What is mach tuck?

Mach tuck refers to the aerodynamic tendency of an aircraft to pitch down as it approaches transonic speeds, typically around Mach 0.8 to Mach 1. This phenomenon occurs due to changes in the airflow around the aircraft as it nears the speed of sound.

As the aircraft accelerates, the airflow over the wings increasingly compresses, leading to a shift in the center of pressure—the point where lift is considered to act. At high speeds, this shift can cause a decrease in effective lift at the tail while lift at the wings remains relatively constant or even increases, resulting in a nose-down pitching moment. Pilots must be aware of this effect as it can lead to challenges in maintaining controlled flight if not managed properly.

The other options describe concepts that are not aligned with the specific behavior associated with Mach tuck. The increase in lift at high speeds pertains to a different aerodynamic phenomenon and does not capture the pitch down aspect inherent in Mach tuck. A type of aerodynamic stall refers to a loss of lift which is different from the pitch dynamics, while a design feature to enhance speed typically involves the aircraft's shape or engineering aspects, rather than the aerodynamic interactions at transonic speeds.