Makin' a Mess

Ironflight · #1 08-19-2007, 07:46 PM

"Whoops!" I thought to myself, "That sure didn't work out right!" There I was in the vertical part of the second loop in a cloverleaf, only I was rapidly approaching no airspeed and hanging without any G on the airplane. I pulled back a little to bring the nose over, rolled inverted, built up a little airspeed, then rolled out level and tried to figure out how I'd botched it...then I smelled oil. Hot oil....not a lot of it, but more than I'd get from flying over the Texas City refineries below me. Nope, I was still up about 10,000', so that wasn't it. All that thought in about half a second, and then I settled on the logical conclusion - I'd gone negative when I had the engine oil pooled at the back of the case, and must have burped the crankcase vent.

The smell dissipated in about 30 seconds, and several checks of the gauges confirmed all was fine, so I finished up playing and headed back to the barn. After I shut down and climbed out, mys first thought was "my, those are pretty streamlines on the left upper gear leg faigin..." oh nuts - Guess I DID spill some oil. I saw a little running out the back of the cowl into the NACA scoop - there was the cockpit smell! Not one to leave things to speculation, I pulled out the screwdrivers and got the top cowl off. Sure enough, there was oil over on the left side of the lower cowl and most everything in the lower left quadrant. Off came the lower cowl, and a quick glance up the breather confirmed it had spat out the messy stuff. I grabbed a bunch of paper towels and some Coleman fuel and spent a good quality hour with the Val cleaning things up. There was no measurable drop in quantity on the dipstick, but a little bit of oil with a slipstream goes a LONG way!

I guess that this is one argument that if I had my breather outside the cowl, instead of inside, over the exhaust, I might have had less mess (that was an interesting thread in the last week!). But I still like the overall less belly mess of having it that way, and this was the first time I'd had this problem in all the hours we've been flying together, so I think I'll keep things the way they are. Still, I was amazed that I actually had oil DRIPPING off the tail wheel knuckle! Like I said, a little oil goes a long way.....

Ah well, all in all, an hour of cleaning for the joy of acro in the cool clear air above the cumulus-laden, hot and humid gulf coast air is not a bad trade. I'd spent three days in MCC working the detailed contingency plans for Hurricane Dean, and now that we have those plans in place, and the storm no longer looks threatening, I could take the time to relax and enjoy. I have to go back on console tomorrow until the end of the mission, but it's nice to be able to get away and relax the way I like - throwing the val around a bit in a mutual enjoyment of life!

As I closed up the hangar, I looked both ways to make sure no one was watching, then patted the spinner and said "sorry about that...I'll try not to let it happen again." I think that Val smiled, accepted my apology, and I pulled the door shut for the evening.

Paul

mike newall · #2 08-19-2007, 08:39 PM

I get the same on my Citabria - 5 gallons of dope to refinish and airplane - 1/2 pint of oil does a similar job !

That's why we have fittted an Andair oil sep on our RV7 to help trap any 'burps' and let them trickle back into the sump.

When we fly next year hopefully, I will let you know if it works

p.s. Stuck in Florida due to Dean stopping us positioning to MBJ - oh how sad I am ! Hope to get out to Cocoa Beach on Tuesday to watch the landing. Have heard the boom in the hotel before, let's see if the real thing is better.

Rick6a · #3 08-20-2007, 02:09 PM

Quote:

.........As I closed up the hangar, I looked both ways to make sure no one was watching, then patted the spinner and said "sorry about that...I'll try not to let it happen again." I think that Val smiled accepted my apology, and I pulled the door shut for the evening.

Paul,

Like Pygmalion, me thinks the creator has fallen to love his creation. So natural and sure that special bond is...somehow knowing Val heard and accepted your most heartfelt apology, stands eagerly poised to soar and be happily flung through footless halls of air again.

dan · #4 08-20-2007, 02:32 PM

Paul,

If you didn't get an oil pressure warning and you didn't hear the prop surge, nothin' to worry about imho. When doing my initial acro testing during Phase One, I managed to completely cover my belly with oil (no inverted oil) to the point where the tail was still dripping after I landed.

Every once in a while if I go a little negative I get the smell -- just oil breathing onto the exhaust like it should (breather outlet positioned right over the exhaust). Like you said, less than a minute later the smell is gone. If you really go at it, the prop will surge (assuming you're running less than 2700 RPM to begin with). My AF2500's "lady voice" is quick to alert me audibly if the oil pressure drops. Hammerheads and anything more than a brief period of slight negative, and I get the warning & prop surge.

I have to admit that during Phase One I didn't test beyond -2G. I know many builders like to test the airframe to the design limits during Phase One, but without an inverted oil system it would (imho) potentially cause much more damage (to the engine) than serving a positive purpose. It's just one of those things I trust with my life...I have faith in the design that if I had to push this airplane to its negative G limit, it would hold up.

Ironflight · #5 08-20-2007, 05:39 PM

I made a quick flight this morning just to make sure that I didn't have some coincidental leak...(yeah, like I needed an excuse to go make a "dawn patrol"...), and all is tight.

I didn't do negative g-limit structural testing either Dan - I trust Van's engineering on that, they built all of my primary structure (QB),....and that stuff just flat out HURTS!

kevinh · #6 08-20-2007, 05:55 PM

Hi Paul,

I had the same "woah, I'm not going to make it up this one, push it over, oh no what's that smell" reaction recently. I bet you had similar oil lines on your plane:

http://flickr.com/photos/funkym0nkey/1111276008/

omerward · #7 08-20-2007, 09:49 PM

Paul,

I got that a lot until I installed an air/oil separator I bought from Aircraft Spruce for about $40. It is about 4 or 5 inches in diameter and it really works.

On the up line for a hammerhead, I pull the throttle back about half way just before the rudder turn. That keeps the prop from running away. I put the power back up after I get some positive G on the pull out.

We met at Hooks about a month ago. Love your airplane.

Sam Ward
"Deuce"

pierre smith · #8 08-21-2007, 05:27 AM

Quote:

Originally Posted by kevinh

Hi Paul,

I had the same "woah, I'm not going to make it up this one, push it over, oh no what's that smell" reaction recently. I bet you had similar oil lines on your plane:

http://flickr.com/photos/funkym0nkey/1111276008/

Hi Paul, Kevin,
There is a maneuver the military pilots were taught, called a vertical recovery. It's designed to avoid exactly what you guys mentioned...negative G's and oiling the belly. IIRC, when you're vertical and want to recover, pull elevator and aileron. You'll start to go over on your back but the aileron will roll you over, all the while pulling positive g's....the maneuver looks kinda like a messed up immelman. Do the maneuver with your hand and you'll see it. Perhaps Groucho will chime.....

Regards,
Pierre

Kahuna · #9 08-21-2007, 05:29 AM

Paul my experience was the same as yours in my rv-6. A botched humpty bump always resulted in oil. I love that maneuver when its done well, and i hated myself when I botched it. Even during the hatred, I always have fun.

I had mine over the exhaust and still managed to get the belly wet if I tossed some oil and the plane was not making fwd progress.

With the inv oil in the 8, I never see any oil on the belly. Just smoke oil.
Best,

Dave C · #10 08-21-2007, 08:49 AM

I'm glad to hear all you guys 'fess up about spewing oil all over your belly! I thought I was the only one to spew that much oil out!

My first attemp at hammerheads had alot of negative G at the top... not sure what I was doing wrong, I think I might have been inadvertently pushing forward on the stick as I put in rudder to kickover.

When I landed there was oil dripping off the entire belly all the way to the tailwheel. I thought I had ruined my engine, but it was really only about 1/4 quart. A little oil goes a long way.

Dave C
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