Leading-edge device function: which statement is true?

• A. They are high lift devices on the trailing edge of the airfoil
• B. They reduce drag only
• C. They are used for steering
• D. They are high lift devices on the leading edge of the airfoil

Answer: (D)

Leading-edge devices are high-lift devices located on the front edge of the wing. When deployed, they modify the airflow by creating a slot or energizing the boundary layer, which helps keep the airflow attached at higher angles of attack. This delays stall and increases the wing’s maximum lift coefficient, enabling takeoff and landing at lower speeds and with shorter distances. They are not used for steering—that role belongs to control surfaces on the trailing edge or elsewhere—nor do they reduce drag in general; in fact, they can add drag when extended. They’re specifically designed to boost lift at slow speeds, which is why statements describing them as high-lift devices on the leading edge are correct.