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Author Topic: runway elevation  (Read 3553 times)

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pcochrane12

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runway elevation
« on: June 08, 2008, 07:06:08 AM »
hi all
is there any way to have landing aircraft regestering 0ft on landin.Newcastle rwy25 elevation is 266ft and i have QNH set currently 1023 yet aircraft still say 300ft whilest taxing
cheers paul

Allocator

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Re: runway elevation
« Reply #1 on: June 08, 2008, 08:16:02 AM »
Paul,

Civilian airports use QNH - pressure at sea level.  Military airfields often use QFE - pressure at airfield elevation.  Only when you have QFE set will the aircraft read 0ft on landing, unless the airfield is at sea level and QNH is in use.

If you want the aircraft at Newcastle to show 0ft, then you will need to subtract 8.8 mb from the QNH

One mb = 30 ft
266 divided by 30 = 8.8
Pressure decreases with height
The airfield is higher than sea level, so subtract 8.8 mb from the QNH

Of course, if you do this, then what you see will not correspond to ATC instructions as the aircraft will be flying on QNH.

See here for more details:

http://en.wikipedia.org/wiki/QNH

pcochrane12

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Re: runway elevation
« Reply #2 on: June 08, 2008, 08:24:57 AM »
thanks allocator will try that see how it goes thanks