High Lift Devices
August 1, 2025
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What’s High Lift Devices?
High-lift devices are components on aircraft wings that increase lift, especially during takeoff and landing.
Examples?
- Trailing edge flaps
- Leading edge devices
Principles? or Mechanisms?
Everything is designed revolving around “lift formula” , for example, movable trailing edge flaps can further divided into various categories:
- plain flaps, when they are extended ( by just pivot down), they increase the camber
- split flaps, similar purpose
- slotted flaps, used more on airliner, when they are extended, a slot will be created,
high pressure air from the bottom of the wing flows through the slot into the upper surface. This adds energy to the wing’s boundary layer, delays airflow separation, and produces less drag. Of course, they increase the camber as well - flower flaps, similar to slotted flaps, the difference is that they slide backward on tracks or rails before hinging downwards. This causes increasing wing’s surface area
What about leading edge devices?
thx for the internet, we can get the insights more easily, types of leading edge devices:
- fixed slot, as its name implies, it is static on leading edge. They are used as a mean of airflow management, by facilitating airflow over the wing, smoothing the flow and preventing separation (turbulence), which in turn increases CL
- movable slat, the function is similar to the slot, but they can be retractable
- Krueger flap, when they are deployed, the aerodynamic effect is similar to that of slats; however, they are deployed differently. Krueger flaps are mounted on the bottom surface of the wing and are hinged at their leading edges. Actuators extend the flap down and forwards from the under surface of the wing thus increasing the wing camber which, in turn, increases lift. The B747 has this device.
- Leading edge droop, in movable form. They are deployed by hang down (droop) which increase the camber of the wing and reduce the stalling speed. For example, the Airbus A380 has droop flaps between the fuselage and each inboard engine, at the leading edge of the thickest part of each wing. The A350 has leading edge droop as well
More references
https://pilotinstitute.com/flaps-types-explained/
