One of the most common questions on forums concerns which propeller to use. The following article describes a simple formula to estimate propeller equivalents:


[link=http://www.ampaviators.com/index.php?option=com_content&task=view&id=51&Itemi d=42]Propeller Equivalencies[/link]

The formula: PLF = Diameter^3 x Pitch

I have read and used a formula for PLF some years, but they stated the PLF = dxdxp...
Now I get confused... [X(] Which is right?

I asked Lucien about this and his response is below:

"There are several formulas out there that are close but not accurate over a wide range of props. I did a very in-depth study of propeller loads about 15 years ago, and through actual experimentation and extrapolation, I came up with the simplified formula that I use today.

You can use a D x D x P formula in a very narrow range of props for one size motor or even a group if motor sizes, but what you are doing is taking the slope of a curve, and as you get further and further away from your initial starting point, the equation gets less and less accurate.

When I used the D x D x D x P formula, I tested it on everything from a 4x2 prop all the way up to a 76x56 prop used on a Cessna 172, and it worked for every single prop."

OK, thanks for the explanation
Then my "old" way to calculate when testing props on one motor were not bad then. You gave me a good input here CitaFly!