True with the MT. Not sure about any other brands.
I am very skeptical that there is a 10 knot loss with a 3 blade compared to the two blade. I would believe 2-3 knots...maybe.
If you have definitive, not anecdotal data, please share it...
Posts like Paul?s above mean nothing; there?s too much variation from plane to plane. The only good test is A-B on the same plane. I?ve only seen one such post; that owner put his 3 blade up for sale after trying a 2 blade and gaining 5 knots, iirc.
To each their own.
Saying the other airplane was faster because one had a 2 blade and one had a 3 blade means nothing.
The only way to verify for sure is to take the same airplane, at the same weight and power settings, and fly it under the exact same atmoshpheric conditions (pressure/temp/altitude, etc). Period.
BTW, we did that with my RV-10 (swapped props) and noticed no measurable difference in speed. We even took my RV-10 back to the mothership and let Van fly my airplane right next to the factory RV-10, with both Van and I in mine (Van doing the flying) and Ken Krueger flying the company RV-10. At 8500' and full throttle, we were neck and neck. The GPS's on each airplane were within 1 knot of each other. Everyone was surprised. Without swapping the props it still didn't mean anything except it put to rest all of the hullabaloo that the MT is 10 knots slower.
There are advantages and disadvantages to each prop. one might be smoother, have more ground clearance, and better climb performance. The other might be more durable on unimproved runways, easier to get cowling off, cost less, etc..
Racing is a totally different arena.
Build the airplane for you.
Vic
Some actual data. Vic is of course correct.
http://mstewart.net/super8/performance/propcomparisons.htm
Vic is of course correct.
To each their own.
BTW, we did that with my RV-10 (swapped props) and noticed no measurable difference in speed. We even took my RV-10 back to the mothership and let Van fly my airplane right next to the factory RV-10, with both Van and I in mine (Van doing the flying) and Ken Krueger flying the company RV-10. At 8500' and full throttle, we were neck and neck. The GPS's on each airplane were within 1 knot of each other. Everyone was surprised. Without swapping the props it still didn't mean anything except it put to rest all of the hullabaloo that the MT is 10 knots slower.
There are advantages and disadvantages to each prop. one might be smoother, have more ground clearance, and better climb performance. The other might be more durable on unimproved runways, easier to get cowling off, cost less, etc..
Racing is a totally different arena.
Build the airplane for you.
Vic
Why not have the best of both worlds and install the MT 2 blade prop like I did on my 182.
Paul (and others),
I apologize for sounding harsh - that was not my intent. But please re-read your own post. ?The winner was 5 knots faster for unknown reasons?. If the winner had chosen to run a brand X prop, lost 5 knots and run even with everyone else, would the correct conclusion be that brand X was just as good? You need to vary the prop, and only the prop (same airframe, wx, etc) to reach a supportable conclusion.
Spoke to Vans support today. They (one guy) thinks I'll lose 5-10 kts with the Hart 3 blade prop over the two blade. Is this true? My RV10 will have a Thunderbolt 260hp and POSSIBLY a 3 blade. I sure as snot don't want to lose 10 kts! Any truth to this?
Does MT or Hartzel prime their props?
Was trying to take another never ending debate and if we combine them...maybe they will both be solved
Yes, the do indeed.
I have just been test flying a new -10 with the Hartzell 3 blade and it is heaps slower. 10 knots possibly.
When I get a chance with some known to be good data, I will try to remember to come back and post it.
From a single photo the other day with verified static, I had at 5500' 163KTAS at 25.2"/2320 76 LPH. This thing is a pig LOP, or was, we are correcting that, but my RV10 would be TAS 164 on 44-45LPH. My guess is about 7 knots, but that is a guess for now. But it sure is not 2.
Last night I was seeing
174 TAS, 24.5", 2300RPM, 14gph LOP, 2700' DA, 5500' MSL, 2?F.
Thunderbolt IO-540, Hartzell c2yr-1bfp/8068d (I think that's the number, from memory)
Just a data point for you.
I hate to say it again, but comparing TWO different airframes is not a valid test in any way.
Somehow we keep missing that through this thread. Randy did some testing, I did, and I think that is about it.
Vic
Vic, could you look at my post quoting you on page 3? I'm curious what your thoughts are. I hear you have a new Thunderbolt engine from Jeff at Lycoming but I'm wondering about the article. Thank you.
So, I was annoyed at that article, quite candidly. The engine manufacturer, which had a reputation for exaggerating HP, claimed 310 HP at 2800 RPM. Most of our engines will make a lot more than 260 HP at those RPM's. That's what the racer's do, and they take a pretty good life out of the engine doing just that.
From the numbers I saw cross-referenced to Lycoming power charts, using fuel flow/MP. etc. mine may have made 5 HP more at most due to the 9:1 pistons. The reality is that during that flight, fuel flows, and power settings were matched. My airplane was actually heavier, as we had all of our luggage in it.
BUT, and I say a BIG BUT, it still didn't mean anything as we had 2 DIFFERENT airframes. We did not swap the prop. The only thing, if anything, we learned that day was that just maybe the MT prop wasn't 10 or more knots slower.
Vic
BUT, and I say a BIG BUT, it still didn't mean anything as we had 2 DIFFERENT airframes. We did not swap the prop. The only thing, if anything, we learned that day was that just maybe the MT prop wasn't 10 or more knots slower.
Vic
So, I was annoyed at that article, quite candidly. The engine manufacturer, which had a reputation for exaggerating HP, claimed 310 HP at 2800 RPM. Most of our engines will make a lot more than 260 HP at those RPM's. That's what the racer's do, and they take a pretty good life out of the engine doing just that.
From the numbers I saw cross-referenced to Lycoming power charts, using fuel flow/MP. etc. mine may have made 5 HP more at most due to the 9:1 pistons. The reality is that during that flight, fuel flows, and power settings were matched. My airplane was actually heavier, as we had all of our luggage in it.
BUT, and I say a BIG BUT, it still didn't mean anything as we had 2 DIFFERENT airframes. We did not swap the prop. The only thing, if anything, we learned that day was that just maybe the MT prop wasn't 10 or more knots slower.
Vic
Vic,
You can say it until you are blue in the face, but the data does not stack up in your favour. The OP asked about a hartzell 3 blade did he not?
You claim no difference with an MT......I am not even going to comment on what that might be as i have never flown one on a -10. But I can tell you that the stretched RV8 down here has a MT 3 blade and it is dreadfully slow, borrowed a 2 blade hartzell and it was 14 knots quicker. The prop was given back and the plane dropped back to its original slower speed.
Now back to RV-10's. I have 4 of them at my disposal for data collection. In terms of weight and A/C systems , one of the 2 blades has the same a/c and similar weight as the 3 blade Hartzell machine. So as close as you can get as apples to apples. Same builder too. The other two are 2 blade and similar in spec except one is a fraction lighter.
To a knot in terms of TAS and litre in terms of fuel flow, thats 1/4Gallon close, the 2 blades ( all three aircraft) are all the same speed. Data and side by side testing.
As I said previously if I remember and can be bothered I will get back here with some real data.
And by the way this is on verified static (minimal error on GPS box) and correct OAT, as the TAS is OAT dependent.
If the MT 3 blade for the RV10 is knot for knot, everyone wanting 3 blades should go that way.
Can you detail the pro's and cons of that MT Vs the others? It might be beneficial for everyone in the shopping mode.
At the speeds we cruise at, a difference of around 5 kts would be reasonable. I am skeptical of a 14 kt increase... (due to prop efficiencies)
"If it sounds too good to be true, it probably is"
"...But I can tell you that the stretched RV8 down here has a MT 3 blade and it is dreadfully slow, borrowed a 2 blade hartzell and it was 14 knots quicker..."
I would like to see some hard data on that one...14 knots is a bunch...and some quick napkin calculations do not support that much of a difference with everything else being held constant...
Is the 3 blade slower in cruise? The math says yes. How much slower is the issue. When the anecdotal evidence does not reflect the theoretical calculations, you have to ask why...
Respectfully, what is the explanation for those that have performed an actual change from a 2-blade constant speed to a 3-blade constant speed on the same plane and only report 2-3 knots degradation? Is everyone fooling themselves, too prideful to admit the truth, or wishing it to be different?
. Cirrus only puts 3 blade props on their planes. Maybe they know something...
!
Why not have the best of both worlds and install the MT 2 blade prop like I did on my 182.