ATIS wind information, true or magnetic?
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ATIS wind information, true or magnetic?
METAR, TAF, etc, wind information is given in reference to true north and wind info given by tower is given in reference to magnetic north.
Now I've been told by instructors at school that wind information given in ATIS is in reference to true north. Can it really be!? Doesn't make any sense to me, you'd obviously want the magnetic wind before landing or taking off.
Hope someone here can shed some light on this one.
Now I've been told by instructors at school that wind information given in ATIS is in reference to true north. Can it really be!? Doesn't make any sense to me, you'd obviously want the magnetic wind before landing or taking off.
Hope someone here can shed some light on this one.
Last edited by OsPi; 17th Nov 2007 at 16:57.
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When I did the manual ATIS/DATIS broadcasts, I read the wind off the same piece of kit[VIASALA] that the ATCO used...so I did it magnetically...the Automated wind in the SAMOS/[D]ATIS broadcasts are also [AFAIK] in Magnetic too.
watp,iktch
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The only place in the world where I could see True winds being given in an ATIS are in areas where the runways are numbered in degrees True (ie. Northern parts of Canada). So maybe the instructors were talking in that context.
Other than that I follow the adage of "if its written its true, if its spoken its magnetic".
Other than that I follow the adage of "if its written its true, if its spoken its magnetic".
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The only way that I can see them being right is if they mean the raw data that the tower gets may be in degrees true; then they convert it to magnetic for the pilots (except in extreme northern and southern areas where the compass becomes unreliable). Im not sure if Im correct, but it at least makes their answer plausable...still wrong in context though.
But no, you are correct that what you are given by ATIS and by tower are in magnetic (excepting for the conditions already mentioned)
But no, you are correct that what you are given by ATIS and by tower are in magnetic (excepting for the conditions already mentioned)
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I heard when you get it in the air, it's magnetic.
So if you check the metar or taf it should be true.
A general rule in Canada is that if you read it, its true. If you hear it, its magnetic. (might be true worldwide)
Seen post 3?
So if you check the metar or taf it should be true.
A general rule in Canada is that if you read it, its true. If you hear it, its magnetic. (might be true worldwide)
Seen post 3?
Why are some runways in Canada numbered in degrees true ? I know that true and magnetic can vary up there by 20 degrees or more, but your aircraft still has a magnetic compass which you will be using to find the runway alignment.
Junior trash
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Because in the far north close to the pole a magnetic compass becomes unreliable and eventually useless. Sondestrom in Greenland is magnetic but Thule which is a few hundred miles further north is True.
Only half a speed-brake
My training was always:
aerodrome message - METREPORT - magnetic (2 minutes average)
published METAR/TAF - true (10 minutes average)
ATIS should be METREPORT, but local installations say "... metar at 1300Z ..." which is different, but at least you know it. I tried to look in Annex 3 that such practice is incorrect, but didn't found any evidence.
FD (the un-real)
aerodrome message - METREPORT - magnetic (2 minutes average)
published METAR/TAF - true (10 minutes average)
ATIS should be METREPORT, but local installations say "... metar at 1300Z ..." which is different, but at least you know it. I tried to look in Annex 3 that such practice is incorrect, but didn't found any evidence.
FD (the un-real)
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in Australian all information is given in degrees true, the only exception is the ATIS and any information given by the tower is always in degree magnetic.
Last edited by jamesvki; 18th Apr 2008 at 12:51.
It's about time that ICAO switched to using TRUE worldwide for all bearings. Apart from convenience (for 99.9999% of aviators), the cost savings would be significant - no more repainting of runways numbers, re-calibration of VORs etc.
Admittedly a tiny number of GA pilots who are still flying around using their compasses would have to learn the magnetic variation in their local flying area and add or subtract it from their wobbly compass bearings. But if they are capable of correcting for their compass deviation then it is hardly a big calculation to also correct for variation.
Admittedly a tiny number of GA pilots who are still flying around using their compasses would have to learn the magnetic variation in their local flying area and add or subtract it from their wobbly compass bearings. But if they are capable of correcting for their compass deviation then it is hardly a big calculation to also correct for variation.
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In which publication is this written in Canada? I cannot find anything in the AIM explaining whether ATIS winds are T or M. Very grey area for sure. I'm curious to find it. Any tips would be appreciated.
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I have recently had to find references for this info, and I provide them below for you guys to see the answers. Don't forget, any country can deviate from these but must publish those deviations.
ATIS
2 minute average and magnetic
Reference for this (bizarrely) from: ICAO Annexe 11 ATS
4.3.7. L) surface wind direction (in degrees magnetic)
4.3.6.1 (See Note) surface wind direction and speed are to be averaged over 2 minutes
METAR
ICAO Annexe 3 Appendix 3 APP 3-6
4.1.3.1 The averaging period for surface wind observations shall be:
a) 2 minutes for local routine and special reports and for wind displays in air traffic services units; and
NOTE - In UK for small aerodromes with traffic <5700kg, the instant wind is usually given see UK AIP GEN 3.5 3.1.1)
b) 10 minutes for METAR and SPECI, except that when the 10-minute period includes a marked discontinuity in the wind direction and/or speed, only data occurring after the discontinuity shall be used for obtaining mean values; hence, the time interval in these circumstances shall be correspondingly reduced.
4.1.5.1 In local routine reports, local special reports, METAR and SPECI, the surface wind direction and speed shall be reported in steps of 10 degrees true
ATIS
2 minute average and magnetic
Reference for this (bizarrely) from: ICAO Annexe 11 ATS
4.3.7. L) surface wind direction (in degrees magnetic)
4.3.6.1 (See Note) surface wind direction and speed are to be averaged over 2 minutes
METAR
ICAO Annexe 3 Appendix 3 APP 3-6
4.1.3.1 The averaging period for surface wind observations shall be:
a) 2 minutes for local routine and special reports and for wind displays in air traffic services units; and
NOTE - In UK for small aerodromes with traffic <5700kg, the instant wind is usually given see UK AIP GEN 3.5 3.1.1)
b) 10 minutes for METAR and SPECI, except that when the 10-minute period includes a marked discontinuity in the wind direction and/or speed, only data occurring after the discontinuity shall be used for obtaining mean values; hence, the time interval in these circumstances shall be correspondingly reduced.
4.1.5.1 In local routine reports, local special reports, METAR and SPECI, the surface wind direction and speed shall be reported in steps of 10 degrees true
Only half a speed-brake
Ah, that's it: The ATS (hence Annex 11) give pilot what he needs, providing service -->> magnetic. The experts from MET services measure and share data scientifically into large databases and communication systems -->> true.
