Mc (the cruise Mach) is an operational cruise Mach, while Mmo is the design cruise Mach. On the Citation X the Mmo and Mc are both the same, Mach 0.92 above 30,650 ft. Below that altitude the Vmo is 350 KCAS.
The Md (Mach dive speed) on the Citation X is Mach 0.99. This is to meet the 0.07 Mach increment between Mmo and Md for flutter clearance and upset maneuver certification.
During the flight flutter testing and envelope testing the Citation X broke Mach 1. It did it the first time on September 26, 1994. A T-38 was used as the chase aircraft.
[Edited 2004-04-02 16:26:52]
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