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No, not that QFE/QNH debate.

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No, not that QFE/QNH debate.

Old 6th Feb 2020, 11:12
  #21 (permalink)  
 
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Originally Posted by oggers View Post

Quote:
30 feet per Millibar has worked well for the past 50 years

I second that.
At sea level, yes
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Old 6th Feb 2020, 15:07
  #22 (permalink)  
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Originally Posted by chevvron View Post
No it's as bob says; the 'highest point on the landing area'. And it's the CAA not NATS.
My mistake chevvron - apologies. Could you point me to where on the CAA site I should be getting these data? I've been using the AIP on the NATS site (section 2.2 part 3 - which I see is "Aerodrome Elevation" and NOT ARP elevation).
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Old 6th Feb 2020, 17:44
  #23 (permalink)  
 
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Getting back to reality, I see no need for QFE.
If you were a sailplane pilot you probably would see a need. When working out if you can reach your destination on a glide your key numbers are your height above the airfield, the distance to run and your current glide angle. With a performance of 45:1 you can cover a little over 7 nm per 1,000 feet so to get there with 1,000' spare to do the circuit and landing you need to be at or around 2,000' QFE with 7 miles to run or 3,000 at 14 nm. Trying to do that calculation based on QNH just complicates the issue.

Eurocontrol Definition of Aerodrome Reference Point
The aerodrome reference point shall be located near the initial or planned geometric centre of the aerodrome and shall normally remain where first established.

Eurocontrol Definition of Aerodrome Elevation
The vertical distance above Mean Sea Level (MSL) of the highest point of the landing area.

Hence the aerodrome elevation is not necessarily determined at the reference point.
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Old 6th Feb 2020, 17:51
  #24 (permalink)  
 
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CAA sets rules and standards for the UK, NATS currently has the contract to publish the AIP which includes such reference data. The definition for aerodrome elevation is quite specific, and comes from ICAO. The Aerodrome Reference Point definition is rather less specific - the designated geographical location of an aerodrome - and varies between States and aerodromes within a particular state. In some cases the centre of the runway, or the main runway, is used, in others where there are three runways the centre of the 'cocked hat' has been used. As the world moves toward more comprehensive and accurate aeronautical data, the data which are required to be available are defined to a much greater degree so you'll be able to work out which stands are above below a runway threshold, and pretty much anything else you might want.
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Old 6th Feb 2020, 23:25
  #25 (permalink)  
 
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Originally Posted by Jim59 View Post
If you were a sailplane pilot you probably would see a need. When working out if you can reach your destination on a glide your key numbers are your height above the airfield, the distance to run and your current glide angle. With a performance of 45:1 you can cover a little over 7 nm per 1,000 feet so to get there with 1,000' spare to do the circuit and landing you need to be at or around 2,000' QFE with 7 miles to run or 3,000 at 14 nm. Trying to do that calculation based on QNH just complicates the issue.
That's only true if you intend to land at the field you departed from. How do you translate QFE to an off-field landing site? It's easier with QNH and a chart.
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Old 7th Feb 2020, 09:10
  #26 (permalink)  
 
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Originally Posted by MarcK View Post
That's only true if you intend to land at the field you departed from. How do you translate QFE to an off-field landing site? It's easier with QNH and a chart.
An off-field landing in a glider is usually a field landing. Everything is flown by eye, the altimeter is ignored. Even if it's landing at another glider site the circuit etc. would be flown by eye.
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Old 7th Feb 2020, 16:09
  #27 (permalink)  
 
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Originally Posted by ZG862 View Post
Thank you for your contribution gentlemen. However, please see post 1....
So why would anyone not living in a flat country even care about QFE? What's the QFE for Denver (KDEN) on a standard day?
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Old 7th Feb 2020, 16:29
  #28 (permalink)  
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Originally Posted by Jim59 View Post
Eurocontrol Definition of Aerodrome Reference Point
The aerodrome reference point shall be located near the initial or planned geometric centre of the aerodrome and shall normally remain where first established.

Eurocontrol Definition of Aerodrome Elevation
The vertical distance above Mean Sea Level (MSL) of the highest point of the landing area.

Hence the aerodrome elevation is not necessarily determined at the reference point.
Good shout Jim - I will need to look beyond UK eventually.

Originally Posted by MarcK View Post
So why would anyone not living in a flat country even care about QFE? What's the QFE for Denver (KDEN) on a standard day?
I don't doubt that the subject of whether or not QFE is a good thing is very interesting, as is Denver's elevation. It's just not the subject of this topic.
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Old 7th Feb 2020, 17:02
  #29 (permalink)  
 
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Originally Posted by ZG862
Thank you for your contribution gentlemen. However, please see post 1....
A feature of these mainly-recreational discussion boards is the Chinese Whisper effect that takes place and the resulting thread drift. It is part of the interest in following a thread and, perhaps, making the occasional comment. If you want to ask a question such as that in post 1 and get a straightforward reply to your question without any deviation, repetition or hesitation then ask a good flying instructor.
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Old 7th Feb 2020, 17:14
  #30 (permalink)  
 
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Provided cct. heights are nice round numbers (800', 1000 etc.) above airfield height, QNH is simplest for me over the last 50 years of light aviation mostly UK, but a few in Australia, Jamaica, USA & Europe.

I can add 1000 quicker in my head to an airfield's charted elevation to instantly get the correct pattern height reading which is of course just the same figure as the a/f + 1000
Whereas QFE afficionados require ATC to tell you theirs, then remember the figure a few seconds, or write it on your knee pad, then head down again a short while for knob fiddling - just to get that round 1000' number onto the dial.

I agree that annoyingly, well in my bit of the UK, most Ground Radio operators insist on calling out QFE, but not QNH (which I can't be fagged to ask for & I get earlier from an ATIS or Farnborough,Gatwick etc],

So I just acnkowledge the QFE and ignore it - I prefer looking out of the window when nearing a cct that may be holding NR.traffic too..

I know dyed in the wool folk always bang on about their favourite way, so logic and ease of QNH will still mean zilch if you have become accustomed to one [or the other] !
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Old 7th Feb 2020, 18:06
  #31 (permalink)  
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Originally Posted by Jim59 View Post
A feature of these mainly-recreational discussion boards is the Chinese Whisper effect that takes place and the resulting thread drift. It is part of the interest in following a thread and, perhaps, making the occasional comment. If you want to ask a question such as that in post 1 and get a straightforward reply to your question without any deviation, repetition or hesitation then ask a good flying instructor.
Thanks for your invaluable thoughts.

Last edited by ZG862; 7th Feb 2020 at 22:51. Reason: The brevity of life.
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Old 8th Feb 2020, 10:18
  #32 (permalink)  
 
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Altimetry referenced to atmospheric pressure will before too long be relegated to history:

International Altimetry Changeover Date

. . . standing by for incoming from 862 . . .
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Old 8th Feb 2020, 19:43
  #33 (permalink)  
 
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I'm with SND ( Cheers, "Two Six" )

I've done a whole load of flying over Norway and Sweden operating from countless aerodromes where there was often nobody on the wireless to read out any numbers. A QNH from a local-ish big airport was obtained by listening to big stuff and ATII, and paying close attention to terrain and aerodrome elevations. Aerodrome Elevation is far more important than any 'QFE'...
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Old 9th Feb 2020, 12:09
  #34 (permalink)  
 
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On the other hand QFE is invaluable in circuit flying, especially in ab-initio training. Flying circuits on QNH seems utterly daft to me.
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Old 9th Feb 2020, 13:32
  #35 (permalink)  
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It appears that there has been lots of discussion on the original topic, thanks for that.

The value to fly with reference to QNH vs QNE was outside the scope of the original question, fair enough, and why I did not make any contribution to the question asked. The only experience I have landing on a runway with my altimeter indicating zero, were those landings I've flown to the ocean, or on sea level runways. I've been comfortable with that, so did not feel I could contribute much to this topic.

If there are any other helpful comments to be made on topic, please do, otherwise, we'll call it a day for this thread.

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