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bob888

Well Known Member
My -10 has the standard Van's recommended two blade Hartzell metal prop. I have noticed that for a particular fuel flow, I get about 4 kt faster TAS at a low RPM (2150 vs 2500). The engine seems happy enough at the low RPM but I wonder if there are any RPM limitations for this engine/prop combo. Is it safe/sane to run it even slower? Anyone with thoughts on this subject?
 
Try your same RPM experiment running LOP and let us know how the data plays out. All data should be taken at WOT just for consistency - this translates to typical RV-10 cruise above 8K’.

I did similar data taking on the RV-8 with the Hartzell 74” CS prop. Below 2400 the miles per gallon when LOP dropped off.

Carl
 
bob888 said:
My -10 has the standard Van's recommended two blade Hartzell metal prop. I have noticed that for a particular fuel flow, I get about 4 kt faster TAS at a low RPM (2150 vs 2500). The engine seems happy enough at the low RPM but I wonder if there are any RPM limitations for this engine/prop combo. Is it safe/sane to run it even slower? Anyone with thoughts on this subject?
Click to expand...
Most tested engine/propeller combinations and any resulting limitations are published in Hartzell Manual 193, Volume 1 available on our website and/or on the appropriate propeller type certificate datasheet.
 
bob888 said:
My -10 has the standard Van's recommended two blade Hartzell metal prop. I have noticed that for a particular fuel flow, I get about 4 kt faster TAS at a low RPM (2150 vs 2500). The engine seems happy enough at the low RPM but I wonder if there are any RPM limitations for this engine/prop combo. Is it safe/sane to run it even slower? Anyone with thoughts on this subject?
Click to expand...
Depending on the engine, example IO-540D, the lowest rpm is 1800 rpm.
Pdf pg 57.

Good luck
 
Avanza said:
Depending on the engine, example IO-540D, the lowest rpm is 1800 rpm.
Pdf pg 57.

Good luck
Click to expand...
Page 39 of that same manual show's economy cruise at 2350.
The page you ref'd is a fuel consumption chart.
I have seen where 2200 is used by many and ref'd in a few places for the 540, never heard of anyone actually running below that typically.
Generally speaking, engine vibration is increasing at lower RPM's, the 4 bangers are ideally run at 2400+ for lowest vibs.
 
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