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Christen Inverted System

B

bob turner

Registered User
I just joined an International Aerobatics forum. Format is exactly like Supercub.Org, so I assume we are related. However, as with other fora, nobody goes there, so my question may go unanswered.

Anybody got any downloadable info on the Christen/Lycoming inverted oil system, as used on the AEIO 360? I am having a teeny bit of a problem when upside down. I may have fixed it, but it would sure help to know if what I am doing bears any resemblance to reality.

First time it happened, I washed out the shuttle valve, and it fixed itself. I am hoping for a repeat performance - but I know I was just lucky the first time.
 
There really isn't much to it. If you don't fly inverted often enough you need to clean the slime out of the valve to keep it from sticking.
 
Steve - I have the Decathlon manual with the schematic. There are some O rings reportedly in there that can give problems, and they are not shown on the Dec. Schematic. Lycoming manual is supposed to have a section, but I can't find it in mine or in the latest CD.

Mark- I think that may be the problem. When I got the airplane, no inverted pressure, so I cleaned the slime out and all was well. After two years of flight - minimum ten slow rolls a month - it did it again, and I just cleaned the "slime" out again. Test flight tomorrow. Slow rolls should actuate the inverted circuit, and at the end of each set, I park upside down and do dutch rolls. Thanks, you guys.
 
Most folks I know around here remove and clean the shuttle valve at least once a year. Probably overkill but many of these guys are serious competitors and detail oriented to a fault.
 
Re: Christen Inverted System Manual

bob turner said:
I just joined an International Aerobatics forum. Format is exactly like Supercub.Org, so I assume we are related.
Click to expand...

Hi Bob, no relation at all between those forums, other than they both probably use the same forum software - Phpbb - which is used by TONs of forums everywhere.

sj
 
CubCrazy - that worked! I now am smarter than I was before. Thanks for the useful link.

Test flight was not as successful as I would have liked. All was fine until I rolled inverted. Oil went immediately to zero, and I rolled right side up. It stayed at zero long enough for me to consider which field I was going to dead-stick into! And long enough for me to start formulating an answer to the questions: Where are your certificates? Your granny glasses? Your current chart? All of which usually wind up on the ceiling on such a flight anyway. It probably was not more than four seconds total, but it seemed like an eternity. Calling the factory tomorrow . . .
 
Gee Bob, you sure seem to have a lot of problems with that thing. Maybe it'e time to sell the POS and buy a Super Cub. :D
 
Probably need to spend more time upside down. The three way valve in my Pitts gets worked 10-12 times, couple times a week.
Push harder, more often. :D
 
Pushing harder makes me sick. It has been inverted fifteen times in August; only the last was totally without oil pressure! Calling the factory this morning - an expert is going to call back . . .
 
You have a hose collapsing. I'd bet my first born on it.(He comes with student loans) It has been 18 yrs since I plumbed one of these but as I recall the hose coming off the normal vent line is under suction while inverted. It should have a coil in it to prevent collapsing. I would have said the O ring on the bottom fitting or the shuttle valve until you mentioned no oil pressure after rolling upright. This would explain that.

Fix it. And if your eyes are not blood shot, blood vessels ruptured on your forehead and bruises across your lap when you land, you have not had enough fun.
 
Finally got my hands on the Lycoming manual. It says that the first flight it takes 3-5 seconds for the air to purge out of the upper lines. I had kind of wondered about that. I didn't have the nerve to sit there upside down while the oil said zero.

As for collapsed hoses, these things are the sexy Aeroquip lines, fairly new, and with those pink heat shields on them. I might run a snake down the overflow line if the 3-5 second inverted flight tomorrow is not successful. I think I'll take my chart just in case I have to land in a field.
 
I will be checking for collapsed hoses over the weekend. They are heavy duty Aeroquip, but four years old now.

Rolled upside down today, timed it for eight seconds with zero oil pressure, then right side up with instantaneous rise to 75 psi. Tried it again; same result. Then did a slow roll, with pressure to zero, and it took four seconds to regain pressure after rolling right side up! Repeated all of that multiple times with identical results.

Christen (Aviat) is not interested in talking to me. Their phone ladies are very polite, but it is clear that their inverted system expert is not at all interested in helping. I'll try ACA and Lycoming next week, and maybe Rare Aviation. Rare was really helpful with a Waco problem I had.

This forum is probably my number one resource for aircraft issues. Thanks!
 
Bob
Just because the hoses look pretty on the outside, doesn't mean they are good. I had a brand new hose that went from the Bendix RSA5 fuel servo to the flow divider fail after 25 hrs. The inner wall was failing and letting small pieces of rubber clog the injector nozzles.

These hoses are designed for pressure not suction. Additionally, even with hard mounts, aerobatic engines move and twist a lot more than a normal engine. The hoses are also subject to higher temps than normal.

I have flown numberous aircraft with both Frank's system and the Acroline system. You should never be waiting for oil pressure unless you are flying in knife edge . (left or right I forget)

You can test the shuttle valve and canister with regulated air pressure to eliminate them for sure. There is an O ring, I think it is in the fitting going to the oil pump. I had to replace one of these in a 150hp flat wing once. It had low oil pressure inverted, not no pressure.

Good luck
 
I've talked to a couple guys that had problems with the slobber pot. If the ball doesn't seat inverted, the three way doesn't get oil. I also had a buddy with an RV4 who had a bad o-ring on the plug that goes into the sump. It's flooded right side up, but needs to seal up side down, or it the pump pulls air instead of oil. In the 811 sump kit it is the little plug that you put in place with the threaded rod.
Sorry about the smart-ass reply earlier. I'd just got back from flying the Pitts and musta still had a bit of what we call the fuel pump dance going on.
 
Yes - solved it today.

First, Christen wouldn't even return my phone calls - Champion (Pat) not only talked to me, he also walked over to the parts department to check on something, then called me back.

The problem: There is a plug in the oil sump, designed to block the pump from pumping directly from the sump. It is easily seen with a mirror, and is easily inserted and removed. It takes a big fat o-ring. I'll post the part # as soon as I get it. Pat said 99.99% sure it is the plug/o-ring that is leaking.

Opened up the port, pulled the 4 1/2" screen out (all easy) and tried to insert the 10-32 Christen puller. No dice. Looked in there, and all I saw was a steel cylinder of 1/2" ID, and a dead-end. Made a special puller to remove what I thought was a bogus part, and ordered the correct plug. Couldn't pull what I thought was a plug out, no way. Removed the sump. (Not difficult, but a pain in the neck, for such a small deal). Heard a rattle - it was the sump plug - it had gotten loose, and fell into the oil pump cavity just to the left of the screen area. O-ring was obviously old, shrunk, and maybe even not the correct size.

Hopefully, my attempt to pull that strange looking thing out of there did not damage its sealing surface - I'll check it with fiber optics tomorrow.

Moral of the story: If you don't see what you expect to see, look around a bit. Had I looked all around in that cavity, I would have saved about eight hours of labor, and I would have been doing aileron rolls today!
 
How about that! Six years of successful inverted flight, and now my symptoms are back! It is definitely that O ring in the plug behind the screen.

The strange thing is that this has not happened to enough folks to warrant any serious attention. I did a search today, and found the same thing had happened to a poster on the IAC forum, and in 2009 he posted the same circuitous path, leading to the same O ring. Had I posted to the IAC forum, I could have saved him some time.

I found this thread from so long ago in a google search. Surprise! It was my thread!

It would be trivial to design a better plug with more O rings. Maybe I shall start replacing the O ring at three year intervals.
 
A year and a half later, and my symptoms are back. I bet the new O- ring installed August 2012 was new old stock. I am now considering a more permanent fix, like maybe a pipe plug.

My theory is that the oil pump is sucking against that O ring, and even the teeniest bit of air seeping through when inverted and the sump is empty will cause the pump to cavitate. I am really surprised that I am the only Decathlon owner who has had this problem. Oh, well . . .
 
Bob, do you have the part numbers for the Sump plug and O-ring. I purchased a system that didn't come with one.
Loeds
 
Yes. I will look them up. There is an outfit in Dallas that sold me the O- ring for seven bucks and actual postage. I was reluctant to use just any old O Ring. I will see if I have their info.
 
Thanks Bob,
I would hate to go through the pain you went through. I really do appreciate this.

Loeds
 
The O ring is Lycoming part #50004-111. I got one from Air Power for $5.05 plus actual shipping (unheard of) in 2012.

The part number sounds suspiciously like MS9021-111 or maybe AS3578-111. I wasn't willing to experiment.

The entire plug assembly is Lycoming P/N LW-13752G #5377 - that was $28 from ACA in 2006.

You probably already know this -the oil screen has to be the 4 1/2" version, since it holds the plug in place. And the plug is retrieved with a 10" pole threaded 10-32. It is easier than it sounds, but if your original O Ring has shrunk, as mine did, you can jostle the plug and it will drop into the cavity. Insertion is just as easy- you will feel the plug seat itself with the end of the threaded pole.

Why they didn't just put a pipe plug in there is beyond me.

This is the only forum where you can actually get answers like this - the aerobatic forum folded, and the Bellanca Champion forum requires membership. I was a member for a while, and got nothing out of it. And the Aeronca forum sort of died, apparently because they all went to Facebook. I admit - I do not yet understand Facebook. It seems very active, but innane.
 
Lycoming Plug

Well times have changed. ACA wants $146.80 for that same Plug. And 8.50 for the O-ring. I have the plug coming from the person I purchased the system from. He hasn't removed it yet.
 
Thanks for the info guys. A friend and I have just gone partnerships in a Skybolt within the last two months. The first annual for us is next week. I've never had any thing to do with this 'Christen' inverted oil system before. I've downloaded and will print out the above link and study.
But my question is what things would you cover or replace on a schedule each annual? Remove and clean the shuttle valve I see.
 
If this is your first annual on this plane. I would remove and clean the shuttle valve, Slobber pot, and sump screen. You would be surprise in what I found in the sump screen on my Decathlon.

Loeds
 
Yes, and if you invert it once a week, you will find that the shuttle will be perfectly clean the next time you take it apart. My engine has over a thousand hours on it, and the screen is always perfectly clean. If you fly only occasionally, all kinds of unpleasant things start to congeal/rust/go dead.

Do spend money on those expensive fine wire plugs, and when you figure out the hot start on an AEIO 360, tell me. I have no success with anything other than flooding it, and cranking throttle open/mixture closed. Takes ten blades! Yuk!
 
Ha. The theories there. Odessey Batteries alway help.

I've got a great Continential CD that explains the workings of the engine and importantly it's fuel system.
Does anyone have similar for the Lycoming so as I can get my head around why the Lycoming is started in mixture cutoff and visa versa for the other brand?

In my old days of Chieftain flying, on very short turn arounds we could open up the mixture, pause, then mixture idle cutoff, and start. No touching of the pumps, and throttles remain closed. But that was the 540. But who knows.
 
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