Airfield QNH - what's the point?
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On the otherhand, I can't particularly see why a VFR pilot needs more than one mental math cacluation in a QNH system, to add 1000 to the field elevation to get the circuit height (which can normally be acheived simply by reading the pre-calculated number off the airfield plate). The rest of the process is by eye anyhow.
I'm not trying to fix anything, if it works for you to fly on QFE, Fly on QFE. It works better for me to use QNH. Pretty much everywhere I fly or have flown is close enough to controlled airspace or terrain for me to use QNH so I know my altitude is the same as everybody elses altitude and the numbers on the chart and I am not flying to a height.
The AIP Entry for Redhill sets out the local proceedures based on QNH.
http://www.redhillaerodrome.com/imag..._aip_mar12.pdf
Look at "3. Redhill Local Flying Area (LFA) and Procedures"
I have never heard anybody either ask for or be given QFE
It works for me to have one universal process .... and I have flown around the US Airforce Academy.
The AIP Entry for Redhill sets out the local proceedures based on QNH.
http://www.redhillaerodrome.com/imag..._aip_mar12.pdf
Look at "3. Redhill Local Flying Area (LFA) and Procedures"
I have never heard anybody either ask for or be given QFE
It works for me to have one universal process .... and I have flown around the US Airforce Academy.
Last edited by Dave Gittins; 13th Jul 2012 at 13:32.
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I seriously cannot see why we need several different Q things for altimeter settings. It seems totally illogical that the altimeter reading should need changing in the vicinity of an airfield. Shirley one setting based on a single base line should suit?
If everyone, including CAT below TL, were on the same setting & we all fly at 2000ft on the same setting, heading for the same spot, there will be an almighty bang! Which would be a simple thing to avoid.
I may be missing something, but does an aircraft on an autoland approach rely on the altimeter setting (set by the Captain) to make a precision touchdown? I really don't know how these things work. If so, one digit out & it will land 32ft too early or late?
No doubt this argument will perpetuate ad infinitum. Can someone answer the question. How many CAS altitude busts are there in America caused by the pilot using the wrong Altimeter Setting compared to the UK? To my mind the whole confusing pile of utter ****e is a recipe for disaster. And it is high time the Government, CAA, AOPA, LAA, BMAA, BGA & Uncle Tom Cobleigh and all, including the Military, got their heads out of their arses & sort it out.
Just the opinion of a low hrs NPPL with a worn out altimeter setting knob.
Yes. I remain on RPS till the a/c is in the hangar.
If everyone, including CAT below TL, were on the same setting & we all fly at 2000ft on the same setting, heading for the same spot, there will be an almighty bang! Which would be a simple thing to avoid.
I may be missing something, but does an aircraft on an autoland approach rely on the altimeter setting (set by the Captain) to make a precision touchdown? I really don't know how these things work. If so, one digit out & it will land 32ft too early or late?
No doubt this argument will perpetuate ad infinitum. Can someone answer the question. How many CAS altitude busts are there in America caused by the pilot using the wrong Altimeter Setting compared to the UK? To my mind the whole confusing pile of utter ****e is a recipe for disaster. And it is high time the Government, CAA, AOPA, LAA, BMAA, BGA & Uncle Tom Cobleigh and all, including the Military, got their heads out of their arses & sort it out.
Just the opinion of a low hrs NPPL with a worn out altimeter setting knob.
If you fly from a strip why on earth do you use QFE? Don't most farmstrip flyers just eyeball it?
Last edited by Crash one; 13th Jul 2012 at 15:31.
From a Pprune thread a thousand years ago:
Having spent four decades flying aircraft both large and small I am convinced that GA altimeter setting procedures in the UK are far too complicated. Do we really need Regional Settings? Do we really need QFE? The VFR pilot flying in Class G airspace has to reset his or her altimeter several times. Two problems arise: firstly, there is always a chance of setting an incorrect subscale setting every time it is adjusted and secondly, distraction during resetting can draw the pilot’s attention away from other vital tasks, such as lookout and navigational monitoring.
A simpler procedure would be to set local QNH for the whole flight, resetting only if the QNH changes. Rarely does barometric pressure change rapidly, so even if the subscale was not reset at all during the flight the resulting altimeter error would be unlikely to exceed 100 feet or so. Is this significant for VFR flight?
Two further advantages of ‘local QNH’ flight are improving terrain awareness (which QFE degrades) and reducing the potential for violation of controlled airspace, which in the lower levels usually has a base expressed as an altitude. For student pilots doing circuit work, patterns flown with QNH set would not be difficult to learn. When they came to land away from base, adding field elevation to pattern heights to determine pattern altitude would be part of their pre-flight preparations and could be recorded on the nav log. If a MATZ controller specifies a QFE-based penetration height it is easy to convert this to a QNH-based altitude, rounding up or down to the nearest 100 ft.
Finally, it should be noted that commercial airliners around the world fly local QNH below transition altitude and 1013 above it. If it works for the big boys and girls, why not for GA traffic too?
Having spent four decades flying aircraft both large and small I am convinced that GA altimeter setting procedures in the UK are far too complicated. Do we really need Regional Settings? Do we really need QFE? The VFR pilot flying in Class G airspace has to reset his or her altimeter several times. Two problems arise: firstly, there is always a chance of setting an incorrect subscale setting every time it is adjusted and secondly, distraction during resetting can draw the pilot’s attention away from other vital tasks, such as lookout and navigational monitoring.
A simpler procedure would be to set local QNH for the whole flight, resetting only if the QNH changes. Rarely does barometric pressure change rapidly, so even if the subscale was not reset at all during the flight the resulting altimeter error would be unlikely to exceed 100 feet or so. Is this significant for VFR flight?
Two further advantages of ‘local QNH’ flight are improving terrain awareness (which QFE degrades) and reducing the potential for violation of controlled airspace, which in the lower levels usually has a base expressed as an altitude. For student pilots doing circuit work, patterns flown with QNH set would not be difficult to learn. When they came to land away from base, adding field elevation to pattern heights to determine pattern altitude would be part of their pre-flight preparations and could be recorded on the nav log. If a MATZ controller specifies a QFE-based penetration height it is easy to convert this to a QNH-based altitude, rounding up or down to the nearest 100 ft.
Finally, it should be noted that commercial airliners around the world fly local QNH below transition altitude and 1013 above it. If it works for the big boys and girls, why not for GA traffic too?
Whilst I would admit to being a supporter of QNH only, it doesn't matter whether you use QFE or QNH so long as you manage the altimeter(s) correctly.
I am not at all surprised by the comments made by those who prefer QFE because they have probably never flown QNH only so it seems a bit like going to the moon for them.
I invite all those who fly QFE to trial flying QNH for, say. the next 20/50 hours - I think you'd probably find you prefer it after a while - there is far less significant change of subscale setting on a flight and therefore. I would suggest, less likelihood of incorrectly setting the subscale.
As has been correctly stated we don't really have any high elevation airfields in the UK but if you had learned to fly at Nairobi which is circa 5,000 ft amsl I don't think you would have been brought up to use QFE - or would you prefer to change the subscale by about 167 millibars (ahem I am sorry Hectopascals) every time you come back into the traffic pattern or whilst you are flying the missed approach from the ILS?
I am not at all surprised by the comments made by those who prefer QFE because they have probably never flown QNH only so it seems a bit like going to the moon for them.
I invite all those who fly QFE to trial flying QNH for, say. the next 20/50 hours - I think you'd probably find you prefer it after a while - there is far less significant change of subscale setting on a flight and therefore. I would suggest, less likelihood of incorrectly setting the subscale.
As has been correctly stated we don't really have any high elevation airfields in the UK but if you had learned to fly at Nairobi which is circa 5,000 ft amsl I don't think you would have been brought up to use QFE - or would you prefer to change the subscale by about 167 millibars (ahem I am sorry Hectopascals) every time you come back into the traffic pattern or whilst you are flying the missed approach from the ILS?
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I may be missing something, but does an aircraft on an autoland approach rely on the altimeter setting (set by the Captain) to make a precision touchdown?
Funny how the thread stated with how we should get rid of QNH and has turned into getting rid of QFE.
For the people who use QFE it works just fine, most are occasional GA pilots who are happy joining a circuit at a known height. Some even fly an entire local flight on the QFE from wherever they departed.
It's one of those things that makes the UK different, and I don't see it changing anytime soon.
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Quote:
I may be missing something, but does an aircraft on an autoland approach rely on the altimeter setting (set by the Captain) to make a precision touchdown?
Aircraft with Autoland would have a very precise Radar Altimeter which shows the exact HEIGHT of the aircraft above the terrain below, therefore the aircraft knows exactly when to flare and reads zero when the wheels are on the ground.
I may be missing something, but does an aircraft on an autoland approach rely on the altimeter setting (set by the Captain) to make a precision touchdown?
Aircraft with Autoland would have a very precise Radar Altimeter which shows the exact HEIGHT of the aircraft above the terrain below, therefore the aircraft knows exactly when to flare and reads zero when the wheels are on the ground.
No doubt QFE works for some people but that doesn't mean that it is ok to use multiple systems, just because this is the UK & we are allowed to be different. Personally I have done circuits at my strip without even re-setting the altimeter from several days ago, & prob on RPS then.
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Personally I have done circuits at my strip without even re-setting the altimeter from several days ago, & prob on RPS then.
Just out of interest, have you ever thought what you would do if you were flying locally on a "several day old" altimeter setting and inadvertently found yourself in IMC?
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Silvaire, the transition level(s) in UK are under total review by the authorities at this present time. At the moment we have areas with different TLs, which isn't ideal (!) but it's likely that the UK will have an overall raised level in the not too distant future.
I'm often given the RPS, usually by the military controllers but I don't often set it, preferring to use local QNH unless operating further than 25 nm from an airfield, such as over certain areas in the north of UK. At such times I wind it on the smaller, third altimeter for reference.
Having been trained by the military to use QFE and RPS as "bread and butter", I hardly ever set it these days unless directed to fly on it during a MATZ crossing. I would probably set it for training circuits, but very seldom do those as I don't fly for a training organisation.
I'm often given the RPS, usually by the military controllers but I don't often set it, preferring to use local QNH unless operating further than 25 nm from an airfield, such as over certain areas in the north of UK. At such times I wind it on the smaller, third altimeter for reference.
Having been trained by the military to use QFE and RPS as "bread and butter", I hardly ever set it these days unless directed to fly on it during a MATZ crossing. I would probably set it for training circuits, but very seldom do those as I don't fly for a training organisation.
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Just out of interest, have you ever thought what you would do if you were flying locally on a "several day old" altimeter setting and inadvertently found yourself in IMC?
And if I were taking a CAA check ride I would behave correctly.
I like to enjoy my flying, I also like to practice flying the thing without ref to instruments, I like to practice accurate eyeball circuits & landings.
Or perhaps I should just say, Get a grip!!
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However, IF I were that stupid I would call someone on the wireless & ask for the Local Regional QFE. Simples.
Last edited by flybymike; 13th Jul 2012 at 23:15.
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I have never heard of a local regional QFE, and my granny used to call them a wireless...
And it ran off an Accumulator
Last edited by Crash one; 13th Jul 2012 at 23:21.
Flyingmac: I don't know where you got your info about the 'vast majority' of airfields not using QNH, but it's not true, especially when you take into account the CAA mandate the use of QNH as the main pressure setting to be used below TA. OK the QFE may be available for those who 'have' to use it, but as the 'vast majority' of airfields use circuit patterns based on QNH, they're very much in the minority!
When an aircraft joins the circuit and I pass QNH, and the pilot reads back 'QFE is....' I often wonder how they manage to pass their biennial.
When an aircraft joins the circuit and I pass QNH, and the pilot reads back 'QFE is....' I often wonder how they manage to pass their biennial.
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I use QNH only.
QFE is pointless, and most airports are not going to give it to you anyway. The RAF ones still love it though
You cannot fail the biennial, so long as the instructor is alive afterwards to sign your logbook.
QFE is pointless, and most airports are not going to give it to you anyway. The RAF ones still love it though
I often wonder how they manage to pass their biennial.
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However, IF I were that stupid I would call someone on the wireless & ask for the Local Regional QFE. Simples.
I find some of the responses on this thread deeply disturbing. How on earth could you possibly have a Local Regional QFE? Bizarre.
Last edited by JW411; 14th Jul 2012 at 09:28.
Flyingmac: I don't know where you got your info about the 'vast majority' of airfields not using QNH, but it's not true, especially when you take into account the CAA mandate the use of QNH as the main pressure setting to be used below TA. OK the QFE may be available for those who 'have' to use it, but as the 'vast majority' of airfields use circuit patterns based on QNH, they're very much in the minority!
When an aircraft joins the circuit and I pass QNH, and the pilot reads back 'QFE is....' I often wonder how they manage to pass their biennial.
When an aircraft joins the circuit and I pass QNH, and the pilot reads back 'QFE is....' I often wonder how they manage to pass their biennial.
If you fly from a strip why on earth do you use QFE? Don't most farmstrip flyers just eyeball it?
Last edited by Flyingmac; 14th Jul 2012 at 10:01.