What are the implications of compressibility on flight instruments?

The implications of compressibility on flight instruments, particularly in the context of airspeed measurement, relate to how changes in air density at different speeds and altitudes affect instrument readings. Compressibility effects become significant as an aircraft approaches transonic speeds, where the air pressure and density differ markedly from standard atmospheric conditions.

When discussing the overreading of dynamic pressure, it refers to the phenomenon where an increase in airspeed leads to an overestimation of the dynamic pressure exerted on the pitot tube. This occurs due to the compressibility effects that alter the relationship between airspeed and the pressure measurements. As aircraft speed increases, especially beyond a certain threshold, the increase in dynamic pressure does not directly equate to an increase in airspeed due to these compressibility effects. As a result, speed readings from instruments that do not account for these effects can be inaccurately high.

This understanding is crucial for pilots and engineers, as it impacts flight safety and performance calculations; failing to recognize how compressibility affects measurements can lead to incorrect assessments of the aircraft's speed and, consequently, its performance.