I took an oil bath today :( doing acro. Need advice.

[Darren S]

Ok that's a bit of an exaggeration but my plane is a mess. I knew it was coming but not this bad.

I want to compete in Sportsman this year which is a move up from Primary last year. The two new manoueuvres for me are the 1/2 reverse Cuban and the hammerhead turn.

I have inverted fuel but only a dumb, cheap air/oil separator from Aircraft Spruce. For weeks I've been reading threads on different air/oil separators, 1/2 Raven systems, accusumps, Christen inverted systems and now I'm all disoriented, no pun intended.

To do the 1/2 Cuban I pull to 45, do a quick 2 count, roll inverted, push and count 3 before pulling to finish the maneuver. Oil pressure is normally in the 55 psi. range and drops to mid 30's during the inverted segment. It recovers as soon as positive G is applied. I don't think this is harming the engine one bit.

I typically keep my oil level at 5 quarts, I guess I lost a good 3/4 quart today in a 20 min. practice session.

I want your opinions on what I should do. Sportsman is as high as I'm going with this plane and I have no interest in sustained inverted acro.

1. Get a better air/oil separator ?
2. Run the breather tube all the way to the tail ?
3. Bite the bullet and install a: 1/2 Raven, full Raven, Christen system ? I'm not sure how they differ.
4. Leave as is and just buy oil and paper towels ?

I personally would like to find an air/oil separator or something that would minimize the oil loss and then also run the breather tube to the tail. The oil pressure drop doesn't concern me as it's so short in duration.

Thanks for any advice and suggestions,

Darren

[rvbuilder2002]

Originally Posted by Darren S

To do the 1/2 Cuban I pull to 45, do a quick 2 count, roll inverted, push and count 3 before pulling to finish the maneuver.

The solution is really pretty simple....
If you do not have inverted oil you must always maintain some level of positive G's (like 1/2 G)

To maintain positive G's you can not Push when inverted.

Sounds like you need an inverted oil system.

Also sounds like you have learned what still confuses so many people even after all of these years... A inverted fuel system on an RV (or any other airplane) is just about worthless unless you also have inverted oil. The second most misunderstood issue is related to installing inverted fuel on an airplane equipped with a carburetor (totally pointless).

[tkatc]

People have suggested the half Raven system to me and from I've read they like it. At least you KNEW it was coming. My oil bath was unexpected and I almost had a cow!!

Happy cleaning!! Sounds like a fun job in the brisk air of Canada.

[WillyEyeBall]

I can tell you've already got the acro bug, and you're really not going to be happy until you have a full inverted system. I have the Raven and at least half my flying is upside down, using about 1/2 quart in 10 hours with the Raven. For Sportsman known and a free style, my G meter shows 1.5 to 2 negative Gs. I really hope you do well, and holding the inverted positions will score higher. RVs can compete with those Pitts with the right equipment.
Cheers,
Bill McLean
RV-4 slider

[frankh]

Or minus 2.8G in the inverted spin...I'm quite pleased with that one...

Oh yes the raven system is great, just don't use a swivel hose end in addition to the Raven swivel fitting...The swivel hose end will fret and eventually suck air into the oil on start up.

Frank

[jrs14855]

If you go with inverted oil system you will still need the breather out the tail so why not try just the breather first. I would crank that oil pressure up to at least the high 70's, the more pressure you have upright the more you will maintain for brief negative G.

[Darren S]

Good advice so far, thanks.

Fitting the inverted system during the build is one thing but the retro fit is a little worrisome; because of the firewall space and the need to move things around.

I still don't fully understand the Half Raven System. Is it just a large canister that holds all the expelled oil and then dumps it back into the sump?

Good suggestion to crank up the oil pressure a bit. That's an easy one.

The tube to the back is an easy one too. The only portion of the sequence, I think, that's an oily issue is the 1/2 reverse cuban. The hammerhead, Cuban and shark tooth aren't too oily (amount of oil loss) as the zero G/ negative G segments are even shorter.

I spoke to my instructor tonight. He also said that it's not the end of the world if you take a downgrade on the Reverse Cuban because you shortened up the inverted segment. The carbureted sect. has to for the most part. Just make up for it during the rest of the round

I've been checking ACS and I'd like to try either the Andair or Airwolf air/oil separators. Searching the forum for either of these brings a wide range of opinions so I may have to make a gut decision.

Tomorrows forecast is for a low of -18 degrees C!! I think that oil is going to have to stay for at least another day

Thanks for the replies so far.

Darren

[boeing737driver]

Hi,

I just installed a full Christen system on my -6. I found a new second hand complete system on the classifieds here for $1250. The installation took about 3 days and everything fit fine. The air-oil separator is attached to the engine mount with adel clamps on the pax side with the oil valve on the firewall below it. Either a half Raven or the air-oil separator from the Christen system will take care of short duration inverted flight. They both have a ball check valve that will keep a breather line full of oil from escaping on to the belly when you roll upright.

I currently have fuel injection, but no inverted flop tube on the fuel so my inverted time is limited to about 15-20 seconds, and so far not a trace of oil on the belly. Which is better than I expected. No other air-oil separators that I know of will do the job since they don't have the check valve that Raven and Christen use.

HTH,
Bruce

[Darren S]

See that's what I didn't know. The Raven has a check valve to keep at least some oil from coming out of the breather. Makes sense. It may not be perfect but better than just a regular air/oil seperator.

I'm calling Raven tomorrow. Paul Dye said their service was excellent. I'll report back.

Darren

[sandifer]

Originally Posted by frankh

Or minus 2.8G in the inverted spin...I'm quite pleased with that one...

-2.8? Sounds like a hammerspin entry! Or a negative snap entry.

Originally Posted by Darren S

I spoke to my instructor tonight. He also said that it's not the end of the world if you take a downgrade on the Reverse Cuban because you shortened up the inverted segment.

Darren, if you're going to shorten the inverted line, shorten the positive line too, but still draw both long enough to be perceptible as lines. I would not recommend shortening only the inverted line. I say this because if you apply the judging criteria as defined, it could be easy for the line before the half roll to appear more than twice as long as the line after. This would be a 3 point deduction. And any additional imperfection in the looping portion or attitude before or after the roll could score you a 5 for the whole figure real quick. If you drew NO line before OR after, it would be only a 2 point deduction. Any visible line length variation is 1 point, and that doesn't take much. 2 points is more likely (for a 2:1 line length variation). Draw a short line before AND after, and you can get a 10. The shorter lines will just create a larger looping segment, which is fine.