What occurs to the center of pressure as an aircraft passes Mcrit?

As an aircraft approaches and passes the critical mach number (Mcrit), the aerodynamic behavior changes significantly due to the onset of compressibility effects. Specifically, when an aircraft is flying at or near Mcrit, the flow over the wings can transition from subsonic to supersonic.

On swept wings, which are designed to manage airflow and control the effects of higher speeds, the center of pressure—the point where the total aerodynamic lift force can be considered to act—tends to move rearward as the aircraft crosses Mcrit. This rearward shift happens due to the changes in airflow characteristics and the resulting impact on lift distribution across the wing. As the airflow accelerates and begins to transition to supersonic speeds, the pressure distribution changes, which can influence stability and control characteristics.

Understanding this shift is crucial for pilots and engineers in terms of aircraft stability and control during flight at high speeds, as it can impact the handling characteristics and the required adjustments to maintain level flight or maneuvers. The movement of the center of pressure signifies a significant change in aerodynamic forces acting on the aircraft, particularly when dealing with high speed or near-supersonic flight.