The Mach number is not at all a stupid unit. Furthermore it's not a "unit" itself, it tells you the fraction of the speed of sound.
It is a very important number when dealing with aerodynamics, as it will tell you if you are flying subsonic (slower than sound) or supersonic (faster than sound). The airflow around your plane is very different in subsonic and supersonic flow - when you go supersonic shock waves will spread out in a cone starting at the plane's nose. The way lift is generated by the wings is even different sub- and supersonic.
Current (subsonic) airliners can't go faster because of the speed of sound - I think the Boeing 747 cruises at app. Mach 0,8. If it goes faster (into so-called transsonic speeds near Mach 1), shock waves will appear at the upper surfaces of the wings, resulting in high drag and control problems.
It would actually be more complicated to fly these kinds of planes without knowing the Mach number directly, just because it varies.
Ola
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You don't have to. I registered myself as having no religion when I moved to Germany. No church tax then.
The Mach number is not at all a stupid unit. Furthermore it's not a "unit" itself, it tells you the fraction of the speed of sound. It is a very important number when dealing with aerodynamics, as it will tell you if you are flying subsonic (slower than sound) or supersonic (faster than sound). The airflow around your plane is very different in subsonic and supersonic flow - when you go supersonic shock waves will spread out in a cone starting at the plane's nose. The way lift is generated by the wings is even different sub- and supersonic. Current (subsonic) airliners can't go faster because of the speed of sound - I think the Boeing 747 cruises at app. Mach 0,8. If it goes faster (into so-called transsonic speeds near Mach 1), shock waves will appear at the upper surfaces of the wings, resulting in high drag and control problems. It would actually be more complicated to fly these kinds of planes without knowing the Mach number directly, just because it varies. Ola
Ola