Hello,

Did you ever get a reply?

I have an Ivo Ground Adjustable Ultralight prop on my 912 ULS powered Model 5 Vixen. Last December when I flew it for the first time with a new engine, I had little idea of where to set the pitch, static rpm or what the pitch should be for cruise. Truthfully, I do not recall what my current wide open static rpm is, mostly because I am convinced that it is not so important as the cruising rpms, with the ultimate goal being to not overload the propeller (a bite too coarse or too high of a pitch, so as to make the engine work too hard) and/or over speed the engine (with a pitch too flat). Where it’s set now produces a maximum rpm of 5600 WOT (wide open throttle) at my commonly traveled altitude of 2000 feet MSL in my neighborhood. I am adjusting my climb pitch for no less than 5000 rpm in a climb and my cruise rpm is generally about 5200 (trusting my new Grand Rapids EIS more than the older analog dialed electronic tachometer). I arrived at this configuration by reading various back & forth comments between Roger Lee and a collection of Rotax 912 users in various makes of airframes and brands of propellers. Roger is one of the main Rotax technical guys on the Rotax Owners subscription site.

I am also convinced that many Rotax 912 operators are running their engines at rpms too slow. I am trying to get a mind set to make myself cruise at between 5000 and 5300 rpms. I, like many of us, also regularly fly other Continental powered aircraft that cruise in the low to mid 2000’s rpms, so I must overcome my habits and Continental prejudices to run that Rotax too slow. I’ve been told a Rotax 912ULS runs best (and all day long) if run in the low 5000’s.

At my current Ivo Ultralight ground adjustable setting (WOT 5600 at 2000ft msl), I am getting excellent climb (by myself, full fuel, a heavy bag of tools and a fire extinguisher) and I am cruising at an average gps ground speed of 115mph with indicated air speeds in the high yellow part of the arc. I often see a ground speed of 140mph and rarely see less than 90.

Skot