I have a B.S. degree in A.E. There is an irritating question on the topic of wing sweep that was not answered to my satisfaction. Wing sweep solves the problem of wave drag at transonic speeds and this is the first thing we learn. It acts by reducing the thickness-to-chord ratio the air flow encounters as it passes over the wing. Another way of saying the same thing is the wing is less curved in the plane parallel to the fuselage. But sweep also creates a lot of accompanying problems, some of which are are poor aileron flow-adhesion from additional span-wise flow at low speeds, added difficulty in manufacturing, and a poor lift curve slope affecting landing and takeoff performance as well as lowering the stall speed. The latter leads to more complex slats and flaps. Another complication associated with wing sweep is the shift in the center of lift with speed. So, if the active principle in wing sweep is reducing the curvature the air flow encounters and reduction in the effective thickness-to-chord ratio, why not simply keep the wing straight but use a thinner, lower thickness-to-chord wing? The most convincing answer I find is that you can opt for a straight wing thin enough to avoid wave drag, no problem there, but you will also have a wing so thin that it will have the same problems with slow speed flight but will also be too small inside to contain wing spars, fuel, guns, and landing gear. But is that all? Can you add to the reasoning that wing sweep is always preferable to a high-speed straight wing?
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