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Aircraft speed: Difference between revisions
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The aircraft's behaviour at Mach 1 at sea level is about the same as the behaviour of the aircraft at an altitude of 60000 feet. | The aircraft's behaviour at Mach 1 at sea level is about the same as the behaviour of the aircraft at an altitude of 60000 feet. | ||
A Mach number below 1 means that the plane moves subsonic. A Mach number above 1 indicates supersonic flight. The Mach number is critical because a number of phenomena take place just around Mach 1 (transonic speed), for example a sudden increase in drag induced by shock-wave generation (sonic-boom). The speed of sound changes with the compressibility (and hence temperature) of air, the Mach number is dependent on [[altitude]] (as the air temperature drops at higher altitudes). This implies that Mach 2 at sea level corresponds to a faster TAS than Mach 2 at 30.000 ft. The precise relation between TAS, Mach number and altitude is a complicated formulae and depends in essence on the local weather pattern determining the pressure and temperature gradients in the atmosphere. | A Mach number below 1 means that the plane moves subsonic. A Mach number above 1 indicates supersonic flight. The Mach number is critical because a number of phenomena take place just around Mach 1 (transonic speed), for example a sudden increase in drag induced by shock-wave generation (sonic-boom). Aircraft that are not designed to fly supersonic will break up at Mach 1. The shape of the aircraft can cause parts of the aircraft being at or above Mach 1 while the fuselage is subsonic. Flying near Mach 1 can be quite dangerous, for most fast (but subsonic) aircraft Mach 0.83 is the limit. High flying aircraft, like passenger aircraft, can reach that limit easy while descending. | ||
The speed of sound changes with the compressibility (and hence temperature) of air, the Mach number is dependent on [[altitude]] (as the air temperature drops at higher altitudes). This implies that Mach 2 at sea level corresponds to a faster TAS than Mach 2 at 30.000 ft. The precise relation between TAS, Mach number and altitude is a complicated formulae and depends in essence on the local weather pattern determining the pressure and temperature gradients in the atmosphere. | |||
The Mach number is measured/calculated from the same information as the EAS ([[#Pitot tube]] and [[altimeter]]) | The Mach number is measured/calculated from the same information as the EAS ([[#Pitot tube]] and [[altimeter]]) | ||