I’ve been wondering for most of this summer about the wandering rpm in my D3-110-C motor. I’ve noticed that occasionally the rpm will wander around by 20-40rpm over a period of a second or so. It is obvious to the ear, as well as being shown in the instrument readout, and seems to be particularly prevalent when mooching around in the 1000-1500 rpm range. Haven’t noticed it so much at higher rpm.
I also don’t recall hearing it last year, but we were pretty overloaded with new stuff last year, it’s possible I just didn’t notice it.
Since I’ve now installed a new gearbox, I’ve kind of eliminated any issues on that front (ie pressure drops/shaft brake application)
This year I changed from the original fixed prop to an Autoprop, which is also a new piece of kit to me. Could this be related to the autoprop blades doing something erratic and momentarily loading up the motor?
Do others observe this behaviour? I guess with the trials and tribulations that Porter has gone through this year with his D3-110 we are all paying a bit more attention to this troublesome power plant.