Don Dunbar wrote:

Hi Pual,
There has been much talk about psru ratio's and engine matching!
I would like to join this debate but would like find more information to
understand the problems and efficiencies associated with all the trade
off.
I was looking to use a 3 blade MT variable pitch propeller. Does any one
have data on the theoretical efficiencies of propellers throughout the
RPM range.
Regards Don

Here are some charts.

Paul Lamar

Roger Robertson wrote:

Paul,
We bought a constant speed MT prop a couple of years ago for an exotic
application (non rotary) and they were touting slower speed props above
10,000. Something like 1800 rpm in cruise. Might be able to give you some
performance figures by July 4th at the latest.
Should we should be looking at 2.85 or higher PRSU's and slower props?  1800 x
2.85 is only 5130  cruise rpm.  2400 x 2.85 is 6840 T.O. rpm.
Roger Robertson

If you have the needed landing gear length go for it.

Paul Lamar

vjaqua wrote:

RPM is not a significant driver for prop efficiency, except in how it drives the
selected diameter with tip speed limitations. A controllable prop such as the
excellent MT series will give you a great deal of controll over engine
operating point, and delivered horsepower, while maintaining relatively
good efficiency over the entire operating range. - Vance

 
The AirCraft Rotary Engine NewsLetter.              Powered by Linux.

http://home.earthlink.net/~rotaryeng/            http://www.linux.org