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"B2431" wrote in message ... From: ( SNIP proved how complicated things really were. The downward ducted fan concept has been tried several times and not one vehicle had the performance to justify proceeding to an operational prototype. The results of the tests were as follows: http://www.autobahn.mb.ca/~billzuk/F...aucer%202.html "The results of the testing revealed a stability problem and degraded performance due to turbo-rotor tolerances. Before modifications could be achieved, funding ran out with the final flight test program completed in March 1961. With the problems that the contractor was facing in the wake of the cancellation of its premier fighter program, the Avro Arrow by the Canadian government, Avro was unable to continue the project. " OK so the engineering problem of turbo tollerances is corrected ( a cinch for todays wide bodied cowling manufacturers I expect ) and the stability problems are solved by a gyroscoep based "Fly By Wire" stability augmentation system. ( an FBW system like this is an of the shelf cinch today ) Why wouldn't it work now? From what I can see this system should work. An efficient VTOL device needs large volumes of slow moving air. A helicopter achieves this with a rotor. A "saucer" like this can do so by sucking in air at the top and distributing it to a lip at the edge of the saucer where the high velocity air is converted to low velocity by inducing an airflow. However that is not how the Avro machine worked. See: http://www.laesieworks.com/ifo/lib/avro-graph02.html If you poke around the web you will find all kinds duct being used to hover. You will even find a few that can transition from vertical to horizontal flight. The closest to being practical I can recall was in the 1960s Boeing produced on with four ducts mounted on winglets. Dan, U. S. Air Force, retired There are a number of ducted fan concepts. The Piasaki flying Jeeps worked and had advantages but were fuel hogs that had trouble landing on uneven ground and there were concerns that they were dangerous in gusty conditions. http://www.faqs.org/docs/air/avplatfm.html#m4 It seems to me that the Israeli guy (built the prototype in his apartment and had to knok down the wall to get it out) has adressed most of the shortcommings of these Piasaki aerial platforms. http://www.urbanaero.com/Urban_Main.htm Many VTOL and ducted fan concepts are documented on http://www.vstol.org/ The 'wheel of misfortune' is interesting and the Boeing project you refer to is I think the Bell X22A but there were others such as the Bell model 65 ATV In reference to the Avro canada saucer: http://www.faqs.org/docs/air/avplatfm.html#m4 "A wind-tunnel test model and a flying prototype were built. The test model was sent to the NASA Ames Center in California for wind-tunnel tests. First tethered flight of the flying prototype was at Malton on 29 September 1959, followed by the first untethered flight on 5 December 1959. Although Frost and his staff recognized that the Avrocar was inherently unstable and had incorporated an electromechanical stabilization system, it wasn't up to the job, and once the Avrocar picked itself up to above chest height and got out of ground effect, it bobbled around drunkenly. An improved stabilization system was considered, but Avro was in chaos due to the cancellation of the "CF-105 Arrow" interceptor program. The chaos filtered down to the Avrocar program, and the US backers of the program lost interest. The program was axed in December 1961. Whether it would have ever flown right remains an open question. " The "Electromechanical" stabalisation sytem was surely no more than a single gyroscope and some microswitches mounted on the gimballs to opperate shutters in the air-stream. A 3 axis multi-input multi-output non linear or state space controller was probably needed to achieve rock steady stabillity and that needs to be put together by specialist control theorotecians. |
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