View Full Version : 2 blade or 3 blade prop
andythomasuk
24th Feb 2002, 21:27
Does anyone know if there are any specific advantages of having a 3 blade prop on a SE piston Land Plane, over a 2 blade prop?
depends what you are doing with it.. .A 2 blade has a higher top speed because of reduced drag. A 3 blade has higher acceleration and usually climb performance...
CHeers. .Wino
wysiwyg
25th Feb 2002, 03:25
Many moons ago I used to tow gliders using Pawnees with both 2 and 4 bladed props. With the 2 blade prop you would have to use less than full throttle at take off to avoid the prop tips going supersonic and losing efficiency. The 4 blade prop was shorter allowing full chat and subsequently better initial take off performance.. .With regards to the cruise, I couldn't tell you. You never get to cruise a glider tug!. .In the descent, while keeping power on to avoid shock cooling you could get a much better rate of descent with the 4 blade prop.
regards. .wizzy
Also quieter, pour moins epater les nimbies.
A and C
25th Feb 2002, 14:39
I,v flown only one type that has had both two and three bladed props and that was the PA34 , the three bladers seemed to make less noise and vibration but this was only marginal however it was about 3 KTS slower than the two blader and when it comes to overhaul the extra blade is going to cost you to service.
Michael111
25th Feb 2002, 21:30
Hi
Some years ago Aurigny changed the wing mounted engine props on the Trilander to 3 blades and left the Tail at 2 blades.
From a passengers point of view they seem as noisy and the flight times are the same. Perhaps the savings are in fuel costs?
Michael
[ 25 February 2002: Message edited by: Michael111 ]</p>
Silvertop
27th Feb 2002, 05:00
I belive that its all about converting the power the engine develops into thrust i.e. the total blade area is matched to the power output of the engine,blade area can be varied by increasing chord,span(limited by tip speed or ground clearance),or by increasing the number of blades
Mark 1
27th Feb 2002, 17:40
If its a VP prop, or set to give the same nominal torque/RPM balance, then the 2-blade prop will have a higher static thrust, as it accelerates a larger disc of air at a lower speed, than the lower diameter 3-blade prop. At cruise the 3-blade will have a small advantage.. . . .The lower diameter (tip Mach no.) and increase in tone frequency of the 3-blader will also make it subjectively quieter.