Clean configuration
Clean configuration is the flight configuration of a fixed-wing aircraft when its external equipment is retracted to minimize drag, and thus maximize airspeed for a given power setting.
For most airplanes, clean configuration means simply that the wing flaps and landing gear are retracted, as these are the cause of drag due to the lack of streamlined shape. On more complex airplanes, it also means that other devices on the wings are retracted. Clean configuration is used for normal cruising at altitude during which lift, or rise in altitude, is not needed.
