VOR accuracy

[The Scud 911]

Hi,

I've been looking for an information about accuracy of VORs. I believe that the accuracy is +/-1° which gives 1NM accuracy 60NM from the station, but I also found some other things on the web:

- Wikipedia says the accuracy of VOR/DME is 900m (?)
- Accuracy off VOR is supposed to be +/-5° 95% of the time (someone posted that on that forum).

What is true then (I would also appriciate an explenation)? Thanks for answers.

[FlyingStone]

The average accuracy is approximately 5°, which consists of:
- site error (terrain and other obstacles) - up to 1°
- propagation error (signal travel) - up to 1°
- airborne equipment error - up to 3°

The maximum internal error of VOR is 1° and is measured by a monitor in vicinity of the VOR, which puts VOR into standby mode if:
- bearing mesured changes by more than 1°
- the drop in signal strength is more than 15%
- the monitor fails (altough the VOR may remain functional provided the NOTAM is issued stating the VOR isn't monitored and should be used with caution)

[40&80]

Scud....Be aware I found some VORs in Africa and India up to 30 degrees off.
Not a bad idea to use all available means of navigation available to you and not totally hang your hat on just one nav aid in some areas of the world.
Also they were not notamed...and they idented perfectly..they just indicated crap.

[aterpster]

The Scud 911:

I've been looking for an information about accuracy of VORs. I believe that the accuracy is +/-1° which gives 1NM accuracy 60NM from the station, but I also found some other things on the web.

FAA uses +/- 4.5 degrees for along track total system error including FTE (pilot error). +/- 3.6 degrees cross-track error because there is no FTE in cross-track; i.e., using a cross radial for a fix.

The PANS-OPS numbers are more conservative: 5.2 along track and 4.5 across track.