Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP Posting-Version: version B 2.10.1 6/24/83; site bonnie.UUCP Path: utzoo!watmath!clyde!bonnie!dpw From: dpw@bonnie.UUCP (David P. Williams) Newsgroups: net.aviation Subject: Re: X-29 Message-ID: <234@bonnie.UUCP> Date: Wed, 26-Sep-84 13:37:56 EDT Article-I.D.: bonnie.234 Posted: Wed Sep 26 13:37:56 1984 Date-Received: Thu, 27-Sep-84 05:17:46 EDT References: <229@haddock.UUCP> Organization: AT&T Bell Laboratories Whippany NJ Lines: 33 With regard to forward-swept wings: The aeronautical engineers can put together an aircraft with forward-swept wings that is dynamically stable - witness numerous sailplanes, the Hansa corporate jet (made in Germany), and a bomber prototype the Germans were working on at the close of World War II. Advantages of a dynamically unstable aircraft are better maneuverability and tailoring of the response of the aircraft to different flight regimes. The F-16 and Space Shuttle are dynamically unstable and use different control responses depending on speed, angle of attack, and other facters. The penalty is that you have to maintain redundant control systems for safety. The X-29 is not a radically different aircraft for employing new wing technology and dynamic instability. For high speed aircraft, the big advantage of forward-swept wings is that separation of flow over the wing while maneuvering occurs at higher angles of attack than for conventional swept wings *if the wing can be kept from twisting under the load (aeroelastic divergence)*. Since steel and aluminum are more than happy to twist without a prohibitive amount of stiffening, forward-swept wings have not been usable until now. With graphite epoxy and other composites, wings can be tailored to bend and flex in specific ways by aligning the grain of the cloth and using varying numbers of layers. So, it is now practical to build aircraft with forward-swept wings - many of the designs for the Advanced Tactical Fighter (ATF) feature them along with canards for better maneuverability than the current generation of fighters. David Williams AT&T Bell Laboratories Whippany, NJ (bonnie!dpw)