I have the following problem, maybe someone will be able to help. The propeller stopped responding. After the initial diagnosis, I had to do the propeller and governor overhaul. After the installation of the “new” propeller and governor, everything seemed to work perfectly. After an hour of work, the problem returned, the propeller does not react. Shop said they were trying everything. The pressure on the engine is normal, propeller and governor are overhauled. The question is, has anyone encountered a similar problem?
I wonder if this is like the other TB20 owner reported here recently. The “maintenance” company said they changed a b c d but actually they changed only a b d 
I think this happens a lot.
I would bet the governor wasn’t overhauled, or perhaps even looked at. Or it was “overhauled” by that company in central Europe which just paints the outside (but their pricing is ever so good, and of course they are EASA145).
There isn’t much else involved in that system.
I think that MT Propeller from Straubing is quite reputable, and for sure not cheap ;) They got both EASA and FAA papers. I don’t believe that Germans would be risking such things (and human life).
I agree MT are very unlikely to deliver a bad job. I would suggest to consult them. Something is very weird.
Other than propeller and governor, you have the oil connections:
The thing is that if either of those two things happened, I would not fly the plane at all.
If the gasket is backwards, a real muppet was in there and you have to wonder what else was done badly. And there is enough sludge to block the governor working, it is likely blocking the oil galleries all over the engine.
One could also over-rev the engine, and that is a large bill; the limits above which you need to strip+NDT the engine and the prop are quite strict.
A dodgy prop rpm control is an absolute no-fly case.
Yup, I think we are all assuming that if the pre-flight propeller governor check fails and is totally unreactive then you would not proceed to take-off…that would be a sure way of overrevving your engine…
I am also assuming the RPM control has the correct movement all along (ie blue knob/lever is not jamming in any position between minimum and full rpm on the ground or in flight, engine off or on)
Thinking further, an incorrectly installed propeller governor control cable (loose/sliding sleeve) or a damaged cable (ie control end bending under load) could drive some or all of those symptoms (ie you move the knob/lever but there is no RPM change) . In that case the governor would still be governing but only at fixed (normally full) RPM. You need to make sure not only the knob/lever but also the control arm on the governor itself are moving smoothly through the whole control range.
One sure way to discriminate this is whether, in flight, the governor is still governing: (ie when you lost control, did RPM remain unchanged at max RPM or some other value until you throttled- or slowed-down- way back?).
Thank you all for comments. Seems that Antonio suggested what really is going on. Prop and governor are ok, but probably other oil passage is clogged. The problem is, that it is really difficult to find the exact place, and even if, it could be dangerous. So I decided to dismantle the engine, review and clean each pice.
I suspect you narrowly avoided a forced landing, or worse…
For the oil to not be reaching the governor, it is amazing the engine was rotating for that long.
