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QNH 999 hPa?

Old 21st Oct 2019, 20:39
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QNH 999 hPa?

Hi all,

We have a discussion at our unit and I cannot find the right answer in any doc. If the local QNH is lower than 1000 hPa, is it mandatory to add hPa in all your calls? Someone says yes and someone says no but I cannot find the right source.

Many thanks in advance!
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Old 21st Oct 2019, 21:13
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I was guilty of saying "millibars" after any pressure setting. If you do that you can't go wrong!
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Old 21st Oct 2019, 21:32
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To my knowledge PANS ATM does not mandate the inclusion of the unit being used in the RTF message.......

Words in square parentheses indicate optional additional words or information that may be necessary in specific instances.
RUNWAY (number), WIND (direction and speed) (units) QNH (or QFE) (number) [(units)]
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Old 21st Oct 2019, 21:39
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The UK answer is MATS1 Section 1 Chapter 7 Paragraph 6.2 “When transmitting altimeter pressure settings that are lower than 1000 hPa, controllers are to specify clearly the unit of measurement and pay particular attention to the read- back.”
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Old 21st Oct 2019, 21:41
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Only really relevant for the UK but a lot of airlines use it as reference.

From CAP414 Radiotelephony Manual ed 22
3.9
NOTES: 1 Use of the word ‘hectopascal’ for pressures lower than 1000
Appreciate it may not be pertinent to you, but there it is in a manual.
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Old 21st Oct 2019, 23:11
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I was at the UK Phraseology Working Group (UKPWG) meeting where this was discussed along with the change from millibars to hectopascals, the UK always having required the units to be transmitted after the pressure setting when less than 1000 in order to differentiate between mb/hPa and the 'abbreviated 'inches (of mercury), the thinking behind it being that 'QNH 992' transmitted to a crew from a country where inches was used might be misinterpreted as '9.92 inches (or actually 29.92 inches) I presume this must have arisen as a result of an incident sometrime in the past when someone actually did this..
There happened to guest from the IAA (Irish Aviation Authority) and he was asked what they did in Ireland, replying that the use of mb/hpa was not required in Ireland.

Last edited by chevvron; 22nd Oct 2019 at 00:59.
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Old 21st Oct 2019, 23:21
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Also, within CAP413 Radiotelephony Manual, 2.69 - hectopascals is a mandatory read back item when units are below 1000.
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Old 22nd Oct 2019, 00:58
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Originally Posted by Scrotchidson View Post
Also, within CAP413 Radiotelephony Manual, 2.69 - hectopascals is a mandatory read back item when units are below 1000.
The main aim of the UKPWG is to edit CAP413.
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Old 22nd Oct 2019, 04:13
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Originally Posted by HEATHROW DIRECTOR View Post
I was guilty of saying "millibars" after any pressure setting. If you do that you can't go wrong!
Please don’t follow this, it is incorrect.
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Old 22nd Oct 2019, 05:34
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I know an airfield whose ATIS (spoken by an assistant, not automatic) says 'hectopascals' irrespective of whether the pressure setting is over or under 1,000 hPa; is this incorrect?
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Old 22nd Oct 2019, 05:56
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Folks,

The OP is in The Netherlands.

MATS Part 1/CAP413 doesn’t apply.

....and it’s not ‘incorrect’ to add the word ’hectopascals’ after any pressure setting, just as it’s not incorrect to add degrees after any heading, or metres after any RVR.
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Old 22nd Oct 2019, 06:08
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Originally Posted by chevvron View Post
I know an airfield whose ATIS (spoken by an assistant, not automatic) says 'hectopascals' irrespective of whether the pressure setting is over or under 1,000 hPa; is this incorrect?
No it’s not incorrect, because it says hectopascals.
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Old 22nd Oct 2019, 06:10
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Originally Posted by Gonzo View Post
Folks,

The OP is in The Netherlands.

MATS Part 1/CAP413 doesn’t apply.

....and it’s not ‘incorrect’ to add the word ’hectopascals’ after any pressure setting, just as it’s not incorrect to add degrees after any heading, or metres after any RVR.
But it would be incorrect to say millibars after every pressure, because it is incorrect.
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Old 22nd Oct 2019, 06:20
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On that note, yes, but HD is referring to the time in the UK before we used hPa.
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Old 22nd Oct 2019, 08:57
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Originally Posted by Gonzo View Post
On that note, yes, but HD is referring to the time in the UK before we used hPa.
Well hopefully anyone reading the post will be a better mind reader than me.
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Old 22nd Oct 2019, 11:52
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Originally Posted by chevvron View Post
I presume this must have arisen as a result of an incident sometrime in the past when someone actually did this.
Pan Am 707, Calcutta (as was), 1968.

And probably others.
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Old 22nd Oct 2019, 14:08
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Thanks all! So just to confirm, this is a UK rule and no ICAO standard? And we are indeed Schiphol operators .
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Old 22nd Oct 2019, 16:01
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Originally Posted by Rwy1234 View Post
Well hopefully anyone reading the post will be a better mind reader than me.
Or just read the bit where HD said ‘I was...’ rather than ‘I do/I am.....’



If we’d have addressed the original question, rather than all confusing matters with UK-specific answers, that would have been best.
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Old 22nd Oct 2019, 18:06
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Originally Posted by Gonzo View Post


Or just read the bit where HD said ‘I was...’ rather than ‘I do/I am.....


Originally Posted by HEATHROW DIRECTOR View Post
If you do that you can't go wrong!

If you do that you can't go wrong!“ Pretty easy to misunderstand, probably best not to post at all regarding how you used to do things if they might not be relevant today?

Originally Posted by Gonzo View Post
If we’d have addressed the original question, rather than all confusing matters with UK-specific answers, that would have been best.
True, many of these UK specific variations probably create more questions than they answer.
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Old 22nd Oct 2019, 18:19
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Originally Posted by Gonzo View Post
Or just read the bit where HD said ‘I was...’ rather than ‘I do/I am.....’
You may know that poster or their history, I don’t, I was referring to

Originally Posted by Heathrow Director
If you do that you can’t go wrong!
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