Path: utzoo!utgpu!jarvis.csri.toronto.edu!mailrus!csd4.csd.uwm.edu!uakari.primate.wisc.edu!ames!amdcad!military From: shafer@drynix (Mary Shafer) Newsgroups: sci.military Subject: Re: F-111s, long-winged Canberras, and World War II Message-ID: <27078@amdcad.AMD.COM> Date: 1 Sep 89 08:02:56 GMT Sender: cdr@amdcad.AMD.COM Lines: 69 Approved: military@amdcad.amd.com From: Mary Shafer In the referenced posting, miket@brspyr1.brs.com writes: >In sci.military Digest Wednesday, 05 July, 1989 Volume 2 : Issue 37 >henry@zoo.toronto.edu (Henry Spencer) writes: >> F-111 wing pivots too far outboard; Tornado pivots are in fuselage. >Okay, I'll bite. Why does this cause a problem? It seems that most Soviet >swing-wing planes (Tu-26, Tu-160, MiG-23/27, Su-17/20/22) have configurations >that swing a rather small percentage of the wing, far further outboard than on >most western aircraft (one exception may be the Su-24). Do the Soviets >have problems with this? Also, of course, the USAF has the B-1B, which seems >to follow the "Soviet" style of swing-wings. Henry's mistaken--the F-111 wing pivot is right at the root of the wing, contained in the fuselage. The _entire_ wing pivots around its inboard end at a point 70" from the fuselage midline. There is, however, a glove over the wing root, which may have given a casual observer the impression that the pivot is further outboard. All the swing-wing aircraft I'm familiar with pivot the entire wing on at the wing root, within the fuselage, rather than using a pivot at some outboard span position. These aircraft are the late-40s German plane, the NACA version thereof (X-5?), the F-111, F-14, Tornado, B-1, AD-1, Oblique-wing F-8, and, in its own peculiar way, the X-Wing or RSRA. Except for the first two and the F-8 (which was never built), my familiarity is based on first-hand observation. The last three pivot at precisely the fuselage midline. The reasons for this are aerodynamic and structural. First, the inboard pivot is better for the flow. Second, it's harder to build a wet wing with a pivot in the middle of it and the pivot also reduces the number of hard points you can put on the wing. The weight of an outboard pivot is going to mess up your wing loading, so that you will either have to build a very strong (and heavy) wing or you will have to accept a narrower g envelope. On the other hand, it's a lot easier to put the structure into the fuselage, where you already have a lot of structure already. It's probably also better from a maintainence point to have the pivot within the fuselage. Think about the wing as a cantilever beam, which it is. It's better to pivot the beam at the attach point than at a point halfway down the beam. On these swing-wing aircraft, the attach point is inside the fuselage. Before someone gets excited at catching me in an inconsistancy, I'll admit that some aircraft do indeed _fold_ their wings at some outboard span position. However, this is just folding and is only loadbearing in the down and locked position. >And unocss!mlewis@uunet.UU.NET (Marcus S. Lewis) writes: >> I remember seeing a Canberra recce (looooong wings) bird on the flight line >> [at Ramstein in the late 60s] and being told not to talk about it. Also >> can't rememer markings on it. >I used to see a lot of these at Davis-Monthan AFB (Tucson, Ariz.) in the early >1970s. I think the designation was RB-57H (could be wrong on that final >letter). This is commonly called a "B-57 Long-wing"--talk about original names. :-) -- Mary Shafer shafer@elxsi.dfrf.nasa.gov arpa!elxsi.dfrf.nasa.gov!shafer NASA Ames-Dryden Flight Research Facility, Edwards, CA Of course I don't speak for NASA