Scott Hersha
Well Known Member
Not wanting to hijack someone else’s thread, I’ll start my own thread.
I have an RV4 (purchased) with a Lycoming O-360-A1A, carbureted with a Sensenich 72-FM8S9-1-85 (85” pitch). If I set wide open throttle (WOT) at just about any altitude I’m seeing 2850-2900 RPM. I don’t do this normally, but after discussing with Nicole at Catto, she recommended I do it once more to collect some data. What I found:
7500’ DA
37* OAT
174 Knots TAS
2870 RPM
What I would like to see is 2700 - 2750 RPM at WOT. Seems like I need more pitch. I’m not too worried about loosing some runway performance, because with my current under pitched ‘cruise prop’ I still get off the ground in less than 500’ and climb at 1500 - 2000 FPM once the speed increases to about 110 and RPM has accelerated to about 2400 - 2500 RPM, which happens very quickly.
I don’t have very much experience with fixed pitch props, so I am seeking advice from those more knowledgeable about my choices relative to Catto. 2-blade? 3-blade? What kind of performance differences am I likely to see? Is a prop change warranted or worthwhile in your experience? Please explain. I’m used to cruising at 23-2400 RPM in my RV8 (former) with it’s constant speed prop, and cruising at 2600 RPM in my new RV4 seems a little uncomfortable, but if I set 2400, I’m at less than 55% power usually. I can get 75% power at 7500’, but to do so, I’m north of 2700 RPM, and I don’t want to do that.
Nicole is working on a quote/recommendation for me, but the 2-blade, 3-blade choice is mine, and I don’t want to chase after something that won’t make much difference. Maybe what I have is almost as good as it gets with a FP prop.
I know I can install a CS prop with this engine, but to do so I’ll have to pull the engine to modify the firewall for a governor installation, and then spend a minimum of $11K to make it all happen. I really don’t want to do that.
Advice/experience appreciated.
I have an RV4 (purchased) with a Lycoming O-360-A1A, carbureted with a Sensenich 72-FM8S9-1-85 (85” pitch). If I set wide open throttle (WOT) at just about any altitude I’m seeing 2850-2900 RPM. I don’t do this normally, but after discussing with Nicole at Catto, she recommended I do it once more to collect some data. What I found:
7500’ DA
37* OAT
174 Knots TAS
2870 RPM
What I would like to see is 2700 - 2750 RPM at WOT. Seems like I need more pitch. I’m not too worried about loosing some runway performance, because with my current under pitched ‘cruise prop’ I still get off the ground in less than 500’ and climb at 1500 - 2000 FPM once the speed increases to about 110 and RPM has accelerated to about 2400 - 2500 RPM, which happens very quickly.
I don’t have very much experience with fixed pitch props, so I am seeking advice from those more knowledgeable about my choices relative to Catto. 2-blade? 3-blade? What kind of performance differences am I likely to see? Is a prop change warranted or worthwhile in your experience? Please explain. I’m used to cruising at 23-2400 RPM in my RV8 (former) with it’s constant speed prop, and cruising at 2600 RPM in my new RV4 seems a little uncomfortable, but if I set 2400, I’m at less than 55% power usually. I can get 75% power at 7500’, but to do so, I’m north of 2700 RPM, and I don’t want to do that.
Nicole is working on a quote/recommendation for me, but the 2-blade, 3-blade choice is mine, and I don’t want to chase after something that won’t make much difference. Maybe what I have is almost as good as it gets with a FP prop.
I know I can install a CS prop with this engine, but to do so I’ll have to pull the engine to modify the firewall for a governor installation, and then spend a minimum of $11K to make it all happen. I really don’t want to do that.
Advice/experience appreciated.
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