One of my activities while I was active in Geneva was to introduce practical radio-navigation to students, using the club simulator. This was a preparation for the radio-navigation part of the in-flight syllabus, and this hopefully saved time and money.
Many students were slightly lost with the course selection and the use of the TO / FROM flag. As an IFR pilot this is so obvious that it was even hard to explain it. Students tended to focus on keeping the needle. This is a good start, but VORs are just as good as the pilots using them, and mistakes are possible.
As far as I understood this form of radio-navigation, there is a single rule to know which course must be selected using the OBS:
Be Coherent With What You Fly
Ok, this might seem obvious, but here’s what that means, in two parts:
1) If you fly towards the VOR, you must have a TO flag, if you fly away from the VOR, you must have a FROM flag.
2) The heading you fly must be in the top part of the VOR indicator. Centered if you fly the radial with no wind, but anyway in the upper part.
If you follow these two simple rules, your VOR indicator will never betray you. After all, this is simple common sense. Why fly to a VOR with a FROM flag ? It’s true that if you’re flying to the VOR from the south you’re flying radial 180 inbound… but if you want a commanding instrument – fly towards the needle to center it – your heading must be coherent with your OBS selection.
And if you fly to the VOR from the south, you fly heading 360, not 180. So to fly radial 180 inbound, select 360 on your OBS. There is a trick to remember that, but it works in French only: “radial XXX inbound – radial XXX en-bas”. For non-french speaking readers, “en-bas” means “in the bottom”, and sounds like “inbound”.
So when you fly to the VOR, select the radial you’re on in the bottom of the OBS, or select your heading on top of the OBS. You will then get a TO flag. If not, you’re may be lost…
Flying away is somehow simple. If you passed the VOR and fly towards east, you fly radial 090, you’re heading is 090, and the OBS is set to 090. Piece of cake.
If you had any doubts how to set your OBS in any circumstance, I hope this solved them. If not, feel free to ask for more details.
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Very useful thank you – do you know how to get a simplified map of all VOR locations in CH?
Thank you very much,
@Sandra: you’ll find what you need in the Swiss AIP. If you don’t have it, here’s a list of all Swiss VORs that you can find in your favorite simulator:
PAS – GVA – SPR – FRI – WIL – KLO – GRE – ZUE – TRA – SIO – MOT.
It wrote that out of my head so I probably forgot a couple of them.
thank you for youre article on vor it helped to stop over complicating vor navigation i find i was thimking to much on what the ground source was doing.
thank you very clive
Clive, thanks for your kind words.
By the way, if you’re iPhone or iPad equipped, you should check my latest app Radionav Sim: http://itunes.apple.com/us/app/radionav-sim/id427469516?mt=8&ls=1
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