Pluses and Minuses of Inverted Oil

Hi all,

I have started doing acro in my RV8. At first, I just wanted to get the basics done in phase I so I could do them later. Turns out, this is really fun. I am thinking about low level competition, for which I am sure my airplane will be fine.

I was practicing a roll yesterday and found myself pausing at the inverted part to sort out how much forward elevator I needed to keep the nose up. 1/2 second later it occurred to me that this was not a particularly good idea without inverted oil. Got back and was rewarded with a moderately oily belly.

I started thinking about putting inverted oil in. There are the Christen and Raven systems I have found. I have also found that there are some problems with the systems, stuck valves, etc.

The question I am posing is, how difficult is it to do the installation and how frequently to do problems arise? Is there a lot of additional servicing to the inverted system? Will it keep my belly clean?

My experiance is strictly for fun, but I did install the full Christian system. I like the clean belly, now I don't get much more than exhaust residue on it. I flew about 100 hours with out it.
There is a service bulletin to remove, disassemble, clean and inspect valve and pot at 250 hours.
I read that stuck valves are due to neglect.
If you have fuel injection and a fuel flop tube and don't mind the extra weight, complexity and cost....why not make it a full inverted system.
Others might add their experiance with the half Raven for a smaller less complex system.

If the priority is a clean belly / not losing oil, half raven is the "top" method (top as in most complete / expensive). There are other air/oil separators - simpler.

Some do not like the fact the oil lost from the breather is returned to the sump, saying acidic etc.

Stuck valves - yes, can cause engine failure. Does not take long at each annual to remove, dismantle, flush, reassemble.

An advantage of the "half Raven" is that if you later decide you want the full inverted, you are just adding the second half - work done to date is not wasted.

We started with nothing, went half Raven, now full inverted

I have the Half Raven setup on my 8. Works great for those momentary negative push situations and the belly stays clear of oil. As I have progressed with aerobatics I've found you can do quite a bit without going negative for more than a moment or two. But I won't say I haven't thought about a full inverted setup.

Provided you have an injected engine, I would agree with the previous.

Keep the engine sorted with an inverted system, or keep plenty of J Cloths ready

What is a Raven 1/2 sytem

Andy mentioned a Raven half system. I have an andair oil separator that dumps the excess into a little bowel. Before I started on aerobatics, I would periodically empty the bowl of mostly water and a little oil residue. Post aerobatics, it is full of nice clear oil and then dumps the rest on the belly.

I wondered if I couldn't just have a bigger collector and dump it periodically. Is that what a Raven half system consists of?

mlwynn said:

Andy mentioned a Raven half system. I have an andair oil separator that dumps the excess into a little bowel. Before I started on aerobatics, I would periodically empty the bowl of mostly water and a little oil residue. Post aerobatics, it is full of nice clear oil and then dumps the rest on the belly.

I wondered if I couldn't just have a bigger collector and dump it periodically. Is that what a Raven half system consists of?

Click to expand...

HERE is the post concerning the half Raven system. I was quite pleased with the performance of the half Raven and used it for a few years. I have since installed a flop tube and the other half of the system. For most aerobatics the half Raven is all you need. It collects oil while inverted and returns it to the sump once you return to upright flight. If all I was doing was Sportsman level competition aerobatics the half Raven would be all that is necessary.