QFE / QNH
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Originally Posted by High Wing Drifter
Interesting Chilli. I was taught that QFF is a mean sea level pressure calculated using the actual temprature at the sensing point (as opposed to ISA for QNH). Apparently it is the pressure shown on met charts.
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Oh hell !! I thought I had it sussed 
I just use QFE when flying circuits and local. Seems to work for me, although I'd happily work out what it should be on QNH. Now let's see.... Conington is elev 26 ft, circuit height is 1000ft = 1026ft on QFE. So round out at circa 41ft QNH instead of 15ft QFE
Yeah, gottit 
I'm not reading any more threads about QNH/QFE as this old codger gets confused
I just use QFE when flying circuits and local. Seems to work for me, although I'd happily work out what it should be on QNH. Now let's see.... Conington is elev 26 ft, circuit height is 1000ft = 1026ft on QFE. So round out at circa 41ft QNH instead of 15ft QFE
Yeah, gottit I'm not reading any more threads about QNH/QFE as this old codger gets confused
Last edited by microlight AV8R; 3rd Jul 2006 at 21:02.
The Original Whirly
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Right, I think I just possibly begin to see....
If you use QFE you have to remember whether you've got the QNH set or the QFE. Now that's just hellishly confusing, innit?
But wait! If you DON'T use QFE, you have to remember how high the airfield is, and take that into account when landing. Awwwww, now I don't think I could cope with that.
Isn't it just awful! You've either got to cope with TWO (a HUGE number) different altimeter settings, or you've got to add and subtract a few hundred feet at every airfield. Those are really, really complicated things to do. And to make it even more confusing, you have a CHOICE of which to do, since no-one has ever held a gun to a pilot's head and demanded he do one or the other. So you have to decide for yourself!!!
I feel quite exhausted with working all this out, and comparing the strong views for and against each method. I just can't imagine how I've flown in both the UK and other countries for all these years and managed to cope. I would have thought it would give any poor pilot a nervous breakdown, just thinking about it.
Come to think of it, I need a drink.......
If you use QFE you have to remember whether you've got the QNH set or the QFE. Now that's just hellishly confusing, innit?
But wait! If you DON'T use QFE, you have to remember how high the airfield is, and take that into account when landing. Awwwww, now I don't think I could cope with that.
Isn't it just awful! You've either got to cope with TWO (a HUGE number) different altimeter settings, or you've got to add and subtract a few hundred feet at every airfield. Those are really, really complicated things to do. And to make it even more confusing, you have a CHOICE of which to do, since no-one has ever held a gun to a pilot's head and demanded he do one or the other. So you have to decide for yourself!!!
I feel quite exhausted with working all this out, and comparing the strong views for and against each method. I just can't imagine how I've flown in both the UK and other countries for all these years and managed to cope. I would have thought it would give any poor pilot a nervous breakdown, just thinking about it.
Come to think of it, I need a drink.......
A little less conversation,
a little more aviation...
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Originally Posted by IO540
So instrument pilots usually use QNH only.
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As an instructor I taught to land on QFE - zero=ground which is good for students and kind of makes sense.
Flying commercially I always land QNH - a very simple reason, the missed approach is always a climb to an altitude and not a height and therefore saves changing the pressure setting at a particularly stressful time.
RAD ALT is not used for CAT 1 approaches (hmmm...) as decision altitude or height is from the altimeters.
So for private flying depart on QNH, as all airspace surrounding a Class D airfield will be based on QNH so you arent going to bust airspace - land on QFE cos the altimeter will read zero so you know when you have hit the ground.
Flying commercially I always land QNH - a very simple reason, the missed approach is always a climb to an altitude and not a height and therefore saves changing the pressure setting at a particularly stressful time.
RAD ALT is not used for CAT 1 approaches (hmmm...) as decision altitude or height is from the altimeters.
So for private flying depart on QNH, as all airspace surrounding a Class D airfield will be based on QNH so you arent going to bust airspace - land on QFE cos the altimeter will read zero so you know when you have hit the ground.
The RAF has been going from QNH to QFE and back again for years....
RPS is a pretty useless concept these days, I agree.
It used to amuse me that the Brize CTR has a top level of 3500 ft QNH - yet the RAF flies on QFE and changes to 1013 at 3000ft - even when TA is different. Pointed the error of this out to the Benson ATC folk, whose airspace is under the LTMA and who should therefore obesrve the associated TA and London QNH - not sure if they've changed anything though.
RPS is a pretty useless concept these days, I agree.
It used to amuse me that the Brize CTR has a top level of 3500 ft QNH - yet the RAF flies on QFE and changes to 1013 at 3000ft - even when TA is different. Pointed the error of this out to the Benson ATC folk, whose airspace is under the LTMA and who should therefore obesrve the associated TA and London QNH - not sure if they've changed anything though.
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Always thought that the radio altimeter should be called a radio heightimeter as it always measures height. Suppose the barometric altimeter could be classed as a "heightimeter" when set to QFE. Just my brain working in a bizarre way again.
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Ooooh, thanks all for the input - looks like a hot subject 
I understand that QFE is the airodrome pressure, which gives you a 0 on your Altimeter, but in fact you may actually be several hundred feet above mean sea level.
The QNH being the regional pressure in your current area based on your current height above mean sea level.
The pros for using QFE is that when you land it reads 0 on your altimeter.
The pros for using QNH are that you are given a height which allows you to corrolate with the height obstacles marked on a map and it's the only thing used outside.
Hopefully I got it!
I think at this point I'll stick to QFE while I'm learning so I know I got my 1000 ft over the a/d for the circuit.
ps. I didn't know QFE was related to Military ATZ's. Hope that question comes up in one of my exams.
I understand that QFE is the airodrome pressure, which gives you a 0 on your Altimeter, but in fact you may actually be several hundred feet above mean sea level.
The QNH being the regional pressure in your current area based on your current height above mean sea level.
The pros for using QFE is that when you land it reads 0 on your altimeter.
The pros for using QNH are that you are given a height which allows you to corrolate with the height obstacles marked on a map and it's the only thing used outside.
Hopefully I got it!
I think at this point I'll stick to QFE while I'm learning so I know I got my 1000 ft over the a/d for the circuit.
ps. I didn't know QFE was related to Military ATZ's. Hope that question comes up in one of my exams.
Avoid imitations
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"The QNH being the regional pressure in your current area based on your current height above mean sea level."
No, you got this wrong. The term height and QNH shouldn't be used together. Altitude is the correct term.
Height is read using QFE.
What you describe is the Regional QNH, not the local /airfield QNH.
Regional QNH is forecast and published in advance and is used for en-route terrain clearance, whilst local/airfield QNH is measured at the time and is set prior to making an approach.
No-one should try to make an instrument approach on regional QNH.
No, you got this wrong. The term height and QNH shouldn't be used together. Altitude is the correct term.
Height is read using QFE.
What you describe is the Regional QNH, not the local /airfield QNH.
Regional QNH is forecast and published in advance and is used for en-route terrain clearance, whilst local/airfield QNH is measured at the time and is set prior to making an approach.
No-one should try to make an instrument approach on regional QNH.
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Sparky,
When referring to QNH or sea level etc. then we use the word altitude.
When referring to QFE or distance above a fixed datum then we use the word height.
Controlled airspace surrounding a civilian airfield is always defined by flight level or QNH.
For example, if you flew under East Midlands controlled airspace on the Barnsley regional pressure setting you could potentially bust controlled airspace because you should be flying on the East Midlands QNH and there will usually be a difference between the two.
Regional pressure settings are useful in areas where there is little controlled airspace, for terrain avoidance. Flying cross country in England usually means setting an airfield QNH along the length of the route.
edited to add that I agree with shytorque, but you cannot legally make any sort of instrument approach on regional QNH
When referring to QNH or sea level etc. then we use the word altitude.
When referring to QFE or distance above a fixed datum then we use the word height.
Controlled airspace surrounding a civilian airfield is always defined by flight level or QNH.
For example, if you flew under East Midlands controlled airspace on the Barnsley regional pressure setting you could potentially bust controlled airspace because you should be flying on the East Midlands QNH and there will usually be a difference between the two.
Regional pressure settings are useful in areas where there is little controlled airspace, for terrain avoidance. Flying cross country in England usually means setting an airfield QNH along the length of the route.
edited to add that I agree with shytorque, but you cannot legally make any sort of instrument approach on regional QNH
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I think the CAA should be tasked to sort this one out.
Hmmm ... let's see, what would they do ? Go for QNH or QFE ?
I know ...
"Reuters, London, 2006.
The CAA has today announced the results of it's 14 year study into the use of Q codes to stipulate vertical aircraft positioning. As a result of this intensive work, all airfields are to be relocated to coastal towns and sited on the beach. Once complete, the terms QNH and QFE will be replaced by the common reference WGAT (note 1).
In order to manage these changes, the CAA will recruit 1400 new staff. As only the RAF and GA use the term "QFE", they will bear all associated project costs. In order to apportion the charges fairly, all RAF officer clubs will close 5 minutes earlier, and £4.63 will be added to a litre of AVGAS."
(1) : WGAT = Who Gives A Toss
FF
Hmmm ... let's see, what would they do ? Go for QNH or QFE ?
I know ...
"Reuters, London, 2006.
The CAA has today announced the results of it's 14 year study into the use of Q codes to stipulate vertical aircraft positioning. As a result of this intensive work, all airfields are to be relocated to coastal towns and sited on the beach. Once complete, the terms QNH and QFE will be replaced by the common reference WGAT (note 1).
In order to manage these changes, the CAA will recruit 1400 new staff. As only the RAF and GA use the term "QFE", they will bear all associated project costs. In order to apportion the charges fairly, all RAF officer clubs will close 5 minutes earlier, and £4.63 will be added to a litre of AVGAS."
(1) : WGAT = Who Gives A Toss
FF
Last edited by FullyFlapped; 4th Jul 2006 at 09:23.
High Wing Drifter:
I have personally never come across an example of using QNE for a letdown although I have heard of this practice somewhere in the back of my dim and distant memory. At Nairobi, Addis and Asmara for example, we always used QNH.
I seem to remember that trying to use QFE at Nairobi was the cause of the two BOAC aircraft (a Comet and a 747) which both managed to do a touch and go in the game park well short of the runway and, amazingly, survive the experience.
QFE would have come out to something like 837 mbs but the altimeter was set to 937 mbs - an error of some 3,000 ft!
I have personally never come across an example of using QNE for a letdown although I have heard of this practice somewhere in the back of my dim and distant memory. At Nairobi, Addis and Asmara for example, we always used QNH.
I seem to remember that trying to use QFE at Nairobi was the cause of the two BOAC aircraft (a Comet and a 747) which both managed to do a touch and go in the game park well short of the runway and, amazingly, survive the experience.
QFE would have come out to something like 837 mbs but the altimeter was set to 937 mbs - an error of some 3,000 ft!
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Originally Posted by SparkyBoy
I'm being instructed to use QNH on take off and QFE on landing, this makes sense to me because it's handy to know where 0ft is when your approaching a r/w.
Sparky
Sparky
Now you've seen most of the QFE/QNH debate. I've used several systems.
- RAF Strike & Training Commands. Take-off and land on QFE. Worked fine but rarely (Instrument Rating Tests only in 12 years) had to make ILS approach (where, as someone pointed out earlier, a missed approach almost invariably involves a climb to an altitude (QNH)). We normally stayed with a radar contoller who 'talked' us down and nursed us through a missed approach so we never had to worry about forgetting alimeter setting.
- Civil Airline. Take-off and land on QFE. I was happy using system but saw many alt-busts on sim checks when pilots (myself included) forgot to reset to QNH on missed approach.
- Civil Airline. Take-off QNH and land QFE (the way your instructor suggests). I don't like this system at all. Landing on QFE 'conditions' pilots to see 0ft indicated. These same pilots, with heavy workload after take-off (one-eng inop or windshear encounter for example), tend to 'forget' the elevation of the airfield they've just departed and I've witnessed several (LOFT Sim) controlled flight into terrain (CFIT) events, probably for that reason.
- Civil Airline. Take-off and land on QNH. Worked ok for me and never heard any complaints from other pilots. Still confusion occasionally after take-off but less than in last system. Approaches down to CAT I precision use QNH Decision Altitudes. CAT II or lower use RAD ALT Decision Heights but the pressure altimeters remain on airfield QNH (ready for the missed approach).
rts
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What you describe is the Regional QNH, not the local /airfield QNH.
Regional QNH is forecast and published in advance and is used for en-route terrain clearance, whilst local/airfield QNH is measured at the time and is set prior to making an approach.
No-one should try to make an instrument approach on regional QNH.
Regional QNH is forecast and published in advance and is used for en-route terrain clearance, whilst local/airfield QNH is measured at the time and is set prior to making an approach.
No-one should try to make an instrument approach on regional QNH.
They shouldn't be made on the Regional Pressure Setting either, which is much easier to get hold of
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JW411,
Thanks for getting back to me. I thought as much, although it is mentioned in CAP 413; I suppose when Ben Nevis London International opens QNE might be a possibility
Does seem incredible that they lived. At least the RoD would be slow, just as they captured the glideslope and then "What's that rumbling noise?" 
Thanks for getting back to me. I thought as much, although it is mentioned in CAP 413; I suppose when Ben Nevis London International opens QNE might be a possibility
QFE would have come out to something like 837 mbs but the altimeter was set to 937 mbs - an error of some 3,000 ft!
Originally Posted by Whirlybird
But wait! If you DON'T use QFE, you have to remember how high the airfield is, and take that into account when landing.
You still need to check and remember the numbers when using QFE. The difference is that they are often, but not always, the same when using heights (1000 ft pattern height, 200 ft decision height etc.). The "but not always" part makes me think that using QNH is less likely to catch you out!
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I will never understand why you guys have this problem. Both in Germany and the USA you NEVER get QFE... the only time I even heard of it was in ground school. QNH is used everywhere! Only the glider fliers use QFE but only for traffic patterns...they set the altimeter to 0 while still on the ground... most don't even know it's called QFE! 
And who needs the needle on 0 when landing....I see the elevation of the field in my chart, the traffic pattern is noted in altitude MSL, as is every obstacle and landscape, so I need QNH... and when I land, I look OUT and not at my altimeter anyway!
Maybe the UK uses QFE because your country is so flat!
Westy
And who needs the needle on 0 when landing....I see the elevation of the field in my chart, the traffic pattern is noted in altitude MSL, as is every obstacle and landscape, so I need QNH... and when I land, I look OUT and not at my altimeter anyway!
Maybe the UK uses QFE because your country is so flat!
Westy
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Originally Posted by WestWind1950
Maybe the UK uses QFE because your country is so flat!
On going flying in less flat areas - a joyride from Brnik comes to mind - I've said things like: "I can't see how QFE would be much use to you here, you must do everything on QNH" to get the puzzled reply "yes of course".
Where I usually fly, ATC will give you QFE if you've booked out for circuits, QNH if you've booked out for anything else. But with airfield elevation of 49' it doesn't make a vast deal of difference.