Mach versus Knots

Ouch my brain hurts!

So my understanding so far is that the speed of sound varies with
altitude/temp........ and the Mach number is the a/cs speed in relation to
the speed of sound at that moment in time.

So how much can this speed (the speed of sound) vary and is it actually
modelled in FS2002?

also, what sort of instrumentation could work out the speed of sound or is
it a formula based on temperature?

Very interesting subject BTW, Geoff.

Martin


"GeoffC" <geoff_noise@hotmail.com> wrote in message
news:bdmdh5$m4n$1$8302bc10@news.demon.co.uk...
| Please could somebody clarify why and when we measure speed as Mach rather
| than knots. I do have a loose appreciation about the speed of sound in air
| changing with alititude, as does IAS due to air density. However I have
| never seen a good explanation of why this used and as such my gauge stays
on
| Knots. For all I know my aircraft should have fallen out of the sky, but
it
| hasn't.
|
| I know that my FMC shows Mach at certain times (Altitudes) but would like
to
| know what I should be doing in consideration of this.
|
|
| Thanks
|
| Geoff
|
|

"Handsome" <martin@REMOVEfspaints.com> wrote in message news:<bdojl7$e$1@sparta.btinternet.com>...


Thanks everybody for the feedback, and I'm glad it wasn't just me that
didn't know much about this subject. It would appear that a lot of
simmers don't take this into account (I bet that generates some
response!!), and if they did would the software even behave
differently.

In summary it is used to avoid the speed where the aerodynamics get
upset by the compression of air and its flow over the wings, which
will vary with altitude.

I also found the URL which gives an explanation, and found the
calulator useful to play with:

http://www.womanpilot.com/past%20iss...0/airspeed.htm

Geoff