Re: Airshares SR-20

On  2-Dec-2003, "Peter Duniho" <[EMAIL PROTECTED]> 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