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What is a slotted flap?
Slotted Flap – Similar to a Plain Flap but incorporates a gap between the flap and the wing to force high pressure air from below the wing over the upper surface of the flap. This helps reduce boundary layer separation and allows the airflow over the flap to remain laminar.
How does the slot in a slotted flap work?
By opening a slot between the wing and the flap, 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. Lots of additional lift, without the excessive drag.
How does the slotted flap work in an airfoil?
The reason for this difference is simple: While the plain flap has only the old, thick and tired boundary layer coming from the fixed part of the airfoil to work with, the slot allows the slotted flap to create a new, thin and vigorous boundary layer which can tolerate much higher pressure gradients.
How are slotted flaps similar to Junkers flaps?
Junkers flaps are similar in principle to slotted flaps but do not retract, being simply aligned with the airflow when “retracted” to minimise drag. Placing the pivot point for a slotted flap below the wing causes flap extension to not only alter the camber but add to the wing area as well, providing additional benefit.
How does the slotted flap happen to be superior?
However the principle is air passing between the wing and the flap. This seems counterproductive as this airstream could also prevent the upper stream to follow the airfoils shape, and lead to air being less rotated downward than with a plain flap. How does the slotted flap happen to be superior?
How are Zap flaps similar to split flaps?
Zap flaps are similar in concept to split flaps, but the extension mechanism moves the flap rearwards as it rotates giving an increase in wing area along with the increase in camber: For more recent designs both plain and split flaps have fallen out of favour, leaving slotted flaps as the most popular choice.