When calculating back from the ETP to point A, which ground speed do I use when finding time? Is it ground speed on or ground speed home?
First, which way are you going on the way home ? Back from the ETP to A, therefore one appropriately uses the G/S home as the G/S on wouldn't make a whole great deal of sense ?
should I make sure I used ETAS for all GS calculations in the exam?
If you are using a Dalton computer (ie, the typical E6B style of instrument with a slide) ETAS is totally, absolutely, and irrevocably irrelevant so forget it - it never gets calculated on a Dalton. Also, should you see comments along the lines that the Dalton somehow does ETAS calculations in the background or some other strange suggestion, just ignore it. ETAS just does not play any part in the Dalton's graphical wind triangle solution.
If you are using a CR instrument, the correct geometric calculation ALWAYS involves calculating ETAS (unless the drift is zero, in which case TAS=ETAS so calculating ETAS is moot). I suggest that you forget all about the 10 degrees do-I-or-don't-I-calculate-ETAS nonsense as not calculating ETAS deliberately injects an error into the G/S calculation. As the drift gets closer and closer to zero, this error also gets closer and closer to zero. However, using ETAS in the sums is mathematically correct and is what CASA does. Why would you want to inject an error into your answer in a CASA exam ? That just sets you up to get the final answer wrong in the CASA school of thought.
If I get a wind component, am I better using my whizz wheel or the aip table?
Pick whichever you prefer as the AIP table is calculated mathematically and, providing you are using a CR, the instrument contains sine and cosine tables which allow you to calculate H/W T/W and X/W values. That is, the answers will be the same, once you allow for the AIP table's rounding off. Using the CR to do so is both quicker and will give you a more accurate answer.
On the other hand, if you are using a Dalton, it doesn't have any sine or cosine information (which you need for the wind calculations) so I suggest you use the AIP table as that is quicker and more accurate than wasting time trying to get the answers graphically.
if the wind is coming from 90 degrees, am I to flip the runway?
Not too sure what you mean by "flip the runway". However, for takeoff and landing, you are constraining the aircraft to maintain the runway track so a direct crosswind will have no material effect on the distances and can be ignored. You still, however, have to make sure that the X/W is within the aircraft's limitations.
For fuel and ballast I round up and for what do I round down?
You round off conservatively for each and any calculation unless the examiner says to do something different in the question.
So for ballasting (assuming you are ballasting to either the forward or aft envelope limit), you round off to make sure that you remain within the envelope, at least just a little bit. That gives you an argument in your favour should you get into a punch up with CASA or find yourself in court after an expensive or fatal accident.
For fuel, likewise, make sure you don't put more or less fuel on that is appropriate for the calculation. There is a range of different calculations. so you need to think each one out to come up with an appropriate rounding off strategy.
