Pressure settings under a TMA
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Pressure settings under a TMA
Apologies for what is I'm sure a simple question, but I'm a simple soul...
BLUF - what pressure setting do I need to use when flying under the London TMA? I'm assuming the London Regional QNH?
Background - I'm a low hours PPL living in carrot cruncher land, where the skies are open, the vistas superb and there are always a plethora of suitable looking fields to force land in if the donkey were to stop making the normal noises. BUT, I want to challenge myself, want to fly further and do more things. Some mates of the wife live in Southend, so I've done a bit of flight planning and reckon that a visit from here to there is perfectly possible, so long as I can sneak under the London TMA. But that puts me below the transition altitude and therefore flying on a local QNH. The last thing I want to do* is infringe some airspace and incur the inevitable wrath of the headmaster, which then raised the question of how is the base of the TMA calculated.
*Not strictly true - I think I'm even more allergic to crashing.
BLUF - what pressure setting do I need to use when flying under the London TMA? I'm assuming the London Regional QNH?
Background - I'm a low hours PPL living in carrot cruncher land, where the skies are open, the vistas superb and there are always a plethora of suitable looking fields to force land in if the donkey were to stop making the normal noises. BUT, I want to challenge myself, want to fly further and do more things. Some mates of the wife live in Southend, so I've done a bit of flight planning and reckon that a visit from here to there is perfectly possible, so long as I can sneak under the London TMA. But that puts me below the transition altitude and therefore flying on a local QNH. The last thing I want to do* is infringe some airspace and incur the inevitable wrath of the headmaster, which then raised the question of how is the base of the TMA calculated.
*Not strictly true - I think I'm even more allergic to crashing.
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Good answer. But I like learning and I enjoy planning. I'd also rather know now for certain than be distracted by uncertainty at a point in the flight which is likely to be fairly high workload - and high stress - and wondering about whether I've got it right or wrong at that point isn't going to help me.
Remember, I'm a yokel. I'll already be digging out my best wellies for a trip to (near) town. I don't want to have to give myself a nosebleed by upsetting the CAA.
Remember, I'm a yokel. I'll already be digging out my best wellies for a trip to (near) town. I don't want to have to give myself a nosebleed by upsetting the CAA.
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what pressure setting do I need to use when flying under the London TMA?
If you haven't already got a QNH of a suitable airport you can pick one up from an ATIS, or you can ask a controller. In the case of London you can ask for "London QNH" without worrying about particular airfields - they'll give you one that can be used to avoid airspace busts.
As an extra safeguard against mis-reading or mis-setting the altimter, most aviation GPS-based nav systems (such as Skydemon) have altimeter readouts based on sea level datum, equating (reasonably accurately) to local QNH.
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Let me emphasise again what Gertrude said Do not use the regional pressure setting!
If the base of controlled airspace is given as an altitude on the chart, use QNH of any airfield under it (as already mentioned) if it's given in flight levels, use 1013 but remember what a big difference in actual pressure will mean in terms of your height above the ground.
If the base of controlled airspace is given as an altitude on the chart, use QNH of any airfield under it (as already mentioned) if it's given in flight levels, use 1013 but remember what a big difference in actual pressure will mean in terms of your height above the ground.
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Regional Pressure Settings (RPS) are the lowest forecast pressure for geographical areas across the UK and may be used for checking terrain clearance. As such they are something if an anachronism dating from times when many aircraft operated without radio, or internet access, and travelled significant distances. The effectiveness of RPS may be judged by the number of high ground wrecks that scattered this country.
Despite what it may say in some documents, RPS are not a QNH, which is the sea level barometric pressure for a specified location at a specified time and, in these information overloaded times, can be readily obtained from ATIS, ATC and online sources through such amazing technologies as Sky Demon, iPhone and Android apps and so on.
Anyone planning to operate in the vicinity of any form of Controlled AirSpace (CAS) where the base is defined as an altitude would be well advised to use the QNH of the nearest or most appropriate airfield. A look at the relevant chart will provide clues. e.g. Daventry CTA around Stoke on Trent; base 4,500ft use Manchester QNH, Manchester Low Level Route; the clue is in the name, but as the QNH at Manchester and Liverpool are usually the same use Manchester QNH, London TMA around Chelmsford; base to north 2,500ft, to south west 3,500ft use either Stansted or London QNH
As a former controller I always hated having to file reports on airspace infringement which were in the vertical plane, however, so many of those were caused by people operating on an RPS believing that they were remaining below CAS.
My own view is that the use of RPS is unnecessary and the sooner we all operate on QNH and plan carefully, the better.
Despite what it may say in some documents, RPS are not a QNH, which is the sea level barometric pressure for a specified location at a specified time and, in these information overloaded times, can be readily obtained from ATIS, ATC and online sources through such amazing technologies as Sky Demon, iPhone and Android apps and so on.
Anyone planning to operate in the vicinity of any form of Controlled AirSpace (CAS) where the base is defined as an altitude would be well advised to use the QNH of the nearest or most appropriate airfield. A look at the relevant chart will provide clues. e.g. Daventry CTA around Stoke on Trent; base 4,500ft use Manchester QNH, Manchester Low Level Route; the clue is in the name, but as the QNH at Manchester and Liverpool are usually the same use Manchester QNH, London TMA around Chelmsford; base to north 2,500ft, to south west 3,500ft use either Stansted or London QNH
As a former controller I always hated having to file reports on airspace infringement which were in the vertical plane, however, so many of those were caused by people operating on an RPS believing that they were remaining below CAS.
My own view is that the use of RPS is unnecessary and the sooner we all operate on QNH and plan carefully, the better.
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As an extra safeguard against mis-reading or mis-setting the altimter, most aviation GPS-based nav systems (such as Skydemon) have altimeter readouts based on sea level datum, equating (reasonably accurately) to local QNH.
If you are flying near controlled airspace: at best get a LARS service or, if you can't or don't want to do that, use a listening squawk. That way you should get a warning if you are about to infringe. I say SHOULD because it's still your responsibility not to.
Last edited by Jonzarno; 10th Jan 2017 at 12:58. Reason: Typo
This whole issue stems from the idiotic organisation of airspace and traffic services in the UK. At all other places I know, each one given point, as defined by latitude/longitude/elevation, belongs to one and exactly one part of airspace, with one and exactly one service in charge. So, depending on where you are, you call the relevant service and they tell you what QNH to set. Solved. Why the UK absolutely wants all this vagueness and confusion is beyond me.
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For exactly the same reason as why we need Basic, Traffic, Deconfliction and Procedural services which, AFIK, almost nobody outside the UK understands.
You have to accept, Jan, it's not the UK that's out of step: it's the rest of the World....
You have to accept, Jan, it's not the UK that's out of step: it's the rest of the World....
I think I might be a bit careful using that method if planning to fly anywhere near the base of controlled airspace. That altitude measurement equates pretty much to a QNH of 1013.
I would agree with those who say that UK altimeter settings are far too complicated and therefore prone to human error. Local QNH below TA and 1013 above would reduce such errors (and the likelihood of airspace busts).
I haven't set QFE on an altimeter for 25 years. Given a QFE-referenced MATZ transit I fly QNH plus field elevation rounded up or down to the nearest 100 feet.
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Transponder Mode C altimeter readouts are referenced to 1013 hPa. GPS altimeter readouts are referenced to mean sea level.
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At all other places I know, each one given point, as defined by latitude/longitude/elevation, belongs to one and exactly one part of airspace, with one and exactly one service in charge. So, depending on where you are, you call the relevant service and they tell you what QNH to set. Solved. Why the UK absolutely wants all this vagueness and confusion is beyond me.
When flying outside controlled airspace at or below 4 500 FT AMSL, the altimeter shall be set to the regional QNH given on pilot's request by Brussels FIC, Semmerzake ATCC or by any ATC unit. The regional QNH is the lowest of the QNH values for the following stations: EBAW, EBBE, EBBR, EBCI, EBCV, EBFS, EBBL, EBFN, EBLG, ELLX, EBOS, EBSH and EBSP.
Altimeter Setting Regions (ASR). To make up for any lack of stations reporting actual QNH, the UK has been divided into a
number of ASRs for each of which the National Meteorological Office calculates the lowest forecast QNH (Regional Pressure
Setting) for each hour. These values are available hourly for the period H+1 to H+2 and may be obtained from all aerodromes having an Air Traffic Service, from London AC (Swanwick) and Scottish AC (Prestwick), or by telephone.
number of ASRs for each of which the National Meteorological Office calculates the lowest forecast QNH (Regional Pressure
Setting) for each hour. These values are available hourly for the period H+1 to H+2 and may be obtained from all aerodromes having an Air Traffic Service, from London AC (Swanwick) and Scottish AC (Prestwick), or by telephone.
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I have done a considerable part of my flying to / from airfields under the London TMA.
If you come from the north, talk to Farnborough North on 132.800
If you come from the South-East, talk to Farnborough East on 123.225
If you come from the West, talk to Farnborough West on 125.250
If there is nobody there - talk to London Information on 124.600 (if memory is right)
All of which will be happy to provide you with a Basic Service (or if Farnborough, they will happily pass on Traffic and Deconfliction services providing controller workload). They will pass on the local QNH on first contact with the ATC unit.
Bear in mind the accuracy of the altimeter vs accuracy of transponder reported altitude - as a general rule I make sure to be at least 100ft below the TMA, I often fly at 2,200ft to avoid the possibility of accidental zone incursion. There are a few "corridors" which are a little tight, and you need to keep a good lookout at all times. ie: between Luton & Standsted where there are a few airfields in between, and relatively stringent crossing requirements and between Heathrow and Gatwick where you have people from Redhill, Kenley and Biggin. It has never been an issue for me, but just "keep your eyes peeled, and your ears flapping"!
If you need any more help with your flight planning - I'd be happy to help!
Good Luck For Your Flight!
Alex
If you come from the north, talk to Farnborough North on 132.800
If you come from the South-East, talk to Farnborough East on 123.225
If you come from the West, talk to Farnborough West on 125.250
If there is nobody there - talk to London Information on 124.600 (if memory is right)
All of which will be happy to provide you with a Basic Service (or if Farnborough, they will happily pass on Traffic and Deconfliction services providing controller workload). They will pass on the local QNH on first contact with the ATC unit.
Bear in mind the accuracy of the altimeter vs accuracy of transponder reported altitude - as a general rule I make sure to be at least 100ft below the TMA, I often fly at 2,200ft to avoid the possibility of accidental zone incursion. There are a few "corridors" which are a little tight, and you need to keep a good lookout at all times. ie: between Luton & Standsted where there are a few airfields in between, and relatively stringent crossing requirements and between Heathrow and Gatwick where you have people from Redhill, Kenley and Biggin. It has never been an issue for me, but just "keep your eyes peeled, and your ears flapping"!
If you need any more help with your flight planning - I'd be happy to help!
Good Luck For Your Flight!
Alex
@PW: if your "BS" means what I suppose it to mean, well, err, I am really disappointed, I always respected you for a polite gentleman.
I gladly agree that Belgium, like most countries, knows the concept of a "Regional QNH" though, AFAIK, the UK is the only country to base it upon forecasts rather than upon actually measured pressures.
But that was not my point. I do not want to argue the merits of the "regional" setting, it has its advantages and its disadvantages, I can see how it came to be though it might indeed be considered an outdated concept.
Neither was it the point of the topic starter. My point was and is that in BE (and, as far as I know, all over Europe except in the UK) the opening question has an easy and unambiguous answer: if flying at a place such and such, determine in what bit of airspace you are, and talk to the service (the one and only!) in charge of that bit of airspace. They will tell you what setting to apply; in fact, most of the time they will tell you the QNH on your initial call for entering their area. Basta. Everything clear. And you know you will have the same setting as any other aircraft nearby, if their pilots followed this easy procedure; as they must.
I gladly agree that Belgium, like most countries, knows the concept of a "Regional QNH" though, AFAIK, the UK is the only country to base it upon forecasts rather than upon actually measured pressures.
But that was not my point. I do not want to argue the merits of the "regional" setting, it has its advantages and its disadvantages, I can see how it came to be though it might indeed be considered an outdated concept.
Neither was it the point of the topic starter. My point was and is that in BE (and, as far as I know, all over Europe except in the UK) the opening question has an easy and unambiguous answer: if flying at a place such and such, determine in what bit of airspace you are, and talk to the service (the one and only!) in charge of that bit of airspace. They will tell you what setting to apply; in fact, most of the time they will tell you the QNH on your initial call for entering their area. Basta. Everything clear. And you know you will have the same setting as any other aircraft nearby, if their pilots followed this easy procedure; as they must.
Last edited by Jan Olieslagers; 10th Jan 2017 at 16:33.
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Also - I just found this about Farnborough radar... A little out of date - but the information http://flyontrack.co.uk/wp-content/u...1/EGLFLARS.pdf is still pretty accurate.
Remember that Southend now has a class D zone around it, and contact them well before getting close to the boundary. They are still very much a GA friendly airfield though, never been badly received there, ATC have always been really nice and the landing fees were still cheaper than Shoreham (Brighton) but you get to land after an Easyjet which is a bit different. Could be worth giving them a call ahead though to know if they're expecting a lot of commercial traffic during the time that you're thinking of arriving (so as to miss the rush!)
Hope this helps.
Alex
Remember that Southend now has a class D zone around it, and contact them well before getting close to the boundary. They are still very much a GA friendly airfield though, never been badly received there, ATC have always been really nice and the landing fees were still cheaper than Shoreham (Brighton) but you get to land after an Easyjet which is a bit different. Could be worth giving them a call ahead though to know if they're expecting a lot of commercial traffic during the time that you're thinking of arriving (so as to miss the rush!)
Hope this helps.
Alex
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Jan,
I am sorry if you found BS distasteful and admit that rubbish would have a response better suited to your description of the organisation of airspace and traffic services in the UK as idiotic.
You have many misconceptions about aviation in the UK and the best way to remedy that is to come over in your microlight. You will be presently surprised.
I am sorry if you found BS distasteful and admit that rubbish would have a response better suited to your description of the organisation of airspace and traffic services in the UK as idiotic.
You have many misconceptions about aviation in the UK and the best way to remedy that is to come over in your microlight. You will be presently surprised.
OK, fair enough.
(regarding a visit to that haunted airspace
: I will be pleased to visit the UK, as soon as I am legally allowed to fly high enough to always remain within glide distance of terra firma - which I am afraid might take some time. Always have a plan B is my motto, and it has served me well; and ditching my high-winger in the English Channel is not a valid plan B for me. Yes yes, I do know it's only a couple of minutes and countless people have done it and yes, I know the engine doesn't know it is over water. That is exactly my reason to always want a Plan B: the engine can quit at any time, including those few minutes when I cannot glide to land. If the engine did know it was over water it could promise me to not fail right then - but it cannot. End parenthesis)
As for my misconceptions: I am willing to learn better, feel free to explain what I have misunderstood about the organisation of UK airspace and services. I still understand that at many places, pilots have a free choice of whom to talk to and that seems very unnatural to me, and needlessly confusing, and a potential cause for miscommunication.
As for my _many_ misconceptions: which are the others?
(regarding a visit to that haunted airspace
: I will be pleased to visit the UK, as soon as I am legally allowed to fly high enough to always remain within glide distance of terra firma - which I am afraid might take some time. Always have a plan B is my motto, and it has served me well; and ditching my high-winger in the English Channel is not a valid plan B for me. Yes yes, I do know it's only a couple of minutes and countless people have done it and yes, I know the engine doesn't know it is over water. That is exactly my reason to always want a Plan B: the engine can quit at any time, including those few minutes when I cannot glide to land. If the engine did know it was over water it could promise me to not fail right then - but it cannot. End parenthesis)As for my misconceptions: I am willing to learn better, feel free to explain what I have misunderstood about the organisation of UK airspace and services. I still understand that at many places, pilots have a free choice of whom to talk to and that seems very unnatural to me, and needlessly confusing, and a potential cause for miscommunication.
As for my _many_ misconceptions: which are the others?
Last edited by Jan Olieslagers; 10th Jan 2017 at 20:37.
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Thank you one and all, some useful info there. I especially like the Farnborough LARS leaflet, I shall re-read that more than once to ensure all is fully understood. And I think I'll have a good chat through with an experienced chum before I start to think too seriously about it. I may even pop back into the flying school and ask them to cast an eye over the scribbles I've drawn on my chart to double check I've not missed the obvious anywhere.
Airpolice - I'd dearly love to go through the TMA with a choice of altitudes available to me, but on my chart it's shown as Class A airspace, and as I hold only a PPL and no IR, I'm not allowed to - for jolly good reasons which I fully understand. A 'spam can' isn't of nearly the same performance as an airliner, so would get in the way quite a bit. And it would probably be swallowed up whole by the big sucky, spinny, noisy things hanging under the wings of (say) an A380 if I did get in the way. Add that to my list of things I'm allergic to.
Airpolice - I'd dearly love to go through the TMA with a choice of altitudes available to me, but on my chart it's shown as Class A airspace, and as I hold only a PPL and no IR, I'm not allowed to - for jolly good reasons which I fully understand. A 'spam can' isn't of nearly the same performance as an airliner, so would get in the way quite a bit. And it would probably be swallowed up whole by the big sucky, spinny, noisy things hanging under the wings of (say) an A380 if I did get in the way. Add that to my list of things I'm allergic to.