Is there any effect on the stealth features due to variable wing geometry? If not, why have such aircraft not been designed till now? Please explain the limitations using any structural principles if possible.
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asked Jul 29, 2015 at 2:24
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4$\begingroup$ Possible? Probably. Useful? Maybe. Practical? Doubtful. $\endgroup$– egidCommented Jul 29, 2015 at 5:23
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$\begingroup$ What about flaps? $\endgroup$– user3528438Commented Apr 16, 2018 at 16:02
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Of course it is possible. But it does not improve the outcome.
Swing wings were a fad of the Sixties. They never fulfilled their early promises, because the actuation mechanism is heavy. Variable sweep is only justifiable when the aircraft will fly both sub- and supersonically for extended periods. It turned out that the part of most missions which is spent at supersonic speeds is a lot smaller than anticipated in the Sixties. Just take the Rockwell B-1: Designed for supersonic penetration (B-1A) it became a subsonic low-level terrain following strike aircraft (B-1B).
For stealth, edge alignment is an important design principle. Making wing sweep variable is to throw this overboard, compromising the whole strategy of stealth. Also, the best stealthiness is only possible in subsonic flight - airframe heating at supersonic speed will broadcast the aircraft's presence to everyone with a low-cost infrared sensor.
answered Jul 29, 2015 at 7:20
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$\begingroup$ I think the basic idea currently is to make a plane either invisible or so fast that it doesn't matter whether you see it or not, because you can't do anything about it. $\endgroup$ Commented Jul 29, 2015 at 10:43
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2$\begingroup$ @JörgWMittag: The speed route worked in the Sixties, but has since then proven to be too expensive. Surface-to-air missiles are now too powerful to make this viable. Better switch to a low earth orbit instead. $\endgroup$ Commented Jul 29, 2015 at 10:54
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$\begingroup$ Swing wings “a fad of the 60s” - very true. Whatever performance gains were available never justified the gain in weight. $\endgroup$ Commented Apr 17, 2018 at 20:08
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$\begingroup$ @CarloFelicione: Absolutely! They did offer performance gains, namely the ability to fly Mach 2+ while still having acceptable field length, but it turned out that this particular performance gain was useless in real life. $\endgroup$ Commented Apr 17, 2018 at 22:12
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$\begingroup$ @JörgWMittag - that is not entirely true any more. The F-22 is designed specifically to have a range/speed/altitude envelope that puts it outside the S-300 and S-400 engagement envelope. One complaint about the F-35 is that it is not fast enough in this regard and will spend enough time within the detection range that they can't safely approach them. $\endgroup$ Commented Apr 24, 2018 at 13:17