ATIS - Wind direction in True or Mag?
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ATIS - Wind direction in True or Mag?
We all know that TAFs and METARS give the surface wind in True. The aircrew in our crewroom are all under the impression that ATIS winds are supposed to be magnetic(cos that's wot we were taught and runways are in mag!) This has recently caused heated discussion with the chaps in ATC who simply copy down the true wind that's passed by the Met Office and put that out on the ATIS.
A trawl through the books finds a quote in JSP 318A (Military ATC Bible) that says that ATCOs are responsible for applying variation to the true wind supplied by the Met Office when choosing a runway direction. We've found nothing yet that explicitly states whether you should use true or mag in the ATIS.
Of course with 4 degrees variation it doesn't really matter here but most of us regularly operate into windy airfields with big variations so we'd like to clear up any confusion!
Any comments
A trawl through the books finds a quote in JSP 318A (Military ATC Bible) that says that ATCOs are responsible for applying variation to the true wind supplied by the Met Office when choosing a runway direction. We've found nothing yet that explicitly states whether you should use true or mag in the ATIS.
Of course with 4 degrees variation it doesn't really matter here but most of us regularly operate into windy airfields with big variations so we'd like to clear up any confusion!
Any comments
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I think you will find that the ATIS is only a verbal rendition of the METAR. Consequently, you should treat the information with the same amount of caution as it may be the best part of an hour out of date. Remember, met 'specials' are only issued on a significant change of weather.
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ATIS, and correct me if I'm wrong, was supposed to relieve r/t congestion by saving the ATCO the need to relay a/d essential information, which included runway in use, wind etc. therefore the application of variation to wind was implicit, as it is when given on approach by the twr. Yep methinks it should be degrees mag. Not to bad if it's in the UK but try missing 20 odd deg VAR or so when operating out of BIKF on a windy day.
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When I wa trained as an assistant I was indeed told to add the variaton and round up/down to the nearest 10 before broadcasting on the ATIS.
However surely the next part of the argument is, should I be applying that variation to the wind checks I give as a tower controller?
However surely the next part of the argument is, should I be applying that variation to the wind checks I give as a tower controller?
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no sig... All the bloke in the tower does is to read the anemometer dial. Whether that's mag or true I don't know, although I've always assumed it to be mag. (I never saw any adjustments applied to the equipment when I worked in Heathrow Tower). I did a spell as a met observer yonks ago and my reports simply quoted the wind off the anemometer and I assume that's the info we all get in metars so precisely "which" wind it is I don't know.
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Logic says the anenometer in the tower should give the magnetic wind as it's useful to know when you're landing on a magnetic runway (sic). Are there any met chaps out there who want to comment about which wind they intend to put out on the ATIS?
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"Take-off is optional, Landing is mandatory"
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"Take-off is optional, Landing is mandatory"
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The wind 'off the clock' in the Twr is always mag because that's the way it's calibrated(usually)and it would be pointless a controller passing a surface wind to a/c on finals in true as it would require a mental calc from the pilot.
I'm glad to see that there is a difference of opinion between what is actually done on the ATIS and what should be done. I can't seem to find any document that states whether ATIS winds should be in true or mag. From a pilots point of view I would prefer it in mag because that's the info I use for initial take off/ landing calcs and at places like Gander it makes a lot of difference.
I get the impression that in the UK, because the variation is so small, no one has really noticed that some pilots think they're getting mag on the ATIS when they're actually getting true.
I'm glad to see that there is a difference of opinion between what is actually done on the ATIS and what should be done. I can't seem to find any document that states whether ATIS winds should be in true or mag. From a pilots point of view I would prefer it in mag because that's the info I use for initial take off/ landing calcs and at places like Gander it makes a lot of difference.
I get the impression that in the UK, because the variation is so small, no one has really noticed that some pilots think they're getting mag on the ATIS when they're actually getting true.
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On the old Munro dials (remember them?) there was sub-scale that could be adjusted by the Met Technician for variation. The one that was in the observer's room had zero variation but the ones in ATC had the variation added.
As for our new digital kit - who knows?! But it should be magnetic!
As for our new digital kit - who knows?! But it should be magnetic!
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Was told by one of our ATCOs today that the civvy ATC bible states that ATIS winds should be passed as mag. This RAF station uses the true wind supplied by Met as does the RAF ATC school at Shawbury, not sure what happens at other UK bases but would assume they do the same. Not a real problem while flying in the UK but a chap could be caught out if he gets it wrong overseas.
[This message has been edited by Specaircrew (edited 06 March 2001).]
[This message has been edited by Specaircrew (edited 06 March 2001).]
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Looking at the U.S. systems ATIS is magnetic north referenced (Airman's Information Manual para 4-1-13) The automated surface observing system (ASOS) and other automated systems produc ea true north referenced output for METAR and SPECI reports, 5 minute observations and the daily wx summary. When the asos is fitted with the ground to air radio feature it converts to magnetic before broadcast. Not sure what the digital ATIS in oepration at some locations over ACARS provides.
Seems the problem might be when whoever created METARs and internationally standardized them maybe they forgot who used them. Then the automation and automated wx observing engineers just provided what was demanded at the output.
references: www. faa.gov/ATPubs/AIM
www.nws.noaa.gov/asos/magwind.htm
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I think UK military ATC should put their hands up on this one and say they have got it wrong. If they haven't known all this time that they were supposed to be converting the Metar from true to mag then they have been found SEVERELY wanting.
Correct it soon, please.
Correct it soon, please.
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Scatters
1. ATC is not responsible for the info - it is the met department.
2. The info given over the radios (by ATC, standfast ATIS) is Mag, as pointed out above - the anenometers are calibrated (and are maintained by the Meteorological office - the civil service)
3. ATIS is only changed when the weather changes significantly i.e. a QFE, cloud, Vis change. Therefore the wind is a mean wind - not changed unless strength or direction changes significantly. ATIS could be the same all day.
4. Therefore - the wind on ATIS is not instantaneous and could be way out - that is why you are given the wind on finals or at the commencement of an instrument approach, and at any other time that it significantly changes. This wind is corrected.
5. Even if it was a cock up - which it is not really when you consider the facts above - why should the ATC or even Met department have noticed it? You obviously did not until the thread was started!!
Yes, I have bitten on your comment - but with just cause.
Steps off soap box
[This message has been edited by Bizzy (edited 06 March 2001).]
[This message has been edited by Bizzy (edited 07 March 2001).]
1. ATC is not responsible for the info - it is the met department.
2. The info given over the radios (by ATC, standfast ATIS) is Mag, as pointed out above - the anenometers are calibrated (and are maintained by the Meteorological office - the civil service)
3. ATIS is only changed when the weather changes significantly i.e. a QFE, cloud, Vis change. Therefore the wind is a mean wind - not changed unless strength or direction changes significantly. ATIS could be the same all day.
4. Therefore - the wind on ATIS is not instantaneous and could be way out - that is why you are given the wind on finals or at the commencement of an instrument approach, and at any other time that it significantly changes. This wind is corrected.
5. Even if it was a cock up - which it is not really when you consider the facts above - why should the ATC or even Met department have noticed it? You obviously did not until the thread was started!!
Yes, I have bitten on your comment - but with just cause.
Steps off soap box
[This message has been edited by Bizzy (edited 06 March 2001).]
[This message has been edited by Bizzy (edited 07 March 2001).]
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Bizzy Old Chap/Girl,
The point is that because it is stated in UK/US docs that ATIS winds are to be in magnetic, this is what pilots expect to receive. In fact I've yet to come across an overseas airfield that broadcasts in true!
The whole reason for having an ATIS is to stop pilots having to call the Twr, if I called you from 100 miles out I wouldn't expect you to pass the wind in true!
ATC are responsible for what goes out on the ATIS so I don't think it's unreasonable to expect them to add or subtract the variation to the true wind before making the tape!
I'm afraid the old 'we just pass what the met man gives us' argument doesn't hold much water for military ATC as it clearly states in JSP 318A that ATCOs must remember to convert the wind supplied by the Met office to magnetic (surely this was taught during basic training?)
The real question being asked here is; if pilots and ATC in the rest of the world know that the ATIS wind is supposed to be magnetic why is it that some UK ATCOs don't?
The obvious answer being that 4 degrees variation makes bugger all difference, so the theory has got lost in the sands of time and we're into the 'but we've always done it this way' mentality. A shame really because one begins to wonder what else wasn't taught at ATC school :-)
[This message has been edited by Specaircrew (edited 06 March 2001).]
[This message has been edited by Specaircrew (edited 06 March 2001).]
The point is that because it is stated in UK/US docs that ATIS winds are to be in magnetic, this is what pilots expect to receive. In fact I've yet to come across an overseas airfield that broadcasts in true!
The whole reason for having an ATIS is to stop pilots having to call the Twr, if I called you from 100 miles out I wouldn't expect you to pass the wind in true!
ATC are responsible for what goes out on the ATIS so I don't think it's unreasonable to expect them to add or subtract the variation to the true wind before making the tape!
I'm afraid the old 'we just pass what the met man gives us' argument doesn't hold much water for military ATC as it clearly states in JSP 318A that ATCOs must remember to convert the wind supplied by the Met office to magnetic (surely this was taught during basic training?)
The real question being asked here is; if pilots and ATC in the rest of the world know that the ATIS wind is supposed to be magnetic why is it that some UK ATCOs don't?
The obvious answer being that 4 degrees variation makes bugger all difference, so the theory has got lost in the sands of time and we're into the 'but we've always done it this way' mentality. A shame really because one begins to wonder what else wasn't taught at ATC school :-)
[This message has been edited by Specaircrew (edited 06 March 2001).]
[This message has been edited by Specaircrew (edited 06 March 2001).]
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For those that have confidently stated that ATIS is magnetic. ATIS broadcasts exist that are (or have been) generated automatically from a lexicographical scan of the METAR message, without any variation being applied. They are therefore in deg true. In these cases there is no human intervention in the process. Others may be different of course.