As I'm revising the 'POH' for my RV-10 I got to thinking about cruise power settings. My plane has an experimental fuel injected IO-540x rebuild with 9:1 compression coupled with a 3 blade composite Hartzell propeller. Looking at other builders 'POHs' some use say 2300 RPMs for cruise while others use 2350 and it got me thinking about how I learned in the first place.
For me it all started with different CFIs in different planes transition training. For the 182 I was instructed to 'square everything'... so 24" manifold I should be 2400, 23" 2300, 22" 2200... ect.
When I did training on an A36 it was all about managing CHTs and less about the specific power setting but in extended climbs he instructed me to use 2400 - 2500 RPMs, then once I level out pull it back to 2300 to cruise... he suggested if to be more of an economy cruise leave it at 2300 and just pull back power and as long as it stays in the 'green' it's fine... I think green went to maybe 15". So when you went that low even with full prop you weren't getting 2300.
When I did my RV-10 transition training on a friends plane the CFI didn't care what power/prop combination I was using as long as it was smooth and controlled. I kept it usually squared around 2300 - 2400 RPMs and 23 - 23" MAN... because that's what I learned previously.
I assume each instructor had their preferred method and that's what they passed down. Why do some builders prefer say 2300 over 2350. Is this a limitation on engine/prop settings? I did find a limitation in some Hartzell documentation that I'm not sure if it applies to my engine, prop combo (Emailed Hartzell) that states "Avoid continuous operation below 103,4 kPa pressure between 1950 and 2350 RPM".
For me it all started with different CFIs in different planes transition training. For the 182 I was instructed to 'square everything'... so 24" manifold I should be 2400, 23" 2300, 22" 2200... ect.
When I did training on an A36 it was all about managing CHTs and less about the specific power setting but in extended climbs he instructed me to use 2400 - 2500 RPMs, then once I level out pull it back to 2300 to cruise... he suggested if to be more of an economy cruise leave it at 2300 and just pull back power and as long as it stays in the 'green' it's fine... I think green went to maybe 15". So when you went that low even with full prop you weren't getting 2300.
When I did my RV-10 transition training on a friends plane the CFI didn't care what power/prop combination I was using as long as it was smooth and controlled. I kept it usually squared around 2300 - 2400 RPMs and 23 - 23" MAN... because that's what I learned previously.
I assume each instructor had their preferred method and that's what they passed down. Why do some builders prefer say 2300 over 2350. Is this a limitation on engine/prop settings? I did find a limitation in some Hartzell documentation that I'm not sure if it applies to my engine, prop combo (Emailed Hartzell) that states "Avoid continuous operation below 103,4 kPa pressure between 1950 and 2350 RPM".