Is there such a thing as "Regional QNH"?
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Kirstey - your pants are well in order and are not talking for you. The RPS is the lowest forecast "QNH" for the WHOLE region and as such covers all those points that are normally used to measure the QNH.
It is a forecast, not a measurement, and so does not need to be "taken at a point" as the actual QNHs may not even get that low - it is just the most pesimistic guess (sorry, estimate) that the met man can come up with.
It is a forecast, not a measurement, and so does not need to be "taken at a point" as the actual QNHs may not even get that low - it is just the most pesimistic guess (sorry, estimate) that the met man can come up with.
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Kirstey,
Because it is not measured at a point, it does not fit the definition of a QNH which is defined as follows:
The pressure setting which causes the altimeter to read the height above mean sea level of the touchdown on landing, plus the height of the altimeter above the ground.
QFF is the barometric pressure at a stated place, reduced to mean sea level.
A Regional Pressure setting is a QFF not a QNH.
MET.O 630/AP3340 Capt 9.
[ 09 November 2001: Message edited by: Noggin ]
Because it is not measured at a point, it does not fit the definition of a QNH which is defined as follows:
The pressure setting which causes the altimeter to read the height above mean sea level of the touchdown on landing, plus the height of the altimeter above the ground.
QFF is the barometric pressure at a stated place, reduced to mean sea level.
A Regional Pressure setting is a QFF not a QNH.
MET.O 630/AP3340 Capt 9.
[ 09 November 2001: Message edited by: Noggin ]
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we seem to have an outbreak of pedantic semantics. Technically the RPS is NOT a QNH, in practice it is! It functions like a QNH, it reads a (pessimistic) altitude AMSL and will help you to avoid a) the ground, b) aeroplanes, c) controlled airspace.
OK, it is a forecast regional pressure (not a measured pressure) but still works the same.
OK, it is a forecast regional pressure (not a measured pressure) but still works the same.
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and will help you to avoid ................ c) controlled airspace
Unfortunately it has quite the reverse effect. There is no controlled airspace anywhere defined on the basis of regional pressure. More people infringe controlled airspace with this ridiculous setting by flying higher than they think they are.
Unfortunately it has quite the reverse effect. There is no controlled airspace anywhere defined on the basis of regional pressure. More people infringe controlled airspace with this ridiculous setting by flying higher than they think they are.
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Oh dear....
QNH - The observed pressure at a station, reduced to sea level using the International Standard Atmosphere
QFF - The observed pressure at a station, reduced to sea level using actual atmospheric conditions
Regional Pressure Setting - The lowest forecast QNH within a defined area, valid for one hour and forecast one hour in advance.
Source: Forecasters Course Notes, Shinfield 1976.
Since both QNH and QFF depend upon observed pressure and RPS does not, it is clear that 'Regional QNH' is a misnomer and, therefore, that there is, strictly speaking, no such thing as Regional QNH.
However, it really doesn't matter whether you call it RPS, Regional QNH, FOQNH or Joe Bloggs - it all means the same thing, so what's all the fuss about?
Which seemed to annoy GoneWest, for some strange reason?
QNH - The observed pressure at a station, reduced to sea level using the International Standard Atmosphere
QFF - The observed pressure at a station, reduced to sea level using actual atmospheric conditions
Regional Pressure Setting - The lowest forecast QNH within a defined area, valid for one hour and forecast one hour in advance.
Source: Forecasters Course Notes, Shinfield 1976.
Since both QNH and QFF depend upon observed pressure and RPS does not, it is clear that 'Regional QNH' is a misnomer and, therefore, that there is, strictly speaking, no such thing as Regional QNH.
However, it really doesn't matter whether you call it RPS, Regional QNH, FOQNH or Joe Bloggs - it all means the same thing, so what's all the fuss about?
Which seemed to annoy GoneWest, for some strange reason?
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Gone West, dont worry about it 
As an atco, I would pass you the xxxx Regional Pressure Setting, and all I'd expect is a correct read back, as would any flight examiner.
The vast of majority of the replies have attempted to be helpful, but it simply isnt worth worrying about, it's just a fact of aviation life.
As an atco, I would pass you the xxxx Regional Pressure Setting, and all I'd expect is a correct read back, as would any flight examiner.
The vast of majority of the replies have attempted to be helpful, but it simply isnt worth worrying about, it's just a fact of aviation life.
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Noggin- although RPS is not ideal for avoiding controlled airspace it is better than b*gger all. Iddeally, everyone has an IR, flies IFR in receipt of an air traffic sevice and flies high enough in their FMS equipped jets to all be on 1013.
Yes it is flawed but it is still better than nothing when operating OUTSIDE controlled airspace latterally and if operating UNDER controlled airspace you should be on something more appropriate or giving a good 1000' plus clearance. If I remember correctly (and I don't have a chart handy), most airways have their bottom level defined as a flight level so 1013 is a good setting. If they have an altitude as bottom level then RPS with 1000' should do (the RPS is unlikely to be over 30mb off the actual QNH/QFF).
Yes it is flawed but it is still better than nothing when operating OUTSIDE controlled airspace latterally and if operating UNDER controlled airspace you should be on something more appropriate or giving a good 1000' plus clearance. If I remember correctly (and I don't have a chart handy), most airways have their bottom level defined as a flight level so 1013 is a good setting. If they have an altitude as bottom level then RPS with 1000' should do (the RPS is unlikely to be over 30mb off the actual QNH/QFF).
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"If (airways) have an altitude as bottom level then RPS with 1000' should do (the RPS is unlikely to be over 30mb off the actual QNH/QFF)."
From the AIP (ENR 1.7)
3.9 Airspace within all Control Zones (CTRs), and within and below all Terminal Control Areas (TMAs), Control Areas (CTAs) except Airways and the Daventry and Worthing Control Areas, during their notified hours of operation, do not form part of the ASR Regional Pressure Setting System.
3.10 When flying in airspace below TMAs and CTAs detailed above, pilots should use the QNH of an adjacent aerodrome when flying below the Transition Altitude. It may be assumed that for aerodromes located beneath such areas, the differences in QNH values are insignificant. When flying beneath airways whose base levels are expressed as Altitudes pilots are recommended to use the QNH of an adjacent aerodrome in order to avoid penetrating the base of Controlled Airspace.
Why invent procedures when suitable, published ones already exist? That is the way that accidents happen.
From the AIP (ENR 1.7)
3.9 Airspace within all Control Zones (CTRs), and within and below all Terminal Control Areas (TMAs), Control Areas (CTAs) except Airways and the Daventry and Worthing Control Areas, during their notified hours of operation, do not form part of the ASR Regional Pressure Setting System.
3.10 When flying in airspace below TMAs and CTAs detailed above, pilots should use the QNH of an adjacent aerodrome when flying below the Transition Altitude. It may be assumed that for aerodromes located beneath such areas, the differences in QNH values are insignificant. When flying beneath airways whose base levels are expressed as Altitudes pilots are recommended to use the QNH of an adjacent aerodrome in order to avoid penetrating the base of Controlled Airspace.
Why invent procedures when suitable, published ones already exist? That is the way that accidents happen.
I'm now convinced that Noggin is Henry Fowler, pedant of English grammar, risen from the dead. 
I have no idea what "MET.O 630/AP3340 Capt 9" is. Aviation works with the framework of ICAO, which is often unpleasantly ambiguous. But imposing arbitrary restrictive definitions is not the way to solve that.
Annex 3 Meteorological Service for International Air Navigation does not define QNH, except in that it says that an altimeter "when set to a QNH altimeter setting will indicate altitude". It regularly uses the term "forecast QNH" or "forecast lowest QNH".
PANS-OPS Vol 1 (Doc 8168) describes QNH as an altimeter sub-scale setting to obtain elevation when on ground. It then goes on to say in the section on altimeter setting that an aircraft is "flown at altitudes determined from an altimeter set to sea level pressure (QNH)" [oh dear!]
UK AIP ENR 1.7.3.7 says:
"the UK has been divided into a number of ASRs for each of which the NMO calculates the lowest forecast QNH (Regional Pressure Setting) for each hour".
It seems pretty clear from the above that the Regional Pressure Setting is a QNH, not a QFF. I can also see nothing in the above that says that a QNH is measured at a point, and it's certainly not restricted to observed quantities.
QNH is a physical quantity, and it is no more restricted to a measurement site than a temperature -- you can only measure a temperature with a thermometer at a single point, but presumablly you don't object to the use of the term "forecast flight level 100 temperature" on the grounds that it could only be measured at one point at FL100. Temperature describes the physical quantity, whether forecast or observed, local or regional.
If it walks like a QNH and quacks like a QNH, it's probably a QNH...
I have no idea what "MET.O 630/AP3340 Capt 9" is. Aviation works with the framework of ICAO, which is often unpleasantly ambiguous. But imposing arbitrary restrictive definitions is not the way to solve that.
Annex 3 Meteorological Service for International Air Navigation does not define QNH, except in that it says that an altimeter "when set to a QNH altimeter setting will indicate altitude". It regularly uses the term "forecast QNH" or "forecast lowest QNH".
PANS-OPS Vol 1 (Doc 8168) describes QNH as an altimeter sub-scale setting to obtain elevation when on ground. It then goes on to say in the section on altimeter setting that an aircraft is "flown at altitudes determined from an altimeter set to sea level pressure (QNH)" [oh dear!]
UK AIP ENR 1.7.3.7 says:
"the UK has been divided into a number of ASRs for each of which the NMO calculates the lowest forecast QNH (Regional Pressure Setting) for each hour".
It seems pretty clear from the above that the Regional Pressure Setting is a QNH, not a QFF. I can also see nothing in the above that says that a QNH is measured at a point, and it's certainly not restricted to observed quantities.
QNH is a physical quantity, and it is no more restricted to a measurement site than a temperature -- you can only measure a temperature with a thermometer at a single point, but presumablly you don't object to the use of the term "forecast flight level 100 temperature" on the grounds that it could only be measured at one point at FL100. Temperature describes the physical quantity, whether forecast or observed, local or regional.
If it walks like a QNH and quacks like a QNH, it's probably a QNH...
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Interesting to see that CAP 413 seems to use both Regional Pressure Setting and Regional QNH - is this what BlueLine meant about it being updated?
I'm afraid I'm with many others on this one - as a controller if someone asks for the 'XXX Regional Pressure Setting', the 'XXX Regional', the 'XXX Regional QNH', the 'XXX Regional Setting' or the 'XXX QNH', I know exactly what they want. If I'm in any doubt I'll check - that's the beauty of R/T.
I trust that GoWest is as correct and precise whenever he passes a position report or requests a clearance.
We're all human.
I'm afraid I'm with many others on this one - as a controller if someone asks for the 'XXX Regional Pressure Setting', the 'XXX Regional', the 'XXX Regional QNH', the 'XXX Regional Setting' or the 'XXX QNH', I know exactly what they want. If I'm in any doubt I'll check - that's the beauty of R/T.
I trust that GoWest is as correct and precise whenever he passes a position report or requests a clearance.
We're all human.
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Can this discussion move on to the usefulness of RPS ? Why do we use them when no other country bothers ? Is it to cater for a non radio aircraft setting off an IFR flight of 2 hours that might take him,say, over Snowdonia - assuming he remembers to add 1000 ft (plus extra for mountain effect) to his MEF or obstacle -
I cannot see the relevance of flying past Coventry on Barnsley RPS when there is a low pressure system centred on Newcastle miles away but dictating the lowest RPS for that big area. Just as you announce your altitude you receive Coventry QNH and lo and behold it makes your altitude 300 ft different from the aircraft in that area. However, it doesn't matter we are all VFR -set what you want- see everybody don't we. Which leads me onto the next subject - how many times have I flown IFR into Coventry, Cranfield and any other 'training' airfield where aircraft are reported to me, as if I can see them, who are pretending to be VFR. The latest passed half a mile away VFR in a layer of SC stubbornly maintaining his altitude when he could have descended or climbed and I might have seen him earlier -if at all - 'cos I was IFR wasn't I
I cannot see the relevance of flying past Coventry on Barnsley RPS when there is a low pressure system centred on Newcastle miles away but dictating the lowest RPS for that big area. Just as you announce your altitude you receive Coventry QNH and lo and behold it makes your altitude 300 ft different from the aircraft in that area. However, it doesn't matter we are all VFR -set what you want- see everybody don't we. Which leads me onto the next subject - how many times have I flown IFR into Coventry, Cranfield and any other 'training' airfield where aircraft are reported to me, as if I can see them, who are pretending to be VFR. The latest passed half a mile away VFR in a layer of SC stubbornly maintaining his altitude when he could have descended or climbed and I might have seen him earlier -if at all - 'cos I was IFR wasn't I
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Anything flying near my airfield gets my QNH, because that's what the traffic in my hold is flying on and therefore separation is based on that. I'll give the RPS, but just before the aircraft goes off my frequency and is heading away from me. The airport to the south of me, with it's lump of associated class 'D', operates on QNH. I wouldn't dream of working an aircraft flying towards them and giving them the RPS because it causes too much confusion - QNH is best, always 
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