Aircraft Wing Design

Vocabulary:

Mach:

Numbers that describe an airplane’s speed in terms of the speed of sound. A Mach number is derived by comparing the speed of an airplane with the speed of sound in the air it’s moving through. An airplane moving at Mach 1 is traveling at the speed of sound. The Mach number is named in honor of Ernst Mach, a late 19th century physicist who studied gas dynamics. (Note: The speed of sound is different at different altitudes.)

Subsonic:

Usually less than Mach 0.8. Air is flowing slower than sound over every part of the airplane.

Transonic:

About Mach 0.8 to Mach 1.2. Air is flowing faster than sound over some parts of the airplane.

Supersonic:

Greater than about Mach 1.2. Air is flowing faster than sound over the entire airplane.

Hypersonic:

Greater than about Mach 5. Heat becomes a critical factor.