RPM green arc

The low end of the green arc is usually 20 that is 2000 RPM. I'll been told that is the lowest you want to operate because of cooling, combustion temps, lead on plugs, oil pressure, sustain flight, what ever... But that being said, that number might have more meaning pulling a 172 through the sky but it seems I can dial back the RV to 1800-1600 on a long approach without noticing any side effects. Any thoughts?

Wild guess, but I seem to recall when to use Carb Heat if appropriate? Not relevant to FI, and as you say, needs further interpretation if C/S...

Maybe RV's have tighter cowls with less cooling than a 172? So, possibly our engines don't cool off as quickly at low rpm settings on a long approach? I'd be curious to know what rate of cooling (CHT's) is damaging to a Lycoming and do some post-flight analysis of EMS data.

The low power setting on a long approach situation seems somewhat unavoidable with a fixed pitch prop on an RV. Our airplanes are just too darn fast! Such a terrible predicament! Oh, what will we ever do?

For a certified plane the FARs say the green arc defines the normal operating range.

However I can't find this range defined in my Lycoming O-360 Operators manual.

Cadstat said:

The low end of the green arc is usually 20 that is 2000 RPM. I'll been told that is the lowest you want to operate because of cooling, combustion temps, lead on plugs, oil pressure, sustain flight, what ever... But that being said, that number might have more meaning pulling a 172 through the sky but it seems I can dial back the RV to 1800-1600 on a long approach without noticing any side effects. Any thoughts?

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My 6A with the hartzell prop is limited in the 2000-2250 rpm range for extended periods. This is a prop manufactures limitation. I know of no other limitations except the 2700 rpm limit imposed by Lycoming.