humptybump
Well Known Member
I've received several PM's and emails asking about my RV-8. They all inquiries as to what it's like to fly and RV-8 with just a 150hp O320 and a fixed pitch propeller. I'm happy to field emails and messages but I also wanted to give the information a more permanent presence. So here goes ...
I preface all of this with "I a buyer not a builder" but add "it's exactly the airplane I wanted" and "I am very happy with the RV-8 150hp FP as a fun and economical cross country airplane".
Does the RV-8 perform OK at this low end of the engine options?
Yes. As many members of VAF have pointed out, the speed:fuel ratio is pretty consistent. Thus, the O320 pumping out 150hp burns about the same fuel and goes about the same as a bigger engine throttled back to output 150hp. Of course, there are other considerations such as electronic ignition vs mags, quality of the air frame, etc. but within the margin of error, its works out to be the same. Of course, as others have noted, if you are at the limits of the O320, there is no "go faster" lever.
What kind of speeds are you getting ?
Speed is a factor of engine power, propeller efficiency, air frame drag, and more. Right now, my RV-8 has a Aymar-DeMuth 68-71 wood propeller. A recent test showed 2250 RPM static and 161.5 kts TAS (GPS box calculation) at 8000' DA. I hardly ever fly WOT. I cross county up high (10,500' / 11,500') if the winds allow. At those altitudes, I get 145 kts TAS burning about 7.5 gph. As I said before, at those numbers, there is no "go faster" lever.
Update: For most cross country flying I throttle to 2450 rpm and 140kts at perhaps 7gps when I'm in the 3500' to 7500' altitudes.
Just an FYI - I am in the process of changing propellers to a Catto design and Craig is hoping (not guaranteeing) to improve on those numbers slightly. The propeller change was not motivated by speed, rather the fact the wood prop has no tolerance for rain.
Update: my Catto with nickel edges is pitched far into the cruise profile. My static is only 2050 rpm. It added a little to the WOT speed.
What about climb rate ?
My initial climb is always "short field" but once I am above 600' and establish best climb, I can rely on 1200 fpm steady climb (I'm not rock solid on the controls so it really varies from 800 fps to 1500 fpm).
Does it handle acro ok with the 150 and FP?
I have done very little aerobatics in the RV-8. The builder, during phase 2, did rolls, loops, stalls, and spins. (I did not buy the RV-8 as an aerobatic platform. For aerobatics, my preference is a larger engine, constant speed propeller, inverted fuel and oil, and a symmetrical wing.)
Do you wish you had put a different engine and prop on the 8?
I repeatedly tell the original builder that he built the perfect airplane for me
My RV-8 is just what I want. It's a pleasure to fly. Economical. Good useful load. Great on grass and short strips. It's a great looking airplane too (although that has nothing to do with the engine choice.)
Update: after 5 years with the plane I would say there are a few days a year when it's warm and the winds are not idea where I'd like a little more "go" when taking off on a short (1900') grass runway. More "go" could be achieved with a FP propeller pitched a bit more to climb, a CS propeller, or some more hp.
Any other comments ?
Building an RV-8 with a basic O320 and wood fixed pitch propeller yields a different airplane than one with a larger engine and a constant speed propeller. While builders of the latter often need to adjust for a nose heavy configuration, the carbureted O320 and wood propeller has the opposite challenge - it is nose light. My airplane has the battery on the firewall and a 12lb inertia ring on the hub.
Update: I've since removed the inertia ring and moved my constant cargo (canopy cover, flight bad, and small tool bag) to the forward baggage area. My goal has been to remove dead weight. It hasn't affected the starting performance but I am more careful at low idle (590 rpm).
If there are other RV-8's flying with the O320 (especially if they also have a fixed pitch propeller) it would be great to add to this thread. My goal in posting this was not to start a new thread on who's engine is bigger; rather, to archive some useful data for buildings considering using the O320 with a fixed pitch propeller and looking for first hand data.
I preface all of this with "I a buyer not a builder" but add "it's exactly the airplane I wanted" and "I am very happy with the RV-8 150hp FP as a fun and economical cross country airplane".
Does the RV-8 perform OK at this low end of the engine options?
Yes. As many members of VAF have pointed out, the speed:fuel ratio is pretty consistent. Thus, the O320 pumping out 150hp burns about the same fuel and goes about the same as a bigger engine throttled back to output 150hp. Of course, there are other considerations such as electronic ignition vs mags, quality of the air frame, etc. but within the margin of error, its works out to be the same. Of course, as others have noted, if you are at the limits of the O320, there is no "go faster" lever.
What kind of speeds are you getting ?
Speed is a factor of engine power, propeller efficiency, air frame drag, and more. Right now, my RV-8 has a Aymar-DeMuth 68-71 wood propeller. A recent test showed 2250 RPM static and 161.5 kts TAS (GPS box calculation) at 8000' DA. I hardly ever fly WOT. I cross county up high (10,500' / 11,500') if the winds allow. At those altitudes, I get 145 kts TAS burning about 7.5 gph. As I said before, at those numbers, there is no "go faster" lever.
Update: For most cross country flying I throttle to 2450 rpm and 140kts at perhaps 7gps when I'm in the 3500' to 7500' altitudes.
Just an FYI - I am in the process of changing propellers to a Catto design and Craig is hoping (not guaranteeing) to improve on those numbers slightly. The propeller change was not motivated by speed, rather the fact the wood prop has no tolerance for rain.
Update: my Catto with nickel edges is pitched far into the cruise profile. My static is only 2050 rpm. It added a little to the WOT speed.
What about climb rate ?
My initial climb is always "short field" but once I am above 600' and establish best climb, I can rely on 1200 fpm steady climb (I'm not rock solid on the controls so it really varies from 800 fps to 1500 fpm).
Does it handle acro ok with the 150 and FP?
I have done very little aerobatics in the RV-8. The builder, during phase 2, did rolls, loops, stalls, and spins. (I did not buy the RV-8 as an aerobatic platform. For aerobatics, my preference is a larger engine, constant speed propeller, inverted fuel and oil, and a symmetrical wing.)
Do you wish you had put a different engine and prop on the 8?
I repeatedly tell the original builder that he built the perfect airplane for me
My RV-8 is just what I want. It's a pleasure to fly. Economical. Good useful load. Great on grass and short strips. It's a great looking airplane too (although that has nothing to do with the engine choice.)Update: after 5 years with the plane I would say there are a few days a year when it's warm and the winds are not idea where I'd like a little more "go" when taking off on a short (1900') grass runway. More "go" could be achieved with a FP propeller pitched a bit more to climb, a CS propeller, or some more hp.
Any other comments ?
Building an RV-8 with a basic O320 and wood fixed pitch propeller yields a different airplane than one with a larger engine and a constant speed propeller. While builders of the latter often need to adjust for a nose heavy configuration, the carbureted O320 and wood propeller has the opposite challenge - it is nose light. My airplane has the battery on the firewall and a 12lb inertia ring on the hub.
Update: I've since removed the inertia ring and moved my constant cargo (canopy cover, flight bad, and small tool bag) to the forward baggage area. My goal has been to remove dead weight. It hasn't affected the starting performance but I am more careful at low idle (590 rpm).
If there are other RV-8's flying with the O320 (especially if they also have a fixed pitch propeller) it would be great to add to this thread. My goal in posting this was not to start a new thread on who's engine is bigger; rather, to archive some useful data for buildings considering using the O320 with a fixed pitch propeller and looking for first hand data.
Last edited:
