Electric block for prop deice

[M20Kid]

I have an M20K-231 with a hot prop.  During annual my mechanic found something he hadn't seen before.  Admittedly he doesn't work on many planes with prop deice and we were both stumped by what he found.  The deice system is powered by an electric block with a brush system riding on a plate that spins with the prop.  That electric block appears to be leaking a sticky black solution that is clearly not engine oil.  It appears to have a graphite type of base.  The substance covers the rotating plate and even has slung the stuff to create a line of residue all around it.

I've never heard of an electric connector having any fluid of any kind inside it, but that appears to be the case here.  The side of the residue is opposite the direction of rotation of the plate so it can't be deposited by the plate; it must be the other way around.  Any thoughts?

[Guest]

Engine oil and carbon dust from the brushes.  Clean it all with isopropyl alcohol, then look for the source of the oil.

Clarence

[M20Kid]

I thought so, too, but my mechanic pointed out it's on the wrong side of the electric box.  The rotor is coming from the left and the residue is on the right.

Also cleaned it about 15 flight hours ago and it's back already.

[carusoam]

The spinning electrical contact device is pretty common… it has a name….

They are called slip rings… at least in the industrial world, that is what they are called…

Being near the prop, the shaft seal may be the source of a drip of oil every now and then…

PP thoughts only, not a mechanic…

Best regards,

-a-

[M20Kid]

And the answer is - the prop seal needed to be replaced.  Good call, carusoam!

[carusoam]

Great follow-up Kid!

Best regards,

-a-