Plain English Meaning

The speed that keeps the airplane in the air for the longest time when the engine is not producing power. Flying at this speed makes the airplane drop toward the ground as slowly as possible, but it does not cover the most ground.

Full Definition

The airspeed at which an airplane in a power-off glide loses altitude at the slowest possible rate, providing the maximum time aloft for a given altitude. It is slower than best glide speed, which provides the greatest distance covered per foot of altitude lost.

Context Anchor

Encountered when learning glides, power-off descents, and the difference between staying airborne longer versus gliding farther.

Derivation

"Sink" describes the airplane's downward movement through the air when it is not producing enough to . "Minimum sink" means the smallest downward rate possible, so "minimum sink speed" is the airspeed that produces that smallest .