wrote in message
oups.com...
On Oct 10, 9:17 pm, "Kyle Boatright" wrote:


Don't confuse thrust with HP unless you're using the exact same prop and
prop RPM. An 0-360 powered Robinson R-22 generates what, 1500 lbs of
thrust
because of gearing, disc area, etc? But, that thrust is only effective
in a
narrow (vertical) speed range. The same engine, combined with an
RV-style
cruise prop, would only generate (WAG coming) 250 lbs of static thrust.

That Soob had the same diameter of prop and ran at the
same RPM. I'm aware of the diameter/RPM/pitch effects, and that's why
the results were so startling to me. The 150s performance was much
better with the Soob, confirming its output. So either the Soob
produced more power than claimed, or the O-200 was really sick. Yet
the guy said that the O-200 was OK and the 150's performance with it
was typical.

Dan

I still think it is important to have the *exact same* prop, not just the
same diameter. Depending on prop pitch, chord, etc. you could get
significantly different amounts of thrust from props with the exact same
diameter.