tag:blogger.com,1999:blog-8321804912236998273.post2706142310357636330..comments2023-06-27T16:25:50.532+03:00Comments on DESIGN|A|PLANE: Propeller placement article (external link)Anonymoushttp://www.blogger.com/profile/08473990027098421362noreply@blogger.comBlogger6125tag:blogger.com,1999:blog-8321804912236998273.post-15141232945946700032012-12-20T04:52:56.791+02:002012-12-20T04:52:56.791+02:00Thanks for sharing the link about proper propeller...Thanks for sharing the link about proper propeller placement. Placing propellers in a small aircraft or RPV is quite difficult.<br /><br />-<a href="http://www.avionteq.com" rel="nofollow">Avionics Test instrument|AvionTEq</a>Anonymoushttps://www.blogger.com/profile/08473816520775637045noreply@blogger.comtag:blogger.com,1999:blog-8321804912236998273.post-91312698268142460322012-10-29T00:42:10.582+02:002012-10-29T00:42:10.582+02:00In general I like the concept of distributed thrus...In general I like the concept of distributed thrust, but in practice it tends to be inefficient. Certainly you would not create consistent drag reduction through suction as each small blade would only intermittently affect an airspace the size of its its chord width ahead of itself. Regarding articulation, the thrust line change from a flap attachment would probably cause more drag through trim change and sensitivities than lift would be increased by thrust.John McGinnishttps://www.blogger.com/profile/01341293561924160340noreply@blogger.comtag:blogger.com,1999:blog-8321804912236998273.post-31601926622404818952012-10-25T11:17:26.442+03:002012-10-25T11:17:26.442+03:00Nathan: thanks. But summer time been busy riding m...Nathan: thanks. But summer time been busy riding motorcycle (and airplane to some extent) :)<br /><br />That is an interesting question, the relation with the propeller efficiency loss and the gains. These studies are a bit narrow since they study only one parameter at time and drawing conclusions from them is hard because they don't seem to consider the problem as a combination of these individual things.<br /><br />However, not sure how much the efficiency loss will be. Since according to literature, the efficiency loss on pusher propeller is small if it is far enough behind trailing edge. And if it is as far as in this study, it is far enough. Also tractor prop loses efficiency due to objects behind it. E.g. tractor propeller in front of wide airplane fuselage is worse than tractor prop in front of a small nacelle. And optimal tractor prop is like in Stemme S10 VT where the continuity behind propeller is gradual and there are no stagnation points immediately behind the prop.<br /><br />Best person to answer this question would be a aerodynamist like John Roncz etc. However, the answers may vary between persons (as far as I have noticed).<br /><br />There is one catch on increasing lift this way: when the power is out, it is not helping. And the small stall speed is most needed when doing forced landing. In normal operation, faster landing speed is no problem. I could be coming in approach at 100 knots if there was a large airport ahead, but if it was a forest or field in emergency, 100 knots would no longer be anywhere good and the speed should be less than 50 knots forward speed at the time of impact, to not get too hurt. <br />Anonymoushttps://www.blogger.com/profile/08473990027098421362noreply@blogger.comtag:blogger.com,1999:blog-8321804912236998273.post-63620315037174385182012-10-24T04:10:14.237+03:002012-10-24T04:10:14.237+03:00It's been a long time since you posted; it'...It's been a long time since you posted; it's good to see you back! :-)<br /><br />That was a very informative study. Thank you for sharing it. I wonder how much the upstream presence of the wing will effect the propeller. Do you think that the obstruction will make the propeller less efficient by altering the air flow, especially by reducing the pressure in front of the propeller? If so, might the Clift gains be cancelled by the propeller efficiency loss?<br /><br />I understand that if thrust is reduced then some of the energy would be captured as increased lift. This would allow smaller wings, thereby decreasing drag.<br /><br />How do you think these effects will combine in real-world use?Nathanhttps://www.blogger.com/profile/12408740192023468701noreply@blogger.comtag:blogger.com,1999:blog-8321804912236998273.post-92052697096852232162012-10-23T15:20:50.545+03:002012-10-23T15:20:50.545+03:00Apologies, it was not the Boeing B36, but the Conv...Apologies, it was not the Boeing B36, but the <a href="http://en.wikipedia.org/wiki/Convair_B-36" rel="nofollow">Convair B-36</a> I was thinking of.Jon Chttps://www.blogger.com/profile/08528890294045796891noreply@blogger.comtag:blogger.com,1999:blog-8321804912236998273.post-6914269862755660432012-10-23T15:17:46.416+03:002012-10-23T15:17:46.416+03:00I think it would be possible to put several small ...I think it would be possible to put several small propellers along the trailing edge, but they would need to be farther out than how close the flaps would extend. Probably something like a bunch of smaller rear-wing nacelles similar in concept to the ones conceived for the Boeing B36 except on the top of the wing.<br /><br />You're right about now wanting to put them on the flap railings - not only would you have issues with the flap mounts having to withstand more forces, but you would also end up with a changing thrust angle as your flaps came down. Unless you're trying to conceive of a competitor for the V-22, I don't see this as a good idea.Jon Chttps://www.blogger.com/profile/08528890294045796891noreply@blogger.com