Hectopascals
Do Yanks still really get confused by QNH settings less than 1000 mb? Really? I only few outside the US for 28 years so maybe a bit shocked.
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Given the spread of units used in aviation, 'millibars' make sense. I Bar = 1 Atmosphere.
Change for the sake of it, driven by The EU........And an extra syllable to-boot.
Change for the sake of it, driven by The EU........And an extra syllable to-boot.
@ Galaxy Flyer
Certainly when the US military started operating from Prestwick during the Kosovo conflict, we were very careful about readbacks of altimeter settings. Right up until I retired 4 years ago, there was still the very occasional prompt needed with C130 crews. My suspicion is that possibly, being ANG , they were more used to flying domestically in the USA - or maybe it was just habit ?
Do Yanks still really get confused by QNH settings less than 1000 mb? Really? I only few outside the US for 28 years so maybe a bit shocked.
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The unit added on to the number is immaterial. If a US crew were going to set inches, would it Hectopascal, rather than 'millibar' or 'smarties' really have saved the day?
If you would give links to airporox reports where this has occurred I'd be pleased to reconsider.
The unit added on to the number is immaterial. If a US crew were going to set inches, would it Hectopascal, rather than 'millibar' or 'smarties' really have saved the day?
The unit added on to the number is immaterial. If a US crew were going to set inches, would it Hectopascal, rather than 'millibar' or 'smarties' really have saved the day?
I was on the Phraseology Committee where it was discussed and it was a bone of contention for several other members who didn't want to add the word hectopascals in the same way we had been required to add millibars on the grounds no other country did it.
Last edited by chevvron; 14th Sep 2017 at 05:38.
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If you would give links to airporox reports where this has occurred I'd be pleased to reconsider.
The unit added on to the number is immaterial. If a US crew were going to set inches, would it Hectopascal, rather than 'millibar' or 'smarties' really have saved the day?
The unit added on to the number is immaterial. If a US crew were going to set inches, would it Hectopascal, rather than 'millibar' or 'smarties' really have saved the day?
Yes, adding the unit following the value certainly has saved level busts.
I was on the Phraseology Committee where it was discussed and it was a bone of contention for several other members who didn't want to add the word hectopascals in the same way we had been required to add millibars on the grounds no other country did it.
2 s
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Chevron, your last post opens up a new discussion topic. Why should we not know the names of the unelected few who rule our industry? As far as I'm aware, all other government departments are open.
I've already had a slap on the wrist for revealing things about the PWG (in this case the 'change' from Class F to Class E airspace) so I'm not doing it again.
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The 'unelected few who rule the industry' come from a variety of aviation related organisations including airlines, civil ANSPs (not just you know who), MOD, GA and the CAA. They receive briefing papers on the subjects to be discussed ahead of the meeting and you'd hope that they might discuss the issues with their peers. That said, they attend the PWG as themselves, not to represent their organisations.
In relation to the topic of conversation, agree that the unit used is immaterial (millibars or hectopascals) but there continues to be a fairly valid reason for its inclusion and it's not just to mitigate against the acts of our colonial cousins. It's something that has been seen in a number of international carriers; albeit infrequently. That said, there have been occurrences where a controller has persevered with obtaining a full readback of the QNH value and the units and the pilot has still set the QNH in inches of mercury
In previous years I'd mention something about Darwin at this point but I've been trying to act more responsibly
The problem that you have is that we don't gather any evidence to demonstrate how often this has proved effective in preventing a level bust. In order for the CAA to remove the requirement to state the units they'd need to produce a solid safety argument that it was no longer required and I don't think that it would be possible to demonstrate an equivalent level of safety given the absence of evidence. Maybe with enhanced Mode S with reliable barometric pressure setting downlinks so that ATS could identify incorrect altimeter settings but the BPS reliability isn't quite there yet.
In relation to the topic of conversation, agree that the unit used is immaterial (millibars or hectopascals) but there continues to be a fairly valid reason for its inclusion and it's not just to mitigate against the acts of our colonial cousins. It's something that has been seen in a number of international carriers; albeit infrequently. That said, there have been occurrences where a controller has persevered with obtaining a full readback of the QNH value and the units and the pilot has still set the QNH in inches of mercury
In previous years I'd mention something about Darwin at this point but I've been trying to act more responsibly
The problem that you have is that we don't gather any evidence to demonstrate how often this has proved effective in preventing a level bust. In order for the CAA to remove the requirement to state the units they'd need to produce a solid safety argument that it was no longer required and I don't think that it would be possible to demonstrate an equivalent level of safety given the absence of evidence. Maybe with enhanced Mode S with reliable barometric pressure setting downlinks so that ATS could identify incorrect altimeter settings but the BPS reliability isn't quite there yet.
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I'm very surprised that as The Fat Controller points out, hPa is omitted on Scottish VOLMET. I would imagine that a fair proportion of the Scottish airfield METARS include pressure values of less than 1000.