I am trying to work out TAS from IAS, having problems with it on MSFS.

the problem is as follows: 23000 FEET / 0 WIND / -19F (-28C) / IAS 304Knts / TAS (MSFS CORRECT) 426Knts / TAS (VIA E6b Calculator) 441Knts (0 wind for testing of course).

How do I get the correct answer of 426Knts (any online calculator)?

P.S someone on an other forum helped me out but I still don't know why the E6b is giving me 441??

Many thanks!

The E6b calculator gives me this result enter image description here


1 Answer 1


That online calculator appears to use equivalent airspeed in its calculation, but calls it indicated airspeed. And so it is invalid at higher mach numbers. In this case, an equivalent airspeed of 304 knots gives a true airspeed of 440.8 knots.

This online calculator appears to do it correctly.

Note that your question is about a specific online calculator, but a physical E6B makes various approximations and you should not trust it to be accurate at higher mach numbers either.


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