QFE and QNH question
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QFE and QNH question
Hi all!
This is my first post to PPRuNe and I am currently in the early stages of modular training for my PPL with Flying Time Aviation at Shoreham Airport (EGKA).
I have read through various threads by others and find them to be very useful, but have a question of my own regarding the (eye rolls by the most experienced members!) QFE and QNH use. Any help would be much appreciated.
I feel I understand the general difference between the three altimeter pressure settings, QFE, QNH and STANDARD. My difficulty comes into understanding why QFE would actually be used at all? I was under the assumption that QFE being the HEIGHT above the aerodrome is most commonly used during activities remaining in it's proximity, such as circuits. What is its purpose though, when the field elevation is under 30ft, therefore being the same as the local QNH?
The aerodrome I train at (EGKA) has an elevation of 7ft AMSL, so both QFE's and QNH's are generally the same. I have never actually understood what when listening to the ATIS I am tuning into the altimeter pressure window? If I set QFE (which is what I believe I am) for local flights, why do charts use AMSL (QNH) for separation and traffic avoidance? Am I choosing between an easier to read approach over safety?
I appreciate that I am very new to this and probably missing something so straightforward
, but would appreciate any help from anyone regarding this.
This is my first post to PPRuNe and I am currently in the early stages of modular training for my PPL with Flying Time Aviation at Shoreham Airport (EGKA).
I have read through various threads by others and find them to be very useful, but have a question of my own regarding the (eye rolls by the most experienced members!) QFE and QNH use. Any help would be much appreciated.
I feel I understand the general difference between the three altimeter pressure settings, QFE, QNH and STANDARD. My difficulty comes into understanding why QFE would actually be used at all? I was under the assumption that QFE being the HEIGHT above the aerodrome is most commonly used during activities remaining in it's proximity, such as circuits. What is its purpose though, when the field elevation is under 30ft, therefore being the same as the local QNH?
The aerodrome I train at (EGKA) has an elevation of 7ft AMSL, so both QFE's and QNH's are generally the same. I have never actually understood what when listening to the ATIS I am tuning into the altimeter pressure window? If I set QFE (which is what I believe I am) for local flights, why do charts use AMSL (QNH) for separation and traffic avoidance? Am I choosing between an easier to read approach over safety?
I appreciate that I am very new to this and probably missing something so straightforward
, but would appreciate any help from anyone regarding this.
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QFE is used to make your altimeter read zero on the ground, so it will indicate your height above the airfield. There are occasions, as you have found, when it seems silly, especially in America when using QFE would take the altimeter off the scale, but it is useful nevertheless - for example in mountain flying, or using a longline with a helicopter. Nowadays the trend is to use QNH all the time anyway, and the pilot has to get used to reading the airfield elevation on the altimeter when on the ground.
Just remember the the word height relates to QFE and the word altitude relates to QNH. The term Flight Level relates to QNE.
It was early!
Just remember the the word height relates to QFE and the word altitude relates to QNH. The term Flight Level relates to QNE.
It was early!
Last edited by paco; 7th Apr 2014 at 14:50. Reason: oops
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Russia uses QFE below 5,000'. China might too, but I can't remember.
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Thank you paco and particularly LookingForAJob, you have both helped with my understanding!
I guess my understanding what a bit closer to it than I originally thought
I'm guessing that for the circuit, my instructor will want me to stay on the QFE but as I progress, QNH will be adopted.
Many thanks again guys!
I guess my understanding what a bit closer to it than I originally thought
I'm guessing that for the circuit, my instructor will want me to stay on the QFE but as I progress, QNH will be adopted.
Many thanks again guys!
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QFE
The last commercial bastion of QFE that I awere of was the Channel Express HP7 fleet about twenty years back.
The main reason that it is still used by the military is to recover fast jets by PAR, it keeps what is a very high cockpit workload to a minimum.
In normal IFR flight QFE is a hazard as at the time of the highest workload, a go around you are expected to change from QFE to QNH and then back for the next approach, the whole thing is a hazard that is unnessesary and fortunately has been consigned to the flying clubs ( some of who are still teaching people Tiger moth limitations to fly diamonds) and very specialist applications such as the military fast jet world.
The main reason that it is still used by the military is to recover fast jets by PAR, it keeps what is a very high cockpit workload to a minimum.
In normal IFR flight QFE is a hazard as at the time of the highest workload, a go around you are expected to change from QFE to QNH and then back for the next approach, the whole thing is a hazard that is unnessesary and fortunately has been consigned to the flying clubs ( some of who are still teaching people Tiger moth limitations to fly diamonds) and very specialist applications such as the military fast jet world.
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A and C, I haven't heard it used in the "West" but QFE is stilled used in Russia.
Fortunately our a/c can flick easily between feet and metres and we brief the height thing early.
Ah! I see this has moved to the Private Flying forum. I doubt many PPL holders will fly in Russia.
Fortunately our a/c can flick easily between feet and metres and we brief the height thing early.
Ah! I see this has moved to the Private Flying forum. I doubt many PPL holders will fly in Russia.
Last edited by redsnail; 7th Apr 2014 at 22:29. Reason: Shifted forum.
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In normal IFR flight QFE is a hazard as at the time of the highest workload, a go around you are expected to change from QFE to QNH and then back for the next approach
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The main reason that it is still used by the military is to recover fast jets by PAR, it keeps what is a very high cockpit workload to a minimum.
When I was going through training there was a period when the military wanted to switch to using QNH and we 'trialled' it by flying circuits at 1000' + the altitude of the airfield. It just became an unnecessary complication for the airfields in the UK, given their close proximity to sea level, and so the experiment was ditched and we went back to 1000' QFE.
Of course, QNH makes much more sense when you start flying in different parts of the world where the airfields are thousands of feet above sea level. Likewise it proves the low transition altitudes that we see in the UK a complete nonsense. I think it would be jolly nice to standardise with QNH and a decent TA, such as the 18000' used by the septics. Mind you, we'd have to get everyone onboard and at the moment the Chinese seem more determined to make things less standard. Of course they use metres but some airports use QNH, whereas others use QFE. There are recent changes to their approach charts that previously had the altitudes and heights in feet but they're now using metres on those too. Add in their switching to KMs for distance on charts and it all becomes a bit of a mess.
Radalts are great but not when the terrain around the airport in hilly
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I think it would be jolly nice to standardise with QNH and a decent TA, such as the 18000' used by the septics.
As Pontius says, there's no extra workload for a PAR. In fact as one of the few civvies I suspect that uses them I can attest that they are the easiest hand flown approaches by far of the lot.
Each to his or her own. For my part, QFE makes good sense in the circuit. I would also hope it would take some of the workload away in the event of a forced landing although I acknowledge that QFE only gives height above the aerodrome and the surrounding countryside is rarely flat. Nevertheless, not having to do mental gymnastics when everything else is going wrong has got to be a good thing, especially in an EFATO.
This has sparked a thought though. I presume it would not be that difficult for GPS to give a height reading given it knows the altitude and many also know the ground topography - a virtual radalt.
This has sparked a thought though. I presume it would not be that difficult for GPS to give a height reading given it knows the altitude and many also know the ground topography - a virtual radalt.
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When doing circuit work I've always used QFE but as it only relates to the ground height of a specific point (the airfield) then that is the only time it is useful. As soon as I'm out of the circuit, it is QNH.
GPS height readings can't be trusted unless you are using a device which has SBAS (like EGNOS or WAAS). The accuracy can be all over the shop and it also depends on which Geoid is in use as well as how accurate the terrain database is. At best it might be OK as a gross error check.
GPS height readings can't be trusted unless you are using a device which has SBAS (like EGNOS or WAAS). The accuracy can be all over the shop and it also depends on which Geoid is in use as well as how accurate the terrain database is. At best it might be OK as a gross error check.
Binners93, you raise a good question: Why is QFE actually used at all?
The answer: In most countries it's not used at all.
And I have to support British pilots who are campaigning for a common transition altitude. If much larger countries can do it, so can Little Britain.
The answer: In most countries it's not used at all.
And I have to support British pilots who are campaigning for a common transition altitude. If much larger countries can do it, so can Little Britain.
but as I progress, QNH will be adopted.
I suggest you ask your instructor if you can fly circuits on QNH.
I learned to fly in England (QFE, QNH, Barnsley, Portland, etc) and then moved to Canada after 200 hours. Since then, apart from a couple of £200 hamburgers in the UK (
), I've never used QFE again.A lot of my flying was at Calgary International (3550') and the nearby gliding club at Black Diamond (3800'). Students never have any problem adding 1000' to the field elevation in order to fly a circuit, mainly because they've never been exposed to anything else.
Even if you wanted to use QFE, you couldn't because you can't wind the altimeter back that far!
Good luck with your PPL.
The dangers of QFE usage were discussed in this thread.