Definition
A high-lift wing device that combines two flap design features: it slides rearward along tracks to extend the wing's surface area before tilting downward (the Fowler action), and it opens one or more narrow gaps between the flap and the wing through which higher-pressure air from below flows up and over the flap's upper surface (the slotted action). The combination produces a large increase in lift and a controlled increase in drag, allowing slower approach and landing speeds.
Plain English
A landing flap that does two things at once: it slides backward to make the wing bigger, and it leaves a small gap that lets air flow over the top of the flap to keep it working at steep angles. Together this lets the airplane fly safely at much slower speeds.
Context Anchor
Seen in discussions of wing design, high-lift devices, takeoff performance, and landing configuration.
Derivation
Named after Harlan Fowler, the American engineer who developed the rearward-extending flap design in the 1920s. 'Slotted' simply describes the gap (slot) built into the flap. The name tells you the design lineage: it is a Fowler flap with a slot added.
Why Pilots Care
Allows safe operation at lower airspeeds during takeoff and landing, shortening required runway distances and reducing stall speed.
Intuition Check
Do not think of a slotted Fowler flap as just a simple flap with a gap in it. The key idea is that it slides rearward to make the wing effectively larger, then lowers to add curvature and lift.
Example Sentence 1
The Boeing 737 uses slotted Fowler flaps, which is why the wing visibly grows longer and wider when the flaps extend for landing.
Example Sentence 2
With the slotted Fowler flaps fully deployed, the aircraft could maintain level flight at a speed that would otherwise cause a stall.