Flying Approaches on QNH
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Educated Hillbilly
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From: From the Hills
Flying Approaches on QNH
Always when landing at an aerodrome in the past, I have always set QFE, and it is what I would teach my students, however the school I work for has a policy that we and students should be taught to leave QNH set and even fly circuits and appoach to land with QNH set, not a problem at the "home" airfield because the qnh leads to a easy number for flying the circuit. However I feel for landing away at other aerodromes this could lead to confusion, ie; having to remember to add circuit height to local elevation in order to fly the correct circuit height if using the QNH. If flying cross country on a regional pressure setting you would need to reset to the aerodrome QNH,so why not just reset to QFE when inbound. This could be especially misleading flying (that is flying on the QNH) into a high airfield such as Dunkeswell or Compton Abbas.
Just wondering what anyone elses opinion is on this policy? Or am just showing my inexperience as an instructor.
Just wondering what anyone elses opinion is on this policy? Or am just showing my inexperience as an instructor.
Last edited by portsharbourflyer; 29th August 2006 at 23:02.
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From: U.K.
Do you have altimeter bug's? If not, then it is far better to go to QFE when necessary.
Airlines use QNH as a means of keeping terrain clearance simpler, but it does require a bit more mental gymnastics if you try and fly a 1000' agl circuit, as is the norm in GA.
It can just create confusion which can be minimised by sticking to QFE approaches as the rest of the industry uses.
Sticking to standard practices can help cut down confusion.
Airlines use QNH as a means of keeping terrain clearance simpler, but it does require a bit more mental gymnastics if you try and fly a 1000' agl circuit, as is the norm in GA.
It can just create confusion which can be minimised by sticking to QFE approaches as the rest of the industry uses.
Sticking to standard practices can help cut down confusion.
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From: Euroland
Use something that you can use everywhere, can always obtain and will always clearly show your altitude that you can compare to obstacles. Even the obstacles on aerodrome charts are shown AMSL.
As for confusion. Some airfields have circuit height of 800ft, some 1000ft, one I know is 1200ft and another uses 600ft, while yet another uses 1500ft and all are in the southern central part of England.
Prior to operating to another airfield, a pilot should note the level required for the circuit. It is simply a number that they will try to fly at on the altimeter. If that figure is 1700ft QNH then where is the confusion.
The only time I got close to obstacles was flying with a pilot who used QFE but forgot to set the altimeter joining the circuit resulting in the aircraft being 600ft lower than it should have been downwind. With a 800ft AAL downwind level, one would have expected the proximity of the trees and ground to be ringing alarm bells but no, they even initiated their descent out on base leg!..........all on a VFR flight!
Regards,
DFC
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Educated Hillbilly
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From: From the Hills
Thanks for the replies, good arguments either way, however lets keep this in context, it is ppl students we are instructing here flying in the UK and france, so QFE is always available.
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From: Escapee from Ultima Thule
What's their being a PPL student got to do with it? As was indicated earlier, elsewhere in the world QNH is used by everyone.
At least everyone's on a common setting, including transiting a/c. Even if one or the other is using a 'local' QNH & others an 'area' or 'regional' QNH the difference is minor. I know of no chart in common use that gives terrain w.r.t. QFE so what do you use during departure or arrival? What about mixing IFR & VFR traffic etc?
At least everyone's on a common setting, including transiting a/c. Even if one or the other is using a 'local' QNH & others an 'area' or 'regional' QNH the difference is minor. I know of no chart in common use that gives terrain w.r.t. QFE so what do you use during departure or arrival? What about mixing IFR & VFR traffic etc?
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From: Orlando, Florida
Nitpicking!
add circuit height to local elevation in order to fly the correct circuit height if using the QNH
'regional' QNH
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From: Downeast
QFE altimeter settings....yet another UK practice that begs belief.
If one uses QNH only.....that is one less mistake to make.
Yes I know the mental gymnastics of figuring the DH on an ILS is a tremendous burden for some but looking for 551 vice 0 ain't exactly rocket science.
Ever done the dance of setting three altimeters on an IF approach....compounded by a change in handling pilots during the Missed?
Then you have to remember which altimeter is set to what.....just like the old pea under walnut shell game.
If one uses QNH only.....that is one less mistake to make.
Yes I know the mental gymnastics of figuring the DH on an ILS is a tremendous burden for some but looking for 551 vice 0 ain't exactly rocket science.
Ever done the dance of setting three altimeters on an IF approach....compounded by a change in handling pilots during the Missed?
Then you have to remember which altimeter is set to what.....just like the old pea under walnut shell game.
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From: U.K.
In the U.K, the vast majority of GA uses QFE. It does cause problems with people not changing to it when arriving at a field and other similar situations, but it is the norm here.
DFC, don't be facetious, we all know they are a multitude of differing cct heights in use, but most are at 1000'. The confusion comes, because there is not an easy way of working out your height, or how far you have to descend. Simple on QFE, but with QNH you need to think about it, whilst we are talking about VFR flight, why introduce an element of uncertainty?
I don't like changes being forced on people which aren't standard in this environment, unless there is a really good reason, otherwise it is a waste of time. PPL members used to QFE will ignore it. New students will use it, but you then have a situation where half are doing one thing and half doing something else leading ultimately to confusion somewhere along the line.
I can understand the reasons for it. I have operated on both QNH and QFE with an airline and whilst I understand all the arguments for and against, I prefered approaching on QFE, but very quickly got used to QNH, though it really required altimeter bug's on approach to try and minimise the brainwork.
However, if someone is taught from day one to use QNH only, then fine, it is only an issue if you try and force occasional flyers into a new way of thinking. You are asking for trouble there.
For IMC/IR, what does the school use?
It sounds like this has been an edict from on high and making changes like this without discussion or explanation is not good practice. If the FI's aren't sure why they are doing it, then what chance to they have when a PPL demands an explanation to the change. In this case it seems to be "'cos I was told to" rather than having coherent reasoning behind the change.
DFC, don't be facetious, we all know they are a multitude of differing cct heights in use, but most are at 1000'. The confusion comes, because there is not an easy way of working out your height, or how far you have to descend. Simple on QFE, but with QNH you need to think about it, whilst we are talking about VFR flight, why introduce an element of uncertainty?
I don't like changes being forced on people which aren't standard in this environment, unless there is a really good reason, otherwise it is a waste of time. PPL members used to QFE will ignore it. New students will use it, but you then have a situation where half are doing one thing and half doing something else leading ultimately to confusion somewhere along the line.
I can understand the reasons for it. I have operated on both QNH and QFE with an airline and whilst I understand all the arguments for and against, I prefered approaching on QFE, but very quickly got used to QNH, though it really required altimeter bug's on approach to try and minimise the brainwork.
However, if someone is taught from day one to use QNH only, then fine, it is only an issue if you try and force occasional flyers into a new way of thinking. You are asking for trouble there.
For IMC/IR, what does the school use?
It sounds like this has been an edict from on high and making changes like this without discussion or explanation is not good practice. If the FI's aren't sure why they are doing it, then what chance to they have when a PPL demands an explanation to the change. In this case it seems to be "'cos I was told to" rather than having coherent reasoning behind the change.
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From: If this is Tuesday, it must be?
Over more than 20 years I have used both QNH and QFE, and personally I prefer QNH. For VFR it doesn't really make a lot of difference, especially when the circuit height is 1000' - particularly with a "round dial" altimeter. When flying IFR approaches (other than Cat III!) I've never yet seen a procedure with a DH of 0 - so all this nonsense about not having to remember or bug your decision/minimum descent height is total b*ll*cks.
Finally, for the less well travelled there are equally large parts of the world where there is no such thing as QNH - you transition from standard to QFE and back, usually using metres as well.
The absolute bottom line is that as long as the procedures are followed any of the systems work. You just need to make sure that you understand the system you are using. Human nature being what it is most people will swear that the system they were first taught is the only way to do it and anything else is the Devil's own invention!
Finally, for the less well travelled there are equally large parts of the world where there is no such thing as QNH - you transition from standard to QFE and back, usually using metres as well.
The absolute bottom line is that as long as the procedures are followed any of the systems work. You just need to make sure that you understand the system you are using. Human nature being what it is most people will swear that the system they were first taught is the only way to do it and anything else is the Devil's own invention!
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From: Euroland
DFC, don't be facetious, we all know they are a multitude of differing cct heights in use, but most are at 1000'. The confusion comes, because there is not an easy way of working out your height, or how far you have to descend. Simple on QFE, but with QNH you need to think about it, whilst we are talking about VFR flight, why introduce an element of uncertainty?
What VFR pilot descends from circuit altitude without being able to see the runway? One descends at the appropriate time at a rate that will cause the aircraft to land on the runway one is looking at. Can't be more simple!
Pilots who use QFE will generally depart using QNH. They will often plan the following;
Flaps up at 300ft AGL, turn at 500ft AGL, fuel pumps off at 1000ft AGL.
They then actually complete the above at 300ft AMSL, 500ft AMSL and 1000ft AMSL despite the aerodrome and terrain being some 200ft AMSL.
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Originally Posted by portsharbourflyer
Thanks for the replies, good arguments either way, however lets keep this in context, it is ppl students we are instructing here flying in the UK and france, so QFE is always available.
Regards,
DFC
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From: U.K.
There are other reasons for everybody in a circuit being at the same height, rather than just able to get the a/c on the deck safely, so why change a convention.
Especially as neither system is perfect.
My bigger concern is that the FI's at this school don't know why they are being asked to do something different.
Especially as neither system is perfect.
My bigger concern is that the FI's at this school don't know why they are being asked to do something different.
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From: UK
I've done a bit of flying in the UK and now New Zealand, where QFE is not used at all.
From my perspective I have found it simpler to not worry about QFE. In NZ there are a load of uncontrolled (and unattended) airfields so it is impossible to obtain a QFE, so everyone gets by on QNH.
I find the circuit altitude is easily found when you brief for the approach into a new airfield. The elevation is in the top corner of the plate so while you are still some miles away you can decide what your joining and circuit altitudes will be, then round it up to a reasonable figure (no point flying a circuit at 1184ft!). Couldn't be easier!
From my perspective I have found it simpler to not worry about QFE. In NZ there are a load of uncontrolled (and unattended) airfields so it is impossible to obtain a QFE, so everyone gets by on QNH.
I find the circuit altitude is easily found when you brief for the approach into a new airfield. The elevation is in the top corner of the plate so while you are still some miles away you can decide what your joining and circuit altitudes will be, then round it up to a reasonable figure (no point flying a circuit at 1184ft!). Couldn't be easier!
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From: Australia
QFE enthusiasts. Very dicey stuff. Stick to QNH and it is much safer especially when map reading around hills when you can check your height against a known spot height. Although I have never used QFE except by default at a sea level aerodrome, I imagine changing to use QNH is something like using look-over spectacles for the first time. You eventually get used to it and never look back.
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From: UK
Now, why on earth would you want to do that?
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From: UK
Circuits, particularly with students: QFE.
Departure/Take-Off checks on sortie to leave circuit: QNH
Departing ATZ: FREDA or somesuch checks to confirm/set QNH
Rejoining ATZ: FREDA etc checks, so QNH to QFE.
Initial/Intermediate/Final IFR approach checks: QNH
Or whatever it says in your training manual/company Ops Manual.
I think this is the UK system. It's what's been expected of me over the past 35 years both mil and civ. (Having said which, I think we were doing PAR on QFE at MoD airfields and perhaps still are?)
Departure/Take-Off checks on sortie to leave circuit: QNH
Departing ATZ: FREDA or somesuch checks to confirm/set QNH
Rejoining ATZ: FREDA etc checks, so QNH to QFE.
Initial/Intermediate/Final IFR approach checks: QNH
Or whatever it says in your training manual/company Ops Manual.
I think this is the UK system. It's what's been expected of me over the past 35 years both mil and civ. (Having said which, I think we were doing PAR on QFE at MoD airfields and perhaps still are?)
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From: Europe
QFE
As far as i know only in France and in UK pilots fly QFE, the rest fly QNH.
In UK and in most of the french airports you'll have no problem.
Problem will arise when you try to fly an approach on QFE in a high elevation airport, say QNH is 1013 in an airport where elevation is 3000 feet, tell me how are you going to set QFE in an altimeter where in the kollsman window you can only set 960 mb and higher
.
I have flown in several places, including France and UK, i had to use QFE, and in my opinion QNH is the best option.
The funny bit is that if you rquest QFE in most of the places (outside UK and France) it will take them more than a couple of seconds to provide you with it , because they wont be expecting your request in mos of the cases.
In UK and in most of the french airports you'll have no problem.
Problem will arise when you try to fly an approach on QFE in a high elevation airport, say QNH is 1013 in an airport where elevation is 3000 feet, tell me how are you going to set QFE in an altimeter where in the kollsman window you can only set 960 mb and higher
.I have flown in several places, including France and UK, i had to use QFE, and in my opinion QNH is the best option.
The funny bit is that if you rquest QFE in most of the places (outside UK and France) it will take them more than a couple of seconds to provide you with it , because they wont be expecting your request in mos of the cases.
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From: If this is Tuesday, it must be?
As I said before, QFE isn't just a UK & France thing, go East and you find a whole universe where there is no QNH, and you get a similar reaction to the one you describe if you ask for QNH.
When the UK built aircraft, altimeters could be wound down to about 750 for that very reason. Nowadays all the instruments are US made and so are designed for their system, which isn't a problem in the UK as there are no airfields above 1000' amsl. As you say, when you go to higher parts it is a problem, which is one reason why I prefer using QNH these days. However, see my earlier comments about all the systems work if they're used properly, and human nature!
When the UK built aircraft, altimeters could be wound down to about 750 for that very reason. Nowadays all the instruments are US made and so are designed for their system, which isn't a problem in the UK as there are no airfields above 1000' amsl. As you say, when you go to higher parts it is a problem, which is one reason why I prefer using QNH these days. However, see my earlier comments about all the systems work if they're used properly, and human nature!
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From: In a house
My local is 387' MSL and they like the left circuit to be flown at 800' AGL, it's a no-brainer that the student should be flying his/her circuits with the hands pointing to 1200'
I know which method is user friendly and hell of a lot safer where terrain is an issue.