Exhaust grime on bottom of AC from engines

[scott]

Every time I fly, I get a film of exhaust crude on the underside of the aircraft.  It is light brown to brown in color and I expect it is the lead from the fuel. Some on the landing gear and LG door but mostly behind it, then on up through the flaps and some on the underside of the nacelle.

I use fuel to get the bulk of it off, then light aluminum polishing compound and finish it off with Mothers wax. I usually have to do this routine every 10 hours or so and it takes an 1.5 hours each time.  The left engine leaves more residue then the right.  It looks like I may have some corrosion issues beginning to develop from this getting into the faying surfaces.

Does anybody have any comments on this?  (Exhaust mods, leaning practice, screw it and leave it dirty, ...)

[Tim Glubaskas]

Morning Scott -

There are a few areas that always seem to get pretty dirty on our aircraft.
As you noted, the exhaust and breather trails on the left and right wing, and also the exhaust area of the janitrol.

The exhaust trails are not only unsightly, but tend to eat away at rivet heads on the wing, rear of the nacelle underside, and the flap well.
We recently acquired two more chieftains and both had to have one of their flap wells replaced - a pretty big job and quite a hassle.

To help on the flaps themselves we have modified them with the help of a DER to add another layer of sheet metal along the underside, though this was mainly to protect them from gravel (as most our runways are not paved, it also protects the skin of the flaps from the corrosion issues.

I'm afraid this will always be a problem on your plane - kinda the nature of the beast. We try to clean the grime off every inspection and exhaust issues aren't too commonplace, but the planes we see where this is neglected definitely have issues along these areas. Try to make sure these areas are well protected with a good layer of paint etc and that will also help protect what's beneath - we have seen many Chieftains where gravel has taken away the protective layer of paint and the exhaust was allowed to do it's dirty work.


On a side note -
We had a Caravan that had a similar issue with exhaust along the cargo pod. Even with an STC to divert the exhaust is was a problem. In that case, we waxed the area each inspection and at least it was very easy to clean.

The soap we use to clean the heavy and hard to clean areas is called Mark V Products R.E.D - it's great but pretty harsh and you want to be sure and wash it all off on clean; for all other areas and touch up we use Simple Green.

Sorry I couldn't be of any help, and the Chieftain is a great plane when maintained and flown well - it just has a few wild hairs and you have identified one.

Happy Flying

Tim

[scott]

Tim,

Thanks for the response. I will check out the Mark V Products R.E.D. I assume I can get it online. Sorry for the my delayed response.