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Assume I want to use the flaps or ailerons at a specific altitude for some maneuevers on an aircraft. We know that the overall aerodynamic forces like lift and drag on an aircraft wing will change values when these control surfaces are used, but the use of these surfaces will also cause a change in the lift/drag distribution on the wing region/area which is located before these control surfaces or not?

I mean the change in the net aerodynamic forces on a wing only result from the usage of these control surfaces, or the force/drag distribution on the immovable wing parts also change and also contribute to the overall change in the lift and drag forces for that wing?

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  • $\begingroup$ Are you interested just in theory, "how it happens"? Then you have an answer already (for subsonic speeds, the entire surface is affected; for supersonic speeds, not). But if you are concerned about how to calculate/find it, then the standard aerodynamic data already takes whatever happens into account. In many cases you'll have some additive quantities like, say, $\Delta C_L = 0.05$ per degree of deployment, and if you only need to know the net effect of (say) flaps, you just use these data, without the need to recalculate it for the "whole wing". $\endgroup$
    – Zeus
    Nov 11 '21 at 0:24
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This shows the chordwise pressure distribution of a typical airfoil with a slotted flap retracted, at 10, 20 and 30deg, at both constant lift and at constant angle of attack. Deploying flaps changes the lift distribution across the entire chord of the wing. Ailerons have the same effect.

enter image description here

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  • $\begingroup$ An important qualification to this answer would be "only for subsonic speeds". $\endgroup$
    – Zeus
    Nov 11 '21 at 0:12

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