Definition
The slowest speed at which an airplane can be flown under full control, just above the stall, where any further reduction in airspeed or increase in angle of attack would cause an immediate stall. At this speed the airplane is fully responsive to the controls, but only just — small mishandling will cause loss of control or a stall.
Plain English
The slowest speed the airplane can fly while still doing what the pilot tells it to do. Any slower, and it stalls.
Context Anchor
Seen in short-field approach and landing discussions, where the pilot may need to fly slowly but must not get so slow that control is reduced or lost.
Derivation
Minimum comes from a Latin word meaning “smallest” or “least.” Controllable means able to be controlled. Together, the phrase points to the least airspeed at which the airplane still remains under the pilot’s control.
Why Pilots Care
This speed defines the practical lower limit of controlled flight in high-power, high-angle-of-attack conditions typical of short-field operations.
Grounding Statement
As the airplane slows, the controls feel less firm; minimum controllable airspeed is the lower limit before that slow flight becomes unsafe.
Intuition Check
Do not read “minimum” as “the target speed to hold.” Here it means the lower safe limit for control; normal approach speed should stay at or above the speed recommended for the airplane and conditions.
Example Sentence 1
The instructor reduced power and raised the nose until the airplane was flying at minimum controllable airspeed, then had the student make gentle turns to feel the sluggish controls.
Example Sentence 2
During the power-on stall exercise the airplane reached minimum controllable airspeed while aileron and rudder inputs remained fully effective.