Melbourne Air Traffic Control
Something fishy going on here Underfire.
If I listen to ATIS Golf on vhf and the wind is 250/10, and then I order an ATIS via ACARS and golf pops out......it says 250/10.
They are either both magnetic or both true and the common understanding is they are both magnetic.
What's the go?
If I listen to ATIS Golf on vhf and the wind is 250/10, and then I order an ATIS via ACARS and golf pops out......it says 250/10.
They are either both magnetic or both true and the common understanding is they are both magnetic.
What's the go?
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oi vey...
There are the ICAO and WMO standards.
METAR Wind Velocity
Wind velocity in a METAR is stated as the measured or estimated mean of each component over the 10 minutes prior to the time of issue of the METAR, unless there are significant variations during this 10 minute period. For direction, this means 60 degrees or more of arc but less than 180 degrees provided that the mean speed during the previous 10 minutes has been more than 3 knots. In the case of speed, variations from the mean wind speed (both above and below it) are reported when the variation from the mean speed has exceeded 10 kts. Such variations are expressed as the maximum and minimum speeds attained and must also be included if the maximum wind speed in a 10 minute period has exceeded the 2 minute average wind speed at the same location in that period. Any gust value which has occurred in the most recent two minute period will of course also be part of the calculation of average wind speed
Wind direction is recorded in degrees true. Whatever runway(s) is (are) in use, the wind velocity for the METAR is normally taken from one designated anemometer.
ATIS Wind Velocity
ATIS wind velocity is latest two minute average. The wind direction broadcast is given in degrees true. The mean wind speed is supplemented by the value of the highest and lowest gusts within the 10 minutes prior to issue time if either exceeds the METAR-specified minimum difference increment away from the mean.
ATIS broadcasts are usually only updated between the regular change times if the wind direction changes by more than 30 degrees or the 2 minute average wind speed changes by more than 5 kts over a five minute interval.
ATC Wind Velocity Reports
Display of wind velocity information to ATC at major airports usually allows at least the reporting by RTF of both the ‘average wind’ - that over a two minute period updated every minute - and ‘instant wind’ - the value at that exact time. The latter is usually used only where high wind speeds and their associated greater fluctuations in speed and direction prevail. ATC may pro-actively initiate such ‘wind checks’ or this action may be requested by a flight crew. The ATC TWR at most international and major domestic airports have digital displays of wind velocity which can be specific to sensor site or integrated from several sites and can show a selection of trend and extremes data. Smaller airports may still be limited to dual and plotted graphical displays from which to derive both required broadcast information and additional ad hoc assistance. ATC plain language ad hoc wind directions given during final approach or just prior to or during the take off roll are likely to be given in degrees magnetic.
Which AIP?
On a side note, what do your FMS and IRS winds use?
EDIT: Sorry that was a trick question. The FMS and IRS use the digital winds calculated in true. The ND winds are shown in mag. There is always a comparison going on between the input winds and the actual.
There are the ICAO and WMO standards.
METAR Wind Velocity
Wind velocity in a METAR is stated as the measured or estimated mean of each component over the 10 minutes prior to the time of issue of the METAR, unless there are significant variations during this 10 minute period. For direction, this means 60 degrees or more of arc but less than 180 degrees provided that the mean speed during the previous 10 minutes has been more than 3 knots. In the case of speed, variations from the mean wind speed (both above and below it) are reported when the variation from the mean speed has exceeded 10 kts. Such variations are expressed as the maximum and minimum speeds attained and must also be included if the maximum wind speed in a 10 minute period has exceeded the 2 minute average wind speed at the same location in that period. Any gust value which has occurred in the most recent two minute period will of course also be part of the calculation of average wind speed
Wind direction is recorded in degrees true. Whatever runway(s) is (are) in use, the wind velocity for the METAR is normally taken from one designated anemometer.
ATIS Wind Velocity
ATIS wind velocity is latest two minute average. The wind direction broadcast is given in degrees true. The mean wind speed is supplemented by the value of the highest and lowest gusts within the 10 minutes prior to issue time if either exceeds the METAR-specified minimum difference increment away from the mean.
ATIS broadcasts are usually only updated between the regular change times if the wind direction changes by more than 30 degrees or the 2 minute average wind speed changes by more than 5 kts over a five minute interval.
ATC Wind Velocity Reports
Display of wind velocity information to ATC at major airports usually allows at least the reporting by RTF of both the ‘average wind’ - that over a two minute period updated every minute - and ‘instant wind’ - the value at that exact time. The latter is usually used only where high wind speeds and their associated greater fluctuations in speed and direction prevail. ATC may pro-actively initiate such ‘wind checks’ or this action may be requested by a flight crew. The ATC TWR at most international and major domestic airports have digital displays of wind velocity which can be specific to sensor site or integrated from several sites and can show a selection of trend and extremes data. Smaller airports may still be limited to dual and plotted graphical displays from which to derive both required broadcast information and additional ad hoc assistance. ATC plain language ad hoc wind directions given during final approach or just prior to or during the take off roll are likely to be given in degrees magnetic.
Search through AIP for "magnetic".
On a side note, what do your FMS and IRS winds use?
EDIT: Sorry that was a trick question. The FMS and IRS use the digital winds calculated in true. The ND winds are shown in mag. There is always a comparison going on between the input winds and the actual.
Last edited by underfire; 7th Jun 2017 at 09:47.
The Antarctic AIP. Whadya reckon? 
AIP GEN 2.1 Units of Measurement
AIP GEN 3.5:
AIP GEN 2.1 Units of Measurement
Wind direction for runway operations: degrees magnetic
4.4.1 Take-off and landing reports are included on ATIS, where
available, or passed to aircraft reporting taxiing or inbound.
Take-off and landing reports contain, as available, the following:
a. wind velocity, with direction in degrees magnetic;
available, or passed to aircraft reporting taxiing or inbound.
Take-off and landing reports contain, as available, the following:
a. wind velocity, with direction in degrees magnetic;
7.4.3 AWIS will provide some of the following information:
a. Message identifier e.g. “AWS AERODROME WEATHER” OR
“AUTOMATED WEATHER INFORMATION SERVICE”.
b. station identifier as a plain language station name,
c. wind direction in degrees Magnetic and speed in Knots,
a. Message identifier e.g. “AWS AERODROME WEATHER” OR
“AUTOMATED WEATHER INFORMATION SERVICE”.
b. station identifier as a plain language station name,
c. wind direction in degrees Magnetic and speed in Knots,
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Well, that is all good.
There are always interpretations of the ICAO standards, and interpretations of 'broadcast', in regards to D-ATIS vs V-ATIS. The AIP does not differentiate, but there is a difference. I know what I provide as far as wind data and to whom.
Back to the posts in this thread, I was responding to questions that wondered why the ATC winds were different than those reported on ATIS, and other difference noted.
There are always interpretations of the ICAO standards, and interpretations of 'broadcast', in regards to D-ATIS vs V-ATIS. The AIP does not differentiate, but there is a difference. I know what I provide as far as wind data and to whom.
Back to the posts in this thread, I was responding to questions that wondered why the ATC winds were different than those reported on ATIS, and other difference noted.
Underfire you post screeds of information ( copied from wiki?) and tout it as gospel even if it is completely wrong. You may mislead someone one day and for what?
In the context of this conversation ( YMML ATC) the ATIS wind is magnetic. You've stated it is True., probably best to own your mistake rather than talk about different interpretations.
In the context of this conversation ( YMML ATC) the ATIS wind is magnetic. You've stated it is True., probably best to own your mistake rather than talk about different interpretations.
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ICAO Standard:
Annex 3 — Meteorological Service for International Air Navigation
4.3 Routine observations and reports
Note.— Meteorological information used in ATIS (voice-ATIS and D-ATIS) is to be extracted from the local routine report, in accordance with Annex 11, 4.3.6.1 g).
4.6 Observing and reporting meteorological elements
4.6.1 Surface wind
4.6.1.1 The mean direction and the mean speed of the surface wind shall be measured, as well as significant variations of the wind direction and speed, and reported in degrees true and kilometres per hour (or knots), respectively.
If you call tower and get winds, they will be in magnetic.
Specific Pre-Flight Information Briefing enroute and terminal winds will be in true.
Believe me, this drove me crazy for a while. I have the measured wind data, which is always measured true, and the data from the ac from AMDAR for enroute, is true. The ac itself reports the winds in true.
Then, for the ATC screen you see above, this is what the controller sees in relation to each runway, which of course, is in mag. Mag is used to compute the crosswind/head-tailwind/etc component winds for each runway. As the system can be installed worldwide, built in to the interface in the settings, the magvar is input. This is then applied as applicable, but not globally to the wind output! Only the screens where ATC will provide the wind call. Other outputs, such as the METAR and ATIS do not have the magvar couple.
Thus, the surface winds (at 10m) that ATC reports shown are in mag, but virtually everything else is in true, (as are any forecasts)
Annex 3 — Meteorological Service for International Air Navigation
4.3 Routine observations and reports
Note.— Meteorological information used in ATIS (voice-ATIS and D-ATIS) is to be extracted from the local routine report, in accordance with Annex 11, 4.3.6.1 g).
4.6 Observing and reporting meteorological elements
4.6.1 Surface wind
4.6.1.1 The mean direction and the mean speed of the surface wind shall be measured, as well as significant variations of the wind direction and speed, and reported in degrees true and kilometres per hour (or knots), respectively.
If you call tower and get winds, they will be in magnetic.
Specific Pre-Flight Information Briefing enroute and terminal winds will be in true.
Believe me, this drove me crazy for a while. I have the measured wind data, which is always measured true, and the data from the ac from AMDAR for enroute, is true. The ac itself reports the winds in true.
Then, for the ATC screen you see above, this is what the controller sees in relation to each runway, which of course, is in mag. Mag is used to compute the crosswind/head-tailwind/etc component winds for each runway. As the system can be installed worldwide, built in to the interface in the settings, the magvar is input. This is then applied as applicable, but not globally to the wind output! Only the screens where ATC will provide the wind call. Other outputs, such as the METAR and ATIS do not have the magvar couple.
Thus, the surface winds (at 10m) that ATC reports shown are in mag, but virtually everything else is in true, (as are any forecasts)
Knots pretty well everywhere, metres per second in China and Russia (not been to Russia for a while). .)
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Underfire you post screeds of information ( copied from wiki?)
Interesting, never, ever, read or heard winds in km/hr anywhere. (/aviation related)
Bloggs, do the same search of the AIP for degrees true.
On the ATIS, does the broadcast provide crosswinds?
On the ATIS, does the broadcast provide crosswinds?
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Reading this page conjures up visions of some sort of skit that the highly entertaining, acerbic, abrasive, yet deadly serious Nassim N Taleb would have written to prove his point about "knowledge about knowledge".
Here is a quote from a recent piece:
Suggested reading, his first two books, "Fooled by Randomness" and "The Black Swan", then you may realise where the problem lies.
Here is a quote from a recent piece:
The IYI pathologizes others for doing things he doesn’t understand without ever realizing it is his understanding that may be limited.
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A supposed aviation professional (an alleged RNP-AR designer, no less) asking if crosswind is broadcast on the ATIS. That's a worry.
It was not a question, I guess that was lost on you. Providing crosswinds is not a standard broadcast. IF crosswinds are provided, it has to be magnetic...as it is specific to a particular runway. (which, so you do not have to look it up, are in magnetic) that is why I was asking being facetious , not that you were actually able to provide the answer.
Not that there are the standards, and countries and airlines can have exemptions and modifications to the standards.
I can see by your typical responses, why Australia has had to provide as much detail as possible to the 'pilots' so they can figure out how to land the ac.
You call yourself a professional, yet appear to be a cut rate one. How is your AR qualification going? No matter, really.
Getting back to the original questions as to why AWOS, METAR, ATIS, and tower winds are different, I hope that has been answered.
Getting back to the original questions as to why AWOS, METAR, ATIS, and tower winds are different, I hope that has been answered.
So this is the person designing our approaches..... makes sense....
These things tend to get lost in translation.
There is no reason I want true winds on an ATIS... full stop.
These things tend to get lost in translation.
There is no reason I want true winds on an ATIS... full stop.
In Melbourne we get the wind for the ATIS and the wind we broadcast by voice from the same source. So both are either true or magnetic....I suspect magnetic though
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Getting back to the original questions as to why AWOS, METAR, ATIS, and tower winds are different, I hope that has been answered.
The question was never asked!
The question was never asked!
I explained the different reporting standards, and why there are differences. Not only different between mag/true, but simply the differences and changes in the winds.
The difference between true and mag needs to be understood. Different Systems will add the magvar or not, so it is important to understand what to input and where.
As shown by many applications, the magvar for the aerodrome is a setting. The ac uses true when measuring the winds. Forecasts and enroute are in true.It must be understood when inputting winds to the ac, if the winds you are using include the magvar correction or not.
What needs to be understood is what the ANSP has decided to provide. That was the basis for my comment on crosswinds. IF it has been decided to include crosswinds in the broadcast, it is magvar, but this is not typical. When crosswinds are not provided, and up to the driver to compute, the winds are in true. From what I have experienced, most require the driver to calc the wind.
If Aus has decided that is too much, and has provided the crosswinds, that is all good, but it must be understood, when inputting the winds on the ac, if the FMS is going to correct the winds to the magvar in the database or not.
There is the worldwide standard for aviation, and I provided that as the standard, and required reporting back a few posts. Depending on conditions, there will be differences, due to the reporting frequency and averaging.
The provision if you read it it is true, if you hear it, it is mag, is what we use as a guide for the input to the FMS. When sharing wind data between aircraft, is is important to understand the format.
The AWOS winds are measured at the aerodrome in true, and at 10m, per the frequency, averaging and parameters stated in post 286. The AWOS system corrects the winds by magvar for the individual runways to report crosswinds.
The AUS AIP states for runway ops it is mag, and non-runways ops winds re true, it does not detail what runway ops means.
I shake my head at some of the stuff ATC do but today was an example of a Tower controller who was at the very peak of his game. Lined up the turbo-props at Golf, the domestic jets at Juliet and the internationals from the full length of 34 simultaneously. Bravo to whomever that ATC was.
A lot of it comes down to the luck of the draw - you can only do so much when the disposition of the traffic is wrong, but when it's right you can shine. It's fun when it works 
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I shake my head at some of the stuff ATC do but today was an example of a Tower controller who was at the very peak of his game. Lined up the turbo-props at Golf, the domestic jets at Juliet and the internationals from the full length of 34 simultaneously. Bravo to whomever that ATC was.