Originally Posted by
77Whiskey
DME Distance is slant range, not the ground distance. Please don't confuse that.
I know it is slant range. But you didn't read the question which was in effect; 'if the aircraft is at 15 DME from the beacon, how many DME is the aircraft from the beacon?'
If you are having trouble understanding this try substituting the "DME" with "slant range" in the question and see if you get it:
The aircraft flies at FL370, 15 NM [slant range] from the station. [slant range] readout will be?
The answer is still 15 NM, which is the only possible correct answer.