Hectopascals
 

I've just noticed the word hectopascals being added to radio transmissions recently. Previously the controller would just say QHN 1011 and we all knew what he/she meant. This was all much tidier and led to shorter radio transmissions.

Is there a reason for this change, can we go back to the old way of not defining the units for pressure? Or using the word millibar which was less lumpy to say.

We've been having to read this back for quite some years now. We're all Europeans now.

(Except them 'Murricans, one of whom apparently didn't know that you're not supposed to set part of a European/metric setting on the inches subscale and subsequently frightened himself).

Some ATCOs are now totally unneccessary about it. How we managed in years gone by, no-one knows!

You are only required to add hectopascal if the pressure is below 1000.

Usually just used when pressure is below 1000.

"hectopascals" is a non-optional suffix for less than 1000 hPa, but I tend to add it for higher pressures if the accent or airline would suggest regular North American operations. Probably a bad habit.

Could we raise a petition to bring back millibars?

It is a requirement to pass it when the pressure is below 1000 hpa. It is also a mandatory readback.

If it's any consolation, I can speak for the majority of atcos at my unit, we hate having to say it too. And more so when we insist it's readback. However, that's the rules. CAP413 refers.

So the Hpa thing is to stop the umbrellastands reading QNH 992 as 29.92 inches? I think i'm beginning to understand..Thanks!

And the rule about it only being read out when its less than 1000 would account for why I seldom hear it, only flying on beautiful high pressure days...

Yes lets bring back Mb.

Correct! :ok:

I, and I think most other controllers/FISOs/pilots would agree, but unfortunately some ******** at ICAO thinks otherwise.

Why on earth would we (re-)introduce new phraseology that would only be used in the UK? Are we looking to become even more non-standard than we are already?

I'm sure Russian ATC would love to have remained using metres as the unit of level, and US ATC to have remained using 'position and hold' rather than 'line up and wait'.

Is it really that bad? We should be looking at more standardisation across the world, not less.

I agree on the standardisation issue, Gonzo ; but weren't we standardised on millibars before the powers that be decided to replace that with hectopascals (which are exactly the same values as MBs !)

I'd suggest that 99.9% of aircraft operatig over Europe and surrounds ARE NOT flying on the inches subscale and are using millabars/hectopastels day-in, day-out, year-in, year-out nay decade-in, decade-out. The 'confusion' thereby necessitating this needless waste of breath only exists in the minds of yet another ground-based 'safety' committee.

Could be one of the few positives to emerge from Brexit. :O

It could be much worse.

Imagine if, instead of Pascal, the early pressure research had been carried out by by Boyle, or Gay Lussac.

Bring back Millibars and OKTAs. The Wx was much better and the summers were much warmer when we used those babies.

Jest as an aside..

The ISO discourages the use of hecto, centi, deci etc.

After an excellent landing etc...

Mmmmm - QNH 101300 Pascal. Yup, so much easier.

How 'bout Kilo?

Yes, let's ignore the level busts and near-level busts caused by N. American-based crews hearing 992(mb/hpa) and entering 29.92(in) (or similar), let alone the many every U.K. controller has caught at the readback stage.

Ah I miss OKTAs. Better than Frank Sucks Big Ones. It will never leave me , nor any of my students. and yes the weather was better....

It was introduced in 2011.
Was awkward for a couple of days and then business as usual.

Shows the adaptability to change of some in this profession ;) ;) ;)

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.

GF

Still keep saying hectopastels for some reason. Don't think they notice though.

The only reason we have to say hectopascals is because they couldn't think of a word with any more f#@king syllables.

Maybe at your unit but you must be in a minority; I still hear people say 'millibars'.

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.

@ 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 ?

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?

If the CAA say you gotta do it, then you gotta do it.
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.

? Who said anything about airprox? You don't think level busts, or potential level busts, are serious in and of themselves?

Yes, adding the unit following the value certainly has saved level busts.

Perhaps those members of the PWG should be replaced on grounds of inadequate powers of logic and being Bears of Very Little Brain.

2 s

I'd like to tell you who it was but I can't.

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.

Somebody forgot to ask the VOLMET lady to record hectopascals.
On the Scottish version, they are not added when the QNH drops to 999 or below.

Maybe the pilots entering Scottish airspace from overseas are better trained with regard to altimetry....

WE were slow to change - hectopascals in use in Pakistan in the 90s.

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 :ugh:

In previous years I'd mention something about Darwin at this point but I've been trying to act more responsibly :cool:

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.

Alternatively, if there were a move for ICAO to standardise the units worldwide and phase out inches of mercury...

2 s

What annoys me is aircraft that have their tyre pressures quoted in MPa when my pressure gauge is marked in Bar and psi! (Multiply by 10 to get bar.)

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.