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Transonic (or transsonic) flow is air flowing around an object at a speed that generates regions of both subsonic and supersonic airflow around that object. [1] The exact range of speeds depends on the object's critical Mach number, but transonic flow is seen at flight speeds close to the speed of sound (343 m/s at sea level), typically between Mach 0.8 and 1.2.
[1] [2] Supersonic speed is the speed of an object that exceeds the speed of sound (Mach 1). For objects traveling in dry air of a temperature of 20 °C (68 °F) at sea level, this speed is approximately 343.2 m/s (1,126 ft/s; 768 mph; 667.1 kn; 1,236 km/h).
By definition, at Mach 1, the local flow velocity u is equal to the speed of sound. At Mach 0.65, u is 65% of the speed of sound (subsonic), and, at Mach 1.35, u is 35% faster than the speed of sound (supersonic). An F/A-18 Hornet creating a vapor cone at transonic speed just before reaching the speed of sound.
Mach number is more useful, and most high-speed aircraft are limited to a maximum operating Mach number, also known as M MO. For example, if the M MO is Mach 0.83, then at 9,100 m (30,000 ft) where the speed of sound under standard conditions is 1,093 kilometres per hour (590 kn), the true airspeed at M MO is 906 kilometres per hour (489 kn).
where a 0 is 1,225 km/h (661.45 kn) (the standard speed of sound at 15 °C), M is the Mach number, P is static pressure, and P 0 is standard sea level pressure (1013.25 hPa). Combining the above with the expression for Mach number gives EAS as a function of impact pressure and static pressure (valid for subsonic flow):
It is capable of supercruising at Mach 1.5 with an air superiority missile load. [16] Typhoon pilots have stated that Mach 1.3 is attainable in combat configuration with external stores. [21] The General Electric F414G in the JAS 39 Gripen NG is designed for supercruise and has achieved Mach 1.2, [22] or Mach 1.1 with an air to air missile load ...
V 1 is defined differently in different jurisdictions, and definitions change over time as aircraft regulations are amended. The US Federal Aviation Administration and the European Union Aviation Safety Agency define it as: "the maximum speed in the takeoff at which the pilot must take the first action (e.g., apply brakes, reduce thrust, deploy ...
The scientific research aims to optimise for both Mach 0.8–0.9 transonic and Mach 1.5–2.0 supersonic speeds, a similar design is tested in a wind tunnel while the engines are conceptualised at the Central Institute for Aviation Motors and designs are studied by Aviadvigatel and NPO Saturn. [54]