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View Full Version : Looking for help on ATPL - Equal time point to alternates.

Greeny989
14th Oct 2010, 11:39
The basics I have:

Flying from point A to point B, where is the equal time point to get to A or B?

I can do that in still air and with wind using the formula:

Dist to ETP = (total Dist X GS Home) divided by (GS out + GS Home)

Where I am having problems and can’t find the information is

Flying from point A to point B, where is the equal time point to return to A or diver to the Alternate at point C or what is the equal time point to 2 different alternates when flying along route A to B I need to be able to this in both still air and wind.

Is there a way of working this into the above formula or does it need to be done via plotting and if so how?

Any help would be greatly appreciated
Keith.Williams.
15th Oct 2010, 08:50
The answer to your question depends upon your reason for asking it.

This question also appears in the Tech Log Forum. As stated by BOAC in that forum by, in the real-world the solution of this type of problem is quite complex.

If you are preparing to take ATPL exams the question becomes a bit easier. Complex questions of this type are rare in the JAR ATPL exams but quite common in some others such as the Indian DGCA ATPL and CPL exams.

The questions include the distances between the various locations plus the wind speed/direction and the TAS or the ground speed for each leg of the flight. With this information you can apply the formula in the usual way using the appropriate speeds and distances.

Pass rates for JAR ATPL exams are usual better than 90%. Pass rates for the Indian DGCA exams are usually closer to 5%.
Checkboard
15th Oct 2010, 09:02
As stated by BOAC in that forum by, in the real-world the solution of this type of problem is quite complex.

Hi Keith! Not that complex. I have posted my cockpit-friendly method there. ;)
Greeny989
15th Oct 2010, 09:47
Apologies for double posting, I needed a quick answer so was trying to get more people to read it by copying the post into the tech forum as well. Checkboard seems to have covered everything I need in his post there.

Greeny