Using QNH from a phone-in AWS

[Agent86]

I know the subject of "approved source of QNH" has been done before here (Yes i DID use the search function!)
A number of airfields have AWS listed with an associated phone number that you call to receive the info.
Simple if you pair up your Bluetooth headset to your phone (Telstra of course) and call it up.

Not so simple if you : are a bit busy/ don't have Telstra/ have been told to STOP SEXTING AND TURN OFF THAT PHONE! :p

So now your trusty ground handling agent who you can talk to on the company frequency is NOT an approved MET observer.

However he can call a phone number and repeat the words he hears. This is something a primary school student can manage and if a parrot could dial a phone Polly could do it as well.

Can this then be used as an approved QNH source?

Note that AIP ENR 1.5 P34 Para 5.3.2 lists approved sources as
"ATC,ATIS,AWIS and CASA-approved meteorological observers".

and AIP GEN 3.5 P22 Para 7.4.5 states "The integrity of the barometric system in BOM-accepted AWSs is such that they are an approved source of QNH"

My take on it is:
How you get that AWS weather may be by radio/ACARS/telephone/parrot. It is the SOURCE that is approved.

What is the considered opinion of the "experts" here on pPrune?

[Altimeters]

Yep that's exactly what we used to do in the outback. Sometimes if the ground agent didn't want to tell us the weather, he/she would simply put the radio mic over the phone so we could hear.

[YPJT]

I had this discussion with a guy from BoM recently. His advice was that if you are relaying direct from an AWIB or METAR then that is acceptable. However a person who is not an approved observer cannot relay information that is obtained by interpreting weather instruments.

Of even greater concern is the proliferation of off the shelf (read not approved) systems that are being used at some locations.

[alphacentauri]

YPJT
Of even greater concern is the proliferation of off the shelf (read not approved) systems that are being used at some locations.

Not disputing what you are saying, but there is one other company that has CAR120 approval to provide MET services other than the BOM. They are Vaisala, and they have installed their systems at some locations around WA. Primarily mining sites I think. With the approval they have the ability to tap into the TAF system and transmit on AWIS/AWIB or ph.

Be interested to know which locations you are referring to

Alpha

[Mach E Avelli]

Setting aside 'expert opinion' and legality, and being 'practical' for a moment, I do ponder whether the rest of the real world is so anal about such matters.

Assuming you have looked at the synoptic chart for the day (knowing how to read it helps!) and have a valid forecast with area QNH and TAF QNH, you should have a reasonable idea of QNH. By whatever means (phone, radio, PIDOOMA) you dial in a QNH for landing. It turns out to be 3mb in error. If it is more than 3mb, maybe you need to go back to school and study meteorology. Or you are flying a Global Jet to the far side of the world.
Even compounded with an allowable 60ft aircraft altimeter error, worst case could have you 150ft low on an approach. Are there any non-precision approaches out there where such an error would cause impact with obstacles? Granted, it would not be a pretty sight on a Cat I ILS to be 150ft low at DH, but it is highly unlikely that you would ever encounter a non-approved QNH source at an ILS-equipped airport anyway. And if you didn't do your glideslope altimeter check you were a naughty boy. Ditto on GNSS approaches - there are plenty of opportunities to correct for altimeter error before you get too close to the dirt.

Plus, there is always the option to add 100ft to your minima if you are uncertain about the accuracy of QNH. Then you could still be 50ft low, but if you crash in that situation, it certainly wasn't the QNH that was your undoing.

Just don't have this conversation with an examiner on an I.R. renewal, because we all know how they love their approved QNH sources.

[YPJT]

alphacentauri, Yes I am fully aware of the Visala system and have actually used it. I believe it was whilst being run through the various screen displays on that actual type that the BoM guy spoke about passing on the information.

I have been to other smaller sites where a system that you would buy off the shelf and meets no approvals from BoM or anyone else for that matter was being used. :ugh:

Interestingly looks like the Bureau is also going to get back into supplying and installing the systems on a commercial basis.

[Mach E Avelli]

I would certainly have more faith in a good automated QNH system (or a forecast or my PIDOOMA) than one run by an untrained observer. Whether or not CASA had given its seal of approval.

Several years ago a B737 crew had a lucky escape on approach at Honiara. It was summer and for some reason they understood the QNH to be an impossibly high value for that time of year. They read it back to the controller, and set on their altimeters, something like 1024 when the QNH was more like 1004.

Lucky for them they got visual early enough to avoid the ground, because with the aircraft in landing configuration the EGPWS was not going to save them.

Even allowing for some language difficulty or possible controller finger trouble, that crew demonstrated a woeful lack of understanding of tropical meteorology.

[Capn Bloggs]

My take on it is:
How you get that AWS weather may be by radio/ACARS/telephone/parrot. It is the SOURCE that is approved.

Mine too. CASA knows the checkout chick passes the QNH; if it didn't like it, it'd change the rules. As Mach said:

Assuming you have looked at the synoptic chart for the day (knowing how to read it helps!) and have a valid forecast with area QNH and TAF QNH, you should have a reasonable idea of QNH.
compare what she says with the TAF just to make sure she got it right.

Not so simple if you : are a bit busy/ don't have Telstra/ have been told to STOP SEXTING
No longer relevant with your looks and age! :}

[Sunfish]

For VFR , isn't there a declared qnh table in Ersa?

Then of course my Casio watch has an inbuilt baro. Then my garmin gives its version of altitude above the geoid.

[Lasiorhinus]

For VFR , isn't there a declared qnh table in Ersa?


No, but for both VFR and IFR, there is a declared density table in the CAO.

The MSLP chart will tell you the close-enough QNH day-to-day.

[MyNameIsIs]

I have recently asked an FOI about QNHs- shaded boxes, approved sources, accurate qnh, alternates and minimas etc etc.

One of his remarks was that receiving QNH from an AWS (which is approved) via phone is fine and you can use it for accurate qnh (remember within 15 mins blah blah blah).
Thinking logically (:}) what's the difference between getting the AWS weather via radio or via phone? Nada. Your company might have a policy on pilots using phones in flight though.


Now, having someone on the phone listening to the automated service and then advising you over the radio, there are likely going to be differing opinions.
Some could be picky down to the finest detail and say that you are technically not being advised about the QNH from an approved source because your are actually being told by someone who may not be an approved observer (albeit their info is coming from an approved source).
Is it unsafe and going to result in tea and bikkies or a trial though? Probably not.