Flaps are hypersustentators on the edge of wings. There are various types:
This is the most simple flap that exists. Its mechanism is based on a part of the wing which in some cases can reach 30% of the string and deflects downwards.
These flaps increase sustentation increasing the curvature of the wings’ edge and can deflect up to 40 or 50 degrees.
As well as increasing sustentation, they also increase generated resistance, forming a great area of vortexes or turbulence wakes.
These have a design which is similar to plain flaps but once extended, have a hole or slot between wing and leading edge.
This hole sends a small air current upwards, which circulates alongside the lower part of the wing, energising the boundary layer.
As with plain flaps, split flaps have a wing trailing edge that deflects downwards, but only on the underside or intrados whereas the extrados or upper part of the wing keeps its shape.
Split flaps generate the same increase in lift as plain flaps, the difference being that generated resistance is much lower here.
These are the most complex flaps that exist. They not only increase sustentation but also the effective surface wing area.
In the same way as slotted flaps, it creates a hole between the wing and the leading edge of the flap to energise the boundary layer.
The fowler flap produces an increase of the maximum sustentation coefficient with a light increase of generated resistance.