Spoiler and Flap Mechanism of Aircraft Wing

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A slotted flap enables high pressure air from beneath the wing to flow over it, increasing lift by maintaining airflow attachment. Slotted flaps increase primary airfoil's lift by accelerating the exiting air at its trailing edge. Any flap allowing air passage between the wing and itself is termed as a slotted flap. First introduced in Handley-Page research of the 1920s, it gained popularity later. Some slotted flaps use multiple slots to enhance their effect. Distinct from spoilers that create drag and reduce lift by disrupting airflow over wings, slotted flaps improve lift. Spoilers, often larger than Gurney flaps, are retractable and usually installed mid-chord on the upper wing surface or lower surfaces too.