Useful thread as this is a very common misconception regarding OAT and Mach number. Much of the blame is sheeted home to ineffective basic theory training courses, methinks .. or, perhaps, theory instructors' not qualifying their explanations in such courses. (I come from a long ago history of such activity and certainly was not immune to the problem myself).
Temperature has nothing to do with the speed of sound? If so I need to burn a lot of old books
I didn't say that ... indeed, quite the contrary !
Suggest, first, that you re-read the old books. I suspect that they will be talking about temperature's having an involvement in both LSS (directly) and TAS (indirectly), but not Mach number - which is calculated directly from dynamic and static pressures ?
Tullamarine is saying that both LSS and TAS depend on temperature in the same way
Not quite .. what he is saying is that the equation for Mach number involves static and dynamic pressures and has naught to do with temperature.
Put the Cal Airspeed on the Pressure Altitude and read the Mach No in the "Mach Number" window
Precisely and that implements the equation to which I hyperlinked earlier. Once the Mach number is set, subsequent calculations to other values can follow
More particularly, how do you figure your Mach number in flight ?
(a) look at the Machmeter - which implements the equation for Mach number, or
(b) pull out your whizz wheel and set CAS against FL to read off M
If you want to end up with the value in a round about, more difficult fashion, you can work out the LSS, work out the TAS (or read them off the appropriate page on the box) and figure Mach from that .. but why do things the difficult way when there is an easy solution ?