Parasitic Drag Calculator Formula
Understand the math behind the parasitic drag calculator. Each variable explained with a worked example.
Formulas Used
Parasitic Drag Coefficient (CD0)
cd0_out = cf * wetted_area / ref_areaEquivalent Flat Plate Area
flat_plate_area = cf * wetted_areaParasitic Drag Force
parasitic_force = cd0 * dynamic_press * ref_areaVariables
| Variable | Description | Default |
|---|---|---|
cf | Skin Friction Coefficient (Cf) | 0.003 |
wetted_area | Wetted Area (Swet)(m²) | 400 |
ref_area | Reference Wing Area (Sref)(m²) | 120 |
dynamic_press | Dynamic Pressure (q)(Pa) | 5000 |
cd0 | Derived value= cf * wetted_area / ref_area | calculated |
How It Works
Parasitic Drag
Parasitic drag (also called zero-lift drag or profile drag) is the drag that exists even when the wing is not generating lift. It consists of skin friction drag and form (pressure) drag.
Formula
CD0 = Cf × Swet / Sref
where Cf is an average skin friction coefficient for the entire aircraft, Swet is the total wetted (exposed to airflow) area, and Sref is the wing reference area. The equivalent flat plate area f = Cf × Swet is a useful metric for comparing aircraft of different sizes.
Worked Example
An aircraft with Cf=0.003, wetted area 400 m², wing area 120 m², at q=5000 Pa.
- 01CD0 = 0.003 × 400 / 120 = 1.2 / 120 = 0.01
- 02Flat plate area = 0.003 × 400 = 1.2 m²
- 03Drag force = 0.01 × 5000 × 120 = 6000 N
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