In flight mechanics, the skin friction drag coefficient (Cf) is a dimensionless parameter used to quantify the contribution of skin friction drag to the total drag experienced by an aircraft or any object moving through a fluid, such as air. Skin friction drag is a type of drag that results from the friction between the fluid (air) and the surface of the aircraft.
C_D is the drag coefficient (dimensionless).
- L is the lift force generated by the aircraft’s wings (in newtons or pounds-force).
- ρ is the air density (in kg/m³ or slugs/ft³) at the current altitude.
- V is the true airspeed of the aircraft (in m/s or ft/s).
- Df is the skin friction drag (n)