ronschreck
Well Known Member
I recently installed a "Half-Raven" oil system on Miss Izzy.
Basically, the Half-Raven system is just the oil separator part of the Raven inverted oil system. It does not include the inverted oil check valve. It is the oil check valve that directs oil from the top of the sump to the oil pump during sustained inverted flight. The oil separator redirects the oil vent from the top of the engine to the sump during inverted flight and collects some oil in the tank for return to the sump after returning to level flight. Here's a link to pictures:
http://www.ravenaircraft.com/Parts.html
Sustained inverted flight is expensive! You would need to have a full inverted oil system, inverted fuel pickup, fuel injection and a counterweighted constant speed propeller (if not fixed pitch). For the momentary negative or zero "G" maneuvering that we typically perform in the RV all of the above is not required. A second or two of oil pressure loss is not detrimental to the engine. The standard fuel pickup is sufficient, as there is adequate fuel in the lines to sustain engine operation for several seconds. While fuel injection is nice, a carbureted engine may sag or quit during some maneuvers but will quickly return to full power when positive "G" is applied. A standard CS propeller will rarely lose enough oil pressure to drive the blades to fine pitch and if this does occur it is easily recognized in time to reduce power to avoid an overspeed.
I light of all of the above, all I wanted was something to keep massive amounts of oil from flying out my vent and onto the belly of the airplane. A few weeks ago five of our Team RV pilots spent two days practicing and performing aerobatic routines to secure our aerobatic competency cards. (We are intent on interjecting some aerobatics into the Team RV airshow routine.) One of our pilots told me he lost over four quarts of oil during one training session! I flew virtually the same maneuvers as he did and didn?t lose a measurable amount of oil and the belly was clean.
Here is what I bought for the Half-Raven system:
Raven Oil Separator Tank with mount and clamps. Sump fitting. (Direct from Raven Aircraft): $326.71
AN842-12 Brass Hose Elbow (2) (Aircraft Spruce): $15.50 each.
AN816-10D Straight Fitting (Aircraft Spruce): $3.10
6000-12 Oil Hose, 3 feet (Aircraft Spruce): $6.75/foot.
#10, 36-inch braided hose with straight end fittings. (Local race shop): $68.43
The installation took about five hours. You need to mount the separator tank high on the firewall so the bottom of the tank is at least two inches above the top of the sump. It should be at least ten inches to one side of the engine centerline, opposite the side you mount the sump fitting. The sump fitting goes into one of the bosses on the bottom of the sump. (Same place you drain oil.) There are three ports on the tank. The top #12 hose comes from the normal oil vent. The middle #12 hose goes out the bottom of the cowling. The bottom #10 hose goes to the sump fitting. Clamp all the hoses down. Refill the oil sump and go fly!
Now, some of you will question my assertion that a few seconds without oil pressure isn't harmful to the engine. I have no documentation or test results to confirm this and my statement is only supported by statements from several pilots with considerable aerobatic experience. Having said that, my next job will be to install a small oil accumulator to supply several seconds of oil pressure when required. I am going this route rather than installing the Raven oil check valve because my aerobatic routine does not involve extended negative "G" flight. I will only have momentary periods of negative or zero "G" exposure. The Raven oil check valve is basically a ball check valve that re-directs oil flow when in inverted flight. It cannot maintain pressure in zero "G" flight because the ball check valve is unseated. Here's where an oil accumulator will supply pressure.
I have ordered an Accusump one quart accumulator.
http://www.hrpworld.com/index.cfm?tpc=1_Quart_Accusump&form_prod_id=102,1066_3391&action=product
Once I get it installed I'll let you know how it works out.
Basically, the Half-Raven system is just the oil separator part of the Raven inverted oil system. It does not include the inverted oil check valve. It is the oil check valve that directs oil from the top of the sump to the oil pump during sustained inverted flight. The oil separator redirects the oil vent from the top of the engine to the sump during inverted flight and collects some oil in the tank for return to the sump after returning to level flight. Here's a link to pictures:
http://www.ravenaircraft.com/Parts.html
Sustained inverted flight is expensive! You would need to have a full inverted oil system, inverted fuel pickup, fuel injection and a counterweighted constant speed propeller (if not fixed pitch). For the momentary negative or zero "G" maneuvering that we typically perform in the RV all of the above is not required. A second or two of oil pressure loss is not detrimental to the engine. The standard fuel pickup is sufficient, as there is adequate fuel in the lines to sustain engine operation for several seconds. While fuel injection is nice, a carbureted engine may sag or quit during some maneuvers but will quickly return to full power when positive "G" is applied. A standard CS propeller will rarely lose enough oil pressure to drive the blades to fine pitch and if this does occur it is easily recognized in time to reduce power to avoid an overspeed.
I light of all of the above, all I wanted was something to keep massive amounts of oil from flying out my vent and onto the belly of the airplane. A few weeks ago five of our Team RV pilots spent two days practicing and performing aerobatic routines to secure our aerobatic competency cards. (We are intent on interjecting some aerobatics into the Team RV airshow routine.) One of our pilots told me he lost over four quarts of oil during one training session! I flew virtually the same maneuvers as he did and didn?t lose a measurable amount of oil and the belly was clean.
Here is what I bought for the Half-Raven system:
Raven Oil Separator Tank with mount and clamps. Sump fitting. (Direct from Raven Aircraft): $326.71
AN842-12 Brass Hose Elbow (2) (Aircraft Spruce): $15.50 each.
AN816-10D Straight Fitting (Aircraft Spruce): $3.10
6000-12 Oil Hose, 3 feet (Aircraft Spruce): $6.75/foot.
#10, 36-inch braided hose with straight end fittings. (Local race shop): $68.43
The installation took about five hours. You need to mount the separator tank high on the firewall so the bottom of the tank is at least two inches above the top of the sump. It should be at least ten inches to one side of the engine centerline, opposite the side you mount the sump fitting. The sump fitting goes into one of the bosses on the bottom of the sump. (Same place you drain oil.) There are three ports on the tank. The top #12 hose comes from the normal oil vent. The middle #12 hose goes out the bottom of the cowling. The bottom #10 hose goes to the sump fitting. Clamp all the hoses down. Refill the oil sump and go fly!
Now, some of you will question my assertion that a few seconds without oil pressure isn't harmful to the engine. I have no documentation or test results to confirm this and my statement is only supported by statements from several pilots with considerable aerobatic experience. Having said that, my next job will be to install a small oil accumulator to supply several seconds of oil pressure when required. I am going this route rather than installing the Raven oil check valve because my aerobatic routine does not involve extended negative "G" flight. I will only have momentary periods of negative or zero "G" exposure. The Raven oil check valve is basically a ball check valve that re-directs oil flow when in inverted flight. It cannot maintain pressure in zero "G" flight because the ball check valve is unseated. Here's where an oil accumulator will supply pressure.
I have ordered an Accusump one quart accumulator.
http://www.hrpworld.com/index.cfm?tpc=1_Quart_Accusump&form_prod_id=102,1066_3391&action=product
Once I get it installed I'll let you know how it works out.
