Venn av meg som driver med ATPL;
Quote:
Here is the ATPL of the day...
The time taken for the transmission of an interrogation pulse by a DME to travel to the ground transponder and return to the airborne receiver was 2000 micro-seconds, including time delay. The slant range from the ground station was:
A) 296NM
B) 186NM
C) 158NM
D) 330NM
Correct answer should be... Who the F#$/K cares... But our beloved JAA/EASA wants C)158NM And here is why!
Time for pulse to hit target and return is 2000 micro-seconds. Minus 50 micro-seconds delay = 1950
So the one-way distance travelled is 1950/2=975 micro-seconds.
Speed of electromagnetic radiation is 161800NM per second
distance = speed * time = 161800 * 0.000975 = 158NM
If you like math this is fairly simple and straight forward. But for the love of god! When will i EVER need to do this in real life. Why would i care. I dont have an instrument in the airplane telling me the time it took for the signal to return, so that i could calculate the distance in case DME broke.
DME break = placard and go on with your day!
NO PROBLEMS the plane will not crash 
End of my daily rant
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