Plain English Meaning

A chart showing how much the air pushes back on an airplane at different speeds. At very slow speeds drag is high, at very fast speeds drag is also high, and there is a sweet spot in the middle where drag is lowest.

Full Definition

A graph that plots the total drag acting on an airplane against airspeed in level flight. Total drag is the sum of induced drag (which decreases as airspeed increases) and parasite drag (which increases as airspeed increases). The curve is U-shaped, and the lowest point on the curve identifies the airspeed at which total drag is at its minimum, known as L/D max.

Context Anchor

Seen in airplane performance, slow flight, glide, and power-required discussions.