Airfoil twist

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Unread post20 Oct 2017, 13:05

I'm not sure whether this thing have been already touched or not but this is the question. I've noticed that Raptor's wing is somehow convoluted somewhere starting from midsection to the wingtip, leading edge is flexed clearly down and trailing edge is flexed up. I guess F-35 has more or less the same feature. I havnt seen it on F-18s, F-16s, not quite sure about F-15.

What tahat actually is and what it's for? I'm guessing it has to be benefitial from an aerodynamic standpoint.. I dont know, less induced drag, supercruise? Im wondering.

It's quite well visible on a frontal plane



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Unread post20 Oct 2017, 14:12

Though this won't fully address your question (especially as to whether or not this is the reason why the F-22 has it), but this is known as washout.
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Unread post20 Oct 2017, 18:57

Most wings will have different airfoils, etc along the span to allow the aerodynamics guys to tailor the lift distribution, help out with S&C, etc.
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Unread post21 Oct 2017, 03:36

My guess would be that the twist has to do with the angle of attack various parts of the wing stall at.
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Unread post21 Oct 2017, 07:06

Another benefit of twist in the wing is reduced structural weight, both in the wing and the fuselage. There are two kinds of wing twist, static and elastic. Static is the twist with zero load on the wing. Elastic is the twist due to load on the wing. For F-16, static is 3 degrees from wing root to tip. Elastic can be as much as 4 degrees, so total twist can be up to 7 degrees.

So how does that save structural weight? As mentioned earlier the tip area has a lower angle of attack and lift due to the twist. That moves the center of lift inboard and reduces wing bending moment and fuselage bulkhead moment for the required total wing lift.


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Unread post21 Oct 2017, 15:18

This feature is more prominent from the back IMO, and I've often wondered why it's there too.

Gives it an edgier look IMO. From the front or back, she looks real mean...

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