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I think flaps are inspired from eagle feathers which increase the overall wing surface area and help provide the necessary lift at lower speeds. However, fully extended flaps hang lower and cause more fuel to be burnt (might be because they interact and reduce the exhaust thrust and create more drag). Are the current wing flaps fully optimized or is there any possibility of improvement?

Lowering fuel consumption while maintaining same lift and safety of aircraft by possible geometrical modification is good, because it helps reduce the carbon emissions.

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You can rest assured that current flap configurations used in modern aircraft are fully optimized.

Developing new aircraft, and operating them is a multi billion dollar enterprize, and although it would be foolish to claim that design choises are not compromises to some extent, it is certain that no stone is left unturned when aerodynamics of the wing is being designed.

Current solutions are the best that can be achieved with present day materials and budget, not to forget the reliability of the solution.

There are known solutions such as blown flaps, boundary layer suction and so on and so forth, but they all have downsides that make them not utilizable in large scales.

To adress the point of fuel consumption: the current flap configurations are designed to maximize fuel efficiency. Flaps are being used in portions of flight that last for relatively short periods (say, 15 minutes max. for intermediate flap settings, a couple of minutes for full flaps). By utilizing high lift and thus high drag flaps for landing, the wing can otherwise be designed to be very, very efficient for the main part of the flight.

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is it possible to reduce the angle of fully extended flaps

Yes. Fully extended flaps are only used for landing. They allow for a lower landing speeds and more drag, resulting in a shorter roll-out.

For less drag, they can be reduced, or with higher speeds, fully retracted.

With aircraft, lift increases with the square of speed, which is why flaps are generally used only when the aircraft is flying at a slower speed.

Best distance per unit fuel burned is near the lowest drag configuration. Weight is critical too. The best bet for fuel efficiency is to have one wing that is properly sized for the weight and speed desired.

Adding flaps is essentially adding another wing for slower flight. It works, just not (aerodynamicly) as well.

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    $\begingroup$ I’m curious, why did you omit and not answer “without affecting the lift generated?” Did you think this part was irrelevant? Because it’s really the central point of the whole question. $\endgroup$ Commented Apr 10, 2022 at 15:22
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    $\begingroup$ Might be because the idea that flaps "affect... the lift generated" is the wrong way to think about them. Many factors go into the generation of Lift. Changing the lift is not the point of flaps. The point is to lower the minimum speed at which wing can still generate sufficient lift to maintain 1 G flight. In actuality, deploying flaps lowers the maximum available lift at most (cruise and higher) airspeeds because it lowers the wings maximum allowable structural load limit. $\endgroup$ Commented Apr 10, 2022 at 16:20
  • $\begingroup$ Good points. Going by the flaps 0, 10, 20, 30 degrees, 10 increases lift coefficient, 20 and especially 30 mainly add drag. With flaps, the rest of the wing has to stay lower AoA to keep the flaps portion from stalling (what Charles pointed out). When airliners drop full flaps, they have Snoopy, the Red Baron, and the whole Flying Circus going on back there. $\endgroup$ Commented Apr 10, 2022 at 17:05
  • $\begingroup$ @CharlesBretana "The point is to lower the minimum speed at which wing can still generate sufficient lift to maintain 1 G flight." And the flaps do this by... (sheepishly from the back row) "by changing the lift sir?" "NO!" (sharp smacking sound...) $\endgroup$ Commented Apr 10, 2022 at 17:54
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    $\begingroup$ @CharlesBretana - re "Changing the lift is not the point of flaps." - but changing the lift coefficient is. Re "In actuality, deploying flaps lowers the maximum available lift at most (cruise and higher) airspeeds because it lowers the wings maximum allowable structural load limit." - seems odd, as the flaps would appear to cause the inboard portions of the wings to generate most of the lift, reducing bending loads. Do you have a source for this? Maybe should be a new ASE question-- $\endgroup$ Commented Apr 10, 2022 at 18:06

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