On 2-Dec-2003, "Peter Duniho" wrote:

What's the fuel flow at 75% power? For a 200 hp engine, my guess is that
it's significantly more than 9 gph. Or conversely, it seems likely that
the 9 gph isn't 75% cruise.

Art didn't say 130 knots was his "best cruise performance". He said
that's what he gets at 9 gph. I assume he used that figure because that's
close
to the fuel flow in a Cessna at normal cruise settings (with a 160 hp
engine), and so gives a rough apples-to-apples comparison between the
airplanes.


In my Arrow, which like the SR-20 has a normally aspirated 200 hp engine, I
can true 135 kts at 65% with a fuel flow of around 9.4 gph. 9 gph would
probably be about 60%, give or take a little. Since for a given airframe
airspeed varies as the cube root of applied power, assuming equal propeller
efficiency (and that's a good assumption with a constant speed prop) 130 kts
at 60% would correspond to 140 kts at 75%, which, not surprisingly, is
almost exactly what I get in the Arrow. (141 kts to be precise.) That is
still a far cry from the 156 kt "book" 75% cruise speed for the SR-20.
--
-Elliott Drucker