Question

What design features could be used to increase critical mach number of an airplane?

Answer 1

Critical Mach number is that free-stream mach number at which flow becomes locally sonic for the first time at some point over the body.

At Lower Critical Mach number there will be subsonic airflow over the entire aircraft, whereas there will be supersonic airflow at Upper Critical Mach number.

Critical Mach number depends on the shape of the wing hence will be different for an aircraft.

For instance, a thicker wing can deflect the airflow more easily and it will be accelerated to a faster speed more quickly therefore the Critical Mach number will be lower. On the other hand, for the thinner wing, the airflow will be more smooth and it will be accelerated slowly hence making the Critical Mach number higher.

As the desired value of the Critical Mach number is close to unity, thinner wings are preferably used as lower Critical Mach number can lead to loss of control of the aircraft.