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Propeller?

F

fwellman

I'm New Here
Hi. I am a newbie here, on the verge of laying out the cash for a new RV12 kit. There are still just a couple of questions that I have about the completed plane. One of the questions is about the ground adjustable propeller.

Vans website does not clarify what pitch they were using for their performance stats. Was it climb, cruise, or somewhere in the middle. I am wondering if anyone out there has experimented with the different prop pitches, and if so, can you share the performance differences between the pitches?

Thanks
 
Here goes - -

Not a perfect answer perhaps, but not sure there is a perfect answer. For those of us who have gotten some serious hours on this plane, I'd say setting the static RPM to ROUGHLY 4950, seems to come out about the best overall. I will add perhaps some more confusion by saying that I think we are finding that RPM's are also having an affect on temps, oil & coolant. It seems if you run higher RPM's due to a 'thinner' pitch, it adds to temps. Likewise, I don't think it is good to load the engine too heavy either. I'd stay with the 4950 static RPM, and you'll likely be happy with overall performance, and overall running.

John Bender
 
Let me be one of the first to congratulate you on your very fine choice of what to build. The RV 12 won out over all the others for me as well.
Welcome to the forum, between the archives and members, you can get a quick, proper answer to any question that may come up in your build. I know, I got that help just a few short months ago, and would have been lost without that help. I invite you to take a quick look at my kit log shown in my signature, to get acquainted with the process.


fwellman said:
Hi. I am a newbie here, on the verge of laying out the cash for a new RV12 kit. There are still just a couple of questions that I have about the completed plane. One of the questions is about the ground adjustable propeller.

Vans website does not clarify what pitch they were using for their performance stats. Was it climb, cruise, or somewhere in the middle. I am wondering if anyone out there has experimented with the different prop pitches, and if so, can you share the performance differences between the pitches?

Thanks
Click to expand...
 
Great answer, but.....

Thanks for the reply. Your answer makes a lot of sense, but not having my plane yet, I don't know what 4950 rpm equates to as far as which end of the pitch spectrum that is. Climb or cruise? Further, how does static 4950 pitch relate to the published performance? Better climb? Better cruise? About the same? Not a simple question, I know, but I am just looking for generalities, not exact numbers. Thanks again.
 
OK - some more - -

Roughly 4950 static gives you the best overall performance. It will give you the best of everything. As for pitch range, they have a limiting feature built into the prop that only allows a narrow adjustment. I think you will find that about in the middle of that adjustment is where you will want to be. Hope this helps.

John Bender
275.4 hours as of today.
 
fwellman said:
Thanks for the reply. Your answer makes a lot of sense, but not having my plane yet, I don't know what 4950 rpm equates to as far as which end of the pitch spectrum that is. Climb or cruise? Further, how does static 4950 pitch relate to the published performance? Better climb? Better cruise? About the same? Not a simple question, I know, but I am just looking for generalities, not exact numbers. Thanks again.
Click to expand...

In generalities, the flight testing program leads you through doing propeller adjustments to produce airplane performance close to what is published. The reason a ground adjustable propeller is an advantage is because people operate from airports of different MSL altitudes. The adjustable propeller allows them to tailor the pitch for where they fly the most.
I.E. a person operating from airports near sea level will be adjusted slightly different than someone at an airport at 5000 ' MSL
 
Thanks again for the replies. I guess what I was hoping to hear was that the published numbers for performance were in the mid range prop setting. Living close to sea level, I was hoping that I could pitch the prop for better cruise speed. I think that the RV12 is the best bang for your buck in the lsa kit bunch, but the cruise speed is kind of anemic. My antique plane cruises almost as fast. But it's still the best one out there overall for the price.
Thanks again.
 
fwellman said:
Thanks again for the replies. I guess what I was hoping to hear was that the published numbers for performance were in the mid range prop setting. Living close to sea level, I was hoping that I could pitch the prop for better cruise speed. I think that the RV12 is the best bang for your buck in the lsa kit bunch, but the cruise speed is kind of anemic. My antique plane cruises almost as fast. But it's still the best one out there overall for the price.
Thanks again.
Click to expand...

I just flew an RV-12 from Portland Oregon to OSH and back (3500 miles round trip)
It consistently trued out at 116-117 kts. If it had been equipped with the optional wheel pants and nose gear leg fairing, it would have trued out at 120 kts. 120 kts is the max. speed allowed as an LSA so as LSA's go, I wouldn't call it anemic. If you want to go faster than that you should probably look at something other than LSA airplanes.
 
rvbuilder2002 said:
I just flew an RV-12 from Portland Oregon to OSH and back (3500 miles round trip)
It consistently trued out at 116-117 kts. If it had been equipped with the optional wheel pants and nose gear leg fairing, it would have trued out at 120 kts. 120 kts is the max. speed allowed as an LSA so as LSA's go, I wouldn't call it anemic. If you want to go faster than that you should probably look at something other than LSA airplanes.
Click to expand...

How much fuel did you use over that distance, or the fuel burn?

Thanks
Ben
 
I am not trying to knock the RV 12. Its a great plane but the 120 knot limit is at sea level. You gain speed with altitude. I would assume that you were above se level. There are LSA planes out there that will legally do 130 to 140 knots true at 8500 ft. Again, the RV12 is a great plane for the price. I am probably going to buy one. But the sad fact is it is not as fast as others out there.
 
rvbuilder2002 said:
I just flew an RV-12 from Portland Oregon to OSH and back (3500 miles round trip)
It consistently trued out at 116-117 kts. If it had been equipped with the optional wheel pants and nose gear leg fairing, it would have trued out at 120 kts. 120 kts is the max. speed allowed as an LSA so as LSA's go, I wouldn't call it anemic. If you want to go faster than that you should probably look at something other than LSA airplanes.
Click to expand...

Scott, Those are real good numbers, what is your static run-up max rpm? I am experimenting with the pitch right now and was told last week by Phil Lockwood to try 4900. I was at 4980 and had impressive take-off performance. If memory serves, your numbers are consistent with Mitch's 12 during the demo ride. Thanks.
 
The CubCrafter Carbon Cub SS is touted as Light Sport. Yeah, Right. It has a 180 hp engine which is "limited" to full power for 5 minutes. Then you are supposed to throttle back to 80 hp. The gross weight is likewise limited to 1320 lbs. No one would ever cruise at higher power settings or load it above 1320 lbs, would they? By the same logic you could take a Cassutt and limit it to say 2000 RPM and it would then be a Light Sport.It only weighs 850 or so gross so it is well within the weight limit. The RV-12 with wheel pants is right at the LSA limit. I'm used to a Cherokee so 115-120 knots is a definite step up.
 
propeller ( sort of)

Sonex with a Jabiru motor (according to their website). I also had the opportunity to test fly an Arion Lightning LS-1. It was cruising at 120 knotS at 1800 ft. It would have EASILY done 130 knots at 8500 msl. Both planes are LSAs. You can get more info on the legality in the FARs and also on the Sonex website. 120 knots is the LSA speed limit at sea level.
 
fwellman said:
Sonex with a Jabiru motor (according to their website). I also had the opportunity to test fly an Arion Lightning LS-1. It was cruising at 120 knotS at 1800 ft. It would have EASILY done 130 knots at 8500 msl. Both planes are LSAs. You can get more info on the legality in the FARs and also on the Sonex website. 120 knots is the LSA speed limit at sea level.
Click to expand...

I expected that Sonex would be one of the airplanes you might mention...

I am actually familiar with the FAR's and ASTM F2245 (The actual consensus standard the design of LSA are regulated by).

Some manufacturers seem to have chosen to twist the rules a bit, but Van's Aircraft has not.

The actual rule specifies that the limit is 120 kts at gross weight, at sea level, at maximum continuos power.

Maximum continuos power is a function of manifold pressure and RPM, not just RPM alone. Because of this, it doesn't work to just set a low pitch value and let the RPM limit, limit the max speed. So, if you use a propeller pitch that requires reducing the throttle setting to 22 " manifold pressure to be at maximum continuos RPM, and be cruising at 120 Kts, that airplane does not meet the requirements of LSA (pretty much all engines need at least 25" Mp for max cont. power, the 912 Rotax needs about 27.5 inches)

The requirement is Max. Continuos Power, not Max. Continuos RPM. There can be a big difference between the two as far as how the airplane will perform.
 
Ok. You win. I wasn't trying to start a p****** contest. Clearly the RV12 is the fastest LSA out there, all the rest are fudging the numbers. Again I'm not knocking the plane, just being realistic. However they get there, they get there.
 
Hey Fred - -

Lets back up a bit. I'd suggest you fly in any and all models you have interest in. Try to get more than 15 minutes around the patch. As has been said on these forums many times - what is your mission. The RV-12 is as good a LIGHT aircraft as you will find FOR THE MONEY ! Hauls a good load. Visibility is the best I have ridden in. Try out several.

John Bender
 
fwellman said:
Ok. You win. I wasn't trying to start a p****** contest.
Click to expand...

And neither was I (And I have no interest in being the winner), but you pointed out the rule which is what this type of dicussion should be based on. I simply pointed out that some are over looking the details of that rule. Because of this, there is a lot of misunderstanding floating around as to what the LSA max. speed is based on.
 
For the tenth time.....THE RV 12 IS A GREAT PLANE!!!! I ike it!!! I am going to invest in one. The only thing I said that seems to be a problem is that I wish it were a little faster. That's just my opinion and I didn't mean to offend anyone. Apparently I am wrong about its cruise performance compared to others? Sorry No airplane is perfect. The RV 12 is the best all around value that I have found.
 
Another way to fudge, is to just change the data plate if you are an engine maker. I know of two that have done that.
Now, if you wish, you can EXCEED the Continuous Max RPM or Power and go faster all day long - legally.
 
fwellman, I think I understood where you were coming from, beginning with your first post. Your Q is a natural one within the LSA arena: just how fast, in the real world, will this particular LSA a/c fly when compared to the rest of the field? Not only is this a normal thing to wonder about as a buyer - and as a pilot - but it's also one way some LSA mfgrs. try to distinguish their product over the vast field (120 different, approved LSA models now?) they compete against.

And right away, the Lightning, CubCrafter and Sonex (with the 3300) did all pop into my mind. And also Renegade's new Falcon which is being flight tested with Lycoming's new IO-233 engine. Here's an exchange between Dan Johnson and one of Renegade's two principals at Oshkosh:

"I [Dan Johnson] asked how fast it was now at full power. ?You don?t want me to tell you that,? he said with a laugh. ?It?s fast. We?ll placard it at 2400 rpm for 120 knots. We had a CFII bring it out here from Kansas City. He was doing 140 knots at 2700 rpm.? *** ?People ask me, ?Why not restrict the engine?? That?s a huge safety issue for me. If you?re downwind to land and the wind falls out, you may need all the power you can get. Why restrict that? If you go over that 2400 rpm setting, it?s on you legally but I?m not going to take it away. It?s like CubCrafters did with their 180 hp engine, placarding it to a max of five minutes full power.?
Cite: http://www.bydanjohnson.com/index.cfm

The marketplace tells us all that the RV-12 is a great plane, given that it's sales have far, far exceeded all of the E-AB LSA/E-LSA competition. That means that it's a great 'package'. But it doesn't earn that reputation based on its speed alone, and I think that's what you were simply trying to get a finer cut on.

Jack
 
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