Definition
The airspeed at which an airplane produces the greatest amount of lift for the least amount of drag, resulting in the most efficient aerodynamic performance. At this speed, total drag is at its minimum value, which is why it is also called minimum drag speed. It produces the best glide range in an engine-out situation and the maximum range in a jet airplane.
Plain English
The speed where the airplane gets the most lift for the least drag. Flying at this speed means the wings are working at their most efficient point, which gives the longest glide if the engine quits.
Context Anchor
Seen in performance, glide, and drag discussions when comparing slower and faster speeds.
Derivation
L stands for lift and D for drag. The ratio L/D measures how many pounds of lift the wing produces for each pound of drag it creates. MAX simply means the highest value of that ratio, the speed where the wing is at its aerodynamic best.
Why Pilots Care
It is the speed that maximizes glide distance after an engine failure or provides maximum range in unpowered flight.
Grounding Statement
Picture an airplane slowing down from a fast cruise: drag decreases at first, reaches a lowest point, then rises again as the airplane gets too slow.
Intuition Check
Minimum drag speed does not mean the slowest speed the airplane can fly. It means the speed where total drag is lowest.
Example Sentence 1
After the engine failure, the pilot pitched for L/DMAX to stretch the glide toward the nearest airport.
Example Sentence 2
The performance section lists L/DMAX as the target speed for determining maximum glide distance in the clean configuration.