need some guidance please

[tony norman]

Could someone please tell me how to test a VOR on the ground as part of my pre-flight instrument test.

I know how to test in the air but not on the ground.... my instructor showed me a few days ago but I gone a stone forgot!

Hope someone can help

Thanx

[Flingingwings]

Select the required frequency.
Ident freq.
Adjust CDI until no deviation is displayed.
Does radial indicated match any fitted RMI needle, and does needle direction correspond with beacon location relative to your position on the airfield?

If so adjust CDI 10 degrees in each direction to check that beam bar goes to full scale deflection on both sides correctly. Then rotate CDI needle 360 degrees. Checking that after 90 degrees to/from flag changes and then changes back again as you reach the last 90 degree portion.

[EGBKFLYER]

Just remember that you may not be in range of a VOR if you're on the ground (e.g. my home airfield has no beacons within 20 miles). When you select the frequency, be sure you get a good ident (morse beeps) for the beacon. No ident means you can't use the signal, so you will have to sort it out when you're airborne.

Note also that most VOR indicators fitted in small aircraft have a warning flag. When you switch on the nav kit, the warning flag goes away unless there's a problem (no power, no signal etc). So the simplest check could just be 'VOR on, no flags displayed'

[tony norman]

thank you for the replies - i thought it might have been a bit more complicated than that. im based at stapleford so we have a vor on our doorstep.

ta muchy

[theresalwaysone]

Why do you need to test them on the ground apart from do they switch on and remove flags and thats subject to range so unreliable-- you test then before use in the air--thats were they are designed to work. A corrrectly identified morse signal is the only guaranteed indication on the ground if the aid is within range. Directional signals received on the ground are subject to errors.

[unfazed]

Theresalways one


In that case why do some larger airports have VOR test areas marked on the ground ???

Wouldn't be so that you can test the VOR would it

Better to test it before you launch off and then rely on it

[theresalwaysone]

Unfazed--Thank you-- i have never heard of this please tell me more, I think I have been into every large airport in this country and never heard of testing VORS on the ground before flight in a a specified area. As most airlines use FMS/FMGS GPS based navigation I wouldnt have thought it necessary these days.

The most relied upon radio aid in public transport is the ILS and every day 1000s of flights launch off and rely on it (as you say) without testing it, the dedicated few listen to the ident but the accuracy test comes when you try to fly it! You cant test everything before you fly otherwise every aircraft would need a C of A each morning! Thats also the reason behind public transport aircraft being required to carry more than one of any critical instrument etc

Ive just looked at the AERAD Heathrow, quite a LARGE airfield, aerodrome chart and can find no such VOR test area and can you imagine the chaos if every aircraft went to an area before departure to test the VORs--If there is such an area its probably like the compass base, used for maintenance.

The IR is primarly a test for pilots going onto public transport operations and should reflect the operation of an AOC public transport operation. With respect (and i have been through the IR and completed around 30 IR renewals)some instructors introduce folk lore into the scenario which would be better left to the airfield bar.

[unfazed]

Theresalwaysone


I assume that your knowledge and interest finishes at the UK border

But just in case you wanted to know there are indeed VOR test areas at airports overseas

Suggest you check out FAR/AIM pART 91.171 (2) AND HAVE A READ

Then again I am probably talking gibberish now aren't I ?

Knowledge has no boundaries !

[SD.]

Originally Posted by theresalwaysone

Why do you need to test them on the ground apart from do they switch on and remove flags and thats subject to range so unreliable-- you test then before use in the air--thats were they are designed to work. A corrrectly identified morse signal is the only guaranteed indication on the ground if the aid is within range. Directional signals received on the ground are subject to errors.

Accuracy? +/- 4 degrees for a ground check? -/+ 6 degrees for airborne check? Could find yourself in some nasty situations if your VOR is indicating a bearing error of 20 degrees at 30 miles.

Think you'll find it a requirement to test your VOR's before using them as IFR nav aids every 30 days (FAA that is, don't know about JAA land).
You can climb off up into the soup without knowing the accuracy or indeed if the VOR's work but I sure wont.

[theresalwaysone]

Originally Posted by unfazed

Theresalwaysone
I assume that your knowledge and interest finishes at the UK border

But just in case you wanted to know there are indeed VOR test areas at airports overseas

Suggest you check out FAR/AIM pART 91.171 (2) AND HAVE A READ

Then again I am probably talking gibberish now aren't I ?

Knowledge has no boundaries !

Is there any need to make a response as above, with respect you can make the same point without trying to be smart or sarcastic.

Since you made your post I have looked up the AERAD booklet and you are indeed correct there is a VOR check point symbol shown, thank you for bringing that to my attention, however that does not prove that a VOR needs a ground test as described on here before an IFR flight.

I fly and train on an aircraft with a autoland CAT3B capability (no decison height) and I never check the accuracy of the ILS on the ground (nor am I required to) and we undergo specific Cat 2/3 revalidation/recurrent training every 6 months) and do bear in mind that the aircraft not only flys the ILS it steers the roll out as well in 75 metres RVR! I mention this because I would suggest this is a bit more critical than a VOR let down or en route use of a VOR which in fact is a very reliable aid.

I would ask you how many IFR VOR approaches are carried out in this country every day and how many ILS are carried out, I suspect the number of VOR approaches are not significant. So then how many IR pilots check the accuracy of their ILS receivers on the ground before flight in fact I know of no way of making such a check between the stand and airbourne.


To answer your question my interest extends to all the countries I fly in and have flown in-- Europe-Scandinavia-Africa-Canada- Iceland-Greenland and the USA. However I repeat i have never come across a VOR test area before or heard of anybody going to such an area to test a VOR before flight, as mentioned i know of many airfields that have compass bases so does that mean for instance at Heathrow for instance each departure should taxy there first to check compasses each morning? ( I would come in on a day off to see that!)

I have also been involved in many CAA observed base and IR tests on public transport aircraft and never heard an examiner ask for an accuracy test for a radio aid--only that all aids are to be identified before use as was the position when I did my IR. Good airmanship however would dictate that you would look for an obvious sensible reading.and an RMI sensible needle movement if you have a VOR on the RMI.


As you brought this to our attention and its something you obviously do on a regular basis, can you tell us which of these large airports overseas have VOR check points?


SD--- not being an engineer i know nothing of testing the accuracy of VORs every 30 days etc but i am sure you are correct. Your IFR flying would be severely limited in the UK if you wouldnt go IFR before checking the accuracy of a VOR on the ground you may later use in the air. Please also let me know how you confirm the quoted limits while in the air with a basic IFR aircraft.

Unfazed If you read back, the original post was from a pilot who was talking about taking an IR test in this country and being based a Stapleford which I seem to remember is an airfield within the UK FIR boundary.

You are quite correct knowledge has no boundaries but I believe the IR test in the UK does!

[unfazed]

Theresalwaysone

Your right I was having too much fun so apologies as I have obviously upset you.

Toronto is one example of a large airport with a VOT

If you wan't to know more just search on VOT

Yes I know that we don't do this in the UK and yes a UK IR pilot would not necessarily know about this.

If you are flying big jets internationally I don't think you need to worry about this but if any of your aircraft have VOR;s fitted and have an N on the tail then you might wan't to know about this (as well as the requirement for a full pitot/static test every 24 month, now that is thorough).

[unfazed]

Why do you need to test them on the ground apart from do they switch on and remove flags and thats subject to range so unreliable-- you test then before use in the air--thats were they are designed to work. A corrrectly identified morse signal is the only guaranteed indication on the ground if the aid is within range. Directional signals received on the ground are subject to errors.

Then again looking at your first posting in response to this query perhaps you should have a rethink about your answer

[sir.pratt]

as an engineer/pilot i always thought that the vor was checked before flight simply to establish that the orientation of the needle in relation to the rotation of the card (and subsequently the aircraft) was correct, and that the flag was out, and that the instrument was powered up. it is a given that its accuracy falls within the manufaturers test limits.

[unfazed]

Sir Pratt

Depends on where you studied engineering

Have a search and read up on VOT's , from an engineering perspective there is some good info out there.

[Wrong Stuff]

Originally Posted by theresalwaysone

You are quite correct knowledge has no boundaries but I believe the IR test in the UK does!

Originally Posted by unfazed

Yes I know that we don't do this in the UK and yes a UK IR pilot would not necessarily know about this.

That's not true now. Test VORs, how to use them and tolerances are all part of the IR Theoretical Knowledge syllabus - see JAR-FCL 062 01 03 00. I was certainly told to do VOR/ILS and ADF checks using whatever navaids were available for both my IR and IMC examinations and I was picked up in an IR renewal the year before last for not checking the ADF thoroughly enough.

[unfazed]

Wrong Stuff

What you say is quite correct however on the subject of VOT (vor ground tests at specific marked parts of an airport), these are specific ground areas to conduct the tests in.

Popular in USA and Canada, not sure if used in UK ? Suspect not.

[Wrong Stuff]

Just to make it clear, Test VORs (VOTs) are part of the JAA IR theoretical knowledge syllabus.

[unfazed]

Thanks for confirming that !

Looks like this knowledge is relevant to UK IR after all

Excellent !