Definition
Graphs that show how the total drag on an aircraft changes with airspeed. The total drag curve is formed by adding two components: induced drag, which is highest at low airspeeds and decreases as speed increases, and parasite drag, which is low at low airspeeds and rises sharply as speed increases. The lowest point on the total drag curve identifies the airspeed at which drag is minimum, which corresponds to the speed for maximum endurance and best lift-to-drag ratio (L/D max).
Plain English
A drag curve is a chart showing how much the air pushes back on the aircraft at different speeds. Slow speeds and high speeds both create more drag; somewhere in the middle is the speed where drag is lowest and the aircraft flies most efficiently.
Context Anchor
Seen in aircraft performance and instrument flying discussions when explaining speed control, power required, and why very slow flight can require more power instead of less.
Derivation
Drag comes from an old word meaning to pull or draw along. In aviation, drag is the air’s backward pull on the airplane. Curve comes from Latin for bent, but here it means a line on a graph, not a curved aircraft part.
Why Pilots Care
They identify the speed of minimum total drag, which affects best glide range, endurance, and fuel efficiency decisions.
Analogy
Think of riding a bicycle. Going faster makes wind resistance stronger, but going too slowly can also feel inefficient because you must work harder to stay balanced and moving. A drag curve shows that kind of changing effort for an airplane.
Intuition Check
Do not read “curves” as curved parts on the airplane. Here, “drag curves” means graph lines showing how drag changes with speed.
Example Sentence 1
The instructor used the drag curve to show why best glide speed sits at the bottom of the curve, where total drag is at its minimum.
Example Sentence 2
Reviewing the drag curves helped confirm the best glide speed after an engine failure.