QNH/QFE question

[arrak0z]

Hello. I have got a following question from my instructor and I would appreciate a little help

between 2 scenarios:
1) QNH 1020, QFE 1002 set on the altimeter
2) QNH 1002, QFE 1020 set on the alimeter

which one could be dangerous during approach?

[ShyTorque]

1) Would be quite normal for an airfield with a 540’ elevation.

[ant1]

Originally Posted by arrak0z

Hello. I have got a following question from my instructor and I would appreciate a little help

between 2 scenarios:
1) QNH 1020, QFE 1002 set on the altimeter
2) QNH 1002, QFE 1020 set on the alimeter

which one could be dangerous during approach?

All I can say regarding the second scenario is: when setting QFE 1020, the altimeter reading will be 0 at the airport to which the setting is referenced. If you then wind down the setting to 1002 QNH, you will get the AMSL altitude of that airport, which will be significantly below 0. Perhaps it's close to Death Valley! 😜

[DIBO]

It is such a basic question, that I would suggest to spend more time in your books, and less on this forum.

[172_driver]

Are you a glider or a jet flying a non-precision approach? The only thing I can conclude is a QFE greater than QNH is not real.

[homebuilt]

Originally Posted by arrak0z

Hello. I have got a following question from my instructor and I would appreciate a little help

between 2 scenarios:
1) QNH 1020, QFE 1002 set on the altimeter
2) QNH 1002, QFE 1020 set on the alimeter

which one could be dangerous during approach?

Sorry, I don’t understand the question.

How could QNH = 1002 with QFE = 1020 ?🤔

Unless you’re at Death Valley airfield ?🙂

[Bogner]

Originally Posted by arrak0z

Hello. I have got a following question from my instructor and I would appreciate a little help

Do you fly from an airfield that’s quite close to sea level, by any chance? Not much difference between QNH and QFE?

Try and imagine you’re sat on the end of the runway. If you have the correct QNH set on the altimeter, you will read the elevation of the airfield. If you have the correct QFE set, the altimeter will read 0ft.

Now imagine you’ve accidentally set the wrong QNH/QFE. If you’ve made the error in one sense (you’ve set a higher pressure than intended) what will the altimeter read? If you set it in the other sense, what would it read then? Which scenario would be more dangerous to you if you were in the air, maybe if there had been some unforecast fog or low cloud?
I think maybe that’s what the instructor was getting at.

Oh, and not all flying clubs have a crew room with enough people in to ask questions like this, or pilots friendly enough to ask, so don’t worry about asking questions on here. 😉