What is the definition of the "clean aircraft concept" in terms of takeoff?

The "clean aircraft concept" is a critical principle for ensuring safety during takeoff in aviation, particularly concerning the performance of the aircraft. Under this concept, the aircraft must be free of any frost, ice, snow, or slush on critical surfaces, such as the wings, elevators, and control surfaces. These contaminants can significantly affect the aerodynamic properties and handling of the aircraft, leading to a higher risk of accidents during takeoff, where reliable performance is crucial.

By mandating that takeoff is prohibited with any contamination present, the clean aircraft concept helps pilots ensure that the aircraft’s performance parameters remain within safe operational limits. This is especially important in cold weather operations, where the potential for ice formation is greater. Ensuring the aircraft is "clean" provides a safety framework for flight crews to evaluate the aircraft's readiness for safe takeoff conditions.