Air Law exam on Saturday
Pompey till I die
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Join Date: Nov 2006
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Qfe & Qnh
I understand the differences between QFE & QNH but I don't understand how you convert heights between the two pressure scales, like this question:
Your aerodrome elevation is 24 ft, and the QFE you have just been given is 1021 millibars. What would you expect the aerodrome QNH to be?
A 1015 millibars
B 1020 millibars
C 1022 millibars
D 1027 millibars
There must be some mapping between the 2, but I just don't get it. Somehow I have to work out what the pressure difference is across 24ft and add it to 1021. Anyone ?
Your aerodrome elevation is 24 ft, and the QFE you have just been given is 1021 millibars. What would you expect the aerodrome QNH to be?
A 1015 millibars
B 1020 millibars
C 1022 millibars
D 1027 millibars
There must be some mapping between the 2, but I just don't get it. Somehow I have to work out what the pressure difference is across 24ft and add it to 1021. Anyone ?
Pompey till I die
Thread Starter
Join Date: Nov 2006
Location: Guildford
Age: 51
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Qfe & Qnh
I understand the differences between QFE & QNH. I don't understand how you map one to the other though, i.e.
Your aerodrome elevation is 24 ft, and the QFE you have just been given is 1021 millibars. What would you expect the aerodrome QNH to be?
A 1015 millibars
B 1020 millibars
C 1022 millibars
D 1027 millibars
Obviously I need to work out the pressure difference 24ft makes and add it to 1021 to get the result. Is there some constant mapping per foot of pressure ? Anyone ?
Thanks
Your aerodrome elevation is 24 ft, and the QFE you have just been given is 1021 millibars. What would you expect the aerodrome QNH to be?
A 1015 millibars
B 1020 millibars
C 1022 millibars
D 1027 millibars
Obviously I need to work out the pressure difference 24ft makes and add it to 1021 to get the result. Is there some constant mapping per foot of pressure ? Anyone ?
Thanks
Join Date: Aug 2005
Location: Hampshire
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You will be pleased to know its very easy.
Pressure drops as you get higher by approx 1mb per 30ft
so if your QNH is 1000mb (at MSL), your QFE at 30ft would be 999mb....
HTH
Steve
Pressure drops as you get higher by approx 1mb per 30ft
so if your QNH is 1000mb (at MSL), your QFE at 30ft would be 999mb....
HTH
Steve
Join Date: Oct 2006
Location: Ooh arrgh land
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I understand the differences between QFE & QNH. I don't understand how you map one to the other though, i.e.
Your aerodrome elevation is 24 ft, and the QFE you have just been given is 1021 millibars. What would you expect the aerodrome QNH to be?
A 1015 millibars
B 1020 millibars
C 1022 millibars
D 1027 millibars
Obviously I need to work out the pressure difference 24ft makes and add it to 1021 to get the result. Is there some constant mapping per foot of pressure ? Anyone ?
Thanks
Your aerodrome elevation is 24 ft, and the QFE you have just been given is 1021 millibars. What would you expect the aerodrome QNH to be?
A 1015 millibars
B 1020 millibars
C 1022 millibars
D 1027 millibars
Obviously I need to work out the pressure difference 24ft makes and add it to 1021 to get the result. Is there some constant mapping per foot of pressure ? Anyone ?
Thanks
I'm pretty sure that's right!.. I hope. It is past my bed time!
Well done on the exam pass!!