Which of the following describes a fixed slot on a wing?

• A. A movable slot on the trailing edge of the wing.
• B. A fixed opening on the fuselage for cabin air.
• C. A fixed, nozzle-shaped opening near the leading edge of a wing that ducts air onto the top surface of the wing.
• D. A wingtip device that reduces wingtip vortices.

Answer: (C)

A fixed slot on a wing is a stationary opening near or at the leading edge that directs a stream of air onto the top surface of the wing. This air is channeled in a nozzle-like fashion to energize the boundary layer, helping the flow stay attached to the wing at higher angles of attack and thereby delaying stall and increasing lift. The description in this option matches that idea: a fixed, nozzle-shaped opening near the leading edge that ducts air onto the top surface.

Movable slots, cabin air vents, and wingtip devices serve different purposes or configurations, so they don’t describe a fixed slot on the wing.