I still think that it has to do with passing the snow-filled clouds. Because last year we flew FL200 and had less than -20°C up there, but did not encounter this. I recapitulated the flight and for descent I lowered RPM to 2000, it was no problem. So to me it doesn’t sound like there’s something wet or water stuck somewhere in the cable or engine. But the conditions could have been that the snow melted in the air intake, where the actuation unit is arranged, and refreezed there or along the cable. However, I’ll put an eye on it.
LeSving wrote:
A Cap 10 (if I remember correctly) had moisture turn into a solid block which destroyed the engine in flight due to blockage, some years ago.
Either you don’t recall correctly, or the engine was non-standard, as the French Mudry Cap 10B is usually equipped with a Hoffmann fixed pitch wooden propeller, and therefore no governor installed.
Not familiar with this case, but was it maybe moisture icing up and blocking up the breather tube, in turn blowing out the front seal to disperse the engine oil?
Looked it up. It was a Cap-10C in 2011. It was -28 C (that isn’t the important thing) as engine heating was always on. The important thing is it has a Christen inverted oil system.
The line from the breather (on top of the engine) to the Christen oil valve will eventually be fully filled with condensates water if the plane isn’t flying inverted in some time. The plane had not had negative G for some time, and at -28, the heater is not enough to prevent that water from freezing.
Running all engine tests showed nothing wrong, since that line is closed at positive g in any case. That day they flew negative G and the ice blocked oil to the pump 100%. The engine stopped due to oil starvation, and they managed to glide back.
Nothing to do with the propeller. But perhaps a similar thing is going on with the governor? Or maybe not. It seems these thing can be very mich in the minute details.
UdoR wrote:
I still think that it has to do with passing the snow-filled clouds.
To get back on this: I got replies from two Comanche owners, where one of them has another turbo Comanche. What shall I say. This is normal behaviour. Got some tips on how to prevent this. If possible set RPM lower or move prop lever.
So for me the file is closed. There’s nothing here. Everything normal. That’s not the droids you’re looking for. (from a well-known movie..) 
Not normal. Just accepted as normal 
I still think that it has to do with passing the snow-filled clouds.
Really??!! does it happen on the ground when you park under snow? or taxi through snow?
Ibra wrote:
does it happen on the ground when you park under snow? or taxi through snow?
No PIREP available.
UdoR wrote:
What shall I say. This is normal behaviour. Got some tips on how to prevent this.
Did they explain what bit get blocked and why?
A couple of times I have experienced a stuck prop lever in the Dakota, preventing RPM reduction, when descending in cold moist air, so I always presumed it was the prop lever cable that froze.
I wonder if it indeed is one of those things I have accepted as normal although it isn’t, so I shouldn’t. But it has never lasted longer than a few minutes and so far always sorted itself out before approach.
As recent as yesterday it happened when descending from FL 100, I think after having passed through a thin cloud layer in maybe 10-15 degrees below zero.
My bicycle’s gear cable freezes when having been parked outside in moist subzero air. I think of it as the same thing happening to the Dakota’s prop cable.
Xtophe wrote:
Did they explain what bit get blocked and why?
No. I’ll follow that issue but cannot promise results anytime soon. If someone has some further information about how to possibly prevent this from happening I’d be glad to listen.
@huv yes clouds were at about minus 10 to 15 degrees in my flights, too. However the blockage on my flights happened during climb and lasted about 20 minutes (cruise phase), whereafter we descended again through the clouds and blockage stopped.
OK so maybe something specific to Piper with big bore engines?
I wasn’t prepared to encounter this and initially thought that something was broken, that distracted me a lot. This is why I wanted to share this and possibly get to know how to prevent it.
