Speed

S

peed is the rate of an object’s motion usually expressed as the distance traveled per unit of time, such as miles per hour or meters per sec­ond. Aircraft fly at a wide range of speeds, from an airship gliding slowly through the air to a fighter plane streak­ing across the sky faster than the speed of sound. Spacecraft travel even faster.

Regimes of Flight

Aircraft speeds are divided into bands. From the slowest to the fastest, the bands are: low speed, medium speed, high speed, supersonic, and hypersonic. These speed bands also are called regimes of flight.

The low-speed regime includes light­weight craft, such as hang gliders and

airships, that fly up to 100 miles per hour (160 kilometers per hour). The medium-speed regime includes propeller planes flying up to about 350 miles per hour (560 kilometers per hour). High­speed aircraft fly up to about 700 miles per hour (1,100 kilometers per hour)— these aircraft are mostly jet airliners. Supersonic planes, such as the F-22 Raptor fighter, fly between Mach 1 (the speed of sound) and Mach 5 (five times the speed of sound). Hypersonic craft fly faster than five times the speed of sound. The Space Shuttle is an example of a hypersonic craft.