Critical Mach number

Explanation

Critical Mach number M_cr is the lowest Mach number of an aircraft at a subsonic or transonic flight where the local airflow at some parts like the upper surface of the wing accelerates to the speed of sound and causes shock waves to form. Usually every aircraft will have a designated critical Mach number, above which the local flow becomes supersonic and the stronger shock waves cause a rapid increase in the drag of the aircraft, also known as wave drag.

Frequently Asked Questions

How can critical Mach number be increased?

The following are the different aerodynamic approaches that can be combined efficiently to increase the critical Mach number of an aircraft.

• Using a thin airfoil.
• Sweeping the wings back at an angle.
• Using a supercritical airfoil instead of a normal airfoil.
• Area ruling the fuselage following the Whitcomb area rule.