Indicated Pressure altitude depends on the reference pressure surface selected by the pilot through the altimeter’s pressure setting knob.
–QFE is the pressure at the airport reference point. With the QFE setting, the altimeter indicates the altitude above the airport reference point (if the temperature is standard).
–QNH is the Mean Sea Level pressure. The QNH is calculated through the measurement of the pressure at the airport reference point moved to Mean Sea Level, assuming the standard pressure law. With the QNH setting, the altimeter indicates the altitude above Mean Sea Level (if temperature is standard).
QNE (Standard) corresponds to 1013 hPa. With the standard setting, the altimeter indicates the altitude above the 1013 hPa surface (if temperature is standard).
Author – Zinhom Mohmoud – Aviation Training Consultant