VOR time and distance to station
A VOR gives you a bearing but no range. Fly across the radials, time how long a set number of degrees takes, and the geometry gives you an estimate of how far out you are.
Calculator
This is an educational and planning aid. Use current official weather, your aircraft flight manual, and the rules that apply to your flight before you act on any figure here. See the aviation disclaimer.
What the result means
The result is time to the station at your current groundspeed, and the distance that corresponds to. It is an estimate from a geometric approximation, not a measurement.
The technique works because the closer you are to a station, the faster the bearing changes as you fly past it. A slow bearing change means you are a long way out.
When this is useful
- In an aircraft with a VOR but no DME, where there is no other way to get a range.
- As a cross check on a position when other navigation sources disagree.
- For instrument rating study, where the technique is a standard examination topic.
How it is calculated
Turn to place the station roughly 90 degrees off your nose, hold a steady heading, and time how long a chosen bearing change takes. The time to the station in minutes is 60 multiplied by the minutes flown, divided by the degrees of bearing change.
Multiplying that time by groundspeed gives the distance. The calculator does both and warns when the geometry or the numbers make the result unreliable.
time to station (minutes) = 60 x minutes flown / degrees of bearing change
Worked example
- Bearing change
- 10 degrees
- Time taken
- 2 minutes
- Groundspeed
- 120 kt
You are about 12 minutes from the station, which at 120 kt is 24 NM.
Check: 60 multiplied by 2 minutes divided by 10 degrees gives 12 minutes. At 120 kt you cover 2 NM per minute, so 12 minutes is 24 NM. Both the standard worked form of this technique and the arithmetic agree.
Limitations
- The geometry only holds if you fly roughly perpendicular to the radial. Tracking straight towards the station produces almost no bearing change and the technique gives nothing useful.
- Small bearing changes are hard to time accurately, and a timing error of a few seconds on a short interval produces a large error in the answer.
- A result far beyond normal VOR reception range means one of the inputs is wrong, since you could not have received the station at that distance.
- A DME gives slant range directly and is far more accurate. Use one if you have it.
Common mistakes
- Not holding a steady heading through the timed interval, which invalidates the geometry entirely.
- Entering the elapsed time in seconds into a field expecting minutes.
- Using true airspeed instead of groundspeed for the distance step.
Sources
- Instrument Flying Handbook (FAA-H-8083-15), navigation systems , US Federal Aviation Administration