Why QFE and QNH altimeters in the UK and rarely anywhere else in the world?
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Why QFE and QNH altimeters in the UK and rarely anywhere else in the world?
I am getting old and senile and I am sure that while completing my UK ATPL, it was explained to me the necessity for the use of QFE altimeter settings and not using QNH settings alone as is done in the ex-colony to the west....but could someone please re-educate me on this? I swear I won't be rude or in any way use phrases like "but in the US we...." or "if it is so unsafe then why in the US don't we...." or anything like that in my additional responses. This among some other rather esoteric topics has bemused me for years. I recall using the QFE setting while earning my US Army wings back before recorded history, thus at one time it must have been part of our system too. I would genuinely like to gather an appreciation for this difference in operating practices. Can anyone help me out here?
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With an airfield QFE set, your altimeter should indicate zero feet when you are on the ground at the airfield datum. If it doesnt then that value is the inaccuracy of your altimeter.
With an accurate QNH set, the indication at the airfield datum should be the published elevation of the field... if it is not, you can work out the inaccuracy of your altimeter from that set of numbers..... but I know that you already knew that!!!
I think QFE was very much a UK military thing from the early days in that when the instructor tells Bloggs to fly a circuit at 1000'... Bloggs flies the cct at 1000' indicated and doesnt have to think too hard (I know, I was that Bloggs!!) QNH/RegionalQNH/AreaQNH has to be safer as little or no calculation is required to work out/climb to your Min Lowest Safe Alt (should you need to) as you are at an Altitude already and not a height as you would be on QFE..... end of sermon!!
"Clear as mud??"
With an accurate QNH set, the indication at the airfield datum should be the published elevation of the field... if it is not, you can work out the inaccuracy of your altimeter from that set of numbers..... but I know that you already knew that!!!
I think QFE was very much a UK military thing from the early days in that when the instructor tells Bloggs to fly a circuit at 1000'... Bloggs flies the cct at 1000' indicated and doesnt have to think too hard (I know, I was that Bloggs!!) QNH/RegionalQNH/AreaQNH has to be safer as little or no calculation is required to work out/climb to your Min Lowest Safe Alt (should you need to) as you are at an Altitude already and not a height as you would be on QFE..... end of sermon!!
"Clear as mud??"
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You confirmed part of what I remember about the QFE thing. I understand the ease and safety of using a QNH setting...only one setting once below transition altitude...for us that is 18,000 feet....thus one less thing to screw up at low altitude and when workload tends to be the busiest. Also as you say...doesn't required Bloggs to do any mental gymnastics as he flys away from the airfield and in case of something ugly happening...MSA's on the charts apply to the altimeter setting he is using. And if I recall correctly, the QFE setting is predicated upon the landing portion of the runway in use and thus the actual indication of the altimeter can be quite different for other locations upon the airfield.
All things being considered...and the safety stats being the same for the US and other Western nations....why does the UK continue in using what appears to be a more cumbersome if not less safe procedure (in light of miss set altimeters)?
All things being considered...and the safety stats being the same for the US and other Western nations....why does the UK continue in using what appears to be a more cumbersome if not less safe procedure (in light of miss set altimeters)?
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I think the main reason for the UK still (?)utilising the QFE pressure datum has to do with the probibility of rapidly changing atmospheric pressures that can occur with frontal passages. It does make life easier to be able to fly an instrument approach to minima based on accurate QFE datum which is given by tower or approach control as required ( and it is reqd in the UK!)..also in the UK IFR A/C are required to have two altimeters on which you play 'musical altimiter settings'usually just when you think you've got everything set up correctly! ...problems then occur with other aircraft who arrive with an area QNH set and expect you to be able to maintain separation ....makes life interesting dunnit! 
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The scene: A US Army airfield in southern Germany sometime in the 1980's where a flight of British Army helicopters were operating on exercise.
The duty US ATC Controller had become so accustomed to passing the pressure setting in millibars to British crews, that when a US Army helicopter arrived it too was given the pressure setting in millibars.
The female pilot of the US helicopter was heard to ask the controller: "Could you give that to me in inches please?" Great amusement amongst British helicopter crews!
The duty US ATC Controller had become so accustomed to passing the pressure setting in millibars to British crews, that when a US Army helicopter arrived it too was given the pressure setting in millibars.
The female pilot of the US helicopter was heard to ask the controller: "Could you give that to me in inches please?" Great amusement amongst British helicopter crews!
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I thought I saw this on a pprune humour board, but couldn't find it. I'll paraphrase. Wish I could give credit to the originator.
American flying near London requests clearance through airspace.
ATC: "ATC clears N#### through London airspace requested routing. Climb and maintain 6,000'. Altimeter 1015.7."
N####" "Ummmmm...could you give that to me in inches."
ATC: "ATC clears N#### through London airspace requested routing. Climb and maintain 72,000". Altimeter 1015.7."
On another note, I understand that the Snowbirds use QFE during their shows. It makes sense to keep your altimeter reading the same no matter where you're doing your show.
Matthew.
American flying near London requests clearance through airspace.
ATC: "ATC clears N#### through London airspace requested routing. Climb and maintain 6,000'. Altimeter 1015.7."
N####" "Ummmmm...could you give that to me in inches."
ATC: "ATC clears N#### through London airspace requested routing. Climb and maintain 72,000". Altimeter 1015.7."
On another note, I understand that the Snowbirds use QFE during their shows. It makes sense to keep your altimeter reading the same no matter where you're doing your show.
Matthew.
Jayfer - is that the jayfer ex CFS at Strawberry? If so, g'day mate. Re QFE/QNH - it was long though to be safer to have height above touchdown indicated when on approach. Problem is that in many countries with high ground, the subscale of the altimeter don't go that far. Therefore height abouve sea level was the only practical solution.
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Ok....sounds good...quickly changing pressure due a frontal passage situation....now we address that situation by the ATC chappies reporting any altimeter change when it occurs and when making contact with an aircraft. Would it matter whether you use the QFE or QNH setting...so long as you have the current altimeter setting? I still fail to see the advantage of line slime seat warmers like myself having to determine whether to set Area QNH, Regional QNH, Airfield QNH, or QNE, or QFE on which altimeter and when....do we have to reset all three of the darn things upon doing a missed approach or some other gravity defying maneuver when the "handling" pilot status changes....golly...this is simple!
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Yes ...."musical Altimeter settings" a game played in UK airspace....just when you've got nothing else to do (?) leave airways With QNE setting, to commence an approach ..set area QNH...then QFE...screw it up commence missed approach... do it all again in reverse....and ifn your doing an I/R test/renewal make sure you do it all correctly and in the right bloody sequence!!! "God Bless the Airship Pilots at Kingsway"!
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I can’t explain why, some use QFE and others use QNH.
The difference is? Math!
When an airport measures the local air pressure, then this pressure is called QFE. An aircraft which uses the setting for QFE; it will read zero feet on the altimeter when it is on the ground at this airport!
When we speak of QNH we mean the altimeter value reference level is MSL otherword how high are we above sea level?.
Now I am sure that you think you know the difference. But wait. We can take QFE and correct it for non-standard temperature, non-standard-humidity etc. the resulting value we can call QFF. This QFF value is then corrected for field elevation, that means that it is transformed into a pressure as it would have been at mean sea level (MSL) under standard conditions. The resulting value is a local pressure value which some call QNH. An aircraft, which has set the QNH value, will read the field elevation on the altimeter when it is on the gorund at the airport. So why not use QFF corrected for field elevation and then we all would be standardize.
Its my understanding that the only ones that insist on using QFE are the British and the Chinese (but Chinese use three NBD’s for one ADF Approach, one for the procedure turn, one inbound and one going away). I like QFE myself because I don’t have to do the higher MATH to know how high Iam above the ground.
your truly just pullin32
The difference is? Math!
When an airport measures the local air pressure, then this pressure is called QFE. An aircraft which uses the setting for QFE; it will read zero feet on the altimeter when it is on the ground at this airport!
When we speak of QNH we mean the altimeter value reference level is MSL otherword how high are we above sea level?.
Now I am sure that you think you know the difference. But wait. We can take QFE and correct it for non-standard temperature, non-standard-humidity etc. the resulting value we can call QFF. This QFF value is then corrected for field elevation, that means that it is transformed into a pressure as it would have been at mean sea level (MSL) under standard conditions. The resulting value is a local pressure value which some call QNH. An aircraft, which has set the QNH value, will read the field elevation on the altimeter when it is on the gorund at the airport. So why not use QFF corrected for field elevation and then we all would be standardize.
Its my understanding that the only ones that insist on using QFE are the British and the Chinese (but Chinese use three NBD’s for one ADF Approach, one for the procedure turn, one inbound and one going away). I like QFE myself because I don’t have to do the higher MATH to know how high Iam above the ground.
your truly just pullin32
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Again....problems with QNE/QNH/QFE usage in the UK are complicated by the use of quite low 'Transition Altitudes/Levels in UK airspace....I vaguely remember 6000' being the average with some areas down to 4500' which required an altimiter re-setting to QNE...this of course is quite different to us here in Oz (10,000') transition Alt. and the USA 18,000' Transition Alt. ....all seems like too much too handle and anyway if I fly too high I'll probably get a nose bleed! 
