Well yes, and following that argument TAS could be used as the displayed speed on EFIS. But the TAS of critical speeds changes with air density so that wouldn't be a good choice. I think the argument is that the speed that has the same critical values with changes in mach number and density is EAS, not CAS or TAS, so, if the ADC can calculate it, why not use that?
LOMCEVAK's second point may be the conclusive answer, that the standby instruments should display the same speed as the main instruments. I can see the sense of that. I have been told that one type of modern jet does display EAS, was it the Phenom?
PS, Ghengis, CAS to TAS is two corrections, not one, compressibility and density. Picky I know.
Last edited by Alex Whittingham; 6th Jun 2015 at 16:25.
Reason: to add postscript