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  #11  
Old 09-22-2019, 04:50 PM
NinerBikes NinerBikes is offline
 
Join Date: Dec 2018
Location: Granada Hills
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Quote:
Originally Posted by rvbuilder2002 View Post
An RV-12 with the prop pitch set to provide the best overall performance will not be at full throttle in cruise flight until flown in the low to mid teens.

An RV-12 that requires full throttle to attain 5500 RPM (max. continuous rated rpm) at lower altitudes in cruise has the pitch setting of the prop set to course.
Low to mid teens, in elevation... 2% loss/1000 x 12500 ft is 25% loss of power, or 75% load at full throttle. Probably less than that, not sure how well the Bing carbs adjust fuel mixture flying under those atmospheric conditions, unlike the IS motor.
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  #12  
Old 09-22-2019, 05:18 PM
rvbuilder2002 rvbuilder2002 is offline
 
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Location: Hubbard Oregon
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Correct, and that is my point.
The prop pitch that most owners find to be best won't allow full throttle operations and remain at or below 5500 RPM (max. Continuous allowed) until altitude in the low teens because of the altitude induced power loss.

The carbs work fine at those altitudes. They just aren't nearly as economical as the iS can be.
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Last edited by rvbuilder2002 : 09-22-2019 at 05:20 PM.
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  #13  
Old 09-22-2019, 09:30 PM
Cammie Patch Cammie Patch is offline
 
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The sweet spot for a 912 is 5200 RPM.
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  #14  
Old 09-23-2019, 02:04 PM
AeroDog AeroDog is offline
 
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Location: New London, NC (near Charlotte), Boulder, CO
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Quote:
Originally Posted by NORM T View Post
My one time test experience is quite similar to others with wheel fairings, approx: 5000 RPM/112 kts/4 gph; 5200 RPM/122 kts/4.3 gph (best economy); 5500 RPM/127 kts/5 gph; 5800 RPM ran a little too close to Vne for me, more than 130 kts,(didn't note fuel burn rate!) but liked results.
Norm
Those are the best numbers I've heard of for a -12. I'd be curious to see if they were repeatable. I know you described it as a "one time test."

Jerre
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  #15  
Old 09-23-2019, 03:28 PM
rvbuilder2002 rvbuilder2002 is offline
 
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Originally Posted by AeroDog View Post
Those are the best numbers I've heard of for a -12. I'd be curious to see if they were repeatable. I know you described it as a "one time test."

Jerre
Some equally important info missing is what the climb performance was.

Based on the speed #ís, it was (is?) not as good as it should be, along with having a neg. influence on oil temp and lugging the engine in climb.
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  #16  
Old 09-23-2019, 03:54 PM
andover16a andover16a is offline
 
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Location: Saint Augustine FL
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Other data points:
* Approximate weight when data was taken
* Engine type, carb. or fuel injected (I know, not many out there... yet)
* Prop pitch settings
Thank you
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  #17  
Old 09-23-2019, 04:30 PM
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DaleB DaleB is offline
 
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Quote:
Originally Posted by rvbuilder2002 View Post
Some equally important info missing is what the climb performance was.

Based on the speed #ís, it was (is?) not as good as it should be, along with having a neg. influence on oil temp and lugging the engine in climb.
I'd be interested to know what prop pitch could produce numbers like that, regardless of climb performance.

When I bought my RV-12, the prop was set somewhat over-pitched in an apparent attempt to squeeze a few more knots out of it. I don't think it ever would exceed 120 KTAS at altitudes below 7000 MSL (regardless of temps), but it burned gas like it was going out of style. I used 6 GPH and 115 kt as flight planning numbers. Reducing the pitch to Van's recommended setting improved both speed and fuel burn. Next time we've got the prop off, I'm taking another .1 or .2 degrees out and see how it likes that. Right now our static RPM is just under 5000; I'm going to shoot for at or slightly over 5000. Shouldn't take more than a nudge.
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  #18  
Old 09-25-2019, 09:09 AM
NORM T NORM T is offline
 
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Default My RV-12 Performance

Hey guys, my data was just that, data, not a controlled test and obviously not repeatable. I am sorry if my numbers upset people I simply flew it on an early spring day to find my comfort zone regarding engine rpm and fuel burn. The airplane is a 2015 with the 912 ULS that I purchased flying with 18 hrs on the meter, in 2017. Flying with whatever the conditions were that day, autopilot on straight and level, with me and a maybe a half tank of non-ethanol premium mogas, much less than max gross weight, about 3000 ft msl, 2800 agl, noted the Dynon readings for what I believed were steady state for IAS in kts, fuel gph and RPM. The data indicated to me that I could comfortably cruise at about 5200 RPM with best MPG, but above that the fuel economy goes down rapidly. Flying at slower RPM resulted in data that indicated less MPG, but more hours flight time per gallon for just flying around. As for absolute values for airspeed and fuel burn, I can't control them except with throttle setting in level flight, they are whatever they are, and I accept that. I do not know the prop pitch, but I see about 5200 RPM in full power climb at about 80 kts and maybe 1000 fpm. Full power in level flight will rapidly exceed redline RPM. This is when flying near sea level.

I did not intend to stir the pot nor try for bragging rights. I think my RV-12 does what Van says it does. I like it a lot.
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  #19  
Old 09-25-2019, 09:49 AM
NinerBikes NinerBikes is offline
 
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Quote:
Originally Posted by NORM T View Post
Hey guys, my data was just that, data, not a controlled test and obviously not repeatable. I am sorry if my numbers upset people I simply flew it on an early spring day to find my comfort zone regarding engine rpm and fuel burn. The airplane is a 2015 with the 912 ULS that I purchased flying with 18 hrs on the meter, in 2017. Flying with whatever the conditions were that day, autopilot on straight and level, with me and a maybe a half tank of non-ethanol premium mogas, much less than max gross weight, about 3000 ft msl, 2800 agl, noted the Dynon readings for what I believed were steady state for IAS in kts, fuel gph and RPM. The data indicated to me that I could comfortably cruise at about 5200 RPM with best MPG, but above that the fuel economy goes down rapidly. Flying at slower RPM resulted in data that indicated less MPG, but more hours flight time per gallon for just flying around. As for absolute values for airspeed and fuel burn, I can't control them except with throttle setting in level flight, they are whatever they are, and I accept that. I do not know the prop pitch, but I see about 5200 RPM in full power climb at about 80 kts and maybe 1000 fpm. Full power in level flight will rapidly exceed redline RPM. This is when flying near sea level.

I did not intend to stir the pot nor try for bragging rights. I think my RV-12 does what Van says it does. I like it a lot.
Assuming you have 750 # bird and 60# of fuel on board, how close are you to being the mythical 225 # pilot in command? If you climb at Vx and 75 kts, what do you get for rpm readings then, since you would be 200 -275# under max gross of 1320# ? My friend, Bob, weighs 225 and with full fuel in a 753# bird, starting at 1040 ft ASL, he says that in all seasons except summer, he sees about an indicated climb rate of 1300 fpm, here in So California.

Last edited by NinerBikes : 09-25-2019 at 09:55 AM.
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  #20  
Old 09-25-2019, 10:23 AM
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DaleB DaleB is offline
 
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Norm -- I certainly didn't take any offense to your post. The 12 is a great little airplane, and will do what Van's claims it will. The only place I've seen performance lacking on ours, really, was fuel burn... mine is higher than what you'd expect. We could get 120 TAS out of it, but the fuel burn was way higher than expected. I know part of that is due to some issues with the carbs and choke cable (recently corrected), and the plane was out of rig a little (also recently corrected). We've gone from 6+ GPH in cruise to 5 or 5.5, depending on how much you feel like pushing it. We've still got some improvements to make, but it's settling in nicely. I think a little tweaking to the prop pitch for the flying we do will be the last major improvement.
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