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Aerodynamics Intermediate

02 The Lift Equation

Everything so far compresses into one line: L = 12 ρ V² S C_L Density, speed squared, wing area, and a coefficient hiding the shape and the angle. This lesson is pure calculation. Work in SI units, state the unit with every answer, and round only at the end; answers are checked against a tolerance, not a keyword list.

Step 4 / 4

Hot day, high airport: the air density drops to ρ = 1.007 kg/m³ (roughly 2000 m density altitude). Same aircraft, same W = 14700 N, S = 16 m² , C_L = 1.2 . Find the new minimum level-flight speed, in m/s. Notice which direction it moved and by how much: this is why performance charts care about density altitude.

Hints

Only ρ changed; the same rearranged equation applies.
Thin air carries less momentum per cubic metre, so the wing must meet more of it per second.
Speed scales with √1/ρ : expect roughly 10% faster than the sea-level answer.