Definition
The maximum airspeed at which the wing flaps may be extended or operated. It is published in the aircraft's operating limitations and is denoted on the airspeed indicator by the upper end of the white arc. Exceeding this speed with flaps extended risks structural damage to the flaps and their attachment points.
Plain English
The fastest speed at which it is safe to lower the flaps. Slow down to at or below this speed before extending them, and keep the airplane below it whenever the flaps are out.
Context Anchor
Seen when configuring the airplane for slower flight, approaches, and landings, especially before selecting flaps during instrument flight.
Derivation
“Flap” refers to the movable panels on the wing that change the wing’s shape. “Extension” comes from the idea of moving something outward or putting it out. Together, “flap extension” means moving the flaps out from their retracted position.
Why Pilots Care
Exceeding this speed can cause structural damage to the flaps from excessive aerodynamic forces.
Intuition Check
Do not read this as the speed at which the flaps physically move. It means the maximum airplane speed at which you are allowed to lower the flaps.
Example Sentence 1
On downwind she reduced power and waited until the airspeed dropped below the flap extension speed before selecting the first notch of flaps.
Example Sentence 2
During the pre-landing checklist the crew confirmed they were below flap extension speed prior to extending the flaps.