Learning to fly, or thinking of learning? Post your questions, comments and experiences here

Moderator: AndyR

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#1819328
Hi! Why is it that the QNH AMSL is set into an Altimeter and not the QFE of the airport elevation when flying into an airport? Surely you want the Altimeter to read zero when on the ground, not an altitude above sea level. I`ve just been reading this in my PPL Book, it may explain further on but I`m a little confused and need to get this into my head. Ian
#1819334
QFE is widely used and will almost invariably be what is offered to you by FISO and A/G at GA airfields.

Some pilots don't like this and prefer to retain QNH and do the sums needed to calculate the circuit height.

It matters little. Just use whatever works for you.

Rob P
JAFO liked this
#1819338
Flippant answer ....... move to Lincolnshire, they're both the same....

More serious answer ....... think about your next clearance, or the missed approach procedure.
Invariably at a larger airfield the missed approach procedure will be defined with reference to QNH - e.g. climb straight ahead to altitude 2000ft, then blah blah blah, or if doing a practice low approach and go-around, your instruction after the go-around is likely to reference QNH.
If you are flying an instrument approach, the primary references will be to altitudes (e.g. join at altitude 2000ft until intercepting the glideslope).
Therefore larger airfields tend to work with altitudes (QNH) ........ at a smaller airfield you can choose your own preference, and many choose height (QFE) for the simplicity of being at zero on the runway.
Last edited by rikur_ on Sun Jan 10, 2021 5:45 pm, edited 1 time in total.
#1819342
(Depends on the airport. If it's inside or near controlled airspace the QNH is more useful to prevent infringing) This makes perfect sense, we are close to Manchester Airport where the TMA starts at 3,500ft. If I was to set my Altimeter to QFE and was advised to fly at 3,500ft, I would be about 300ft inside the TMA. Thank you so much for the Information. Ian
#1819344
QFE is very much a UK anomaly (although Russia also use it, and in meters!) but these days isn't used in Big Aviation, everything is either QNH or Standard (1013). You can use whatever you like in the circuit, if you want to use QNH then simply add the airfield elevation to the circuit height and fly that. There is less room for mis-setting as well.
johnm, T67M liked this
#1819351
I’m not sure that you can say they QNH is “standard”. In my experience, at a GA airfield QFE is most often offered. As others have said, it’s not a big deal and converting from one to the other is merely a matter of adding or subtracting the airfield elevation pressure difference - about 30ft per HPa.
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