Van's Air Force
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air oil separator
- Thread starter Edd
- Start date
gmcjetpilot
Well Known Member
Air oil separator may not be necessary
If your engine is healthy and you are not leaking oil into the bottom of the cowl (which will also coat your belly) you will see only a little oil on the belly. Your never going to make it zero. Any little bit of oil, no matter what its source will get on the belly at 200mph.
Try flying with out one first. If you are already flying and find oil on the belly, fix the oil drips and leaks, clean the inside of the lower cowl, route the breather right up to the hot exhaust (use a metal tube at this end). Routing the breather tube near the exhaust burns what little comes out. This is per Van's suggestion, and it worked well for me. If you are really getting a lot of oil out the breather you may have an engine problem. Look into the engine problem before covering up the symptom. I have seen tubes get routed down the gear leg or out the tail on aerobatic planes. You end up with a oil on the gear leg or tail wheel.
When you say Aerobatics I assume you mean positive G maneuvers. I would admit if you are going to push the zero G's may be some separator might help, but if you are going that far with your Acro, may be you should go all the way with an inverted oil system.
All the little AOS devices are expensive and add weight. If you read the hype for the $360 M20: http://www.m-20turbos.com/separator_facts.htm
Does that look like $360 worth and the "scientifically engineered 5 chamber oil separator galley" they talk about in their literature?
(click to enlarge) I talked to this guy at Oshkosh and he was rude and talked down to me with a bunch of 
. I have a degree in mechanical engineering and this guy just got mad when I asked him how it worked, like why is it "centrifugal". From their web site:
"M-20 crankcase models use a 5-stage, ambient pressure process, which includes two oil collection stages, a tiny sump with a capacity of only a few drops of oil controlled by a weir, an air scrubber and a anti-siphon device. Others have faked a "centrifugal" design....."
Give me a break. "Weir" is simply a wall or dam. All the other stuff, "air scrubber", "centrifiugal", "tiny sump" and "anti-siphon device", is. "AIR-SCRUBBER", please. As far as glowing reports from some articles? Right, well I guess if your engine is sick and pumping out qts from you breather may be it will catch some of it. A healthy oil tight Lycoming will not need it. May be the M20 is the best thing ever invented, but it sure looks very close to the design Tony Bingelis published in the EAA magazine years ago. Since there is no patend pending my guess is this is nothing special.
POT SCRUBBER:
A lot of guys put the cheap round separator on ( http://www.aircraftspruce.com/catalog/eppages/hboilbreather.php ) and stuff it with a stainless steel scrub pad. I hate the idea of anything blocking the breather. There is nasty stuff coming out, blow-by with combustion products. You don't want back pressure. You want the stuff to "breath" and get out. As the scrub pad gets goo'ed up in the separator, back pressure gets worse.
The Myth of running 6 quarts in your engine:
Well it is not a myth, it is true. Running over 6 qts results in it just blowing out. Small Lycoming's that run more than 6 quarts tend to throw the excess off quickly. Also despite M20's hype shaming you for running only 6 qts, as part of their sales pitch, 6 qts is plenty. Not to forget most have added large spin on filters and oil coolers, which makes the actual system volume more than the 6 qt in the sump. Don't worry 6 qts is plenty.
Why does Lycoming have an 8 qt capacity if it was not meant to run 8 qts? Ans: FAR Part 23 requires (paraphrased):
"...an engine oil capacity not be less than the endurance of the airplane under critical operating conditions and maximum oil consumption of engine under the same conditions, plus a suitable margin to ensure adequate circulation and cooling..."
Therefore you have the 8 qt mark on the dip stick to account for the regulatory oil reserve, but 6 qts is the optimal max amount, most know from experience. Back in the day some engines, like round ones, had oil tanks and used oil like gas, so a reserve oil supply made sense. For a little Lyc start with 5.5 qt min for local short flights and no more that 6 qts for long flights. With 6 qts you have 4 qts usable. If you loose more than 4 qts in 4 hours you have serious troubles. An extra 2 qts will not make much difference.
Good Luck George.
Why do you want an air-oil separator. I had one which I collected the drain into a jar. What little came out was nasty, meaning I would not run it back to the engine. The volume that was collected out of the separator was small between oil changes (mostly water and crud). The belly had only a very little film of oil on it. My oil use was a little over a quart between 25-hour oil change. So if you have little oil on the belly and little oil out of the separator drain, why have a speparator. Most of that quart and change was burned by the engine. I am not using a separator on my new project.Edd said:
If your engine is healthy and you are not leaking oil into the bottom of the cowl (which will also coat your belly) you will see only a little oil on the belly. Your never going to make it zero. Any little bit of oil, no matter what its source will get on the belly at 200mph.
Try flying with out one first. If you are already flying and find oil on the belly, fix the oil drips and leaks, clean the inside of the lower cowl, route the breather right up to the hot exhaust (use a metal tube at this end). Routing the breather tube near the exhaust burns what little comes out. This is per Van's suggestion, and it worked well for me. If you are really getting a lot of oil out the breather you may have an engine problem. Look into the engine problem before covering up the symptom. I have seen tubes get routed down the gear leg or out the tail on aerobatic planes. You end up with a oil on the gear leg or tail wheel.
When you say Aerobatics I assume you mean positive G maneuvers. I would admit if you are going to push the zero G's may be some separator might help, but if you are going that far with your Acro, may be you should go all the way with an inverted oil system.
All the little AOS devices are expensive and add weight. If you read the hype for the $360 M20: http://www.m-20turbos.com/separator_facts.htm
Does that look like $360 worth and the "scientifically engineered 5 chamber oil separator galley" they talk about in their literature?
(click to enlarge) I talked to this guy at Oshkosh and he was rude and talked down to me with a bunch of . I have a degree in mechanical engineering and this guy just got mad when I asked him how it worked, like why is it "centrifugal". From their web site:"M-20 crankcase models use a 5-stage, ambient pressure process, which includes two oil collection stages, a tiny sump with a capacity of only a few drops of oil controlled by a weir, an air scrubber and a anti-siphon device. Others have faked a "centrifugal" design....."
Give me a break. "Weir" is simply a wall or dam. All the other stuff, "air scrubber", "centrifiugal", "tiny sump" and "anti-siphon device", is
. "AIR-SCRUBBER", please. As far as glowing reports from some articles? Right, well I guess if your engine is sick and pumping out qts from you breather may be it will catch some of it. A healthy oil tight Lycoming will not need it. May be the M20 is the best thing ever invented, but it sure looks very close to the design Tony Bingelis published in the EAA magazine years ago. Since there is no patend pending my guess is this is nothing special.POT SCRUBBER:
A lot of guys put the cheap round separator on ( http://www.aircraftspruce.com/catalog/eppages/hboilbreather.php ) and stuff it with a stainless steel scrub pad. I hate the idea of anything blocking the breather. There is nasty stuff coming out, blow-by with combustion products. You don't want back pressure. You want the stuff to "breath" and get out. As the scrub pad gets goo'ed up in the separator, back pressure gets worse.
The Myth of running 6 quarts in your engine:
Well it is not a myth, it is true. Running over 6 qts results in it just blowing out. Small Lycoming's that run more than 6 quarts tend to throw the excess off quickly. Also despite M20's hype shaming you for running only 6 qts, as part of their sales pitch, 6 qts is plenty. Not to forget most have added large spin on filters and oil coolers, which makes the actual system volume more than the 6 qt in the sump. Don't worry 6 qts is plenty.
Why does Lycoming have an 8 qt capacity if it was not meant to run 8 qts? Ans: FAR Part 23 requires (paraphrased):
"...an engine oil capacity not be less than the endurance of the airplane under critical operating conditions and maximum oil consumption of engine under the same conditions, plus a suitable margin to ensure adequate circulation and cooling..."
Therefore you have the 8 qt mark on the dip stick to account for the regulatory oil reserve, but 6 qts is the optimal max amount, most know from experience. Back in the day some engines, like round ones, had oil tanks and used oil like gas, so a reserve oil supply made sense. For a little Lyc start with 5.5 qt min for local short flights and no more that 6 qts for long flights. With 6 qts you have 4 qts usable. If you loose more than 4 qts in 4 hours you have serious troubles. An extra 2 qts will not make much difference.
Good Luck George.
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Good discussion. I choked at the price of the m20, especially after paying only $40 for the Spruce homebuilders special. However at Oskosh the salesman for the m20 made me wonder about the 6 quart vs. 8 quart issue. The folks I have talked to all use only 6 quarts and your discussion reassures me that that amount is OK. I put 11 hours on my RV8 going to and from Oshkosh and only used about a fourth of a quart.
gmcjetpilot
Well Known Member
Yep
The M20 guy sales man inventor what ever really me off. Their web site has the same propaganda, so my encounter was not a fluke. 6 qts is plenty despite the shame we should feel for NOT using a M20 and 8qts as they claim. your 11q t in 11 hours is prety good, but even if it was twice the usage it would be 22 hours/qt. George
The M20 guy sales man inventor what ever really
me off. Their web site has the same propaganda, so my encounter was not a fluke. 6 qts is plenty despite the shame we should feel for NOT using a M20 and 8qts as they claim. your 11q t in 11 hours is prety good, but even if it was twice the usage it would be 22 hours/qt. George
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ddurakovich
Well Known Member
George,
I know you said this, but it was somewhat buried after your eloquent rhetoric on "snake oil" sales techniques: the minimum oil level defined by Lycoming for most of their small engines is 2 quarts! No equivocation there.
It never ceases to amaze me how some people can so easily "redefine" the original designers/manufacturers intent to justify their own products!
While I personally wouldn't run with just 2 quarts in the sump, I always considered the 8th quart during the oil change to be both optional and foolish!
Dave
I know you said this, but it was somewhat buried after your eloquent rhetoric on "snake oil" sales techniques: the minimum oil level defined by Lycoming for most of their small engines is 2 quarts! No equivocation there.
It never ceases to amaze me how some people can so easily "redefine" the original designers/manufacturers intent to justify their own products!
While I personally wouldn't run with just 2 quarts in the sump, I always considered the 8th quart during the oil change to be both optional and foolish!
Dave
Once you have some hours on your plane, you will get to know how much oil you need to run with out blowing oil out. I ran my RV6 0320 on 5 qts and refilled when it got to 4 qts and never had problems. More than 5 qts and it blew oil all over the belly. This engine had 900 hrs on it when I sold the RV with no problems. There is no use to blowing good oil out the tube just because it has more in it than it needs. The amounts will be different for every engine, depending on condition.
robertahegy
Moderator/Tech Counselor
I put 8 quarts in with a new filter on my 0-360. Half a quart (or more) goes in the filter leaving 7.5 (or less) in the sump. I go 25 hrs without having to add. I use about 1 qt in 25. Very little gets on the belly. I broke in my new engine using Aeroshell Oil 80. I ran new oil for about 1 hr during ground testing, changed it, ran for 25 during my flyoff, changed it again for our trip out west, and switched to Aeroshell 15W50 when I got home at 50 hrs. I change the oil and filter every 25 hrs and never had at add. It is usually about 6.5 qts when I dump it. I have 100 hrs on the engine now.
My opinion? Forget the oil separator. Let the engine breath and rid itself of the moisture. If you get too much oil on the belly, maybe you need something other than an oil separator.
There is a new Simple Green product out for AL airplanes now. They must have heard us.
JMHO
Roberta
My opinion? Forget the oil separator. Let the engine breath and rid itself of the moisture. If you get too much oil on the belly, maybe you need something other than an oil separator.
There is a new Simple Green product out for AL airplanes now. They must have heard us.
JMHO
Roberta
O-360-a
I have run through several O-360s and my blow-out-level has always been 7 quarts. I always put in 8 quarts at every oil change because that's my tribute to some possible obscure reliability thing but I know better. That 8th quart qoes out so fast I might as well pour in on the ground. All of my engines have stabilized at the 7 quart level however. I routed the metal segment of the breather tube down to the left exhaust pipe in our RV-6A (O-360-A1A) and that keeps the belly pretty clean - even with that 8th quart after oil changes. The O-360-A4Ms in the Archer we owned for 22 years with no such breather routing always coated the belly with a significant amount of crud so I'm convinced that Van's recomendation is a good one. Because of my Archer experience I was planning on installing an AOS until I read Van's recomendation. Excluding the possible aerobatic effects, which I can only imagine, I would not use an AOS either. Yesterday was the first time since returning from Oshkosh that I had time to wash the plane - 1.5 hours - there are times when small is good. Washing the belly itself was probably 5 to 10 minutes. It is not a big deal.
One pro-8 quart experience occurred when I only hand tightened an oil fitting after replacing the oil cooler and blew out all of the oil in flight. The 8 quarts no doubt made it possible for me to land at the airport before the engine seized on the landing rollout.
Bob Axsom
I have run through several O-360s and my blow-out-level has always been 7 quarts. I always put in 8 quarts at every oil change because that's my tribute to some possible obscure reliability thing but I know better. That 8th quart qoes out so fast I might as well pour in on the ground. All of my engines have stabilized at the 7 quart level however. I routed the metal segment of the breather tube down to the left exhaust pipe in our RV-6A (O-360-A1A) and that keeps the belly pretty clean - even with that 8th quart after oil changes. The O-360-A4Ms in the Archer we owned for 22 years with no such breather routing always coated the belly with a significant amount of crud so I'm convinced that Van's recomendation is a good one. Because of my Archer experience I was planning on installing an AOS until I read Van's recomendation. Excluding the possible aerobatic effects, which I can only imagine, I would not use an AOS either. Yesterday was the first time since returning from Oshkosh that I had time to wash the plane - 1.5 hours - there are times when small is good. Washing the belly itself was probably 5 to 10 minutes. It is not a big deal.
One pro-8 quart experience occurred when I only hand tightened an oil fitting after replacing the oil cooler and blew out all of the oil in flight. The 8 quarts no doubt made it possible for me to land at the airport before the engine seized on the landing rollout.
Bob Axsom
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gmcjetpilot
Well Known Member
2 qt unusable
As far as the two quarts min, I thought 2 qts was the "MIN" quantity, from what I had heard before, but actually on further reading the type spec says:
Oil sump capacity: 8 qt,
Usable oil: 6 qt.
So from that, unusable oil quantity is 2 qts, which is a little different than the "MIN" recommended.
What is the real min oil level? I don't think there is an exact Lycoming MIN or needs to be, except that oil pressure and oil temp stay within limits. I don't think there is any contraversy that 6 qts is OK.
What I recall from some small plane AFM?s (airplane flight manuals) powered by small Lycomings, a min oil quantity was specified, I think some say 6 qts and others 5 qts. I also recall the AFM recommend two values, one for oil level to start a local flight and another slightly higher quantity for longer flights. In any case I don't think 8 qts is ever specified as a MIN.
I like to think the oil sump is like a gas tank, as long as you have what you need for the flight (above unusable) plus a little reserve, you are OK. As you said no one would intentionally start a flight with much less than 5 qts (3 qts usable).
Since even the most tired Lycoming on the worst day burns say 0.5 qt every 4 hour in theory! Lets multiply that by a factor of 4, you could take-off for a 4-hours flight with 5 qts and still have reserve oil capacity. Since most Lycs burn 1/8th to 1/10th this, 5 qts is a good MIN with plenty of margin. If we run around 6 qts most of the time we have lots of oil (4 qts usable). If you really do have an engine that is burning 0.5 qts/hr you may want to fill-er up with 2 gallons of oil and fly it to the engine overhaul shop.
(note: 1 qt every 8 hours is a really tired oil burning Lyc.)
So I say follow the airframe manufactures recommended oil mins as a guide. Use nothing more than 6 qts, and a common sense min around 5.5+/-(0.5) qts.
Cheers George
PS Thanks Roberta for the info. I know 16-18qt/hrs is a typical value of a healthy engine. Your 25qt/hr is great and I think sets the high end of a very tight new engine and a good data point. I wounder if they have a little better windage or oil control in the newer engine? Since most people do report a "blow off" of the top 2 qts, I wounder what the differnt is in your installation? What's the secret? Do you have Lycoming or a Clone? The Aeroshell 15W50 is semi-synthetic multigrade ashless dispersant is good stuff.
Yes, Dave eloquent, now may be that is an exaggeration.ddurakovich said:
As far as the two quarts min, I thought 2 qts was the "MIN" quantity, from what I had heard before, but actually on further reading the type spec says:
Oil sump capacity: 8 qt,
Usable oil: 6 qt.
So from that, unusable oil quantity is 2 qts, which is a little different than the "MIN" recommended.
What is the real min oil level? I don't think there is an exact Lycoming MIN or needs to be, except that oil pressure and oil temp stay within limits. I don't think there is any contraversy that 6 qts is OK.
What I recall from some small plane AFM?s (airplane flight manuals) powered by small Lycomings, a min oil quantity was specified, I think some say 6 qts and others 5 qts. I also recall the AFM recommend two values, one for oil level to start a local flight and another slightly higher quantity for longer flights. In any case I don't think 8 qts is ever specified as a MIN.
I like to think the oil sump is like a gas tank, as long as you have what you need for the flight (above unusable) plus a little reserve, you are OK. As you said no one would intentionally start a flight with much less than 5 qts (3 qts usable).
Since even the most tired Lycoming on the worst day burns say 0.5 qt every 4 hour in theory! Lets multiply that by a factor of 4, you could take-off for a 4-hours flight with 5 qts and still have reserve oil capacity. Since most Lycs burn 1/8th to 1/10th this, 5 qts is a good MIN with plenty of margin. If we run around 6 qts most of the time we have lots of oil (4 qts usable). If you really do have an engine that is burning 0.5 qts/hr you may want to fill-er up with 2 gallons of oil and fly it to the engine overhaul shop.
(note: 1 qt every 8 hours is a really tired oil burning Lyc.)
So I say follow the airframe manufactures recommended oil mins as a guide. Use nothing more than 6 qts, and a common sense min around 5.5+/-(0.5) qts.
Cheers George
PS Thanks Roberta for the info. I know 16-18qt/hrs is a typical value of a healthy engine. Your 25qt/hr is great and I think sets the high end of a very tight new engine and a good data point. I wounder if they have a little better windage or oil control in the newer engine? Since most people do report a "blow off" of the top 2 qts, I wounder what the differnt is in your installation? What's the secret?
Do you have Lycoming or a Clone? The Aeroshell 15W50 is semi-synthetic multigrade ashless dispersant is good stuff.
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robertahegy
Moderator/Tech Counselor
It's a new 0-360 A1A purchased through Van's and picked up at the factory in Williamsport (we took the factory tour).
I put in 8 quarts, but as I mentioned, at least a half qt goes into the filter, leaving about 7.5 in the sump. The first half quart goes overboard within 5-10 hrs, then the rest goes south during the next 15-20 hrs. I see about 6.5 on the stick when I change it at 25 hrs.
I also used Van's recommended positioning of the vent tube over the exhaust. I does seem to vaporize the water/oil from the vent, leaving the belly a lot cleaner than my Cherokee. I also had a new 0-360 A4M (it was an STC from Avcon from 150 to 180 hp) in that plane. That engine was installed in 1991 and did use about a qt every 16+ hrs and the belly was always full of slime. Maybe Lycoming has improved oil consumption. I also used 15W50 in the Cherokee, but I did not run the straight mineral oil as long during break in. Maybe only 10 hrs.
Final note: During break in of my 7A Lycoming, I used a qt about every 12-16 hrs when I used the Oil 80. I think the multiweight 15W50 hangs in ther much better as oil consumption slowed when I switched to it.
Roberta
I put in 8 quarts, but as I mentioned, at least a half qt goes into the filter, leaving about 7.5 in the sump. The first half quart goes overboard within 5-10 hrs, then the rest goes south during the next 15-20 hrs. I see about 6.5 on the stick when I change it at 25 hrs.
I also used Van's recommended positioning of the vent tube over the exhaust. I does seem to vaporize the water/oil from the vent, leaving the belly a lot cleaner than my Cherokee. I also had a new 0-360 A4M (it was an STC from Avcon from 150 to 180 hp) in that plane. That engine was installed in 1991 and did use about a qt every 16+ hrs and the belly was always full of slime. Maybe Lycoming has improved oil consumption. I also used 15W50 in the Cherokee, but I did not run the straight mineral oil as long during break in. Maybe only 10 hrs.
Final note: During break in of my 7A Lycoming, I used a qt about every 12-16 hrs when I used the Oil 80. I think the multiweight 15W50 hangs in ther much better as oil consumption slowed when I switched to it.
Roberta
garnt.piper
Well Known Member
Oil level etc
I too basically agree with the consensus above. 6 qts seems to be a good amount at which the level stabilizes without pouring it overboard. I fitted a Raven Aircraft oil catch tank, much cheaper than the Christen and they make them in 4" diameter to fit tight cowls. My -4 has an O-360A1A with their full inverted system. During acro I will smear some oil on the belly, but very little, not measurable on the dipstick. The proper valved catchtank also won't obstruct breathing, whatever the attitude. To fit you only need one AN sump fitting and one -601 or equivalent hose made up, the rest are spigot fittings with hose clamps, so no great expense.
Bottoms Up!
I too basically agree with the consensus above. 6 qts seems to be a good amount at which the level stabilizes without pouring it overboard. I fitted a Raven Aircraft oil catch tank, much cheaper than the Christen and they make them in 4" diameter to fit tight cowls. My -4 has an O-360A1A with their full inverted system. During acro I will smear some oil on the belly, but very little, not measurable on the dipstick. The proper valved catchtank also won't obstruct breathing, whatever the attitude. To fit you only need one AN sump fitting and one -601 or equivalent hose made up, the rest are spigot fittings with hose clamps, so no great expense.
Bottoms Up!
ddurakovich
Well Known Member
Actually George, 2 quarts minimum is exactly what it refers to. The 6 quarts usable is based on maximum oil consumption allowed for a "healthy" engine (I have no idea how an engine burning 1 quart/hour is considered "healthy", but Lycoming does!) factoring in airplane endurance.gmcjetpilot said:
Most of the comments I've seen (including some on the Lycoming website) indicate that flight should not be initiated with only 2 quarts in the sump, but if there is at least 2 quarts remaining in the sump after the flight, that is acceptable! I know my 1972 PA28-140 POH specifically addressed 2 quarts as the minimum oil level in the sump. Go figure!
Not to belabor the point, I think that the aftermarket guys spreading gloom and doom about running less than 8 quarts in your sump in order to sell an oil separator are doing just that: spreading gloom and doom. They are preying on an uninformed potential customer that has spent their whole career keeping the oil level up. Is 8 quarts better than 4 or even 6? Of course it is, if you can keep it in the engine! But since the primary objective of the oil is lubrication and cooling, we can usually tell by oil cleanliness and oil temps if we are doing OK.
There may be many advantages to an Oil Separator, I really don't know. But people that resort to "snake oil" selling techniques really
me!But then, so does global warming, the price of crude oil, and most people that don't agree with me
. Oh well.......Dave
Bill Dicus
Well Known Member
No separator?
We've flown a Pitts S-2A with 200 hp IO-360 for 24 years with no problems. We settled on 6 qts based on other owners' experiences and our own. We do a lot of negative G and quickly blow off anything over 6. Blow by goes out by tailwheel in summer and by metal tube (thin wall EMT) to the exhaust area in the winter. Belly stays fairly clean and the engine has had no problems related to using only 6 qts. My Lyc literature says 2 3/4 qts minimum. I'm sceptical of the need for this expensive device. Good luck! Bill Dicus
We've flown a Pitts S-2A with 200 hp IO-360 for 24 years with no problems. We settled on 6 qts based on other owners' experiences and our own. We do a lot of negative G and quickly blow off anything over 6. Blow by goes out by tailwheel in summer and by metal tube (thin wall EMT) to the exhaust area in the winter. Belly stays fairly clean and the engine has had no problems related to using only 6 qts. My Lyc literature says 2 3/4 qts minimum. I'm sceptical of the need for this expensive device. Good luck! Bill Dicus
OneTwoSierra
Well Known Member
Thanks for this discussion
I've put 8 qts in the last 2 oil changes in my 0-320 with oil screen only. The oil drops to 7.5 quarts rather quickly (4 or 5 hours) and then slowly burns another 1/2 qt over the next 20 hours. I'm going to stop wasting that quart and go with 7 and see what she does. I appreciate all the discussion on this topic.
I've put 8 qts in the last 2 oil changes in my 0-320 with oil screen only. The oil drops to 7.5 quarts rather quickly (4 or 5 hours) and then slowly burns another 1/2 qt over the next 20 hours. I'm going to stop wasting that quart and go with 7 and see what she does. I appreciate all the discussion on this topic.
Oil Mess on Belly
We do some aerobatics in our RV-8 and were getting a lot of oil on the belly with just a little zero G or slight negative. Even an aileron roll with a slight unload was getting oil on the belly. We installed the "cheap" AOS from Aircraft Spruce ($39) and it stopped the oil on the belly. I wouldn't be without it now.
We do some aerobatics in our RV-8 and were getting a lot of oil on the belly with just a little zero G or slight negative. Even an aileron roll with a slight unload was getting oil on the belly. We installed the "cheap" AOS from Aircraft Spruce ($39) and it stopped the oil on the belly. I wouldn't be without it now.
gmcjetpilot
Well Known Member
poor mans inverted oil system
I can see where the cheap ACS unit would make a difference if you like to work in that -0 to 1 G area. I have seen this with my RV-4 that showed under normal use the oil sep was a waste, but doing some semi 0 G or slight negative G's it would pit more in the catch bottle. Also running wide open for almost 2 hours would get a little more in the catch bottle. However normal Ops. it made little differnce. However for all you Acro nuts who want to do extended inverted down lines (neg 1 g) you need and want a full inverted oil system. George
I can see where the cheap ACS unit would make a difference if you like to work in that -0 to 1 G area. I have seen this with my RV-4 that showed under normal use the oil sep was a waste, but doing some semi 0 G or slight negative G's it would pit more in the catch bottle. Also running wide open for almost 2 hours would get a little more in the catch bottle. However normal Ops. it made little differnce. However for all you Acro nuts who want to do extended inverted down lines (neg 1 g) you need and want a full inverted oil system. George
