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Performance Figures for the RV-12

NinerBikes

Well Known Member
In looking at the performance figures, a distance range is listed for the RV-12 running 5000 Rpm, and also at 5500 rpms.

https://www.vansaircraft.com/rv-12is/#aircraft-details-2


Is it possible or advisable to run the Rotax engine at 5500 rpm on a whole tank of fuel?

I was under the impression that the engine should not be run at full throttle for more than 5 minutes.

Depending on how you pitch your prop, for climb or cruise, is running the motor at 5500 rpms for more than 5 minutes advisable? Or is it pretty close to the "edge". What kind of manifold pressure should be expected, at 7500 ft under normal ATM conditions?
 
5500rpm is the max continuous rpm of the engine
5800rpm is the rpm they call ?take off rpm? and they indicate a limitation of 5 mins at that
 
Thank you. The friend I fly with, usually runs between 5100 and maybe 5300 rpm.... we usually see about 102 to 107 kt IAS and 115 kt TAS, both coming and going, average, if close to 20 to 25C OAT. Plane is at 175 hrs, motor broken in, and with wheel pants and nose gear fairing.

Mods, can we close this thread?
 
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My D-180 shows about 5 to 5.2 at 5500 depending on how it settles out on any given day. Doesn't rally matter. I'm not going to quibble about fractions of a gal.
 
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.
 
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re: RV-12 Performance

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
 
Everyone seems to settle with something a little different to match their flying style and the plane. I settled at about 5350-5380 cruise at Vans 71.4 pitch giving about 116 knots with about 5.0-5.5 gph. In the Southeast we have a lot of updrafts and downdrafts over varying terrain and I found if I went higher I would frequently exceed 5500 in updrafts. 5380 gave a comfortable margin both ways to not have to play with the throttle. Also I keep the speed up in climb out not to go lower than 5200 under full throttle to avoid possible detonation.

I wasted a lot of time playing with prop pitch but surprise/surprise found Vans 71.4 best over all compromise for speed and climb. Yes you can pitch for 128+ knots and have Dynon Betty yelling at you but maintaining climb over 5200 gives a very low climb rate especially at full gross and at high summer temperatures.
 
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.
 
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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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
 
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 #?s, 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.
 
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
 
Some equally important info missing is what the climb performance was.

Based on the speed #?s, 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.
 
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.
 
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.
 
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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.
 
On my 12 for one flight I was way over pitched at 3000' on a 50 degree day with 1/2 fuel and a 170# pilot and could hold 128+ knots TAS at about 6.5 gph. Climb performance was anemic and almost impossible to maintain above 5200 rpm in climb out. Reduced pitch some and flew awhile with 124 knot cruise but found climb performance to suffer too much with hot weather and when at full gross. Tried a few more settings ending back at Van's recommendations for all around use.
 
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.

I don't know, I've never flown at max gross weight. Maybe I will check my rate of climb someday. I am happy with whatever it is.
 
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.

Norm,
I didn?t mean to offend with my post.
I was just trying to point out that a little bit of data that only tells a small piece of a story doesn?t really provide any useful info. I don?t mean to offend again by saying that but it is true. With an adjustable fixed pitch prop., it is possible to set the prop so that a specific performance perameter is fantastic, but all other #?s will be abysmal. I can say from experience from literally hundreds of hrs of flight testing it is not possible to get 127 Kts TAS at 5500 RPM at 5 GPH and still have normal climb performance.
I?m not saying you didn?t see this numbers..... just saying that there has to be some other influences ( you were looking at ground speed instead of TAS, the prop pitch was way off to where climb would be severely effected, etc.).

Point being, the performance #?s posted on the web site are real and valid and we?re attained after hundreds of hours of very detailed flight testing, and if anyone thinks they are getting #?s that are different by very much, it is likely because of an inaccuracy in the data or some adjustment that will be effecting a different perameter in a negative way.
 
Scott, my post of some flight data was in response to questions regarding fuel burn experience and I am sorry I included my indicated air speeds. A lightly loaded 12 flying one time in rather ideal conditions, including high density atmosphere, and noting indicated air speed without regard for wind speed or direction as well as using rather short term Dynon readings is not my definition of controlled test results, just interesting data. I hope everyone knew that fact.

As to propeller pitch, airmen have been arguing over the merits and faults of Cruise Props vs Climb Props vs Constant Speed Props for at least most of my years on this earth. One of the features of our experimental world is the option to customize our aircraft to suit our needs and normal flying conditions, with respect for limitations. Flying my lightly loaded 12 here in the relatively open, unobstructed area in the Northwest and near sea level is obviously not universal conditions. By the way, I am slightly under 200 lbs, my 12 weighs less than 770 lbs and suits my needs and wishes quite well. I certainly agree, pilots should be quite aware of the ill effects of "lugging" an engine at full throttle, especially below peak torque RPM, and the need to care for temperatures and oil pressure. I think I am a conservative pilot and try not to push the envelope. I chose the way my 12 is fitted and try fly it accordingly. Maybe Van's designed it just for me, I like it! Thanks for listening.
 
noting indicated air speed without regard for wind speed or direction as well as using rather short term Dynon readings is not my definition of controlled test results, just interesting data.

I don't understand what you're eluding to... air speed, Indicated or True, is entirely independent of wind speed or direction. Wind speed or direction has nothing to do with aircraft performance as it is operating in, and relative to, a moving air mass.
 
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