RV-8 engine oil in my fuselage

[donaziza]

I'm on the injured list right now, ie, can't fly my own airplane. So an RV 8 buddy offered to take my 8 out to keep the engine and oil limbered up. A few weeks ago, the owner of my hangar called and said "Hey Don, why are there "pools" of oil underneath your fuselage on the hangar floor"? WHAT!! So out to the hangar to check---sure enough, literally pools of oil on the the hangar floor and all over the bottom of the aircraft. Well, the oil filter adapter had just been off from my mechanic, so, of course I thought big oil leak. The mechanic checked all over the engine compartment including the filter adapter and said "No oil leak"

Had my buddy done any acro, particularly negative G's the mechanic asked? ( No inverted oil system installed) Yep, nothing negative, but loops, spins and hammerheads. The mechanic said he thinks big slugs of oil were coming out of the breather tube. (Oil had been 5.9 qts before flight, was now 4.2 qts after flight)

Told buddy and he flew it again a few days later. Did only 2 rolls. Heck, I always do a couple of rolls every time I'm out. A few days after that I went to check for oil again. Still some smaller pools on the floor, but this time, only by the tailwwheel. Nothing on the bottom of the fuselage. Cleaned up the floor and area by tailwheel. Then the plane didn't fly for a week. Went out tonight looking for oil, and sure enough, a small puddle by the tailwheel, and some dripping of a radio antenna mast on the bottom center of the fuselage. ( The 2ed oil on the floor was apparently still oozing out from the first flight, and not a result of the 2ed flight)

SO-o-o-o, we got the wall out from in back of the aft baggage compartment, to look down inside the fuselage, and sure enough, still a bunch of oil on the bottom of the fuselage on the "inside" So my question is, how the heck does engine oil get on the inside of my fuselage One would think that if oil came out of the breather, the slipstream would carry it away. Is it possible that 1.7 qts of oil could be driver into teensie little holes in the fuselage ( about where the wing is) and then along the bottom inside all the way back to the tailwheel?? Who's the aeronautical engineer, is it Kevin Horton? Would he know what the air is doing here (on the bottom of the fuselage right behind the engine compartment) Or has my 8 developed some really unique kind of oil leak.

Sorry this is so long, but no other way to explain it. ( Not a builder)

[RVG8tor]

I had the same issue, went slightly negative recovering from a botched loop (1st one this plane) and dumped a 1/2 qt of oil. I had oil on the belly and inside the fuselage floor all the way back to the tail.

My theory is that it entered by the aft corners of the exhaust ramp. I pro sealed the side to help prevent cracking put left the corners open in order to allow moisture to escape.

I washed down the inside with mineral spirits. There was oil in between the front floor sections and every flight I get oil at the aft edge rivet line where the double floor becomes a single floor. This decreased with time, but I still get a tiny bit after a longer flight.

So I would say a big slug of oil came out and some made its way to the inside.

Cheers

[flynwest]

If you lose oil out the bottom I think that is normal. I have a smoke system and I don't have to worry about rust in the tail cone. Smoke oil is back there dripping on the hanger floor every time it's used.

[Ironflight]

I also don't know how it gets in to the fuse, but I suspect that the hammerheads are how it got out of the engine. Once you get the oil someplace, it takes a LONG time for it all to get out. A teaspoon full of oil can look like a major oil spill when it spreads out over the belly.

From your description Don, I'd say you have a well-known annoyance, but nothing to worry about (if you were worried about it).

[wera710]

IF this were MY airport, I would be looking around at my fellow pilots to see who looked the most guilty. Seriously, the B*s***ds have been known to pour oil under an aircraft just for fun...

As far as controlling the oil, try a AntiSplateAero oil seperator. I switched to one about a year ago and its actually helped.

[Geico266]

Originally Posted by wera710

IF this were MY airport, I would be looking around at my fellow pilots to see who looked the most guilty. Seriously, the B*s***ds have been known to pour oil under an aircraft just for fun...

As far as controlling the oil, try a AntiSplateAero oil seperator. I switched to one about a year ago and its actually helped.

+1 on the Anti-Splat Oil Separator.

[donaziza]

I'm still of the notion that its not from the breather tube at all, but rather some sort of very strange leak Anybody got any ideas in that direction?

[BruceEicher]

Originally Posted by donaziza

I'm still of the notion that its not from the breather tube at all, but rather some sort of very strange leak Anybody got any ideas in that direction?

I had the same puddles under each fuselage drain hole. I worried in the same direction as you after acrobatics for the first few times. But my new plane's FWF was clean as before. It had to be coming through the breather, then sucked up into the fuselage through drain holes. I pulled seats panels and found no oil forward of the pilot seat. Full Christen system solved the problem.

[donaziza]

Originally Posted by BruceEicher

I had the same puddles under each fuselage drain hole. I worried in the same direction as you after acrobatics for the first few times. But my new plane's FWF was clean as before. It had to be coming through the breather, then sucked up into the fuselage through drain holes. I pulled seats panels and found no oil forward of the pilot seat. Full Christen system solved the problem.

Bruce, What's a FWF?

[BruceEicher]

Originally Posted by donaziza

Bruce, What's a FWF?

Fire Wall Forward, under the cowl, engine compartment, place where big noise and wind is produced...and some oil.