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Old Dec 15, 2009 | 9:01 am
  #38  
CPRich
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Originally Posted by LarryJ
How can it show mach number if it doesn't know either the true airspeed or temperature at altitude?
Mach number is listed under Ground Speed which, from an engineering standpoint, is a meaningless non-sequitor. I assume it means TAS divided by Mach 1 at sea level, STP. According to this site, my E175 broke the speed of sound, at Mach 1.08 this morning. I'm pretty certain physics wasn't redefined recently and we were probably traveling at or near the Mach 0.82 max cruise speed of this aircraft type.

My engineering professors would continue with a diatribe on frames of reference...
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