The Mach Number System.

Welcome. Mach number is defined as the speed of the aircraft relative to the speed of sound. Unlike the True Air Speed (TAS), Mach number (m) has no dimension. In air- navigation, this new unit of speed is applicable above 300 knots. The Mach meter is the Dead Reference (DR) for the Mach number. The Mach meter derives from two orthogonal air capsules: the dynamic- pressure capsule, and a static- pressure capsule. The instrument is available on super- sonic aircrafts only.

The Mach meter equation is a quadratic in m. Therefore, a turning point (known as the critical mach number) exists.

In civil transport aircrafts the critical Mach number ranges from 0.7 to 0.85. If this limit is exceeded then the aircraft stalls. However, better critical numbers can be achieved by using the thin delta- wing construction. Concorde's extremely high fineness ratio of the fuselage is evident. This excerpt is taken from Grace Lwanga’s book entitled “METEOROLOGY for Airplane NAVIGATION)” page 140. https://www.amazon.com/Mr.-Grace-Nsubuga-Lwanga/e/B07KDJ91W2