QFE, QNH and Elevation MET

For questions like this, firstly draw a diagram. This should have the sea with an airfield on land somewhere above the sea. Now label the various pressure levels. QNHQNH —Static pressure at MSL calculated from QFE using ISA temperature lapse rates belongs at sea level. QFEQFE —Static pressure measured at an aerodrome belongs at the level of the airfield. The physical distance between the sea and the airfield is elevation.

The elevation can be thought of as either a physical distance or a pressure difference. To convert between the two, you either divide the elevation by 27 to get pressure difference, or multiply the pressure difference (the difference between QFEQFE —Static pressure measured at an aerodrome and QNHQNH —Static pressure at MSL calculated from QFE using ISA temperature lapse rates) by 27 to get elevation. If you are asked for elevation, this will solve the question. If you are asked for either QFEQFE —Static pressure measured at an aerodrome or QNHQNH —Static pressure at MSL calculated from QFE using ISA temperature lapse rates, you either add or subtract this pressure difference from the other. The way to know "which way" to go is to note that as you go further up, there is less atmosphere above you and so the pressure is less.