Which wing device is primarily intended to allow a higher angle of attack before reaching the stalling angle?

• A. Flaps
• B. Slats
• C. Fixed slots
• D. Ailerons

Answer: (C)

Leading-edge devices are meant to keep the airflow attached as you raise the angle of attack. Fixed slots are permanent openings in the wing’s leading edge that allow air from beneath the wing to flow to the upper surface, energizing the boundary layer. That energized airflow delays separation, so the wing can reach a higher angle of attack before stall occurs. Because the slots are fixed, this benefit is available whenever the wing is at high angles, without needing any action to deploy the device. Slats achieve the same effect but are movable and only provide the advantage when extended. Flaps increase lift and change the stall characteristics in other ways, often lowering stall speed but not primarily increasing the maximum usable angle of attack in the same continuous, unextended manner. Ailerons control roll and don’t affect the stall angle like leading-edge devices do.