page_title: Transonic
hierarchical_section_title: Transonic
caption_attribution_description: English: Shock waves are visible above the wing of an A320 family airliner during a regular flight. The shock waves appear as faint vertical "creaks" or "wrinkles" in the photo, and move back and forth a few centimeters along the top surface of the wing. They are in fact changes in air density over a very narrow amount of space, causing optical refraction. Shock waves are a normal occurrence above airliner wings, particularly during flights made at speeds in high transonic regime. whose cruise speeds are in the transonic range. They may not always be observable, depending on flight cruise, atmospheric and light conditions.
context_page_description: Transonic flight is flying at or near the speed of sound 343 meters per second, relative to the air through which the vehicle is traveling. A typical convention used in aeronautics is to define transonic flight as speeds in the range of Mach 0.72 to 1.0.
  This condition depends not only on the travel speed of the craft, but also on the temperature of the airflow in the vehicle's local environment. It is formally defined as the range of speeds between the critical Mach number, when some parts of the airflow over an air vehicle or airfoil are supersonic, and a higher speed, typically near Mach 1.2, when most of the airflow is supersonic. Between these speeds some of the airflow is supersonic, but a significant fraction is not.
  Most modern jet powered aircraft are engineered to operate at transonic air speeds. Transonic airspeeds see a rapid increase in drag from about Mach 0.8, and it is the fuel costs of the drag that typically limits the airspeed. Attempts to reduce wave drag can be seen on all high-speed aircraft. Most notable is the use of swept wings, but another common form is a wasp-waist fuselage as a side effect of the Whitcomb area rule.
context_section_description: Transonic (or transsonic) flight is flying at or near the speed of sound 343 meters per second (1,235 km/h; 1,125 ft/s; 767 mph; 667 kn, at sea level under average conditions), relative to the air through which the vehicle is traveling. A typical convention used in aeronautics is to define transonic flight as speeds in the range of Mach 0.72 to 1.0 (965–1,235 km/h (600–767 mph) at sea level).
  This condition depends not only on the travel speed of the craft, but also on the temperature of the airflow in the vehicle's local environment. It is formally defined as the range of speeds between the critical Mach number, when some parts of the airflow over an air vehicle or airfoil are supersonic, and a higher speed, typically near Mach 1.2, when most of the airflow is supersonic. Between these speeds some of the airflow is supersonic, but a significant fraction is not.
  Most modern jet powered aircraft are engineered to operate at transonic air speeds. Transonic airspeeds see a rapid increase in drag from about Mach 0.8, and it is the fuel costs of the drag that typically limits the airspeed. Attempts to reduce wave drag can be seen on all high-speed aircraft. Most notable is the use of swept wings, but another common form is a wasp-waist fuselage as a side effect of the Whitcomb area rule.
  Severe instability can occur at transonic speeds. Shock waves can cause large-scale separation downstream, increasing drag and adding asymmetry and unsteadiness to the flow around the vehicle. Research has been done into weakening shock waves in transonic flight through the use of anti-shock bodies and supercritical airfoils.
  Transonic speeds can also occur at the tips of rotor blades of helicopters and aircraft. This puts severe, unequal stresses on the rotor blade and may lead to accidents if it occurs. It is one of the limiting factors of the size of rotors and the forward speeds of helicopters (as this speed is added to the forward-sweeping [leading] side of the rotor, possibly causing localized transonics).
caption: Shock waves may appear as weak optical disturbances above airliners with supercritical wings
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