the german has started this idea and start to build planes base on this ideas, like Me 163B and the jet-powered Ju 287, but those designs are not very sucuess because they are really heavy and cannot gain enough speed to be effective enough, now the americans have build the X-29 aircraft, test pilot have concluded that is the best plane to control
I’d have to look up my notes to give you a detailed explanation (and I can’t be bothered right now), but from memory forward swept wings give the advantages of backward swept wings in terms of critical Mach number without most of the tip stall problems associated with backward swept wings. From memory, the problem (and it’s an absolute killer) is aeroelasticity - it’s something like there being negative feedback to a small amount of twist in backward swept wings, so that when they twist under load the load drops a little and they steady out. Unfortunately it’s a positive feedback effect with forward swept wings so unless you can build VERY strong and stiff wings they will either twist far enough to stall and so remove the twisting moment, or if you’ve really messed up your design/have battle damage break off.
This is a paradox because to reach the high speeds you need to go to in order to benefit from having wing sweep you effectively have to have very thin wings (there are other ways around it, but they end up giving you high drag in other areas). Extremely strong and stiff wings in a very thin package is something that has only been possible for the last 20 years or so (X-29 and S-37 research aircraft), and even then it is unclear how much fly-by-wire was used to ensure performance.
So a good summary of the German aircraft would be that they tried to build something beyond their capabilities, but it didn’t work. Come to think of it, a heck of a lot of German WW2 kit was full of great ideas with awful engineering letting them down.
Wow thats a cool looking plane…never actually seen it. I heard that Germans experimented with the forward sweept design but never saw a pic. Thanks Dani.
While strong and stiff was important, the breakthrough isn’t merely a matter of strong and stiff. I believe the solution (at least on the X-29) was to make the wing from composite materials, with an anisotropic layup such that it gives a elastically tailored wing with bend-twist coupling.
For the laymen present: as we all know if you’ve looked out of the window on a flight, wings bend spanwise in flight and this isn’t a problem. They can also twist. The layup on the X-29 wing would be such that, due to the anisotropy of composites used in the wing, the wing bending also has a coupling with twist. Tailor the twist to be a leading edge down twist for an upwards bending moment, and your structure will itself dampen (or remove) the natural twist up.
I’m not sure exactly what the layup used was, but it will undoubtedly break away from the usual 0, 90 and +/-45 degree fibre directions commonly used in aerospace composites, and introduce something like 30 or 60 degree fibres. Bending a layup with such fibres in will make it want to twist.
. Maybe our friend Polar will help us…