Question below is from study material for the EASA PPL license MET course.

It's an unlikely question but it's interesting to review.

You are flying from west to east with WCA +6°. How is your true altitude changing with all else remaining un changed.

  • A) It will degrees
  • B) It will increase
  • C) Will remain stable(unchanged)
  • D) None of the above are correct.

My Question, how is this easily explained, does it have to do with Buys Ballot's law ?

enter image description here

  • $\begingroup$ Welcome to the site! It's always a good idea to ask a specific question and show your work before posting. Are you having trouble answering this? If so, what do you need help with? $\endgroup$ – GdD Apr 26 '19 at 15:01
  • $\begingroup$ Hi GdD ;), Agree i´m not very clear!. The answer is i think (B) it will increase i.e Buys Ballot comes into play. Maybe i´m not getting this out correctly, but what is the simplest way to understand this. $\endgroup$ – Gisli Thor Apr 26 '19 at 15:14

The question is confusing because the graphic doesn't match the question being asked. Does the question actually use this graphic? Because if it does then your WCA would be negative if you are heading East because you would be crabbing to the left to account for wind coming from the North.

In any case, if you are flying from an area of high pressure to an area of low pressure (as the graphic depicts) without changing your altimeter setting your true altitude will be lower. Remember this simple mnemonic: "High to low, look out below."

However, if the question is as stated WITHOUT the graphic, then heading East with a positive WCA means that the wind is from the South. If this is the case it would be fair to assume from Buy Ballot's law that you are transiting from an area of low pressure to an area of high pressure. In this case then the answer would be your true altitude would be higher.

  • $\begingroup$ Thank you Michael, question does not include the picture. But your explanation has help me ;) $\endgroup$ – Gisli Thor Apr 27 '19 at 16:13

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