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Samuel created the topic: Refer to the BOURKE WAC.
You plan to fly from NARRABRI (YNBR) (3019S 14950E) direct to ST GEORGE (YSGE) (2803S 14836E). To avoid clouds after departing YNBR, you divert left of planned TR along the YNBR – WALGETT railway line. At WEE WAA township (approximately 20nm WNW YNBR), you decide to track direct to YSGE. Which of the following features would provide the most accurate ground speed check between WEE WAA and YSGE
a. Garah township (approximately 28 nm NW of MOREE)
b. Abeam Moree
c. Gwydir Highway
d. Barwon River
The answer is C) Gwydir Highway
I dont know how to get this answer, please help, many thanks
bobtait replied the topic: Refer to the BOURKE WAC.
All of these types of questions assume that you don't have GPS. If you have GPS you simply look at the GPS ground speed readout! However, the CASA exam is assuming you do not have GPS - most unusual these days!
If you are navigating by dead reckoning, you need two consecutive fixes to give you distance flown. Then you need the time interval between those two fixes. In this question, the second fix is crossing the Gwydir Highway.
The other fixes are either too far away to accurately judge the abeam position or,
too close to the first fix to get an accurate time interval or,
cross the FPT at a very shallow angle so, if you are even slightly left or right of track when you cross the Barwon River, you will have a large error in distance flown.
The Gwydir Highway crosses your track at almost right angles, so its the best of a bad bunch of choices.
