Am I going crazy or is the Whirlwind GA-RW3B propeller manual wrong? What pitch do you use with this combo? The manual clearly states in two places that for the 70" prop I have that the pitch should be set to 17 degrees. The problem is that when I use their setting (confirmed with two different digital levels), I cant even use full power on a 65mph climb without going over 5800 rpm.


After that I did experiments at 19.5 degrees and 21 degrees.


PERFORMANCE MEASURMENTS (with 22" tundra tires)
21 degrees: 109mph @5200rpm. ROC 880fpm @ 1200lbs & 4000'
19.5 degrees:104mph @5200rpm. ROC 950fpm @ 1200lbs & 4000'


CLIMB RPM @ 65mph
21 degrees: 5050rpm
19.5 degrees: 5500rpm


If it was just a performance tradeoff, I would choose the 21 degree pitch and take the faster cruise with only a small decrease in climb performance. Many people seem to say that its bad to "lug the engine" by having full power climb under 5300. Does anyone know if this is actually stated in Rotax documentation or know what is the reasoning for this recommendation?


Thanks!

Relevant pages from Whirlwind manual:
setting-pitch2.jpgsetting-pitch.jpg