f14av8r
Well Known Member
This post documents the installation of a Raven Aircraft Inverted Oil System in a RV-7A. The aircraft owner and I share this plane and both participated in this project. Please view the photos at this SmugMug site:
https://randyking.smugmug.com/Raven-Inverted-System-Installation
The aircraft has an IO-360-B1AD2 with a Superior Cold Air Sump, a Vetterman 4 into 2 Exhaust and a Catto 3 Blade Fixed Pitch propeller.
Before beginning the installation, we determined the approximate locations of the oil separator canister and the oil valve. The location of the Oil Cooler drove the canister location to the right side of the engine. We found adequate real estate for the oil valve on the firewall on the lower left side.
We installed the canister first. We manufactured a simple bracket to attach the canister to the engine mount using adel clamps. The canister needs to be as high as possible and the bottom must be at least 2” above the top of the sump. We were able to accomplish that goal. The canister is also to be offset from the engine centerline by at least 10 inches. Again, no problem. The canister should drain to a port on the opposite side of the sump - check. Finally, the hose from the canister to the sump should be a continuous downward run. We didn’t quite achieve that though the end of the hose is well below the bottom port on the canister. We had to loop under and through the intake pipes to make it to Port E which caused a slight droop in one part of the line. I don’t expect that will cause a problem.
Plumbing the canister was very straightforward with one exception. Accessing Port E on the Superior Sump (forward left port (Port E) on the engine) was not possible with the original mixture linkage. There was only about 1/2 inch of clearance between the linkage hardware and the sump port when the mixture was in the full rich position. We re-rigged the linkage to get it above the port to make room for the fitting.
The oil valve can be located horizontally anywhere on the firewall but the center port should be as close to vertically aligned with the suction port as possible. We came very close with the location we chose.
Plumbing the oil valve is much more difficult than plumbing the canister. The stainless steel covered hoses must be carefully routed, insulated and supported so they don’t cut into anything. The length must also be determined fairly precisely before making up the hoses as they aren’t very flexible and tight bends are to be avoided. We used Summit Racing hoses and hose fittings exclusively which saved quite a bit of money and made making up the hoses much easier. We also obtained all our other nipples and fittings from Summit Racing.
We consulted the Tampa FSDO asking their opinion as to the characterization of this modification. They were of the opinion that the change to the oil system constituted a major modification and would thus require a return to Phase One flight testing. The FSDO gave us a 25 mile radius around KPCM for the flight testing and required five hours of flight testing. Some would probably not think that installing an inverted oil system would be considered a major modification. A good argument can be made either way but, while the paperwork was a little painful, and waiting for approval delayed the project somewhat, the exercise was educational and we felt more comfortable taking this route.
Flight Tests were very successful. It was necessary to adjust the oil pressure relief valve to obtain optimal oil pressure of 75-85 psi. That took three turns IN on the pressure relief valve adjuster. The system functions as advertised. We went from a belly coated in oil and up to two quarts lost during aerobatic flights to a perfectly clean belly and sustained inverted flight with solid oil pressure throughout.
Inverted flight with this system is solid. There is sometimes a very brief drop in pressure when transitioning from positive to negative G but it’s very short. At no time does the pressure drop below 50 psi. The pressure side of the system is probably the most important because it preserves lubrication for the engine. That said, the breather side of the system provides the most user satisfaction as it completely cures the oil loss problem and eliminates the oil covered belly issue entirely.
Raven Aircraft was very supportive of this project. Rob answered every email quickly and always returned our phone calls quickly. Shipment of the system was on time. The instructions are clear and easy to follow. I can’t imagine why anybody would spend the exorbiant amount of additional money for the Christen system. The Raven system uses the same technology at a much lower price and, the Raven support documentation and technical support are much better and more easily accessed than with the Christen product. Kudos to Rob and Raven Aircraft!
https://randyking.smugmug.com/Raven-Inverted-System-Installation
The aircraft has an IO-360-B1AD2 with a Superior Cold Air Sump, a Vetterman 4 into 2 Exhaust and a Catto 3 Blade Fixed Pitch propeller.
Before beginning the installation, we determined the approximate locations of the oil separator canister and the oil valve. The location of the Oil Cooler drove the canister location to the right side of the engine. We found adequate real estate for the oil valve on the firewall on the lower left side.
We installed the canister first. We manufactured a simple bracket to attach the canister to the engine mount using adel clamps. The canister needs to be as high as possible and the bottom must be at least 2” above the top of the sump. We were able to accomplish that goal. The canister is also to be offset from the engine centerline by at least 10 inches. Again, no problem. The canister should drain to a port on the opposite side of the sump - check. Finally, the hose from the canister to the sump should be a continuous downward run. We didn’t quite achieve that though the end of the hose is well below the bottom port on the canister. We had to loop under and through the intake pipes to make it to Port E which caused a slight droop in one part of the line. I don’t expect that will cause a problem.
Plumbing the canister was very straightforward with one exception. Accessing Port E on the Superior Sump (forward left port (Port E) on the engine) was not possible with the original mixture linkage. There was only about 1/2 inch of clearance between the linkage hardware and the sump port when the mixture was in the full rich position. We re-rigged the linkage to get it above the port to make room for the fitting.
The oil valve can be located horizontally anywhere on the firewall but the center port should be as close to vertically aligned with the suction port as possible. We came very close with the location we chose.
Plumbing the oil valve is much more difficult than plumbing the canister. The stainless steel covered hoses must be carefully routed, insulated and supported so they don’t cut into anything. The length must also be determined fairly precisely before making up the hoses as they aren’t very flexible and tight bends are to be avoided. We used Summit Racing hoses and hose fittings exclusively which saved quite a bit of money and made making up the hoses much easier. We also obtained all our other nipples and fittings from Summit Racing.
We consulted the Tampa FSDO asking their opinion as to the characterization of this modification. They were of the opinion that the change to the oil system constituted a major modification and would thus require a return to Phase One flight testing. The FSDO gave us a 25 mile radius around KPCM for the flight testing and required five hours of flight testing. Some would probably not think that installing an inverted oil system would be considered a major modification. A good argument can be made either way but, while the paperwork was a little painful, and waiting for approval delayed the project somewhat, the exercise was educational and we felt more comfortable taking this route.
Flight Tests were very successful. It was necessary to adjust the oil pressure relief valve to obtain optimal oil pressure of 75-85 psi. That took three turns IN on the pressure relief valve adjuster. The system functions as advertised. We went from a belly coated in oil and up to two quarts lost during aerobatic flights to a perfectly clean belly and sustained inverted flight with solid oil pressure throughout.
Inverted flight with this system is solid. There is sometimes a very brief drop in pressure when transitioning from positive to negative G but it’s very short. At no time does the pressure drop below 50 psi. The pressure side of the system is probably the most important because it preserves lubrication for the engine. That said, the breather side of the system provides the most user satisfaction as it completely cures the oil loss problem and eliminates the oil covered belly issue entirely.
Raven Aircraft was very supportive of this project. Rob answered every email quickly and always returned our phone calls quickly. Shipment of the system was on time. The instructions are clear and easy to follow. I can’t imagine why anybody would spend the exorbiant amount of additional money for the Christen system. The Raven system uses the same technology at a much lower price and, the Raven support documentation and technical support are much better and more easily accessed than with the Christen product. Kudos to Rob and Raven Aircraft!
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