Some basics for simulator pilots, even if you have an airplane manual it seems some of you are confused:
- height: always refers to something above some sort of **terrain**, compared to altitude, which refers to something above sea level
- radio height: height above the terrain spot where you are, measured by the radio altimeter. Is only about 2000 ft when you fly at FL260 over the Himalaya.
- desicion radio height: only exists for precision approaches as ILS CAT II/III, but not for a NDB/NDB or whatever non-precision approach
- decision height: only exists in the Russian system as it is a
- height above **field elevation**: this is the relevant value for minima in the Russian system, so "100m" refers to 100m above Smolensk airport level - not the actual spot of terrain. Over the actual point of decision making, the radio height may be 140m, as the terrain below is slopy. -> Can never be measured properly by a radio altimeter, only by setting the baro to QFE. ->The point of decision making can only be measured from the baro altimeter.
The confusion for Westerns comes here as **baro** QFE "height above field elevation" does not exist (anymore) and the term "height" usually refers to **radio** height, while "altitude" refers to baro QNH.