New Transition Altitude UK & Ireland

[2 sheds]

Another four for both parties

Not to mention the "to.." and "...feet" !

2 s

[Sir Herbert Gussett]

And hectoPascals if the CAA get their way

[chevvron]

It is proposed that 'hectopascals' will replace 'millibars' in Nov 2011. An AIC will be issued shortly.

[Piltdown Man]

...even more words than I thought.

PM

[Roffa]

Somehow the Americans manage, unless we believe our own publicity that we are somehow busier and so just won't be able to cope...

You only need to pass the QNH to an aircraft on first descent from FL to ALT, you do not need to add it to every further descent clearance thereafter.

Piltdown Man,

Does Mode S pass an aircraft's current altimeter subscale setting?

Yes, TC can see it and there is already a warning tool in use with LHR approach that will, within certain parameters, warn ATC if an a/c is descending from flight levels to altitudes on the wrong pressure setting. It works very well and I'm sure will be rolled out further in due course.

[Data Dad]

Ok, with a TA of 18000ft there are going to be a lot of turboprops plying their routes round Scotland on QNH. But which QNH? This part of the world can see some pretty steep pressure gradients when deep lows trundle by. A Saab 340 operating its schedule from Edinburgh - Sumburgh at 16000ft can easily find a 10 or more millibar(Hpa) difference between the two and that doesn't take into account that they overfly Aberdeen where the pressure will be different from either the origin or destination. Will they have to reset altimeter approaching Aberdeen (bearing in mind that they will be mixing with Aberdeen departures/arrivals who will be on Aberdeen QNH)? Or (as someone mentioned earlier) will Regional Pressures come more into play? If so the constant resetting of altimeters in the cruise would be a real PITA - and kind of defeats the object imho.

DD

[Roffa]

Dad, given that in the continent that is North America sees odd bit of severe weather causing a pressure gradient (you know, weather that causes tornados, tropical storms, that sort of thing) yet they manage to cope I'm sure we'll be able to figure out something as well.

I just don't get all the negativity to this long overdue change.

[Crazy Voyager]

I'm not going to say what I want to see happen, I don't have enough insight in the subject to comment on it.

How ever I'd be intrested to know how a similar problem to the one Data Dad described is handled in the US (because I'm sure it happens), does anyone know?

[throw a dyce]

You raise the levels that an Approach unit would talk to traffic.The example that DD talked about would mean that Aberdeen could control say up to FL195 and overflights at altitude 16 thousand feet would have to talk to Aberdeen.
The airspace below FL195 would become more of a Terminal area,under the control of approach units.It would certainly cause a unit like Aberdeen some issues about pay etc,and not having the staff to take on the role.
Then again leave the system as it is,and you could have different units(Approach and Area)applying vertical separation,with the possibility of different QNHs being used.Now that's not exactly safe.

[bad bear]

I know its the controller's section of PPRUNE, but as a pilot I would rather have to change QNH in the cruise or early descent when my work load is at its lowest. People always quote the day when a pressure change is 10 mb over 200nm but fail to quantify that it only happens on 35 days of the year, the rest of the time it is much less. The majority of long sectors are flown above 20,000' and it would be a mistake to design the UK air traffic sysyem around the 3 flights a day that route from EDI to LSI. The vast majoity of flights will still be cruising on STD. Of the few flights that dont, they will still take of on one QNH then land on another QNH. The only difference is they will use an intermediate QNH for cruise rather than STD. On a high pressure stable day there might be no altimter changes..... but that would also only be 35 day per year .

What is a problem is having pilots changing from STD to QNH while changing frequency at around 6,000' and the work load is at its greatest.

This excellent proposal will remove a very old but dangerous procedure. Many altitude busts have occurred because of the low TA. The much slated GA pilots will no longer be challenged by lower airspace that could be a FL or altitude with no rhyme or reason as to which it is. This could lead to fewer airspace busts.
Airspace planning will no longer have to stop outbounds at 6,000' for fear of clearing a dim and retarded pilot to climb to a Flight Level with the risk they might forget to change to STD. This will save fuel, reduce noise, increase safety through reduced workload in the cockpit and release airspace/ create more airspace for other airports traffic.
I would prefer to see 24,000' but am equally happy with 18,000'.
As a pilot I can see no down side and found it worked well in the USA in busy airspace.
bb

[mrmum]

I agree with bad bear. As a pilot who flies a fair bit IFR OCAS in the UK, I've always thought the 3000' TA was far too low and caused unnecessary problems.
I'd like to see it at an altitude that most light GA didn't have to bother with it, something like 10,000' would be fine, because as has been said already, other things also change there. Alternatively, how about 19,500', can't really see why 18,000' is being suggested, I understand why it's there in the US but not the UK.

[Surferboy]

I'd rather not lose 1 or 2 levels in my hold when the **** hits the fan, because if it does, we (intermediate ACC/Terminal) get the beating, not the APP sector. And when we do get that ****load of traffic, we need all the room we've got.

Yes, it works in the US. But we are not in the US, so why try to be like them? We don't have the room they have to solve problems!

[Roffa]

We don't have the room they have to solve problems!

Correct me if I'm wrong but isn't this TA change going to make it a common TA across Europe, part of the SESAR programme.

Hopefully at some point in the not tooooooo distant future European ATM will be far more joined up and work much more akin to the American system, and not before time. We need to move away from our parochial thinking.

We could "have the room they have to solve problems" if only there was the will to do so.

[Surferboy]

Ofcourse, but why not implement it after (or simultanously) we have got that bit sorted out?

[Not Long Now]

Don't quite see how a higher TA will create more space between LL, KK, SS, GW, KB, LC, LF and HI.

[Roffa]

Don't quite see how a higher TA will create more space between LL, KK, SS, GW, KB, LC, LF and HI.

It will no doubt just be part of better organised airspace and systems.

Ye gads what a negative bunch.

[Data Dad]

Ye gads what a negative bunch.

Roffa, I am not against raising it at all BUT 18000ft (as suggested) seems excessive for a country where the highest terrain is around 4500ft.

Whilst I agree the majority of airline flights would still be on 1013, up here in Scotland an awful lot wouldn't be - a large number of Aberdeen arrivals and departures are to less than 18000ft and you then have problems with aircraft on varying QNH's (The quadrantal rule could become interesting!) Personally I think 10000ft should be plenty to remove the GA weekend pilot problem.

Making it higher than 10000ft potentially re-introduces the proven Level-Bust problem of the brain misinterpreting/getting confused by one-zero tousand and one-one tousand, a problem largely solved with flight level one hundred.

If its all about a single-europe, then I would much rather see 'Cleared ILS' happen first

DD

[Mister Geezer]

Making it higher than 10000ft potentially re-introduces the proven Level-Bust problem of the brain misinterpreting/getting confused by one-zero tousand and one-one tousand, a problem largely solved with flight level one hundred.

A valid point, however will making the TA higher than 6000 but equal to or less than 10000ft, affect the efficiency and capacity of the holds in the London TMA?

[10W]

I'm not averse to the change, but how does it work in practice in the US ?

Let's say you are flying on Airways over a 600NM leg. You obviously have the departure airfield QNH set first, but what then ? Do en-route ATC give you a regional setting ? Are the 'regions' defined (similar to the UK Regional Pressure Setting regions) ?

If not, do you stay on the possibly subsequently innaccurate QNH until you change to the arrival airfield one on initial approach ? How do ATC cope with aircraft on a Heathrow QNH for example who then interracts with one further up the line who is on the Manchester QNH and another on the Belfast QNH and another on the Copenhagen QNH ?

I'd just like to know how the mechanics work in the US and what the workload and RT loading is ... as well as the possible different datums being used and who works out what is separated and what is not.

Sumburgh QNH today is 982 and Heathrow is 1016. That's 1000' difference near enough. Somewhere along the way, it could go horribly wrong unless the procedures are robust enough to ensure that datum differences are addressed. I'd be interested to hear the US solution.

[anotherthing]

Therein lies the nub of the question - does it work in the US because it has so much airspace, much of it wide open and (compared to Europe, particularly the UK) relatively uncongested?