Explain the design principles of supercritical airfoils.

Supercritical airfoils (developed by Whitcomb) are designed for efficient transonic flight: Flattened upper surface reduces peak Mach numbers and shock strength; rear loading through increased camber near trailing edge recovers lift lost from flattening; thicker sections possible for same drag, improving structural efficiency; shock positioned further aft reducing wave drag. Design methods include inverse design specifying target pressure distributions, optimization using adjoint CFD, and thickness/camber trades. Modern transports use supercritical sections with 12-14% thickness, achieving drag divergence Mach numbers 0.05-0.10 higher than conventional airfoils at same CL.