What is the effect of leading edge slats in the landing approach?

• A. Increase lift coefficient through chordwise flow
• B. Increase drag
• C. Decrease lift coefficient
• D. Cause early stall

Answer: (A)

Leading edge slats are high-lift devices that, when extended, create a slot between the slat and the wing. This slot lets high-energy air from under the wing flow into the upper surface, energizing the boundary layer and helping the flow stay attached as the wing operates at higher angles of attack. That re-energized, chordwise flow increases the wing’s maximum lift coefficient, which is crucial during landing because it lets you fly at a lower approach speed while still maintaining safe lift. In practice, this gives you more margin against stall during the critical approach phase. The slats do add drag, but the primary benefit in a landing approach is the increased lift coefficient achieved by the chordwise flow through the slot.