Which factor will decrease the critical Mach number of an aircraft?

The critical Mach number of an aircraft is the lowest Mach number at which the airflow over some portion of the aircraft reaches the speed of sound. Several factors can influence this number, and understanding their effects is crucial for aerodynamic performance.

Increasing the weight of an aircraft impacts its aerodynamic characteristics significantly. When an aircraft is heavier, it requires more lift to maintain level flight. As the aircraft's weight increases, the angle of attack at which the aircraft can achieve sufficient lift also increases, leading to a higher likelihood that airflow over the wings will exceed the speed of sound at lower speeds. This phenomenon can decrease the critical Mach number since the aircraft reaches transonic speeds sooner in relation to its performance envelope.

In contrast, an increase in altitude generally leads to a decrease in air density and can affect lift but does not directly change the critical Mach number in the same way as weight does. Lowering the load factor may influence aircraft stability but doesn't inherently impact the critical Mach number, and shifting the center of gravity further back can alter the aircraft's balance and handling characteristics, yet does not necessarily have a direct impact on the Mach number at which shock waves form.

Hence, increased weight primarily leads to an earlier onset of transonic effects, thereby decreasing the critical Mach number of an