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Aerodynamics Intermediate

03 Drag

Lift never comes alone. Part of the drag bill is the price of pushing any shape through air; the rest is the price of the lift itself. The two families behave oppositely as speed changes, and that opposition shapes how every aircraft is flown, from best-glide speed to why airliners cruise where they do.

Step 2 / 2

Put a number on it. At ρ = 1.225 kg/m³ , V = 50 m/s, S = 16 m² , the whole-aircraft drag coefficient is C_D = 0.032 . Compute the drag D = 12 ρ V² S C_D . Answer in N.

Hints

Same machinery as the lift equation, one letter different.
You already know q S at these numbers from the lift lesson: 24500 N.
Sanity check the result against the 14700 N of lift: a lift-to-drag ratio between 10 and 20 is normal for a clean light aircraft.