Hi T117Tim,

Could you please confirm which version of the textbook you are currently using?

It looks like there was an error with that question previously and it has since been amended. You are correct 167kts should have been used, and the correct answer is 187nm, which is reflected in the latest version of the book.

Hope this helps,

Harry
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Hi Tim,

Just a couple of notes first:-
From the CR3 manual, if the drift is more than 10º then Effective TAS must be considered, otherwise it is ignored.
Check your magnetic wind direction as it should be 244ºM, but that would not make a great difference.

Yes Time to PNR is 67.2 minutes which gives a distance to the PNR of 187nms. You are correct there.

These answers are reflected in the current copy of the text book. If you have recently purchased your copy, I would ask your supplier for the latest printed version.

Cheers W

The Errata's are generally removed from the Website when the newest version of the book is published, it would appear that your using a much older version of the textbook, that will make passing the CASA exam more difficult for you. CASA is in a constant flux of amendment's of the legislation that we do our best to keep up with and intern offering the most current versions.
Please make sure you are studying from the most current version.

[color=blue]From the CR3 manual, if the drift is more than 10º then Effective TAS must be considered, otherwise it is ignored.[/color]

Just a sideline note.

I have not been able to determine just who started the 10º thing - it could even date back to Lahr - but folks should be aware that it is mathematically incorrect and injects a deliberate error into the answer. It makes no more sense now than it did back in the day. As the magnitude of the error is not all that significant, it matters little if you use it on the line. However, you should be aware that it is geometric nonsense - the correct answer ALWAYS involves the use of ETAS, regardless of drift. More to the point, as you must set up the CR to get the X/W data, that always sets up the ETAS calculation so there is absolutely no benefit in using the TAS/ETAS thing.

In the exams, however, CASA will be generating the correct answers (ie including ETAS). The CASA site indicates that they don't bother when the drift is below 5º. I suggest all that means is that they run the correct calculation but acknowledge that the discrepancy will be near-zero at very small angles. The problem is that CASA is not able to prescribe the use of the CR so they have to account for other computers, such as the Dalton, which doesn't have any interest in ETAS and just gives the correct answer graphically.

My concern is this - why would you inject a deliberate error into your examination answer, for no benefit to you ? All that does is, potentially, move you closer to getting the answer "wrong" according to whatever criteria might be embodied in the computer marking algorithms.