Obtain local altimeter setting on CTAF???
Michael
flying discussion:
Many approach plates come with the notation "Obtain local altimeter
setting on CTAF; when not received, use" and then an alternative
source, generally with higher altitude minima.
I'm fairly familiar with what this really means - there are two
altimeters in a box, and the operator sets them both to field
elevation, then reads the altimeter settings in the Kollsman window.
If they are within some tolerance, he can give one of them out over
the radio.
AFAIK there is no training required for the person performing this
task, but I'm prepared to be proven wrong. I do know that the
instructions for doing this are generally posted right next to the
box. Once I saw it done, and I observed very carefully because the
field was IFR and the boy performing the procedure didn't look old
enough to shave. He did fine, so I stayed out of it, but it made me
wonder just how reliable that service is. Still, that's peripheral.
But what if the field has automated weather - ASOS, AWOS, whatever?
By default, I've always just considered that equivalent, but have been
told this is improper and if I didn't get it on CTAF, it's not usable
so I need to use the altimeter setting from somewhere further away and
raise my minima accordingly. Opinions abounded. I'm not really
interested in opinions, but in something relatively definitive - FAR,
AIM, published opinion, something in writing from an authoritative
source. Anyone know anything?
Michael
Dave Butler
>
> But what if the field has automated weather - ASOS, AWOS, whatever?
> By default, I've always just considered that equivalent, but have been
> told this is improper and if I didn't get it on CTAF, it's not usable
> so I need to use the altimeter setting from somewhere further away and
> raise my minima accordingly. Opinions abounded. I'm not really
> interested in opinions, but in something relatively definitive - FAR,
> AIM, published opinion, something in writing from an authoritative
> source. Anyone know anything?
Well, it's not authoritative, but I raised a very similar
question here a couple of years ago, and the consensus at
the time was the the chartmakers were just slow at updating
the charts to reflect the availability of automated weather,
and that the ASOS/AWOS report was equivalent to hearing it
on UNICOM.
The increased minima for altimiter settings obtained
elsewhere were to account for variations in atmospheric
pressure between the destination airport and the reporting
station. Since the ASOS/AWOS sensors are located at the
destination airport, they don't need to be considered remote
and may be used without taking an altitude penalty on the
approach.
You might search on google and find the old thread. If
you're looking for something more authoritative, I'll be
interested in knowing about it, too.
Dave
Tim Bengtson
>
> Many approach plates come with the notation "Obtain local altimeter
> setting on CTAF; when not received, use" and then an alternative
> source, generally with higher altitude minima.
I also am willing to be educated, but it seems like if you don't follow
the approach plate's instructions exactly, you'll come off looking like
a schmuck in the NTSB report.
Tim
Bob Gardner
Altimeter Setting
/*F/ There have been instances where pilots who have contacted an AFSS for
local airport advisory services have been directed to the local AWOS/ASOS to
retrieve the current altimeter setting. FAAO 7110.10, Paragraph 4-4-2b-3a,
outlines the information that a controller shall provide the pilot when
issuing an airport advisory. Facilities issuing an airport advisory shall
provide the current altimeter setting, unless the scheduled air carriers or
aircraft operators have requested the omission in writing.
FAAO 7110.10, Paragraph 4-3-5, outlines the information that pilots shall
receive during routine radio contacts. If the aircraft is operating below
18,000 feet MSL, issue current altimeter setting obtained from direct
reading instruments or received from weather reporting stations. Use the
setting for the location nearest the position of the aircraft.
Aircraft arriving or departing from a non-towered airport which has a
commissioned ASOS/AWOS, with ground-to-air capability shall be advised to
monitor the ASOS/AWOS frequency for the current altimeter. This requirement
is deleted if the pilot states, on initial contact, that he/she has the
automated weather.
Controllers are responsible for following these procedures and should review
these paragraphs as appropriate. (ATO-300)
Bob Gardner
"Michael" <crwd...@hotmail.com> wrote in message
news:449a3d6e.02032...@posting.google.com...
plnflyingpj
differences are given. It has nothing to do with how you got the reading or
for that matter if it was a person or a computer, it has to do with was the
reading from the field you're shooting the approach at or not. A perfect
example of this is in my old training area, there is an airport KTPL that
has local AWOS, and the controlling field is KGRK gray approach that also
has awos, but, always gives you the altimeter every time you call them. If
you use the GRK altimeter settings, you have to use the higher minimums, if
you use the temple awos settings, the minimums are lower. There are tons of
airports that fall into this rule, they're all the same.. Basically, you're
given an out in case you can't get that local info for some reason or
another.
Peter
"Michael" <crwd...@hotmail.com> wrote in message
news:449a3d6e.02032...@posting.google.com...
Steven P. McNicoll
Is this a hypothetical or are you referring to a real airport? Most of the
fields I know of that have AWOS have the AWOS frequency on the chart and say
nothing at all about the source of the altimeter setting. Nor are there any
increased minima for sources other than the AWOS. The one exception I'm
aware of calls for an off-airport altimeter setting, but this field's AWOS
is a fairly recent installation.
Michael
A real airport close to home - KDWH. There is a part time tower and
ATIS, and when the tower is closed the tower frequency becomes CTAF
and the ATIS frequency transmits automated weather.
Michael
AJ
Thought provoking question from the original poster. Michael, east of DWH
we do the same thing. Part time tower, same comment to obtain the altimeter
on CTAF on the approach plate. The ASOS is considered the official weather
we use to transmit ATIS broadcasts (when we are open), so it would reason
that if an aircraft gets the lastest one minute update from the ATIS freq
set to the automatic ASOS broadcast (that's what we set to be broadcasted
after closing) the aircraft should be able to fly to non-remote altimeter
setting mins. Maybe the solution would be to change the wording on the
plate to "obtain local alitimeter setting on ASOS/AWOS...". But then again,
using the CTAF to get the altimeter statement prescribed for on the plates
may be a liability issue, i.e., towers closed, you used the ASOS/AWOS
altimeter, and the system was wrong/malfunctioning...you should have
increased your mins to comply with the remote setting. Just my thoughts
from a controller and non-pilot.
oneatcer
Steven P. McNicoll
> ATIS, and when the tower is closed the tower frequency becomes CTAF
> and the ATIS frequency transmits automated weather.
>
It doesn't appear the situation you described exists there. The approach
plates do not indicate the existence of ASOS or AWOS on the field.
James M. Knox
news:ua2gpms...@corp.supernews.com:
>
> "Michael" <crwd...@hotmail.com> wrote in message
> news:449a3d6e.02032...@posting.google.com...
> It doesn't appear the situation you described exists there. The approach
> plates do not indicate the existence of ASOS or AWOS on the field.
True, but the AF/D does show an ASOS.
-----------------------------------------------
James M. Knox
TriSoft ph 512-385-0316
1109-A Shady Lane fax 512-366-4331
Austin, Tx 78721 jk...@trisoft.com
-----------------------------------------------
AJ
"Steven P. McNicoll" <ronca...@writeme.com> wrote in message
news:ua2gpms...@corp.supernews.com...
procedures book points you to the A/FD. Look at a plate for a field without
a tower, they'll publish the ASOS/AWOS freq (if they have the system).
>
JPH
This may be a situation where the FLIP hasn't caught up with the
AWOS/ASOS. The ASIS datasheet shows that the airport has had ASOS
since 06/26/2000.
One way to check to see if the airport has AWOS/ASOS is to go to the
website;
http://avnwww.jccbi.gov/datasheet/
When the datasheet comes up, click "choose a report: Airport" then
type in the four letter airport ID. When that airport comes up, click
on the "detail" link for data on weather and runways.
This site can also be used to get data on Navaids, except that you use
the 3 letter NAVAID ID.
JPH
Steven P. McNicoll
"James M. Knox" <jk...@trisoft.com> wrote in message
news:Xns91DE5407B112...@10.0.0.1...
>
> True, but the AF/D does show an ASOS.
>
Yes, but the A/FD does not show a frequency for that ASOS. There's little
reason to show the existence of an ASOS/AWOS on an approach plate if it does
not broadcast the observation.
Steven P. McNicoll
"AJ" <onea...@satx.rr.com> wrote in message
news:9xto8.44290$J53.1...@typhoon.austin.rr.com...
>
> The star by the ATIS freq indicates non-continuos ops.
>
Yes, and not surprising to find at a field with a part-time tower.
>
> The legend in the procedures book points you to the A/FD. Look at a
> plate for a field without a tower, they'll publish the ASOS/AWOS freq
> (if they have the system).
>
Having a tower has nothing to do with it. If the AWOS/ASOS doesn't have
broadcast capability there's little reason to denote it's presence on the
approach plate.
Steven P. McNicoll
"JPH" <jph...@earthlink.net> wrote in message
news:3ca276a0...@news.earthlink.net...
>
> This may be a situation where the FLIP hasn't caught up with the
> AWOS/ASOS. The ASIS datasheet shows that the airport has had ASOS
> since 06/26/2000.
>
Not all AWOS/ASOS observations are broadcast, it appears this one is not.
If the observation isn't broadcast there's little reason to denote the
presence of the AWOS/ASOS on the approach plate.
JPH
Since it's an ASOS vs AWOS, it's also available on Service A. (Only
some, but not all AWOS are available on Service A)
A better website for checking if an airport has a commissioned
AWOS/ASOS than the one I listed yesterday is;
http://www.faa.gov/ASOS/ASOS.HTM
Just click on AWOS or ASOS, then click on "MAP OF AUTOMATED WEATHER
OBSERVING SITES AND CURRENT WEATHER" and then click on the state for a
listing of commissioning status of the listed AWOS/ASOS. Some have
links to get the current weather at the site.
JPH
Steven P. McNicoll
>
> This one has a frequency of 124.95.
>
Not according to the approach plate or the A/FD.
Michael
>
> Not according to the approach plate or the A/FD.
Nonetheless I can assure you that when the tower is closed the ASOS is
broadcast on 124.95, which is normally the ATIS frequency.
Michael
Steven P. McNicoll
>
> Nonetheless I can assure you that when the tower is closed the ASOS is
> broadcast on 124.95, which is normally the ATIS frequency.
>
I don't doubt it, there's usually a considerable lag between these things
being established and the pertinent information being published. When the
ASOS frequency finally is published on the IAPs I'm sure the instruction to
obtain the altimeter setting on CTAF and use the Bush setting when it's not
available will be deleted, along with the higher minima.
Michael
> > broadcast on 124.95, which is normally the ATIS frequency.
>
> I don't doubt it, there's usually a considerable lag between these things
> being established and the pertinent information being published. When the
> ASOS frequency finally is published on the IAPs I'm sure the instruction to
> obtain the altimeter setting on CTAF and use the Bush setting when it's not
> available will be deleted, along with the higher minima.
Well, that's great. But it's been like this for well over a year, and
it's not the only place I've seen this.
My question remains - what to do until the approach plate catches up
to reality.
Michael
Steven P. McNicoll
> it's not the only place I've seen this.
>
It's the federal government.
>
> My question remains - what to do until the approach plate catches up
> to reality.
>
I'd go with reality.
Teacherjh
case, the altimeter settings given when the tower is open may differ from the
remote settings given by machine when the tower is closed. This would be the
case if there was a manual barometer in the tower, but it wasn't the automated
one.
Jose
(for Email, do the obvious)
John Stricker
towers.............
ATIS winds are reported in magnetic heading. I was taught 20 years ago that
ground winds are magnetic, winds aloft are true. However, ASOS/AWOS are
reported as true. So when the tower closes, what happens to the wind
directions reports? Not to critical here in my part of the country (-6°
var), but more important on either coast or Alaska.
--
John Stricker
I didn't spend all these years getting to the top of the foodchain
just to become a vegetarian.
"Teacherjh" <teac...@aol.comspam.not> wrote in message
news:20020404235421...@mb-df.aol.com...
Teacherjh
ATIS winds are reported in magnetic heading. I was taught 20 years ago that
ground winds are magnetic, winds aloft are true. However, ASOS/AWOS are
reported as true. So when the tower closes, what happens to the wind
directions reports?
<<
You'd think they'd get it all together by now.... maybe reporting ALL winds in
degrees counterclockwise from Mecca. Sheesh!
Actually I can see why winds aloft are true (magnetic variation changes) and
ground winds are magnetic (to match runway headings, courses flown, etc), but
why on earth would ASOS be true and not magnetized?
Craig Prouse
> However, ASOS/AWOS are reported as true.
When an automated weather observation is reported by radio, winds are given
as magnetic.
For the purpose of creating a METAR, the true wind is fed into the system by
land line, but that's not what you hear on the radio. The robot corrects
for magnetic variation the same way the guy in the tower does it when he
records the ATIS.
Craig
Steven P. McNicoll
"Teacherjh" <teac...@aol.comspam.not> wrote in message
news:20020404235421...@mb-df.aol.com...
>
What automated weather stations are not at an airport?
Steven P. McNicoll
"John Stricker" <jstr...@NO.russellks.SPAM.net> wrote in message
news:A398D9A847649B1D.5CA9A693...@lp.airnews.net...
>
> However, ASOS/AWOS are reported as true.
>
They are magnetic.
Herb Martin
> They are magnetic.
You may get some [legitimate] arguments on this even though in
practice you are correct....most of the time. <grin>
Technically, ASOS and AWOS winds "Direction in tens of degrees
from true north" [See "A Pilot's Guide to Aviation Weather Services"]
but is reported as magnetic when "voice broadcast."
In practice we get ASOS/AWOS from the "voice broadcast" so we
hear them as magnetic. Usually, the only time we see the "true north"
reported is after the ASOS/AWOS is converted to a METAR.
[BTW, I checked our AWOS by PHONE and it gives the same
magnetic wind as the radio 'broadcast'.]
Herb Martin, PP-SEL
(...and aerobatic student)
Try ADDS for great Weather too:
http://adds.aviationweather.noaa.gov/projects/adds
Steven P. McNicoll
"Herb Martin" <He...@LearnQuick.Com> wrote in message
news:kXhr8.6856$ud6.2...@typhoon.austin.rr.com...
>
> You may get some [legitimate] arguments on this even though in
> practice you are correct....most of the time. <grin>
>
Just most of the time? When would the surface wind be reported to a pilot
as true?
John Stricker
Where do you find anything that says it's converted? Look at AIM 7-1-11 d.
5 and the figure 7-1-2. In the example case, it is shown on the report as
true (for ASOS). For AWOS it isn't quite as clear because AIM 7-1-11 b. 2
just says "The AWOS wind speed, direction and gusts, temperature, dew point,
and altimeter setting are exactly the same as for manual observations". But
the paragraph for manual observations is just ahead of the one for AWOS and
it refers you to AIM 7-1-28 which is the chart figure 7-1-16 "Key to
Aerodrome Forecast (TAF) And Aviation Routine Weather Report (METAR)". It
also shows that the wind direction is true north, not magnetic.
ATIS, however, is magnetic. This came up a while back after reading an
article in a magazine that said this and a couple of us set out to disprove
it. We compared the displayed and reported data at the GBD airport AWOS and
the displayed and reported data at the RSL ASOS. What was printed at a
given time is what was displayed on the terminal screen at the airport and
what was reported by automated voice was what was displayed on the terminal
screen.
Maybe both of these machines are broken, but I can't find anything that says
they're converted and several references that says they're true. I'm
certainly willing to be wrong on this one because the idea of reporting
surface winds as true is crazy in my opinion. I just can't find anything
that says, from an automated station, that they are converted and AIM and
anecdotal evidence that it stays true.
--
John Stricker
I didn't spend all these years getting to the top of the foodchain
just to become a vegetarian.
"Craig Prouse" <cra...@apple.com> wrote in message
news:B8D296A7.4C35B%cra...@apple.com...
Herb Martin
The AWOS and ASOS are officially reported as true,
except for "voice broadcasts". So in practice you are
correct, but someone might argue against you with
partial information.
In theory, a pilot could be given a written ASOS or AWOS
report and by technical definition this would have true winds,
but usually we only 'see' this when it is called a METAR.
Herb Martin, PP-SEL
(...and aerobatic student)
Try ADDS for great Weather too:
http://adds.aviationweather.noaa.gov/projects/adds
"Steven P. McNicoll" <ronca...@writeme.com> wrote in message
news:uarco5h...@corp.supernews.com...
Teacherjh
I don'tremember where I read it, but I just saw it yesterday in the notes on
some charts or perhaps the AFD. I'll check and find the source for you.
Steven P. McNicoll
>
> Where do you find anything that says it's converted? Look at AIM 7-1-11
d.
> 5 and the figure 7-1-2. In the example case, it is shown on the report as
> true (for ASOS). For AWOS it isn't quite as clear because AIM 7-1-11 b. 2
> just says "The AWOS wind speed, direction and gusts, temperature, dew
point,
> and altimeter setting are exactly the same as for manual observations".
But
> the paragraph for manual observations is just ahead of the one for AWOS
and
> it refers you to AIM 7-1-28 which is the chart figure 7-1-16 "Key to
> Aerodrome Forecast (TAF) And Aviation Routine Weather Report (METAR)". It
> also shows that the wind direction is true north, not magnetic.
>
Look at AIM 7-1-12. d. 3.:
NOTE-
Wind direction broadcast over FAA radios is in reference to magnetic north.
Herb Martin
While ASOS (AND AWOS) technically give winds at
TRUE directions, when "voice broadcast" they are given
in Magnetic.
Herb Martin, PP-SEL
(...and aerobatic student)
Try ADDS for great Weather too:
http://adds.aviationweather.noaa.gov/projects/adds
"John Stricker" <jstr...@NO.russellks.SPAM.net> wrote in message
news:5A6A992FDC44F8F3.287D0D5E...@lp.airnews.net...
Craig Prouse
> What automated weather stations are not at an airport?
Sexton Summit, OR (KSXT) 541-471-1460 135.225
Mt. Shasta, CA (KMHS) 530-926-1613 120.625
Sandberg, CA (KSDB) 805-248-2329 120.625
...and several others...
I suppose it's more common in the western states where airports are sparse
and mountain pass weather is important.
Craig
Steven P. McNicoll
>
> Sexton Summit, OR (KSXT) 541-471-1460 135.225
> Mt. Shasta, CA (KMHS) 530-926-1613 120.625
> Sandberg, CA (KSDB) 805-248-2329 120.625
>
> ...and several others...
>
> I suppose it's more common in the western states where airports are sparse
> and mountain pass weather is important.
>
Interesting, I wasn't aware that was done. I notice the Sandberg and Sexton
Summit ASOSs are charted (SXT with a different frequency than you show), but
the Mt. Shasta ASOS is not. Do you know if MHS is a more recent
installation?
Newps
> "Craig Prouse" <cra...@apple.com> wrote in message
> news:B8D336E5.4C550%cra...@apple.com...
> >
> > Sexton Summit, OR (KSXT) 541-471-1460 135.225
> > Mt. Shasta, CA (KMHS) 530-926-1613 120.625
> > Sandberg, CA (KSDB) 805-248-2329 120.625
> >
> > ...and several others...
> >
> > I suppose it's more common in the western states where airports are sparse
> > and mountain pass weather is important.
Not only wx stations where they do some good but there are several webcams
pointed at mountain passes in Alaska and here in the west.
Craig Prouse
> I notice the Sandberg and Sexton Summit ASOSs are charted
> (SXT with a different frequency than you show), but
> the Mt. Shasta ASOS is not. Do you know if MHS is a more
> recent installation?
I found references to a couple of different frequencies for Sexton. There
was a NOTAM about a year or two ago that the frequency was changed.
According to the latest Klamath Falls sectional, it's now 118.375. My
source for the other frequency was http://www.faa.gov/asos.
The current A/FD also lists a new area code for the land line at Sandberg.
Dial (661) 248-2329.
Mount Shasta ASOS is published in the A/FD, although no VHF frequency is
provided. It does not appear on the Klamath Falls sectional.
Commissioning dates:
SXT 1/1/1993
SDB 4/1/1996
MHS 8/1/1996
Steven P. McNicoll
"Herb Martin" <He...@LearnQuick.Com> wrote in message
>
> Did you read my entire note or just the part you quoted?
>
I read your entire note, I've read all of your notes in this thread in their
entirety. I find them a bit contradictory.
>
> The AWOS and ASOS are officially reported as true,
> except for "voice broadcasts".
>
But you've said the AWOS report over the phone provides the same winds as
what is broadcast. That's what I find a bit contradictory.
>
> In theory, a pilot could be given a written ASOS or AWOS
> report and by technical definition this would have true winds,
> but usually we only 'see' this when it is called a METAR.
>
Which brings us back to the question I asked in my previous message, when
would the surface wind be reported to a pilot as true?
Not when it's received over the telephone, you've already determined that's
the same report as what's broadcast. I've requested several printed ASOS
observations from locations where there is significant magnetic variation
and compared them to the telephone report, in all cases the winds were
identical. I've done the same with DUATS, and it appears to be the case
with that system as well.
I can't find any source of true surface winds that would be readily
available to a pilot, but you've said the winds provided to pilots are
magnetic "most of the time". So my question remains, when are the surface
winds reported to a pilot as true?
Jon Carlson
ASOS/AWOS are reported as magnetic. This is because you're presumed to
be in flight when you receive ATIS, so you don't have to bother
translating it from true to magnetic while flying.
On DUATS right now, my home field's METAR (KSQL as of 091545Z) is
reporting wind 180 at 4, while the telephone recorded ATIS is
reporting 160 at 4. The magnetic variation here is between 15 and 16
degrees. All the other reported data is identical between the METAR
and ATIS.
-Jon C.
"Steven P. McNicoll" <ronca...@writeme.com> wrote in message
news:ub62g7o...@corp.supernews.com...
Steven P. McNicoll
"Jon Carlson" <n...@spam.com> wrote in message
news:JAEs8.198588$Yv2.66755@rwcrnsc54...
>
> METARs are reported as TRUE, while ATIS and voice broadcasts such as
> ASOS/AWOS are reported as magnetic.
>
METAR is a French acronym, it roughly translates as Aviation Routine Weather
Report. ATIS, ASOS and AWOS report in METAR format.
>
> This is because you're presumed to
> be in flight when you receive ATIS, so you don't have to bother
> translating it from true to magnetic while flying.
>
If that's the reason, then why is it also magnetic over the phone? Of what
use are surface winds referenced to true north in aviation anyway?
>
> On DUATS right now, my home field's METAR (KSQL as of 091545Z) is
> reporting wind 180 at 4, while the telephone recorded ATIS is
> reporting 160 at 4. The magnetic variation here is between 15 and 16
> degrees. All the other reported data is identical between the METAR
> and ATIS.
>
Any idea why they're true on DUATS and magnetic elsewhere?
Jon Carlson
Weather
> Report. ATIS, ASOS and AWOS report in METAR format.
True, but irrelevent.
> >
> > This is because you're presumed to
> > be in flight when you receive ATIS, so you don't have to bother
> > translating it from true to magnetic while flying.
> >
>
> If that's the reason, then why is it also magnetic over the phone?
Of what
> use are surface winds referenced to true north in aviation anyway?
>
I suspect that the reason they're magnetic on the phone has more to do
with how the recording/transmitting equipment is implemented (i.e.
it's the same recording they play over the radio) than any other
concious design decision. But that's just a guess.
As for what use are surface winds in true, I suppose so you can see
how they compare to winds aloft? But that's just a guess, too. I
ultimately don't know the intent (can only guess at it), I only know
that it's specified in the AIM that METARs (and TAFs, by the way)
should be reported as true.
>
> Any idea why they're true on DUATS and magnetic elsewhere?
METARs should always report wind in true. Refer to the AIM, section
7-1-30 and 7-1-31, the paragraph describing the wind report:
http://www.faa.gov/ATpubs/AIM/Chap7/aim0701.html#7-1-30
-Jon C.
Jon Carlson
> > be in flight when you receive ATIS, so you don't have to bother
> > translating it from true to magnetic while flying.
> >
>
> If that's the reason, then why is it also magnetic over the phone?
Of what
> use are surface winds referenced to true north in aviation anyway?
Oh, and here's the AIM reference where it's stated that ATIS winds are
given in magnetic:
http://www.faa.gov/ATpubs/AIM/Chap4/aim0401.html#4-1-13
-Jon C.
Steven P. McNicoll
>
> I suspect that the reason they're magnetic on the phone has more to do
> with how the recording/transmitting equipment is implemented (i.e.
> it's the same recording they play over the radio) than any other
> concious design decision. But that's just a guess.
>
What about ASOS/AWOS? Those aren't recordings, yet they also give winds in
magnetic over the phone.
>
> As for what use are surface winds in true, I suppose so you can see
> how they compare to winds aloft?
>
Why make the comparison?
>
> But that's just a guess, too.
>
How much of what you write is guesswork and how much do you know for sure?
>
> I ultimately don't know the intent (can only guess at it), I only know
> that it's specified in the AIM that METARs (and TAFs, by the way)
> should be reported as true.
>
Yes, I know what the AIM says. I also know that it's reported as true from
sources other than FAA radios, which means the AIM is wrong.
>
> METARs should always report wind in true.
>
But we've already established that they do not.
>
> Refer to the AIM, section
> 7-1-30 and 7-1-31, the paragraph describing the wind report:
>
> http://www.faa.gov/ATpubs/AIM/Chap7/aim0701.html#7-1-30
>
Thanks. I've seen it. If the AIM agreed with reality we wouldn't be having
this discussion.
Jon Carlson
> >
> > METARs should always report wind in true.
> >
>
> But we've already established that they do not.
>
I wasn't aware that we'd already established that they do not. The
sources that I've seen agree with the AIM, namely that METAR is true,
voice broadcasts are magnetic.
What source does not follow this standard?
-Jon C.
Steven P. McNicoll
> >
> > I ultimately don't know the intent (can only guess at it), I only know
> > that it's specified in the AIM that METARs (and TAFs, by the way)
> > should be reported as true.
> >
>
> Yes, I know what the AIM says. I also know that it's reported as true
from
> sources other than FAA radios, which means the AIM is wrong.
>
Oops, that should have been, "I also know that it's reported as magnetic
Steven P. McNicoll
>
> I wasn't aware that we'd already established that they do not. The
> sources that I've seen agree with the AIM, namely that METAR is true,
> voice broadcasts are magnetic.
>
> What source does not follow this standard?
>
That's it. METAR is broadcast with magnetic winds; ATIS, ASOS, AWOS,
observations received from ATC and FSS.
John Clonts
The AIM is not wrong. The AIM is describing the METAR format, whereby winds
are encoded as "true" by definition.
What you hear when you listen on radio or phone is not "METAR"-- it is a
description of current weather (conveniently similar to METAR).
Another example: the voice does not say "zero nine slash mike zero three" ,
it says something like "temperature nine celsius dewpoint minus three
celsius".
Cheers,
John
Jon Carlson
> > sources that I've seen agree with the AIM, namely that METAR is
true,
> > voice broadcasts are magnetic.
> >
> > What source does not follow this standard?
> >
>
> That's it. METAR is broadcast with magnetic winds; ATIS, ASOS,
AWOS,
> observations received from ATC and FSS.
>
>
You've got me confused now.... Are we agreeing?
-Jon C.
Steven P. McNicoll
>
> You've got me confused now....
>
No, you did that all by yourself.
>
> Are we agreeing?
>
Doubt it.
Steven P. McNicoll
"John Clonts" <jcl...@hot.rr.com> wrote in message
news:a8vk1...@enews2.newsguy.com...
>
> The AIM is not wrong. The AIM is describing the METAR format, whereby
winds
> are encoded as "true" by definition.
>
> What you hear when you listen on radio or phone is not "METAR"-- it is a
> description of current weather (conveniently similar to METAR).
>
You're wrong. What you hear when you listen to ATIS or AWOS or ASOS is
indeed METAR. METAR replaced SA in 1996.
>
> Another example: the voice does not say "zero nine slash mike zero three"
,
> it says something like "temperature nine celsius dewpoint minus three
> celsius".
>
Irrelevant, and incorrect. Temperatures are provided in degrees Celsius,
but "Celsius" is not spoken.
Jon Carlson
understand.
Here's what the AIM says and what I have observed:
- METAR (in text format, e.g. DUATS) wind is reported as true
- Voice broadcasts of same (call it METAR or whatever you want) via
ATIS/ASOS/AWOS are reported as magnetic
You represent that you have seen cases where this is not the case, but
as far as I can tell you give no examples. Do you have any you can
share?
-Jon C.
Steven P. McNicoll
>
> OK, whatever. Your terse missives are ambigous and difficult to
> understand.
>
The problem isn't on my end.
>
> Here's what the AIM says and what I have observed:
>
> - METAR (in text format, e.g. DUATS) wind is reported as true
> - Voice broadcasts of same (call it METAR or whatever you want) via
> ATIS/ASOS/AWOS are reported as magnetic
>
They are METAR, what else would I call them? Whatever gave you the idea
they were not METAR?
>
> You represent that you have seen cases where this is not the case, but
> as far as I can tell you give no examples. Do you have any you can
> share?
>
The examples I gave were ASOS and ASOS observations via telephone. I don't
know how you missed them, given that you responded to those messages. I
also said METAR observations provided to ATC facilities via the Flight Data
Processing computer have magnetic winds.
Steven P. McNicoll
>
> On DUATS right now, my home field's METAR (KSQL as of 091545Z) is
> reporting wind 180 at 4, while the telephone recorded ATIS is
> reporting 160 at 4. The magnetic variation here is between 15 and 16
> degrees. All the other reported data is identical between the METAR
> and ATIS.
>
I wouldn't draw any conclusion from that, it's unlikely the ATIS was
recorded at the same time the weather observation was put in.
John Clonts
>
> "John Clonts" <jcl...@hot.rr.com> wrote in message
> news:a8vk1...@enews2.newsguy.com...
> >
> > The AIM is not wrong. The AIM is describing the METAR format, whereby
> winds
> > are encoded as "true" by definition.
> >
> > What you hear when you listen on radio or phone is not "METAR"-- it is
a
> > description of current weather (conveniently similar to METAR).
> >
>
> You're wrong. What you hear when you listen to ATIS or AWOS or ASOS is
> indeed METAR. METAR replaced SA in 1996.
>
>
METAR is described by Federal Meteorological Handbook No. 1, and there is no
provision therein for reporting wind other than with respect to true north.
Therefore, what you hear over the radio or phone does not conform to METAR.
see http://205.156.54.206/oso/oso1/oso12/fmh1/fmh1toc.htm , specifically
chapter 5 (http://205.156.54.206/oso/oso1/oso12/fmh1/fmh1ch5.htm#chp5link).
> >
> > Another example: the voice does not say "zero nine slash mike zero
three"
> ,
> > it says something like "temperature nine celsius dewpoint minus three
> > celsius".
> >
>
> Irrelevant, and incorrect. Temperatures are provided in degrees Celsius,
> but "Celsius" is not spoken.
>
(254)774-8337 is my example. If you can show me a standard that says
"Celsius" should not be spoken, I will be happy to learn though.
Cheers,
John
Steven P. McNicoll
>
> METAR is described by Federal Meteorological Handbook No. 1, and
> there is no provision therein for reporting wind other than with respect
> to true north.
>
Are you saying wind is never reported other than with respect to true north
in the US?
>
> Therefore, what you hear over the radio or phone does not conform to
> METAR.
> see http://205.156.54.206/oso/oso1/oso12/fmh1/fmh1toc.htm , specifically
> chapter 5
> (http://205.156.54.206/oso/oso1/oso12/fmh1/fmh1ch5.htm#chp5link).
>
Or are you saying that when the wind is reported in magnetic the report
ceases to be METAR? Here's an excerpt from another federal publication that
differs those positions,
see the Note in AIM 7-1-12.d.3.
Aeronautical Information Manual
Official Guide to Basic Flight Information and ATC Procedures
Chapter 7. Safety of Flight
Section 1. Meteorology
7-1-12. Weather Observing Programs
d. Automated Surface Observing System (ASOS). The ASOS is the primary
surface weather observing system of the U.S. (See Key to Decode an ASOS
(METAR) Observation, FIG 7-1-7 and FIG 7-1-8.) The program to install and
operate up to 993 systems throughout the U.S. is a joint effort of the NWS,
the FAA and the Department of Defense. ASOS is designed to support aviation
operations and weather forecast activities. The ASOS will provide continuous
minute-by-minute observations and perform the basic observing functions
necessary to generate an aviation routine weather report (METAR) and other
aviation weather information. The information may be transmitted over a
discrete VHF radio frequency or the voice portion of a local NAVAID. ASOS
transmissions on a discrete VHF radio frequency are engineered to be
receivable to a maximum of 25 NM from the ASOS site and a maximum altitude
of 10,000 feet AGL. At many locations, ASOS signals may be received on the
surface of the airport, but local conditions may limit the maximum reception
distance and/or altitude. While the automated system and the human may
differ in their methods of data collection and interpretation, both produce
an observation quite similar in form and content. For the "objective"
elements such as pressure, ambient temperature, dew point temperature, wind,
and precipitation accumulation, both the automated system and the observer
use a fixed location and time-averaging technique. The quantitative
differences between the observer and the automated observation of these
elements are negligible. For the "subjective" elements, however, observers
use a fixed time, spatial averaging technique to describe the visual
elements (sky condition, visibility and present weather), while the
automated systems use a fixed location, time averaging technique. Although
this is a fundamental change, the manual and automated techniques yield
remarkably similar results within the limits of their respective
capabilities.
1. System Description.
(a) The ASOS at each airport location consists of four main
components:
(1) Individual weather sensors.
(2) Data collection package(s) (DCP).
(3) The acquisition control unit.
(4) Peripherals and displays.
(b) The ASOS sensors perform the basic function of data acquisition.
They continuously sample and measure the ambient environment, derive raw
sensor data and make them available to the collocated DCP.
2. Every ASOS will contain the following basic set of sensors:
(a) Cloud height indicator (one or possibly three).
(b) Visibility sensor (one or possibly three).
(c) Precipitation identification sensor.
(d) Freezing rain sensor (at select sites).
(e) Pressure sensors (two sensors at small airports; three sensors at
large airports).
(f) Ambient temperature/Dew point temperature sensor.
(g) Anemometer (wind direction and speed sensor).
(h) Rainfall accumulation sensor.
3. The ASOS data outlets include:
(a) Those necessary for on-site airport users.
(b) National communications networks.
(c) Computer-generated voice (available through FAA radio broadcast to
pilots, and dial-in telephone line).
NOTE-
Wind direction broadcast over FAA radios is in reference to magnetic north.
4. An ASOS/AWOS report without human intervention will contain only that
weather data capable of being reported automatically. The modifier for this
METAR report is "AUTO." When an observer augments or backs-up an ASOS/AWOS
site, the "AUTO" modifier disappears.
5. There are two types of automated stations, AO1 for automated weather
reporting stations without a precipitation discriminator, and AO2 for
automated stations with a precipitation discriminator. As appropriate, "AO1"
and "AO2" shall appear in remarks. (A precipitation discriminator can
determine the difference between liquid and frozen/freezing precipitation).
NOTE-
To decode an ASOS report, refer to FIG 7-1-7 and FIG 7-1-8.
REFERENCE-
A complete explanation of METAR terminology is located in AIM, Paragraph
7-1-30, Key to Aerodrome Forecast (TAF) and Aviation Routine Weather Report
(METAR).
>
> (254)774-8337 is my example. If you can show me a standard that says
> "Celsius" should not be spoken, I will be happy to learn though.
>
FAA Order 7110.65N Air Traffic Control
Chapter 2. General Control
Section 9. Automatic Terminal Information Service Procedures
2-9-3. CONTENT
Include the following in ATIS broadcast as appropriate:
a. Airport/facility name, phonetic letter code, time of weather sequence
(UTC). Weather information consisting of wind direction and velocity,
visibility, obstructions to vision, present weather, sky condition,
temperature, dew point, altimeter, a density altitude advisory when
appropriate and other pertinent remarks included in the official weather
observation. Wind direction, velocity, and altimeter shall be reported from
certified direct reading instruments. Temperature and dew point should be
reported from certified direct reading sensors when available. Always
include weather observation remarks of lightning, cumulonimbus, and towering
cumulus clouds.
NOTE-
ASOS/AWOS is to be considered the primary source of wind direction,
velocity, and altimeter data for weather observation purposes at those
locations that are so equipped. The ASOS Operator Interface Device (OID)
displays the magnetic wind as "MAG WND" in the auxiliary data location in
the lower left-hand portion of the screen. Other OID displayed winds are
true and are not to be used for operational purposes.
b. The ceiling/sky condition, visibility, and obstructions to vision may
be omitted if the ceiling is above 5,000 feet and the visibility is more
than 5 miles.
EXAMPLE-
A remark may be made, "The weather is better than five thousand and five."
c. Instrument/visual approach/s in use. Specify landing runway/s unless
the runway is that to which the instrument approach is made.
d. Departure runway/s (to be given only if different from landing runway/s
or in the instance of a "departure only" ATIS).
e. Taxiway closures which affect the entrance or exit of active runways,
other closures which impact airport operations, other NOTAM's and PIREP's
pertinent to operations in the terminal area. Inform pilots of where
hazardous weather is occurring and how the information may be obtained.
Include available information of known bird activity.
REFERENCE-
FAAO 7110.65, Bird Activity Information, Para 2-1-22.
f. Runway braking action or friction reports when provided. Include the
time of the report and a word describing the cause of the runway friction
problem.
PHRASEOLOGY-
RUNWAY (number) MU (first value, second value, third value) AT (time),
(cause).
EXAMPLE-
"Runway Two Seven, MU forty-two, forty-one, twenty-eight at one zero one
eight Zulu, ice."
REFERENCE-
FAAO 7110.65, Braking Action Advisories, Para 3-3-5.
g. Other optional information as local conditions dictate in coordination
with ATC. This may include such items as VFR arrival frequencies, temporary
airport conditions, LAHSO operations being conducted, or other perishable
items that may appear only for a matter of hours or a few days on the ATIS
message.
h. Low level wind shear (LLWS) when reported by pilots or is detected on a
low level wind shear alert system (LLWAS).
REFERENCE-
FAAO 7110.65, Low Level Wind Shear Advisories, Para 3-1-8
i. A statement which advises the pilot to read back instructions to hold
short of a runway. The air traffic manager may elect to remove this
requirement 60 days after implementation provided that removing the
statement from the ATIS does not result in increased requests from aircraft
for read back of hold short instructions.
j. Instructions for the pilot to acknowledge receipt of the ATIS message
by informing the controller on initial contact.
EXAMPLE-
"Boston Tower Information Delta. One four zero zero Zulu. Wind two five zero
at one zero. Visibility one zero. Ceiling four thousand five hundred broken.
Temperature three four. Dew point two eight. Altimeter three zero one zero.
ILS-DME Runway Two Seven Approach in use. Departing Runway Two Two Right.
Hazardous Weather Information for (geographical area) available on HIWAS,
Flight Watch, or Flight Service Frequencies. Advise on initial contact you
have Delta."
John Clonts
>
> "John Clonts" <jcl...@hot.rr.com> wrote in message
> news:ktNs8.27836$ud6.1...@typhoon.austin.rr.com...
> >
> > METAR is described by Federal Meteorological Handbook No. 1, and
> > there is no provision therein for reporting wind other than with respect
> > to true north.
> >
>
> Are you saying wind is never reported other than with respect to true
north
> in the US?
>
No. But the fact that it is re-reported in various ways does not make the
AIM wrong.
Cheers,
John
Steven P. McNicoll
>
> No. But the fact that it is re-reported in various ways does not make the
> AIM wrong.
>
Why not? If the AIM says one thing, but something else is regularly done,
how is the AIM not wrong?
AJ
FAAO 7900.5B paragraph 8.4 outlines when the winds will be issued as true or
magnetic, i.e. local dissemination, long-line, etc.
The ASOS handbook states the wind is referenced to true North, though there
is a block on the ASOS screen that has mag winds rounded to the nearest 10
degrees.
oneatcer
>
>
>
Julian Scarfe
> Or are you saying that when the wind is reported in magnetic the report
> ceases to be METAR?
> Here's an excerpt from another federal publication that differs those
positions,
> see the Note in AIM 7-1-12.d.3.
I can't see anything in what you quote that displays a difference. The word
"METAR" appears 5 times and at no point does it say that what is broadcast
is a "METAR". A METAR is a WMO standard code form, and there is no
provision for reporting winds with magnetic directions.
It specifically provides for an ASOS to produce METARS "and other aviation
weather information".
[clipped for brevity, but you can refer to the full text in the original
message]
> Aeronautical Information Manual
> Official Guide to Basic Flight Information and ATC Procedures
>
> Chapter 7. Safety of Flight
>
> Section 1. Meteorology
>
> 7-1-12. Weather Observing Programs
>
> d. Automated Surface Observing System (ASOS). The ASOS is the primary
> surface weather observing system of the U.S. (See Key to Decode an ASOS
> (METAR) Observation, FIG 7-1-7 and FIG 7-1-8.)
...
> ASOS is designed to support aviation
> operations and weather forecast activities. The ASOS will provide
continuous
> minute-by-minute observations and perform the basic observing functions
> necessary to generate an aviation routine weather report (METAR) and other
> aviation weather information. The information may be transmitted over a
> discrete VHF radio frequency or the voice portion of a local NAVAID.
...
> NOTE-
> Wind direction broadcast over FAA radios is in reference to magnetic
north.
...
> 4. An ASOS/AWOS report without human intervention will contain only
that
> weather data capable of being reported automatically. The modifier for
this
> METAR report is "AUTO." When an observer augments or backs-up an ASOS/AWOS
> site, the "AUTO" modifier disappears.
...
> REFERENCE-
> A complete explanation of METAR terminology is located in AIM, Paragraph
> 7-1-30, Key to Aerodrome Forecast (TAF) and Aviation Routine Weather
Report
> (METAR).
...
> NOTE-
> ASOS/AWOS is to be considered the primary source of wind direction,
> velocity, and altimeter data for weather observation purposes at those
> locations that are so equipped. The ASOS Operator Interface Device (OID)
> displays the magnetic wind as "MAG WND" in the auxiliary data location in
> the lower left-hand portion of the screen. Other OID displayed winds are
> true and are not to be used for operational purposes.
Julian Scarfe
Steven P. McNicoll
"Julian Scarfe" <jul...@avbrief.com> wrote in message
news:COat8.4680$tZ1.1...@news2-win.server.ntlworld.com...
>
> I can't see anything in what you quote that displays a difference. The
> word "METAR" appears 5 times and at no point does it say that what is
broadcast
> is a "METAR". A METAR is a WMO standard code form, and there is no
> provision for reporting winds with magnetic directions.
>
While it doesn't say outright that it's a METAR observation the description
leaves no doubt that that's what it is.
Julian Scarfe
> news:COat8.4680$tZ1.1...@news2-win.server.ntlworld.com...
> >
> > I can't see anything in what you quote that displays a difference. The
> > word "METAR" appears 5 times and at no point does it say that what is
> broadcast
> > is a "METAR". A METAR is a WMO standard code form, and there is no
> > provision for reporting winds with magnetic directions.
"Steven P. McNicoll" <ronca...@writeme.com> wrote in message
news:ubbal7g...@corp.supernews.com...
>
> While it doesn't say outright that it's a METAR observation the
description
> leaves no doubt that that's what it is.
But Steve, this is Usenet! There's always room for a little doubt. :-)
Julian