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During the cruise, modern large jet aeroplanes normally fly at speeds faster than MCRIT since the increase in speed is more significant than the increase in drag. This is achieved:
  • A
    By fitting supercritical wings.
  • B
    By decreasing the leading-edge radius of the wing.
  • C
    By flying at lower altitudes where the TAS is higher for a given Mach number and therefore experience a delay in the onset of shock waves and wave drag.
  • D
    By using an advanced wing technology with a greater curvature underneath to balance the acceleration over the top and therefore reduce the severity of the shock waves.

Refer to figure.
A supercritical wing is one that has been designed with specific streamwise segments to delay the onset of the adverse effects of the shockwave, i.e. wave drag and its severity and decreased lateral stability, when the airplane is flying in the transonic speed range or just above MCRIT. It increases the cruise Mach number, the range, and the endurance of the airplane.

Supercritical profiles were designed by searching for the contour that gives adequate pressure distribution. Because of the flat upper surface, shock wave formation is delayed on the upper surface, consequently shock stall happens at higher Mach number. Intensity of the shock wave is also reduced.

Compared with a conventional airfoil section, it has a larger leading-edge radius, a flatter upper surface and both positive and negative camber and enables a relatively thick wing to be used for approximately the same cruise Mach number.

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