Atpl General Nav head scratcher

[oceanicclarence]

Hi there. this one has me scratching my head, anyone care to try it?
it shouldnt be hard but i think im seeing double after a day of study.

aircraft is trying to maintain a track of 153 (T)
wind is 280/50
so heading 158 (T)
Variation 11W so heading (M) is 169
at such and such a time drift is found to be 8 degrees port
what heading (M) is required to parallel track of 153?

A 161
B 163
C 153
D 172

my thinking being that if you are heading 158, then surely alter heading to starboard by 8 degrees gets you to 166 plus var is 177!!!!! aaaargh.

[towser]

172. True heading required to parallel true track of 153 is 161 (153+8 for drift)
Variation 11W so add it on 161+11 =172

[NinerVictor]

Towser's answer is correct. To put it in another way:

Heading = 158 (T)
8 Degrees port drift => Track made good = 158 - 8 = 150 (T)
To parallel track of 153 (T), we need to turn 3 degrees to the right.
Therefore, Heading = 158 + 3 = 161 (T)
Magnetic heading = 161 + 11 = 172 (M)

But from the theoretical point of view, I would think the most accurate method would be to find out what the wind velocity is (provided you have the TAS and groundspeed), put in the track of 153, solve for the heading using your computer and add variation to get your magnetic heading. Cheers.

9V