912 ULS no more than ~4800 RPM problem is back!!!!

Thanks Rotax Wizard, Kevin, Sam, all,

In my uneducated analysis, I think that the prop pitch is not a factor here because, with the same pitch I have obtained the regular ~5000 Static WOT RPM and only twice the constant and kind of restricted ~4800 RPM during the WOT Static and even during the take off roll. 

Just trying to analyze a bit more the pitch possibility, ok, lets say that the pitch is different, makes no sense to me that the ~4800 RPMS are constant even when the plane is accelerating during the Takeoff. I always expect to see the RPMs rise during the acceleration. I have seen ~5100 during TO. Now is like the RPMs are glued to ~4800. That is why the blockage possibility is the one that sounds more logic to me.

Nothing has change from the components perspective. My guy has has a return line according with the specifications, no custom made things. etc. 

There is an school that has the "same" plane and I'm trying to fly one of those guys and see but, again, this thing has happened only 2 times in the last 5-6 months and I use the plane regularly. My intention to fly the other plane is just to tell the shop.. hey.. 2 "identical" planes and the readings are different. maybe something is different, right? and this has and event that has occurred twice? what do you thing? (for me is evident that something is off)

Thank you all again!!!! and please.. keep thinking ?

Hi Carlos

"~4800 RPMS are constant even when the plane is accelerating during the Takeoff. I always expect to see the RPMs rise during the acceleration. I have seen ~5100 during TO. Now is like the RPMs are glued to ~4800. " 

Unfortunately I don't have enough information to really help.  Again, what is your WOT RPM when you get it flying?  5100 on TO to me seems low, this RPM is however is so dependent on angle and other things it is not really a good measure of performance.  WOT level flight would be better to know if you are over or underloaded from my experience.   If your aircraft is not changing RPM in acceleration on the runway then that is indeed very odd.  I dont know of any propellers other than constant speed that can do that.  

Cheers. 

Thanks a lot Rotax Wizard!