"Almost on Top" UCAP #260

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"Almost on Top" UCAP #260

Postby thelaker » Sun Nov 06, 2011 1:42 pm

Regarding the Popular Mechanics article about the 4 DIY airplanes and the RP-4 (featuring 2 counter rotating props in front), this has been tried before by the US Air Force. The last time I was at the Air Force Museum in Dayton, I saw a restoration in progress of a P-75 (http://en.wikipedia.org/wiki/P-75) which was a WW II era fighter with the same type of counter rotating props that never made it past the R & D stage. A museum guide had made a rather cynical remark that this aircraft was what you get when you try to design things by committee. It's not stated in the wiki article, but the guide had mentioned that the transmission that was used for this aircraft (both engines are aft of the cockpit) was problematic and caused some scary vibrations in the airframe.

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Re: "Almost on Top" UCAP #260

Postby MerlinFAC » Tue Nov 08, 2011 3:33 pm

Counter-rotating props have been used very successfully. A few that come to mind are the Griffon engine/CR prop units as used on the Shackleton ASW aircraft (and which have been used on Reno racers including Precious Metal and the legendary Red Baron of the 1970's), the Fairey Gannett, and of course the most famous and successful counter-rotating plane (or, "Big Bad Bolshevik Beast" if you prefer), the Tupolev Tu-95 Bear which is the Russian counterpart to our B-52 bomber and which has been operational about as long. I've never seen one but I have heard that they're very, very noisy. The Russians also have a big transport (an Antonov something or other) using 4 CR props. There were some experimental jet powerplants in the 1980s or early 90's known as "ultra high bypass" fans which were essentially turbofan engines running large counter-rotating propellers, which were supposed to revolutionize the airline industry... IIRC, they were more efficient but the technology hurdles at the time were still kind of high (materials for the highly contoured, scimitar-shaped blades was one area that would be a lot easier to pull off today...) In any case, the improvements weren't quite good enough, or maybe just too costly, for them to launch a full production program. If I'm not mistaken, I think the Bugatti Racer that is in the EAA Museum and which is currently being replicated in flyable form also has CR props.

Now, if the most efficient prop has one blade and a counterweight... can you imagine how odd a pair of CR 1-bladed props would look? hehehe Given enough time, some enterprising EAAer is sure to try it, eventually! :D


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