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#51
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FBW replaces mechanical links with wire; Have to be careful how you phrase that, or the Cub will qualify! Also the brakes on a 1936 Ford! (Has anyone else here lay beneath a Ford on a dark night on a lonesome highway, tightening up the brake cables because the thang didn't stop at the last stop sign?) all the best -- Dan Ford email: (put Cubdriver in subject line) The Warbird's Forum www.warbirdforum.com The Piper Cub Forum www.pipercubforum.com Viva Bush! weblog www.vivabush.org |
#52
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From what I can find, it looks as if the B-2 is designed for
fly-by-wire control, probably to keep it stealthy as much as anything. The flying wing shape by itself does not demand FBW, as the XB-35 and YB-49 designs of the 40's were controllable without computer assistance. The B-2 has FBW controls and a 6000 psi hydraulic system to move the control surfaces for a number of reasons, mainly stability and weight reduction. I have several friends who have flown it and they generally describe it's flying qualities as F-111-like. The B-35 and B-49 designs were unsuitable as bombers because of lack of directional stability expecially on a bomb run. If you notice, the competition (B-36) has a large vertical fin. Steve |
#53
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The flying wing shape by itself does not demand FBW, as the XB-35 and YB-49 designs of the 40's were controllable without computer assistance. Not really. The 35 had those great engine pods, and the 49 had a bunch of vertical fins, so in fact neither one was a true flying wing. Nobody ever managed to fly the 35 enough to determine its utility (the long shafts were the main problem), and the 49 was so afflicted by dutch roll that the bombardier got sicksick. Plus there was the question whether it (and a British flying wing design) wasn't prone to spin around its lateral axis. The latter is disputed. For opposing views see www.warbirdforum.com/cardenas.htm and www.warbirdforum.com/tucker.htm The Germans may have had more success with their nurflugels. It's hard to tell; the most famous Horten design killed its test pilot in disputed circumstances. I once corresponded with a Horten associate who claimed that the problem with the Northrop designs had to do with center of gravity, but I'm not enough of an engineer to follow these arguments. all the best -- Dan Ford email: (put Cubdriver in subject line) The Warbird's Forum www.warbirdforum.com The Piper Cub Forum www.pipercubforum.com Viva Bush! weblog www.vivabush.org |
#54
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Cub Driver wrote:
Plus there was the question whether it (and a British flying wing design) wasn't prone to spin around its lateral axis. Having built and flown experimental flying wings since 1996 I can attest that if you find yourself in a spin around the lateral axis (i.e: a "tumble") better hope you have jam in your pockets cos' your ass is toast... http://www.motolotnie.rsi.pl/mpg/film1s.mpg |
#55
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Cub Driver wrote:
Not really. The 35 had those great engine pods, and the 49 had a bunch of vertical fins, so in fact neither one was a true flying wing. Nobody ever managed to fly the 35 enough to determine its utility (the long shafts were the main problem), and the 49 was so afflicted by dutch roll that the bombardier got sicksick. Plus there was the question whether it (and a British flying wing design) wasn't prone to spin around its lateral axis. The latter is disputed. For opposing views see www.warbirdforum.com/cardenas.htm and www.warbirdforum.com/tucker.htm I read that the YB-35 managed to do without vertical surfaces due to the props providing enough longtitudinal stability; although I'm not entirely clear as to how that would work. In any case, when it came to the YB-49 it was found that the turbines did not provide the same effect and the vertical fins had to be added. The British design would be the Armstrong-Whitworth AW52. Barrie Hygate in British Experimental Jet Aircraft relates that it had severe probelms of pitch sensitivity leading to oscillations, at least partly due to the short control arm provided by the modestly swept back wing. One prototype was lost in 1949 after entering divergent pitch oscillations, the pilot making the first British use of a Martin-Baker seat for real. All three aircraft needed at some stability augmentation system to be safe and usable platforms. The AW52 was only ever intended as an experimental type, to test laminar flow. |
#56
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#57
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I read that the YB-35 managed to do without vertical surfaces due to the props providing enough longtitudinal stability; although I'm not entirely clear as to how that would work. It wasn't the props as much as the drive shaft fairings. Right, the fairings were long and (by the time they reached the prop) high above the trailing edge of the wing, rather like the wing of a paper dart. They would have acted very much like a vertical stabilizer. (And created, as was posted, no end of problems with the XB-35's propeller shafts, which vibrated.) The fairings (and later the vertical fins on the YB-49) also served as air dams, perhaps inadvertently solving a problem with swept-wing designs, where the airstream tends to move laterally toward the wingtips rather than straight back in the line of flight. all the best -- Dan Ford email: (put Cubdriver in subject line) The Warbird's Forum www.warbirdforum.com The Piper Cub Forum www.pipercubforum.com Viva Bush! weblog www.vivabush.org |
#58
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On Tue, 29 Jun 2004 11:13:15 -0500, "Emilio"
wrote: It is hard to believe that F-15 can fly formation with Piper Cub. http://www.pipercubforum.com/intercep.htm I've seen thirty F/A-18s and six "Ducks" fly in formation, too. It didn't last very long, though. Ditto the F-15 and the A-37. They only have to be in the proper relative position long enough for the photographer to get the photo. Do F-15 fly by wire system prevent the aircraft from stalling at that low speed? Last time I saw an aircraft with fly by wire system did such a stunt, Airbus plowed right in to the forest at the end of the forest! The F-15 isn't fly-by-wire. It's augmented, but not fly-by-wire. Mary -- Mary Shafer Retired aerospace research engineer |
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