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  #11  
Old 11-05-2019, 05:41 PM
SPX SPX is offline
 
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Quote:
Originally Posted by jrs14855 View Post
The relatively low utilization of typical EAB aircraft makes any wear from slightly higher r/m irrelavent.
For those who fly 50 hours a year it will take 44 years to reach TBO. In many case the engine will sustain significant damage from rust long before reaching TBO.

Kind of. Don?t forget TBO is based on hours or years, whichever comes first.
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  #12  
Old 11-05-2019, 07:28 PM
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aturner aturner is online now
 
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Bob, I've pondered the same question, here is what I have:



The graph shows mixture sweeps at 2000 to 2400 RPM. DA about 10,000 ft., dead stock setup. I was interested in efficiency...nmpg, so I plotted the isopleths for reference. If you don't care about airspeed, the highest efficiency is at low RPM. Keeping in mind that fuel flow isn't quite the same as power - air fuel ratio may be changing too - the graph also shows that on the rich end of the spectra, speed is increasing with RPM, constant fuel flow. It doesn't hold up though as mixture is leaned. At the very lean end there is a suggestion that speed increases as RPM declines.
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Last edited by aturner : 11-05-2019 at 08:02 PM.
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  #13  
Old 11-05-2019, 09:14 PM
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Originally Posted by BobTurner View Post
As to Marc?s comment: Your numbers are borderline unbelieveable, just from a basic physics perspective (power required proportional to cube of airspeed, etc.) Something else is going on.
I know, huh. I was surprised too! I was at 10500', throttle fire-walled which was (IIRC) about 22 inches. I leveled off and started to lean to my normal ROP setting, saw the speed was faster than my normal 172 kts, then brought the RPM down to 2400 from my 2500 climb RPM. I slowed down! I went back to 2500 and saw the speed go (slowly) back up to 178. I'll play with it again when we do another XC in a couple of weeks.

-Marc
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  #14  
Old 11-06-2019, 12:03 PM
63robskin 63robskin is offline
 
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Default RPM

Shouldn?t propeller design be in this conversation somewhere.
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