Mach number temperature generally decreases with increasing altitude between sea level and , the speed of sound also decreases. For example, the standard atmosphere model lapses temperature to at altitude, with a corresponding speed of sound (Mach1) of , 86.7% of the sea level value. While the terms "subsonic" and "supersonic", in the purest sense, refer to speeds below and above the local speed of sound respectively, aerodynamicists often use the same terms to talk about particular ranges of Mach values. This occurs because of the presence of a "transonic regime" around M = 1 where approximations of the Navier-Stokes equations used
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