The ratio of true airspeed to the speed of sound is called what?

The ratio of true airspeed to the speed of sound is known as the Mach number. This dimensionless value is significant in aviation and aerospace because it describes how fast an aircraft is traveling compared to the speed of sound in the surrounding medium (which can vary with factors like temperature and altitude). The Mach number is crucial for understanding aerodynamic conditions, especially in high-speed flight, and helps pilots and engineers assess performance and safety factors.

Ground speed refers to the aircraft's speed relative to the ground, while indicated airspeed is the speed read from the aircraft's airspeed indicator, which is not necessarily related to the speed of sound. Velocity factor typically refers to mechanical or statistical contexts, rather than aviation dynamics, making them unsuitable answers for this specific question regarding the ratio to the speed of sound.