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Hi there!
I was going through my CPL nav KDR and have a few questions.
The first is ETA.
You are at A at Time 1200, flying to B which is a distance of 25 nm, planning to arrive at B at time 1215 however, you are 2 min Late at B. B to C 50 Nm. Recalculate ETA C.
I thought this was proportional, making time at C, 2 x 2= 4 + the original 2 mins late = 6 mins late, time 1221. What is the correct answer, as I think I got this question wrong.
AAT Head of Operations replied the topic: ETA cpl nav
Your approach assumed that since B to C is twice the distance of A to B, the delay doubles. However, the delay only increases if speed is reduced. Since speed remains the same, the delay is simply carried forward.
Work out the ground speed A-B
25/17 = 1.4705882353 nm/min
Now 50nm at 1.4705882353 nm/min = 33.9 so 34 Minutes
ETA is B @1217+34 = 1251 @ C
Gross error check total 75nm @ 1.4705882353 nm/min = 51 so 1200+51= 1251
Did you use a whizz wheel for this? The answer you have provided was not a choice on the multiple choice exam. From memory, the answers were something like 1216, 1217, 1218, 1219, 1220 and 1221. Thanks!
