Clean configuration

Clean configuration refers to the flight configuration of an fixed-wing aircraft when its external equipment is retracted to minimize drag and thus maximize speed for a given power setting.

Application

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 (such as slats, spoilers, and leading edge flaps) are retracted. Clean configuration is used for normal cruising at altitude during which lift, or rise in altitude, is temporarily not needed. However, during takeoff and landing, slower speeds and lift are needed, so the landing gear and flaps are extended.

Related terms

"Dirty configuration", an airplane will be in dirty configuration with landing gear, flaps, and other devices extended. This creates drag, but the trade-off is that the flaps and similar devices change the shape of the wing and produce more lift than would otherwise be generated at the lower airspeed.