On Mon, 16 Jan 2006 21:15:49 -0800, Bob Fry
wrote:

At 1000 rpm or so, my airplane will taxi and get up to, what, 15-20
kts? But at double the rpm it will fly at 80-90 kts, though it would
take a long time to take off. Surely double the rpm produces more
than double the propellor thrust...or does it? Anyway, it seems very
nonlinear, that is, double the rpm and I get much more than double the
performance. Why is that?

http://www.allstar.fiu.edu/aero/Propulsion2.htm

I'm not an engineer, nor do I play one on TV. I do find it interesting
that the speed or velocity of the aircraft is a factor in figuring
thrust in both the propeller and the jet propulsion formulas.

Perhaps someone else can explain in it terms that you and I can
understand.

TC