Cruise at wide open throttle above 8000 feet sounds like alot of things

are

wrong! Wait a minute maybe a fixed pitched prop could do that. I'm not

use to

that. One of the best advantages to using a rotary engine would be a

variable

pitch prop. Skip

Same for a constant speed prop! WOT 70% power at 8,000 feet roughly.
Manifold pressure down around 22 inches of Hg.
The RPM can be set on almost whatever.

The RPM will also be down I think for a fixed pitch prop
although I don't fly those very often.

Tracy, Ed, Finn, Chuck, Ken, Perry  what are you seeing at 8K WOT?

Paul Lamar

WOT at 8K gives me around 5900 - 6000 rpm.   Oddly enough, with a fixed
pitch cruise prop the WOT rpm does not vary as much with altitude as you
would think.  The power is going down with altitude but the air is getting
thinner so the prop 'slips' a bit more.   The main advantage to a CS prop is
a big takeoff & climb performance boost.    This is a big advantage to
spam-can category aircraft with higher power/weight loading (more pounds per
HP) but sport planes like the RV and many other homebuilts can get by with
fixed pitch props and still take-off in a respectably short distance.  I
break ground in less than 1000 ft. even loaded to full gross.   This does
NOT mean I wouldn't like to have a variable pitch prop!

Tracy Crook
tcrook@rotaryaviation.com
www.rotaryaviation.com

What manifold pressure are you seeing Tracy? Fuel burn? BSFC?

Here are a couple of illustrations from my favorite old pilots
manual called Your Wings published in 1936 by Funk & Wagnalls.
First one shows optimum pitch angle and the second one the performance
for fixed pitch verses variable pitch on supercharged engines.

Paul Lamar
 
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