VOR help!

[EHM-1821 Javier]

I've been thinking for a while, reading up on wikipedia and flying the lesson on FS but i still do not fully understand how to work VORs :s

i do understand that to intercept it at a radial, i enter the radial with the OBS knob(at least thats with the C172, CRS knob with those bigger jets?)

To track the radial with the AP, do i turn the CRS knob to the radial i want to intercept it, tune radios to the VOR's freq, and what do i click for the AP to track it?

and also for the outbound part, that im totally clueless, holding over a VOR too

any help would be greatly appreciated

[EHM-2029 Sotiris]

Hi Javier,

it's a pleasure to help out.
First have a look at another thread that may help you Navigation Help

Well, from your post I see that you understand what radials are (360 beams originating from the VOR and spaced at 1 degree intervals).
If you want to intercept (or in common terms ride) the radial, first you must tune in the right frequency.
Then on the OBS (in lighter aircraft) knob or the 'Course' entry choose the heading with which you want to fly to the VOR.

Notice how I didn't say put the radial in the OBS/Course. This is because if you fly to a VOR then you will be riding a radial 180 degress from your course.
A simple way of explaining this is so: Say your VOR is right above you at 360 degrees. If you fly direct above on a course of 360, you will actually be 'riding' the 180 radial (or beam). This is because as you are south the beam originating from the VOR toward you is the 180 degrees one.
This whole section is only important when a controller asks you to intercept an inbound radial. Otherwise in normal operations you need not take too much notice of this.
For short:
Inbound: Course = Inbound Radial +/- 180
Outbound: Course = Outbound Radial

Anyway, forget the above for a moment.
Now say you have tuned your VOR and set the course toward it. This should get the needle of your VOR receiver to go alive and go towards one side (left or right). All you have to do now, is fly towards the needle. Once the needle is in the centre this means that you are 'riding' or have intercepted the radial and are on your way.

Regarding the AP and the NAV button please note that if you are very far to the side of a radial (too far to the left or right) the NAV button may not pick up the signal and not turn your aircraft toward the radial. Usually it is best to try and get near the radial and once you're 20-35 degrees away (two to three white dots) then flick your nav and watch your plane do it for you.

Three last things:
1) The Course/OBS will always apply to the VOR selected in NAV1
2) If you fly to fast towards intercepting the radial, the AP may end up overshooting the radial and making a correction to re-intercept it. This is normal. To resolve this, use your AP early as described above.
3) Once you're flying a VOR radial with NAV and AP engaged, your plane may have a different heading to the course selected. This is normal and it is done to compensate for crosswinds trying to take you off-course.

I hope this helps. If not, I'm here to help further.

[EHM-1821 Javier]

Thanks Sotiris! that helped a lot! btw thanks for that link to the other topic

just to clarify, are the 2-3 white dots you are talking about the same set as the one you get when your localizer is alive while intercepting ILS? or is it another set?

If i leave the AP as it is, what happens after i cross over the VOR? does it hold the VOR by itself? for example ATC asks me to hold at ABC VOR, how exactly do i hold? flying towards the VOR is the easier part, what i cant get is how to hold :s

Once again, Thanks soooo much

[EHM-2029 Sotiris]

VOR Holdings

I start from the definition of a holding:
A rectangular pattern (similar to the VFR one) that comprises of four right or left turns. The pattern is defined as follows:
Entry point, Inbound heading, direction of turns, downwind leg length.
Example: Hold over RDS VOR, inbound 068, Right hand turns, leg length 1 minute.
This means go to the RDS VOR on a course of 068, once over RDS start your turn to the crosswind leg by turning right.

When it comes to VOR holdings we have two kinds: VOR/DME or simple VOR.

VOR/DME
As above, use the named course to approach the VOR. By checking the DME you can see how far you are from it. Once the distance is zero do a 90 degree turn (crosswind leg) to start your pattern. Then another 90 degree turn (downwind leg) and fly on this heading for the requested amount of time (usually 1 minute). Then another 90 degree turn to join the base leg. Finally another 90 degree turn to join the upwind leg which should bring you to your original course and approaching the VOR point again.

VOR without DME
In such a case you can't tell how far you are from the VOR. But as you follow your course toward the VOR your will have an indication of going 'TO' or a small triangle pointing up.
When the indication changes from 'TO' or up to 'FROM' or down pointing triangle that is where you start the pattern as described above.

[EHM-2029 Sotiris]

Originally posted by EHM-1821 Javier
just to clarify, are the 2-3 white dots you are talking about the same set as the one you get when your localizer is alive while intercepting ILS? or is it another set?

YES it's the same ones but they will probably be a different colour (white instead of green)

]Originally posted by EHM-1821 JavierIf i leave the AP as it is, what happens after i cross over the VOR? does it hold the VOR by itself?

After crossing the VOR it continues on the same course as selected beforehand. After the VOR signal is lost (after you have flown sufficiently far away) then it continues on present heading but without any influence. (After you lose the VOR the winds may alter your heading). By that time you probably need to do something about your plane to put it on its intended course.

[EHM-1821 Javier]

thanks for the explaination

just one last thing, as i head towards a VOR to hold, do i have to do the legs starting in a specific heading +90 the next leg and so on....? or do i just enter by the heading i headed towards the VOR?

[EHM-2029 Sotiris]

Originally posted by EHM-1821 Javier
 as i head towards a VOR to hold, do i have to do the legs starting in a specific heading +90 the next leg and so on....? or do i just enter by the heading i headed towards the VOR?

Uncontrolled Airspace:
Either do as you prefer or as per your chart. Charts that have holdings specify all these things (i.e. approach course) and much more (Min and Max altitude/FL, Max airspeed, etc.)

Controlled Airspace:
Either the controller specifies the entry course for te pattern (also known as the upwind) OR he points you to a published holding in which case you have to consult your charts.

[EHM-1821 Javier]

thanks so much for your quick replies, appreciate it a lot learned something today! (besides in school lol!)

[EHM-1883 Matt]

I thought I explained this? Concentrate more Javier! lol

[EHM-1821 Javier]

hehe, yeah Matt, you did, but i couldnt understand it exactly (or maybe my short attention span :])