[Brian Denk]

So there I was yesterday, flying a line abreast loop in a two ship. Lead pulls waaaay too slow...barely make it over the top. But, being the good winger, I hang in there and wallow across then let the nose drop through and down the backside we go. "Hey, Larry, how about we try that again but this time with a bit more feeling?"

So, a solid 4g pull, up and over we go. Much better. Fifteen minutes later, we land and I pull the plane into my hangar. Hmm...lotta oil drips. No biggee, we were yankin' and bankin', loopin' and rollin' a lot. So tonight, I go into the hangar, cold one in hand (easily done when you live with your airplane) and lo and behold...a generous puddle of oil dripping off the tailwheel spring of my -8. Ack! What happened? Well kids, when you goober up a loop and get ballistic or negative without an inverted oil system, you PUMP A LOTTA OIL OUT THE BREATHER hose. Thus, I rapidly applied a heathy coating of Aeroshell 40wt. anti-corrosion treatment to the belly. After cleaning up the mess from stem to stern, I checked the dipstick. Yep. 1/2 quart low.

So, keep the G's on it or else you'll be on your back doing the belly scrub rhumba.

 

[Frank]

Thats alright Brian. Try being the 4th or 5th guy in an 8 ship in trail loop or 1/2 cuban when lead floats it over the top. All the guys behind you start checking their front mains when they get back!

 

[gmcjetpilot]

Poor mans inverted oil?

I am not for air/oil separators or doing negative G's with out inverted oil, but consider the air/oil separator and a catch container as a poor mans inverted oil system. There is nothing wrong with +Zero G's, but you are right you do get more oil on the belly. Normally you a simple breather on a healthy engine is fine. My air/oil separator did very little for normal flying but doing aggressive acro and holding inverted on down line or hesitation rolls I would fill my little catch bottle up.

 

[N999BT]

I have a story like this...

When I was doing the final assembly of my -4 one of the local wonks who knows everything there is to know about airplane construction told me I needed a small hole in the breather inside the engine compartment so that if the outlet froze there would still be a little bit of breathing going on. This worked great until I was flying off the initial time in my -4 and doing the required aerobatic maneuvers.

I intended to do a hammerhead stall, and pulled a little to far. So, I pushed a little too get back to vertical. You can guess what happened. I saw this mist go by right at the stall, and as I was headed straight down, oil running out the seam between the cowl and the forward fuselage. I thought I had broken an oil hose or something. I pulled the power back to idle and dove for the airport about 5 miles away. When I got to the hanger and shut down, there was oil leaking all over the ground, huge puddles. It turned out to be a whole quart, most of which went out the bottom, but a bunch went out that hole into the engine compartment. It's amazing how far a quart of oil can go when it is on the outside of the engine.

 

[Brian Denk]

Cool guys, thanks. So I'm not the only one spewing petrochemicals into the atmosphere. I also have those little "whistle slots" in my breather hose and they seem to ooze more oil/water/slop than I'd like to see. It does end up going into the engine compartment. I guess it's good insurance, but the odds of freezing up the end of the breather hose, when it's right over the top of the exhaust pipe, seems mighty remote.

I have an uninstalled breather oil separator that will probably stay that way. It might have caught the majority of the mess in this episode, but knowing that it's also sending water and acids back into the engine during all operations just doesn't sit right with me. John Schwaner (Skyranch engineering manual) likens these to hooking up a hose to your biological "vent" and connecting the other end of the hose to your mouth.

Eaagh! No thanks.