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New Transition Altitude UK & Ireland

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New Transition Altitude UK & Ireland

Old 4th Feb 2011, 10:46
  #41 (permalink)  
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Australia has a transition layer between A100 and FL110.

To get over the tyrannies of distance the country is divided into areas here. There is a QNH published for each AREA every 4 hours, on days when there are variations such as a steep pressure front or system passing through an Area QNH may be divided such as North East of a line it's XXXX and south west of that XXYY etc.

The concept is that 5hpa is an acceptable variation. So if we get a terminal QNH more than 5hpa away from the Area QNH we must inform met who review it quickly...

The ATCs have maps on the consoles and often draw lines on screens where QNH divisions happen, when aircraft cross the lines you give them the new A/QNH... VFRs who aren't talking to ATC can operate on departure point or forecast QNH for X miles (I think it's 200) before needing a new A/QNH... They get the new one from an ATIS of a controlled aerodrome nearby, from ATC directly, or from the Area forecast.

No idea how the hold stacks work around here, in Oz most holding is done at high altitudes FL200+... Pretty rare to hold below A100 at the majors anyway.
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Old 4th Feb 2011, 11:04
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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) ?
10W, It would be rare for a 600nm leg to be flown below 18000'. the Longer legs would be above TA and we would be using FLs exactly as we do now.

I'd
rather not lose 1 or 2 levels in my hold when the shit hits the fan, because if it does, we (intermediate ACC/Terminal) get the beating, not the APP sector.
Currently Heathrow holding looses 70 and possibly 80 if the pressure does not allow separation from 6,000', hopefully this problem will be removed by a higher TA
One issue that would need to be looked at is the hold protected area which becomes larger with altitude and markedly bigger above 140 , this tends to discourage airspace designers from holding higher. Us pilots want to hold as high as possible to stay out of turbulence and save fuel and I hate sitting at 70 when the only plane in the hold.
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Old 4th Feb 2011, 17:23
  #43 (permalink)  
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10W, It would be rare for a 600nm leg to be flown below 18000'. the Longer legs would be above TA and we would be using FLs exactly as we do now.
My question wasn't 'How often would this happen ?'. It was asking how it is managed when it does, particularly in the US which obviously has a lot of experience of it.

Let's look at another scenario with a lot less than 600NM instead. Leeds to Edinburgh flights for example will initially maybe only get FL180 (and often stay there), or Glasgow to Manchester might ask for FL170 only. Level difference today between Oop North and Oop Further North is about 270 feet if you fly on the airfield QNH's. 270' plus 200' tolerance on each aircraft occupying the assigned altitude is 670' eating in to the expected 1000' separation. As it's part of my job to separate, I want to know how I am expected to do that when the transition altitude is now at a level where aircraft can regularly be encountered. Whether it happens every day or only 35 days a year, I need a safe procedure.

Currently Heathrow holding looses 70 and possibly 80 if the pressure does not allow separation from 6,000', hopefully this problem will be removed by a higher TA
I think the 'losing multiple levels' often quoted is a perception. The Minimum Stack Level is always going to be a Flight Level equivalent which gives at least 1000' separation from the Transition Altitude. In Heathrow's case, it's always going to be a minimum of 7000'. On some low pressure days, because the UK uses whole Flight Levels, then there will be a need to round up the Flight Level to the next one which gives the minimum separation. That can lose you a bit of airspace (up to but not exceeding 1000') and technically (or numerically) one level. But it will never be more than this. Some people think that when the Stack Level pushes up to FL90, then you are losing 2 Stack Levels. This is not the case since FL90 is no where near an actual altitude of 9000' on those days.

Thanks Blockla for an indication of how it is done in Oz. Makes some sense.
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Old 4th Feb 2011, 17:28
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Whatever the change becomes (as I guessing man, it will be 18,000ft), the UK will also then have to resectorise most of its airspace too. I wouldn't expect it to come in sometime soon due to the huge complexities that will have to be solved as a result (ie, no changes can be made to the Gatwick stacks if they are to stay in their current positions. Willo will have to move about 30nm if a change IS needed).

18,000ft is due to the Upper Airspace in Europe starting at FL195. It is uncommon to lose two FL's due to pressure, so it means that the base levels on UARs that have no associated Airway will be available most of the time. Thats the reasoning I was told anyway.
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Old 4th Feb 2011, 17:50
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Originally Posted by 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) ?
In the US, en-route IFR clearances within ATC sectors below transition will include the altimeter setting in use, eg 'route ALB-SAX as filed, maintain 14,000 Stuart altimeter 30.28'. Seems pretty simple, and effectively operates as a regional QNH. VFR traffic operating in the lower airspace have access to local altimeter setting info from Flight Service Stations (FSS), or, of course, from ATC.

As someone said earlier, the US system of 18,000'/Fl180 transition works well and avoids peak workload. The Australian system of 10,000/FL110 does not, and the current UK system is a mess. I would strongly vote for 18,000, and hope it comes into effect Europe-wide.
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Old 4th Feb 2011, 18:28
  #46 (permalink)  

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Currently I have no strong views either way, and am willing to be persuaded to either side.

From a level point of view though does it not make sense to use the same levels as other parts of Europe/the world where a significant number of our pilots come from or are trained?

I can see that there are advantages and disadvantages, we just need to make sure that all of these are put to the decision makers so that they can be weighed into the balance.

5MB - excuse my being thick but why would WILLO have to move 30 miles?

Cheers,
Northerner


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Old 4th Feb 2011, 18:30
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Northerner - since Willo was "built", HMG designated the ground underneath a National Park therefore any changes to the hold would require it to be moved outside the area!!!

Remember, I am only the messenger
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Old 4th Feb 2011, 18:32
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Didn't know that one... what a piece of genius...
Thanks 5MB.
Cheers,
N
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Old 5th Feb 2011, 10:11
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I think the 'losing multiple levels' often quoted is a perception. The Minimum Stack Level is always going to be a Flight Level equivalent which gives at least 1000' separation from the Transition Altitude. In Heathrow's case, it's always going to be a minimum of 7000'. On some low pressure days, because the UK uses whole Flight Levels, then there will be a need to round up the Flight Level to the next one which gives the minimum separation. That can lose you a bit of airspace (up to but not exceeding 1000') and technically (or numerically) one level. But it will never be more than this. Some people think that when the Stack Level pushes up to FL90, then you are losing 2 Stack Levels. This is not the case since FL90 is no where near an actual altitude of 9000' on those days.
Well, if for arguments sake the AMS FIR would have the same TA at 6000' and you have FL070 as the TL. In the AMS fir that would give me a holding capacity per stack of 18 aircraft (FL070 up to FL240). When the QNH drops and the TL goes up to lets say FL090 you lose FL070 and FL080. So that's a theoretical reduction in holding capacity of 8 in the AMS fir.

With normal traffic this wouldn't be a problem, normally there is no holding done and we stream everything from FIR-entry to the TMA-entry point. But when the Swiss cheeses align it could be detrimental. Had a situation last year where there was a Squall line passing AMS, and SPL-APP didn't accept any inbounds.

To cope with the inboundtraffic on the Eastsector we still got handed to us from Maastricht we had to Ad-hoc create not one but two non-standard holds because the normal ARTIP and NARSO were FULL up to FL240 (upper limit of our airspace). Have fun with that with even less holding capacity.

So therefor I would suggest to first go ahead and redesign all of Europe's Airspace, and then look at the most convenient Transition Altitude allocation. I really do understand the safety issues with having so many different TA's, but they are also there for a reason..
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Old 5th Feb 2011, 20:04
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Sounds like another case of folks in offices trying to justify their jobs.
'Hey, what can we change today?'.
Never found the workload in changing from 1013, to QNH (and then QFE) a problem. Going-around?, certainly sir, re-setting QNH. Piece of p*ss.
5 miles....
If a farmer in a National Park erects a new cattle-shed, does he/she have to inform the CAA?
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Old 5th Feb 2011, 22:10
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Zooker, probably not, but if NATS wants to change the colour of the trim in the hold, they have to consult with everyone across 2 continents....
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Old 8th Feb 2011, 09:27
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What's all the fuss about???

Having worked in two countries, and flown VFR & IFR in one of them, where the TA is 13000ft and TL is FL150 it seems that a number of the posts are making a bit of fuss out of nothing.

New Zealand and Oman are both about the same size and shape as the UK, so make good examples for comparsion. Both countries have sizeable mountains - in the 12-13000ft range.

Oman has fairly beign weather and very little traffic below the TL, consequently it's three QNH Areas/Zones are sufficient. Below the TL all aircraft were given the appropriate Zone QNH.

New Zealand on the other hand has significant low level activity, more than half the country is deemed mountainous terrain and the weather is not only changeable over a very short distance, but can be extreme. Here is how it works in NZ - http://www.aip.net.nz/pdf/_aENR_1.7.pdf - Note there are 12 QNH Zones.
Generally the Zone QNH is the reading from the major airport in that Zone, so the majority of IFR taffic have little need to change from airfield to zone and back again.
The major TMA's are contained in one zone - so all aircraft in that TMA will be on the same QNH.
When on a cross country (VFR or IFR) aircraft are provided with the appropriate Zone QNH prior to entry to that Zone. All VFR position reports are acknowledged with an update of the appropriate Zone QNH - this may include adjacent Zones.

Personally, I would think a low TA/TL around 5-7000 ft would be a pain, both for pilots and controllers. For the controller, when working an approach sequence, the loss of one or even two useful levels so close to the approach commencement level, must make for some wasted space. For the pilot, both on approach and departure, having to change the altimeter setting during high workload periods (fast climbing jets, complex STAR procedurs) must be distracting.

5miles - I'm confused by your statement that UK airspace would have to be resectorised.
If the QNH Zones are aligned to TMA boundaries, there shouldn't be any issues. I'm sure the one or two hPa difference between adjoining TMA's isn't going to be an issue. It works in NZ, and at this time of year there can be a 30+hPa difference over a distance of 50-80NM.
The only issue for Area sectors, will be having to issue different QNH settings as aircraft transit between QNH sectors.

10W - Hopefully the above has given you some insight as to how it all works in a country about the same size and shape as the UK. Everyone in the same bit of airspace gets to be on the same altimeter setting - it's not Rocket Science . Travelling 600NM on your departure aerodrome QNH is just a bit far fetched, and in NZ might result in meeting with some Cumulo-granite.
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Old 8th Feb 2011, 11:34
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zkjaws,
What distance do the approach units generally work out to in NZ.Also do they have access to all the airspace below Transition within their range.
The highest mountains in the UK are 4500ft,so the UK is a lot flatter than NZ.However we are bolted on to ''Europe'' for just about everything nowadays,which is the force that is probably driving this.
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Old 8th Feb 2011, 12:39
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10W - Hopefully the above has given you some insight as to how it all works in a country about the same size and shape as the UK. Everyone in the same bit of airspace gets to be on the same altimeter setting - it's not Rocket Science . Travelling 600NM on your departure aerodrome QNH is just a bit far fetched, and in NZ might result in meeting with some Cumulo-granite.
Thanks zkjaws. It looks a logical system. The problem with our CAA so far is that they have only said they are proposing a change, but haven't give any details about the level involved or provided a draft procedure so we can see that issues have been addressed (perhaps by adopting a system such as yours).

The only thing I would change from the NZ model is to maintain the UK altimeter setting procedure whereby aircraft above the Transition Altitude, who are cleared to an altitude, reset to QNH immediately and don't wait till the Transition Level as per the NZ procedure. In much the same way as late setting of 1013 with our UK low Transition Altitude can increase the chance of busting a level, I think your system could do the same on a low pressure day (not uncommon in the UK in winter, alas). Let's say you are cleared to ALT12000', with a pressure of 980HPa. In NZ, you will reset from 1013 to 980 as you pass FL150 (which is only 14,010). A little bit of lag as you change the setting, a not abnormal descent rate of 2000fpm, and whoops, there goes your cleared altitude of 12000' before you can stop the aircraft !!
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Old 8th Feb 2011, 16:35
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zkjaws, you answered your own questions!
If the QNH Zones are aligned to TMA boundaries, there shouldn't be any issues
That is the first problem that will need sorting out.
The only issue for Area sectors, will be having to issue different QNH settings as aircraft transit between QNH sectors.
Unfortunately not, there is also the issue of what the new TA will be, and if 18000ft is where its at, some sectors that are vertically split will lose half their levels when there is a low QNH (the majority of their sector is currently FL180-FL210, and they have standing agreements at FL180, FL190, FL200 and FL210 which all separate from each other). As the London TMA is quite a compact and complex piece of airspace, whatever the level is below 22000ft will mean rejigging which won't be a simple fix. You can give me almost any level, and I can give you a change that means lots of work.
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Old 8th Feb 2011, 18:06
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Answers

Throw a Dyce - NZ TMA's are generally out to about 40NM from the Major Airport in the TMA and up to around FL250 (there are variations). The airspace in the TMA's aren't sectorised as such, but are shared between 1, 2 or 3 radar controllers (depending on the location). All controlled airspace in the area of responsibility is available to the controllers and they even look after IFR outside controlled airspace within the lateral dimensions.

10W - I don't know of any issues NZ had with level busts due to altimeter settings being done late. NZ also gets QNH values around 980hPa, the TA/TL used to be 11000ft/FL130 and most Area/TMA standard descents are 10-11000ft - if it was going to happen it would have been on my watch

5milesbaby - What about the current situation? From what you have indicated, I'm guessing the problem of vertical split sectors is probably an issue around the current TA/TL as well. Wouldn't moving the TA/TL only be moving that problem, not creating a new one??? But as I don't know my way around the London TMA, I'll bow to your inside knowledge.
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Old 9th Feb 2011, 09:03
  #57 (permalink)  
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And the IAA says...

no clear information
 

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