Jane,
Originally Posted by
Jane-DoH
What units do you use? I'm not just asking this stuff to be difficult
I guess the answer is in the very first sentence of PBL's reply:
"
The speed of sound is functionally dependent only on the square root of temperature in Kelvin." (my emphasis)
Your task is to determine the temperature (real or assumed, as befits your problem) for where you (hypothetical) aircraft is, then you call that 'T' and plug it into the formula that PBL gives you in his third paragraph.
Simple as that. Your real problem is not in calculating a Match number given an airspeed, your real problem is in finding the value for the local speed of sound. PBL goes on to suggest that you might deduce a nominal figure for that variable from tables available on the internet (and in books), which will give you an LSS (or the elements needed to calculate it) from an atmospheric model. Up until that point, pressure has nothing to do with what you're attempting to solve.