"Aluminum Powder" on Side of Cowling?

[delta727]

Hi Everyone,

New to the forums here, seeking some friendly advice!

I've noticed a greasy substance streaking out of the side of the cowling (see picture attached). It starts forward of the dipstick so doesn't look like it's explained by a few errant drops in that area. Have also been researching engine oil leaks but not sure if this looks like that.

The mechanic says it's "just a powder because of the rubbing of two pieces of aluminum" and therefore "it's fine". Does this seem plausible to you? I'm sensitive because the whole prop was recently replaced after a seal blew in the hub. If it was "powder", then where is the moisture coming from, causing it to "stick"?

Thanks for any past experience you can share. Not sure it matters, but it's a T206H with a TIO-540-AJ1A).

delta727

 

[Stewartb]

Aluminum wear streaks. Common after flying in a little rain or when there was water in the cowl seams. No big deal. Wipe it off and go about your day.

 

[denverpilot]

Yes. I think your mechanic is correct. It’s a mixture of aluminum powder and oil usually.

You see it around “smoking” rivets also. Same stuff.

 

[Dan Thomas]

If it's left long enough it consumes the aluminum sheet. Expensive. We have used a top-quality polymer chafe tape to stop that. A thin layer of PRC works as well and stands the heat far better than the tape.

 

[delta727]

Thanks everyone - you've put my nerves at ease! Have a great weekend.

 

[Fearless Tower]

If you don't want to see the streaks, just stay out of clouds. That stuff usually appears after an IFR flight through. The moisture brings it out.

 

[denverpilot]

If it's left long enough it consumes the aluminum sheet. Expensive. We have used a top-quality polymer chafe tape to stop that. A thin layer of PRC works as well and stands the heat far better than the tape.

Yeah. It really should be mentioned that the stuff essentially makes a really “good” rubbing compound or sandpaper when it’s trapped between two surfaces.

You want to clean it up and stop the chafing somehow between the surfaces for a long term thing. It’ll slowly eat right through whichever side of chafing is the weaker metal alloy, very slowly.

We get a little of it on our cowl and between some of the plastic cuffs and aluminum parts on the landing gear struts. It’s a bit of a bear to clean up but should be.

 

[Tom-D]

Super stickem plastic tape stops it without much fuss

 

[MauleSkinner]

If you don't want to see the streaks, just stay out of clouds. That stuff usually appears after an IFR flight through. The moisture brings it out.

Because if you don't see it, it can't be happening...at least that's the attitude of some people I've worked for/with.