In flight mechanics, the equivalent skin friction coefficient (Cfe) is a dimensionless parameter used to quantify the skin friction drag component experienced by an aircraft due to the interaction between its surface and the surrounding air. It represents the modification of the zero-lift drag coefficient (CDo) to account for the effects of skin roughness and flow conditions on the aircraft’s aerodynamic drag.
Skin friction drag is a type of drag that arises from the friction between the air molecules and the aircraft’s surface as it moves through the air. It is one of the major components of total aerodynamic drag, along with form drag and induced drag.
- Cfe is the equivalent skin friction coefficient (dimensionless).
- CDo is the zero-lift drag coefficient (dimensionless).
- Wetted area is the total surface area of the aircraft that experiences direct contact with the surrounding air, including both the upper and lower surfaces of the wings, fuselage, tail, and other components (in square meters or square feet).
- S is the wing reference area (or planform area) of the aircraft, which is typically the area of the wing projected perpendicular to the aircraft’s longitudinal axis (in square meters or square feet).
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