Tuesday, 2 June 2020

What is QNH and QFE?

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In order for pilots to flight their airplanes in accurate separation from each other, they need to know and to set altimeters with the correct values for QNH and QFE.

QNH indicates the atmospheric pressure in relation to mean sea level. It is used to set altimeter with the height above sea level. In other words, if we sit on the ground at an airport and we dial QNH on the altimeter it will display the airport's altitude above sea level. (refer to the picture)

ATC (Air Traffic Control) will provide the current QNH to pilots before take off, or on clearing them to descend below the transition level. Above this level the standard pressure setting of QNH is (1013hPa) and it is used by all airplanes in reference to flight levels for accurate separation.

QFE is the air pressure over specific airfield. It will read zero at the field and once in the air, it will read the height above that field. (refer to the picture)

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