT facilities and frequencies are listed by state in the Chart Supplement (formerly the Airport/Facility Directory). This is the cleanest, most repeatable check because you can do it sitting still on the ramp.

2. Ground checkpoint

Some airports have a surveyed, marked spot on the airport surface with a published radial for that exact point. Taxi to the point, tune the specified VOR, and compare your indication against the charted radial. Tolerance: ±4 degrees. These checkpoints are also listed in the Chart Supplement, and the airport diagram usually shows where the point sits.

3. Airborne checkpoint

Same concept, but the point is in the air. The Chart Supplement publishes a location (often referenced off a landmark), a specific altitude, and the radial you should read when you cross that spot. Because flying a precise point over the ground is harder than sitting on a painted line, the FAA loosens the tolerance to ±6 degrees.

4. Airway or selected radial over a known ground point

If no published checkpoint is nearby, you may select a VOR radial that lies along the centerline of an established airway, then fly over a distinct, identifiable ground point on that centerline at a reasonable distance from the station, and read the receiver as you cross it. Tolerance: ±6 degrees. This one demands honesty - you have to actually be over the point when you read the needle, not off to the side.

5. Dual VOR check

If your airplane has two independent VOR receivers, tune both to the same station, center or read both, and compare. The two receivers must agree with each other within 4 degrees.

For many general aviation pilots this is the practical winner. You don’t need a VOT, a published checkpoint, or any particular location - ramp, run-up area, or in flight all work. The only catch is that you need two receivers and a good signal from the same usable station.

VOR check tolerances at a glance

Here is the part people mix up when a check airman asks:

VOT: ±4 degrees
Ground checkpoint: ±4 degrees
Dual VOR against each other: within 4 degrees
Airborne checkpoint: ±6 degrees
Airway/radial over a ground point: ±6 degrees

The pattern to remember: on the ground or against yourself, 4 degrees; in the air against a published point, 6 degrees. The air buys you the extra two degrees because flying a precise point is harder than parking on a line.

How do I log a VOR check correctly?

A VOR check you don’t record didn’t happen, as far as the FAA is concerned. The regulation requires each check to be entered into a record containing four items:

Date
Place
Bearing error
Signature of the person who made the check

The record does not have to live in the aircraft logbooks. Many pilots keep a small dedicated VOR check log in the glovebox or seat-back pocket and add a line each time - that’s perfectly acceptable. What matters is that the record exists and shows a check within the preceding 30 days of the IFR flight flown.

Pay attention to the bearing error entry. Writing “OK” tells an inspector nothing. If you were two degrees off, write "+2" or “−2.” If a dual check agreed within one degree, note that. The measured number is the point - it proves the receiver was actually functioning and by how much.

Do I still need a VOR check if I fly WAAS GPS?

If you are not going to use the VOR receiver for navigation on that IFR flight, the 30-day check does not attach to it. The rule is triggered by using the VOR for navigation under IFR - no VOR nav, no 30-day check.

Be careful, though, because the operative phrase is “intend to use,” and instrument flying has a way of changing the plan. GPS can be downgraded. You can be assigned a VOR approach you didn’t expect, or cleared direct to a VOR, or given a hold at one. The moment you need that receiver to navigate, it needed to have been checked - and you can’t make it legal retroactively once you’re airborne.

The practical recommendation: if the airplane has a working VOR and you fly instruments in it, just keep the 30-day check current. It costs almost nothing and takes one variable off the table.

How to build the habit

If your home field has a VOT or ground checkpoint, tie the check to something you already do - like the first flight of the month - and log it on the ramp.
If you have dual VORs, fold the dual check into your normal run-up flow: tune a strong station, glance at both needles, write the line. Thirty seconds.
If you share a club or partnership airplane, agree on where the VOR check log lives so nobody’s guessing and two people aren’t each assuming the other did it.

And the trap worth repeating: it’s the preceding 30 days from the flight, not a calendar month. The last day of a long month can quietly stretch you past the window if you count on your fingers. When in doubt, count backward from today - and if the last check is on the wrong side of that line, do a new one before you go.

Key Takeaways

14 CFR 91.171 requires a VOR check within the preceding 30 days for any IFR flight that uses the VOR for navigation; VFR is exempt.
There are five approved methods: VOT, ground checkpoint, dual VOR (all ±4°), and airborne checkpoint or airway/ground-point check (both ±6°).
Every check must be logged with date, place, bearing error, and signature - and the bearing error must be a measured number, not “OK.”
If you don’t intend to use the VOR under IFR, the check doesn’t apply - but because clearances change, keeping it current is the safer habit.
Count the 30 days backward from the flight date, not from a calendar month.

Requirements drawn from the Federal Aviation Regulations, 14 CFR 91.171, with the step-by-step walk-through informed by Boldmethod’s VOR check guide.