wind vector

[Wellsam]

Am doing Oz Nav ATPL at present and finally know what all the weird looking info on the wizz wheel does rather than looking like an alien language it all makes sense now. Except one thing i cant seem to find is the wind speed when working out what direction the wind is coming from in flight. Am fine with finding ETAS and drift and X/W componant, head or tail wind and wind direction but cant seem to figure out how you get the wind speed from that info. eg 90kts right X/W and 20Kt HW. What happens next???

Also has anyone done the exam in Oz recently. How many PSD, CP and great circle questions are there and what were the main tough bits in he exam??? Cheers. Adrian

[Dignerf]

I'm only studying at PPL level at the moment, therefore I do not have a great amount of experience, however I think I know what you mean.

I'll use your example - 90kt Right Crosswind and a 20kt headwind.

You line up the centre dot of your whizwheel with zero on the Crosswind section, and place the index under zero. Then plot the crosswind and headwind as appropriate by placing a dot there, in this case 90 units along the right of the grid and 20 units down.

The length of the line from the centre to your point is the wind speed, and the angle (either by extending the line all the way to the opposite side, or to the nearest side and subtracting it from 180) gives you the relative heading. My whizzwheel has a windarm which is in fact very useful for this particular problem.

Therefore I get approx 97kt wind coming from 77 degrees West of heading.

I hope this is correct!


[Edit: Just checked this using Trigonometry and I get 92kt from 77.5 degrees. It's reasonably close - not sure though whether the 5kt difference in speed is down to an error in my method or just the general inaccuracy of whiz wheels?]