Grey dust on the right side of fuselage just aft of the cowling

[Brett H]

Within the last 25 hours of operation I have started to collect gray dust on the right side of the fuselage just aft of the cowling. I had not noticed this in the previous 150 hours of operation.

I appears to be coming the hinge that attaches the cowling. Switching the bracket that prevents the hinge pin from sliding up from just limiting upward travel to one that fixes its position seems to have reduced but not stopped the dust from reappearing. The coating on the hinge pin has some wear.

Any thoughts?

Thanks.

Brett H
Columbus IN

 

[VA Maule]

Looks like classic smoking rivets, fix is to drill them out and replace. Pop rivets are easy just remove the center stem before drilling.

 

[lr172]

The grey stuff is aluminum dust from fretting. The vibration creates slight, constant movement, including side to side, of the pin in the eyelets. The byproduct is that black dust. The air in the cowl is pressurized and pushes this dust through the cowl seam. Very normal. Oilling the pin on every removal will help to minimize this.

 

[Sam Buchanan]

If you have some Boelube that will lubricate the pin and be less likely to attract dirt than oil. The hinge eyelets are constantly wearing and producing the "dust".

 

[olyolson]

Every time I take those pins out I clean them thoroughly with brake parts cleaner. Don’t lubricate them with things like LPS because it can attract more dust. I used to use LPS or similar but since switching to just brake parts cleaner I don’t see that dust anymore and it’s still easy to slide the pins in and out. Don’t know if any of you remember Dave Domeier, he was “DavidAviator” here on the forum. I learned this from him, he was a wealth of information and wicked smart. He passed away a couple years ago but he was always full of good ideas.

 

[Brett H]

Every time I take those pins out I clean them thoroughly with brake parts cleaner. Don’t lubricate them with things like LPS because it can attract more dust. I used to use LPS or similar but since switching to just brake parts cleaner I don’t see that dust anymore and it’s still easy to slide the pins in and out. Don’t know if any of you remember Dave Domeier, he was “DavidAviator” here on the forum. I learned this from him, he was a wealth of information and wicked smart. He passed away a couple years ago but he was always full of good ideas.

Thanks for the responses to my question.

The RV-12 is a bit unique in that when the bottom cowl is installed it compress the seal between the radiator and the radiator air duct that is part of the bottom cowl. This creates an uneven loading of the hinge pins that attach the cowling. The right side vertical hinge pin is the least loaded and will move upward over time. Many RV-12s have added something to keep this hinge pin from moving upward.

It makes sense to me that this location has the most motion, that itis the location most likely to have fretting and create the gray dust.

My takeaways are: This can only be minimized and not stopped. Continue to use the solid Beolube when reinstalling the hinge pins. Cleaning before relubing and reinstalling would be beneficial.

Thanks.

Brett H
Columbus, IN N4BH