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OldMan___
05-13-2005, 07:36 AM
Well here I am to openly ask if any of the more informed souls around here can enlight-me about a main issue in propeller planes: the propellers.


Any discussion or rich text about this issue to share (euestion mark, keyborad fault here)

What is the difference among 2 blade propellers, 3 balde, 4 blade and so on.. I notice most planes in WW2 were 3 blade, but a few had 4 or even 5. Today propeller driven AC usually have 5.

So wich kind of advantage these layouts bring up..

OldMan___
05-13-2005, 07:36 AM
Well here I am to openly ask if any of the more informed souls around here can enlight-me about a main issue in propeller planes: the propellers.


Any discussion or rich text about this issue to share (euestion mark, keyborad fault here)

What is the difference among 2 blade propellers, 3 balde, 4 blade and so on.. I notice most planes in WW2 were 3 blade, but a few had 4 or even 5. Today propeller driven AC usually have 5.

So wich kind of advantage these layouts bring up..

Deedsundone
05-13-2005, 07:48 AM
I would say,that it has to do with the engine power.A more powerfull engine can rotate more propellers,therfore more thurst.
But,hey,that´s only a guess from me. http://forums.ubi.com/images/smilies/25.gif

LuckyBoy1
05-13-2005, 07:55 AM
This link will get you started and I'm Googling for more...

http://www.thaitechnics.com/propeller/prop_intro.html

LuckyBoy1
05-13-2005, 07:58 AM
Here's a link in case you are Russian or have in some other way grown a second math brain...

http://www.grc.nasa.gov/WWW/K-12/airplane/propth.html

Art-J
05-13-2005, 08:04 AM
The bigger propeller the better http://forums.ubi.com/groupee_common/emoticons/icon_biggrin.gif. Nah... seriously: I guess More blades allows You to maintain high thrust and reduce prop diameter at the same time. (and it's the crucial thing, because You can't make prop too big either - the subsonic speeds of prop blade tips causes nasty aero effects and increases the drag!) That's why You don't see modern turboprop driven liners with less than 4 blades per prop anymore.

But the number of blades is not the most important thing really. The prop needs to cope with an engine's "will" to produce thrust and at the same time with the air flowing through the prop with different directions/speed, causing drag at the same time. This is why propellers are just not simple fans made of wood like in Wright's brother era http://forums.ubi.com/groupee_common/emoticons/icon_wink.gif, and this is where the prop-pitch changing, via manual inputs from the pilot or via automated systems inputs (in CSP props and aeromachanical screws) comes to mind. And this is INTERESTING stuff! http://forums.ubi.com/groupee_common/emoticons/icon_smile.gif
For a brief introduction to a prop topic, take a look at "Prop pitch" excerpt in Airwarfare's article covering CEM in PF:
http://www.airwarfare.com/Sims/FB/fb_cem.htm
For a loooong yet fascinating lecture, I would suggest an outstanding article from Pelican's Perch:
http://www.avweb.com/news/columns/182082-1.html
Happy reading!
Art

LuckyBoy1
05-13-2005, 08:05 AM
In fact, here's the basic trauma I was required to test out in the 90% range before my Father would even consider letting me touch the flight controls of a plane...

http://www.grc.nasa.gov/WWW/K-12/airplane/guided.htm

Rarely do people bother to learn the basics, the true basics before hurdling through the skies in tons of auminum, but I think that because you expressed a desire to know, it will serve you well to comnprehend all the basics even if all you ever do is serious flight sims and not real flight. Why?

Well, Oleg tries his best within the limitations of a PC to make the planes comply with the rules of physics. Understand the science and it is easier to understand what Oleg and the gang are doing and from there, you can go wondering on off to Oleg's Whiney Room to tell him how to do it right, which I think you will rarely do once you actually comprehend all the information given in that last link.

My brain hurts just looking at the index!...

http://www.grc.nasa.gov/WWW/K-12/airplane/guided.htm

Jagdgeschwader2
05-13-2005, 08:16 AM
This is exactly what you are looking for. Everyone can learn something from this. Ooops Art-J beat me to it. Oh well I'll leave the link here anyways.

All about props.
http://www.avweb.com/news/columns/182082-1.html

http://home.earthlink.net/~jagdgeschwader26/sitebuildercontent/sitebuilderpictures/jagdgeschwader2s.jpg

OldMan____
05-13-2005, 03:21 PM
thnak you guys. Usefull links but I still cannot find a good explnation of why some planes use 3 blade propellers while other uses 4 or 5. I would normally send this question to Oleg, but he must be HELL OF BUSY after all the things that are going on there.

JG5_Scorpius
05-13-2005, 03:40 PM
Oldman,

Perhaps this will help:

http://naca.larc.nasa.gov/reports/1939/naca-tn-698/

Scorpius