And.....
Depending on the aircraft and the aircraft system, the indicated MACH may be slightly different from the true MACH. This, even though the
Mach is computed from the ADC, the TAS, etc.....
If you'll have a look at the AFM (FCOM, etc.) you may find a chart that
gives indicated MACH vs. true MACH....the difference being position errors, etc.
This becomes relevant when flying the constant MACH technique, e.g.
over the pond. On my aircraft, an indicated MACH of .80 is really a true MACH of about .787 or so. Over long distances, this is a consideration.
On my aircraft, indicated MACH is approximately equal to true MACH at around .71 or .72. Below that, true is slightly more than indicated...above that, true MACH is less....the difference becoming greater at higher MACH
numbers. For example, at MACH .86 indicated, true MACH is about .843 or thereabouts. (I don't have the actual graph in front of me at the moment.)
I'm not in agreement with 411A on all issues, but in many instances I do agree with him. In all cases, I enjoy the contributions he makes to PPrune.
Fly safe,
PantLoad
edited due to syntax and spelling....
Last edited by PantLoad; 4th November 2008 at 16:18.