What does the "MACH" number indicate?

The "MACH" number is a dimensionless unit that represents the ratio of the speed of an aircraft to the speed of sound in the surrounding medium, which is typically air. This number is crucial in aviation because it helps pilots and engineers understand the aircraft's performance relative to the speed of sound, which varies with altitude and temperature. For example, at sea level under standard atmospheric conditions, the speed of sound is approximately 343 meters per second (1,125 feet per second). As an aircraft approaches the speed of sound, it may experience various aerodynamic phenomena, such as increased drag or shock waves, which are important considerations in high-speed flight. Knowing the MACH number is essential for operating efficiently and safely within different flight regimes.

Understanding the MACH number aids in assessing the aircraft's performance characteristics, which can be critical for managing flight operations effectively, especially in supersonic travel, where speeds exceed the speed of sound.