Mach number which was also unit-first, and may have influenced the use of the term Mach. In the decade preceding faster-than-sound human flight, aeronautical engineers referred to the speed of sound as "Mach's number", never "Mach 1". Mach number is useful because the fluid behaves in a similar manner at a given Mach number, regardless of other variables. As modeled in the International Standard Atmosphere, dry air at mean sea level, standard temperature of , the speed of sound is . The speed of sound is not a constant; in a gas, it increases as the absolute temperature increases, and since atmospheric
Beaujon Mach .07 Beaujon Mach .07 The Beaujon Mach .07 is a single-seat, American high-wing, tractor configuration ultralight aircraft. The aircraft is available as plans from Beaujon Aircraft of Ardmore, Oklahoma. Designed by Herbert Beaujon, the Mach .07 is named for its top speed of . Beaujon Aircraft publishes the plans along with six other designs in book form under the name "How to Build Ultralights". The Mach .07 was specifically designed to comply with the United States ultralight category and its FAR 103 "Ultralight Vehicles" rules, including the category's maximum empty weight. With the specified 250 cc Zenoah G-25 powerplant the aircraft