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75percent rpm

dan carley

Well Known Member
I have a Rv6 180 hp catto prop. At 100 percent power I’m getting
2700 rpm’s. What would be the rpm setting for 75 percent in cruise at a ot 3000
Feet

Thanks
Danny carley
 
In a perfect world, On a standard day, 75% power (135 hp) at 3000 ft occurs at ~ 2250 rpm. Ignore the red dots, they were already on the image I stole from the kitplanes article. If you want to read the full thing: https://www.kitplanes.com/determining-engine-power/

This makes a lot of assumptions, but should get you somewhat close. This chart was built for a certain plane with a specific induction, prop, etc, so it won't apply directly to your plane. Without having a MP gauge, or an identical plane to compare against, it's really hard to tell exactly what rpm will give you 75%
 

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I have a Rv6 180 hp catto prop. At 100 percent power I’m getting
2700 rpm’s. What would be the rpm setting for 75 percent in cruise at a ot 3000
Feet

Thanks
Danny carley

Why do you care what the RPMs are?

If you are lean of peak lean to 9gal/h and you are at 75% power.. . Roughly.

Not sure what you are trying to achieve and what the numbers you provided mean. When you say 2700RPM at 100% power. Do you mean 2700RPM at sea level, standard temperature and 180HP or do you mean you have the throttle all the way in at full rich at whatever temperature and altitude your airport is?

If it is the second I have no idea how to translate that to RPMs at 75% power at 3000ft. You might already be at 75% ... .

Oliver
 
Percent power is determined by manifold pressure, RPM, and density altitude. I’m guessing you don’t have a manifold pressure sensor/indication in the cockpit. You can make some assumptions about what the MAP might be at your altitude, but it’s not very accurate. If you could look at a POH for a cherokee or Cessna with the same engine with no MAP gage, you could come close to estimating % power, disregarding the other numbers on their chart, just looking at RPM and altitude.
 
App for that

Great App if you run an iPad (no iPhone or Android version). It's called AircraftPower. You select your engine first, then input RPM, MP, Temp and Altitude, based on the engine manufactures data the app will give you HP and % Power. Simple and VERY easy to do in flight. I use this when I'm leaning to get LOP only as far as needed to be safe, based on the Redfin graph. These 2 tools come out when I hit cruise and setup for the trip.
 

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Cherokee PA-28-180 with a 180 HP Lycoming O-360-A4A and a Sensenich 76EM8S5-0-60 fixed pitch prop.


i-JX6nMGv-XL.jpg
 
Great App if you run an iPad (no iPhone or Android version). It's called AircraftPower. You select your engine first, then input RPM, MP, Temp and Altitude, based on the engine manufactures data the app will give you HP and % Power. Simple and VERY easy to do in flight. I use this when I'm leaning to get LOP only as far as needed to be safe, based on the Redfin graph. These 2 tools come out when I hit cruise and setup for the trip.

Awesome! Thanks!!
 
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