Page 41 - Beginner's Guide to Aviation

PRESSURE DATUMS
In aviation, pressure refers to the force exerted by the atmosphere. Think about it as weight of a column of air over a given point. The given point is known as a datum.
The diagram below shows the 3 different datums and the 3 pressure altimeter settings (QNE, QNH, QFE) that aircrafts use in flight. The pressure datum selected depends on the pressure set on the altimeter and phase of flight the aircraft is in.
QNE QNH QFE
qfe
Stands for Question Field Elevation. It is pressure observed at the airfield datum point. When set on the altimeter subscale, the altimeter will indicate 0ft.
qnh
Stands for Question Nil Height. It is pressure observed from the Mean Sea Level (MSL). When set on the altimeter subscale, the altimeter will indicate an airfield’s elevation.
qne
Stand for Question Nil Elevation. It is pressure observed at the standard altimeter setting. A standard pressure of 1013.2mb is set altimeter subscale. 1013.2mb is the International Standard Atmosphere for Mean Sea Level pressure.
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Flight path
Airfield
1013.2mb
MSL