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QNH or QFE ?

Old 12th Aug 2018, 08:30
  #61 (permalink)  
 
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Q-Codes;- a brilliant, ground-breaking idea - in 1909. Possibly not that relevant, or even useful, more than a century later? Discuss.
QFE? Ridiculous.
It is interesting to note in the 1949 Air Ministry book of Q Codes that QNH did not exist at that time! The two pressures used were QFE, surface pressure at an aerodrome and QFF, pressure at mean sea level. QNH first appeared in the eraly 1950s following an amendment to the method of determing the Sea Level Pressure when not at sea level.
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Old 15th Jul 2020, 21:01
  #62 (permalink)  
 
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Altimeter index

Originally Posted by India Four Two View Post
That would require changing a lot of altimeters - over 200,000. It's not going to happen.
Is it true that western altimeters don’t have index mark which you set to barometric (pressure altitude) of runway airfield, so that on touchdown you read 0 height (QFE), especially in mountainous areas.
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Old 2nd Aug 2020, 06:48
  #63 (permalink)  
 
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The last bastion of QFE is the RAF , this is largely because it helps those flying a high workload fast jet that has minimal navigation kit recover using PAR ( usually with less than ten minutes fuel remaining) Did not need another thing to think about so having the runway at zero on the altimeter was a good idea.

Things have moved on and the fast jets carry far more navigation kit now so recovering aircraft in IMC is much less fraught so once the “When I was on Lightning’s” brigade has retired you can expect a change to a more international way of doing things.

I expect QFE to continue in UK flying clubs for some time as most of them still teach ancient techniques such as Gypsy style engine management when For the last forty years they have been operating Lycomings.
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Old 2nd Aug 2020, 11:03
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Originally posted 100 years ago - QFE . . . who needs it?
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Old 2nd Aug 2020, 12:43
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Discorde: Until you can persuade flying schools to stop teaching QFE procedures then nothing will change! I have even noticed going into my nearest busy GA field that the A/G operators will refuse to give QNH to arrivals even when requested - only give it for departures!! Go figure.
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Old 2nd Aug 2020, 17:42
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Originally Posted by powtough View Post
Is it true that western altimeters don’t have index mark which you set to barometric (pressure altitude) of runway airfield, so that on touchdown you read 0 height (QFE), especially in mountainous areas.
You might very soon run out of scale. The one I'm using most has 940hPa as smallest value.
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Old 2nd Aug 2020, 18:14
  #67 (permalink)  
 
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I have even noticed going into my nearest busy GA field that the A/G operators will refuse to give QNH to arrivals even when requested
Might well be the same level of "intelligencies" that voted "pro" Br_x_t.

(and by the way, thanks for correctly naming A/G operators - there are those who want to call them controllers, even if they do not control any airspace)

Last edited by Jan Olieslagers; 3rd Aug 2020 at 15:58.
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Old 3rd Aug 2020, 05:56
  #68 (permalink)  
 
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My home airfield is 73ft AMSL thus only 2mb difference - an easy bit of maths if only QFE offered.
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Old 3rd Aug 2020, 05:57
  #69 (permalink)  
 
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Originally Posted by Meikleour View Post
Discorde: Until you can persuade flying schools to stop teaching QFE procedures then nothing will change! I have even noticed going into my nearest busy GA field that the A/G operators will refuse to give QNH to arrivals even when requested - only give it for departures!! Go figure.
ATC, AFIS and A/G should all pass QNH as standard with QFE available only on request according to CAA guidance issued about 15 years ago.
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Old 3rd Aug 2020, 12:08
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Originally Posted by chevvron View Post
ATC, AFIS and A/G should all pass QNH as standard with QFE available only on request according to CAA guidance issued about 15 years ago.
chevvron: thanks for that info - good luck with pointing that out to Headcorn A/G!
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Old 3rd Aug 2020, 12:23
  #71 (permalink)  
 
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I sometimes fly in Colorado and with the airfield elevation at 6870 ft there is no way you'll use QFE.
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Old 3rd Aug 2020, 17:05
  #72 (permalink)  
 
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Originally Posted by Meikleour View Post
chevvron: thanks for that info - good luck with pointing that out to Headcorn A/G!
Presumably you read my bit about Headcorn on the 'other' forum, but I'm told the A/G operator when that occured has left there now.
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Old 4th Aug 2020, 11:25
  #73 (permalink)  
 
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Since the last part of flying is done visually, is it really that relevant having your altimeter show 0 when landing at all? Once you pass the DH or DA you look out the windows anyway... or am I doing something wrong here?
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Old 4th Aug 2020, 16:41
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I guess that most of the anti-QFE contributors don't have display authorisations. The vertical limits are all expressed in heights in "CAP 1724 Display Standards Document". Converting altitudes to heights several times in an aerobatic figure is probably not good for a display pilot's health. Yes, the need to set QFE is not necessary for most regions of flight - but for some activities it makes more sense than QNH. I'm sure contributors can find other examples where QFE is the safest option. Not all flights are take off - cruise - land.
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Old 4th Aug 2020, 18:16
  #75 (permalink)  
 
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Originally Posted by Jim59 View Post
I guess that most of the anti-QFE contributors don't have display authorisations.
In the USA (and other countries) how do pilots performing aerobatic displays above high-elevation airfields set their altimeters?
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Old 4th Aug 2020, 18:54
  #76 (permalink)  
 
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This argument has gone on for as long as I can remember. to the extent its almost pointless. I would hope that anyone performing low level aerobatics will have it firmly implanted in their minds the altitudes or heights that must be achieved both at the top and at the bottom of a manoeuvre. The QNH pilot listens in a wonder of disbelief that anyone would mess around with the altimeter at critical moments (resetting to QFE). Knowing the elevations is part of everyday flying for QNH pilots. The only rule that I demand is that you fly one or the other and then use it at all times, but never mix it. If an a/g operator refuses to pass the QFE or other wise QNH ( a FISO or ATC will never refuse) this will require a very stern chat with the fool after landing such that he/she will never refuse to do so again.

In the majority of countries throughout the world QNH is the norm.
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Old 4th Aug 2020, 19:37
  #77 (permalink)  
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I was born and bred with QFE & used QFE for 33 years of RAF flying.
I much prefer QNH.
(& in my glider always have height + altitude + FL all on display in front of me; modern electronics)
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Old 4th Aug 2020, 23:31
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In the USA (and other countries) how do pilots performing aerobatic displays above high-elevation airfields set their altimeters?


Discorde,

The same way as everyone else - they use the current Altimeter Setting (QNH* to you) and then convert all their gate heights to the appropriate altitude.

Of course, sometimes pilots get it wrong:





Just out of interest, I checked the Winter altimeters in my club’s two-week old ASK21B. With the field elevation of 3700’ set, the sub-scale read 1020 mb. I then made 43 twists of the knob to bring the altitude to 0’ and the sub-scale read 997 mb. I was surprised I was able to do this. Last time I tried this many years ago on an old US altimeter, I ran out of sub-scale.

The observant will notice I used mb rather than inches. This is because our glider was delivered with European altimeters! We shall be having words with the factory!

Using the Altimeter Setting doesn’t seem to cause any problem for new pilots. Our students have no difficulty figuring out that the downwind leg starts at 4500’ (800’ AGL).

* I would guess that 99% of North American light plane pilots would have no idea what QNH, QFE or any of the Q codes are.
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Old 5th Aug 2020, 07:46
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Originally Posted by India Four Two View Post
The observant will notice I used mb rather than inches. This is because our glider was delivered with European altimeters! We shall be having words with the factory!
Those damn europeans!

On a side note, when I flew glider, we had a polish model, and the altimeter was in metres.... which is probably "meters" now that the UK has left the EU.
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Old 5th Aug 2020, 08:13
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Originally Posted by Fl1ingfrog View Post
The QNH pilot listens in a wonder of disbelief that anyone would mess around with the altimeter at critical moments (resetting to QFE). Knowing the elevations is part of everyday flying for QNH pilots. The only rule that I demand is that you fly one or the other and then use it at all times, but never mix it.
What is the "QNH pilot"? Is that someone who never flies above transition altitude?
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