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Best prop for aerobatics

Maxrate

Well Known Member
After reading the “propeller selection” thread with great interest I’m looking for feedback from those that have flown IAC beginners, sportsman and even advanced sequences in their RV and what prop performed the best during Acro. My main concern is prop reliability and longevity.

The Hartzell BA looks like it’s limited to the stock 180HP. The Hartzell G2YR/N7605W-2X carbon fiber looks like the most robust one on the market but comes in at a whopping 14,500$. The WW 200RV is also limited to the stock 180 horse unless going with the additional cost of a counterweighted crank, then there’s the issue of performing aerobatics with a CW crank? Wood is out of the question as I definitely want the flexibility of CS for cross country ops.

Thanks
 
MT makes some aerobatic props. The prop is counterweighted, so works in reverse fashion to normal props. Oil pressure pushes the blades fine, so in a small/short oil pressure interruption to the governor results in the blade angle going coarse. This prevents overspeeds.

Whirlwind also makes some aerobatic props, but they're 77" diameter and probably too long for most 2 seat RVs. Unless I missed something.

I'm not well versed at all regarding the aerobatic competition levels. Maybe there isn't enough negative or 0 "g" operation to make this worth while.
 
I guess I should restate that I’m actually trying to determine the best engine/prop combo for my -7. Aerobatics will be in its future, but xcountry flying will too. The “prop selection” thread raises some serious concerns about the higher HP engines with the wrong prop combos.
 
After reading the “propeller selection” thread with great interest I’m looking for feedback from those that have flown IAC beginners, sportsman and even advanced sequences in their RV and what prop performed the best during Acro. My main concern is prop reliability and longevity.

The Hartzell BA looks like it’s limited to the stock 180HP. The Hartzell G2YR/N7605W-2X carbon fiber looks like the most robust one on the market but comes in at a whopping 14,500$. The WW 200RV is also limited to the stock 180 horse unless going with the additional cost of a counterweighted crank, then there’s the issue of performing aerobatics with a CW crank? Wood is out of the question as I definitely want the flexibility of CS for cross country ops.

Thanks

I have not done any competitions, but I fly aerobatics several times per week. I recently switched from a ground adjustable Sensenich, to a WW 74HRT. The 74 HRT was recommended by WW after explaining that I do a lot of aero, and telling them my engine is rated at 190hp. The prop is a beast, and I’ve had noticeable improvement in the vertical. This data is difficult to quantify. All I can tell you is that the switch to the WW was a big improvement. Lastly, the prop is beautiful. I have the clear coated carbon fiber finish. I hope this is helpful.
 
Matt, on your 190HP engine can you tell me if you have a counterweighted crank? I assume it’s a parallel valve engine. Thanks
 
I have a fixed pitch Cato 3 blade prop on an IO-360 on my RV-8 and am VERY happy.

Would I get longer vertical lines with a constant speed prop. Sure. Do I need longer vertical lines to compete in Sportsman. No.

I do like the extremely low weight of the Cato prop. The gyroscopic force on your crankshaft from a heavy prop is substantial during acro so you not only pay a lot more for the prop but you also put more load on the engine with a heavier prop.

Also tried the new Sportsman known last weekend and I fly the entire routine with full power without going over redline on RPM. Only time I generally have to touch power is in spins despite having fixed pitch.

Oliver
 
After reading the “propeller selection” thread with great interest. My main concern is prop reliability and longevity.

Wood is out of the question as I definitely want the flexibility of CS for cross country ops.

Thanks

I cut down your post to address some of your concerns.. if you want CS for cross country flying, I think you will find the fixed pitch props to be identical or nearly so in cruise. I too want a CS prop, but just wanted you to know where they shine. They climb faster, they land shorter, but in cruise (like 99% of your cross country travels) they are identical. Perhaps you can pull down some RPM and get better fuel burn.. the lightness of a fixed pitch prop is really nice. Maybe your -7 could use the nose weight to prevent an aft CG for the planned baggage...
 
Matt, on your 190HP engine can you tell me if you have a counterweighted crank? I assume it’s a parallel valve engine. Thanks

The crank is not counter weighted. It’s a parallel valve engine with 9:1 pistons.
One more point, for my airplane, the extra weight of the CS prop helped even out the CG. That being said, the WW is one of the lighter CS props you can buy.
 
I cut down your post to address some of your concerns.. if you want CS for cross country flying, I think you will find the fixed pitch props to be identical or nearly so in cruise. I too want a CS prop, but just wanted you to know where they shine. They climb faster, they land shorter, but in cruise (like 99% of your cross country travels) they are identical. Perhaps you can pull down some RPM and get better fuel burn.. the lightness of a fixed pitch prop is really nice. Maybe your -7 could use the nose weight to prevent an aft CG for the planned baggage...

I have a -7 with the 0-360/Catto 3 blade combination and it is a very good all around performer, with respect to the light weight on the nose CG issue rather than add weight (which I have done) there have been some threads on here about using a 0-320 mount which moves the motor forward a couple of inches and helps with the CG issue. If you are not at the finishing kit stage that might be an option to explore.
 
Thanks for the great replies.
The crank is not counter weighted. It’s a parallel valve engine with 9:1 pistons.
Matt, that really helps narrow down the selection of prop and engine combo. WW website lists 9.6:1 as the max comp ratio for use with the HRT 2 blade. It seems like a great combo for acro and cross country flying to keep the CG in a reasonable all around range. The other option is the Hartzell BA that Vans sells. Price wise you can’t beat it. And the TBO is an astounding 72 months or 2400 hours.

I’ve flown with a friend in his 6A with the Cato 3 blade and it’s a great performer in cruise. I think the CG issues that others have described in different threads is not territory I want to venture into.
 
MT makes some aerobatic props. The prop is counterweighted, so works in reverse fashion to normal props. Oil pressure pushes the blades fine, so in a small/short oil pressure interruption to the governor results in the blade angle going coarse. This prevents overspeeds.

Whirlwind also makes some aerobatic props, but they're 77" diameter and probably too long for most 2 seat RVs. Unless I missed something.

I'm not well versed at all regarding the aerobatic competition levels. Maybe there isn't enough negative or 0 "g" operation to make this worth while.

Whirl Wind has 2 constant speed aerobatic propeller options for RV's--The HRT74 is not currently available:

2 Blade HRT 72" for up to 220 hp counter-weighted engines. This weighs about 45 lb with counterweights and costs $13,100.

3 Blade HRT 73" for non-counter weighted engines (although it says minimum hp is 220, it can be used just fine with 190+ hp with only small losses in top speed traded for improved climb.) This weighs about 60 lb with counterweights and costs $15,400.

The ground adjustable GA-200L 72" is also ok for aerobatics on the counterweighted engines and weighs about 22 lb with the RV 2.25" spacer and spinner (kit cost is $3,910). Obvious concerns for ground adjustable propellers doing aerobatics is that it's easy to over speed the propeller (do NOT overspeed the propeller!)

For anyone doing only “gentleman's aerobatics” (NOT using an inverted oil system and only doing positive-g maneuvers), the 300 series 72" can be used on the counter-weighted engines. This propeller does not have a counter weighted aerobatic configuration. (Cost $12,500)
 
Another bit of valuable information. I called the Hartzell tech support line and spoke with their rep who said they did extensive testing on the blended airfoil prop with the non counterweighted crank engine combo and didn’t like the harmonics on the “pumped up” parallel valve motors, 370/375, and didn’t recommend mating anything more than the 360 unless counterweighted. He basically said just too much banging around in there without any dampening effect.

I think I’m going to explore the cost of having an engine built with the counterweighted crank before going with more horsepower. Thanks for all the great input!
 
I think Whirlwind hinted at a big point that I overlooked when I first started looking at props. You have to define what you mean personally by "aerobatics". The entry level IAC maneuvers don't require negative g, the most you'll have is near zero g if you mess something up. Its up to you to decide your personal level of risk tolerance if you want a counter-weighted aerobatic prop when you really aren't planning to subject the engine to oil pressure transients. Our initial plan was for a full inverted oil system and a counter-weighted prop because we want to do IAC competitions. We've now settled on a half-raven system and an oil accumulator to help control those zero g screw up and a standard prop CS prop.
 
I think Whirlwind hinted at a big point that I overlooked when I first started looking at props. You have to define what you mean personally by "aerobatics". The entry level IAC maneuvers don't require negative g, the most you'll have is near zero g if you mess something up. Its up to you to decide your personal level of risk tolerance if you want a counter-weighted aerobatic prop when you really aren't planning to subject the engine to oil pressure transients. Our initial plan was for a full inverted oil system and a counter-weighted prop because we want to do IAC competitions. We've now settled on a half-raven system and an oil accumulator to help control those zero g screw up and a standard prop CS prop.

FWIW, I ditched my oil accumulator after installing a full inverted oil system because the accumulator caused RPM surges, particularly during takeoff roll. If you are serious about IAC competition I recommend going for a full Christen or Raven system. If you stay with a fixed pitch prop the accumulator is an inexpensive alternative to a full inverted oil system.
 
1/2 Raven

Ron,
When I built my tanks acro was not in the picture so I just put in the standard pickup tube. I plan on installing the 1/2 Raven and was wondering what sequences can I expect to be able to perform with that set up? I assume the primary and sportsman. What about the intermediate? RV7, IO 360/180 HP, CS prop.
Thanks for the input.
 
Ron,
When I built my tanks acro was not in the picture so I just put in the standard pickup tube. I plan on installing the 1/2 Raven and was wondering what sequences can I expect to be able to perform with that set up? I assume the primary and sportsman. What about the intermediate? RV7, IO 360/180 HP, CS prop.
Thanks for the input.

Hi Mark. Hi doubt you will notice any fuel starvation events. The duration of negative G during typical IAC sequences, even through Intermediate are probably not long enough to cause a power interruption. If it does it's likely to be very short and not significant enough to worry about. Of course you should run the boost pump at all times while doing aerobatics. Having said that, installing a flop tube is not a really hard job. I have done it in one day.
 
Thanks Ron. What are your thoughts on the 1/2 Raven being sufficient through the intermediate sequence?
 
Aerobatic Prop Operation

When does the aerobatic operation style prop become necessary or required?

I'm planning mild aerobatics. I don't know anything about the IAC levels, so can't draw a comparison. Loops, rolls, spins, some sustained inverted flight, that's about it. The occasional clean switch from positive to negative G, and no 0g. I've got the flop tube and planning inverted oil for the engine, just not sure how to handle the prop dilemma.

I didn't know the HRT 72" was available as a counterweighted aerobatic operation. That's great to know and might just sell me a prop once I get to that stage.
 
Of course you should run the boost pump at all times while doing aerobatics.

FWIW, I don’t run my boost pump during aerobatics. I have fuel injection, and I’ve never had even a hint of a hiccup. That being said, I respect Ron’s expertise, and opinion on the matter.
 
Thanks Ron. What are your thoughts on the 1/2 Raven being sufficient through the intermediate sequence?

You may have trouble with rolling circles at the Intermediate level. The most you will see is a 90-degree turn with a full roll but the roll will be rather slow with two knife-edge components and a long negative G push. I suspect you will be wanting a full inverted oil system when you get to that level.
 
When does the aerobatic operation style prop become necessary or required?

With a non-aerobatic prop (no counterweights) you may have a few instances of runaway RPM when oil pressure at the prop governor drops. You will hear it immediately and it is easy to retard the throttle before the RPM gets too high. Pitts pilots have been regularly running their engines with fixed pitch props and see 3300 RPM all day with no issues so don't think that you have to overhaul your engine if you exceed 2700 RPM for a moment. I have never seen a RV in competition with an aerobatic prop and we all seem to do quite well without. If you would feel more comfortable with an aerobatic prop and have the money to spend on one that's great!
 
The entry level IAC maneuvers don't require negative g, the most you'll have is near zero g if you mess something up.

I do disagree on that. You will never fly a straight roll if you don't see at least -1 to -1.5 g. Yes you can roll at +1g (lots of videos with water, cookies and other things..) but those roles are not straight at all and won't do for an IAC maneuver.

So even THE basic primary figure -- roll -- will get you into negative g.

On the other hand you really don't need anything special for that short negative g load. You have a couple of seconds before your oil pressure drops and much longer before you starve fuel even without flop tube and inverted oil. I tried down to Lycoming oil pressure minimus. I don't have a constant speed prop so I can't tell you if it has any impact on that but with a fixed pitch prop and a fuel injected engine you are good to go including Sportsman.

Oliver
 
Thanks again for the input Ron. I haven’t permanently stabbed the wings on so now is the time to install a single flop tube and look at the full Raven system. Ive watched your IAC sequence video and the RV can be a pretty impressive performer up to intermediate in the right hands and with the right equipment.
 
Would electronic ignitions with a rev-limiter solve the prop over-rev problem?

I've always pictured the ignition rev-limiter as a last chance before bad stuff happens type device. Going from high power to zero power instantly can't be good on the engine. Then because the method was cutting spark, there's a ton of raw fuel in the exhaust system when the ignition turns back on. The recipe is ripe for a nice kaboom in the exhaust system. I suppose exhaust damage is better than throwing a prop blade or overhauling the engine, prop or both. However that's the least bad of several bad options. My thought is to set the EI rev-limiter at some overspeed tolerance for the engine or propeller. 2800 or 2900rpm, depending on what maintenance action is required after the overspeed for both the engine and prop. Basically analyzing the risk at various overspeed RPMs and deciding where having exhaust damage is preferable to what's happening with the engine and/or propeller.
 
There's 3 types of rev limiters.

1. Soft limiters reduce the ignition advance. The farther you're past red-line, the more ignition advance that's taken out. Taking out ignition advance drastically reduces power, and the engine is less likely to keep increasing rpm.

2. Hard limiters cut off the ignition. Then turn it back on when rpm drops a certain amount.

3. It's sort of 1 and 2. Ignition is randomly cut to a cylinder. The higher you're past red-line, the more cylinder cuts there are until ignition is off.
 
So after looking into this a bit. I've absolutely broke my brain trying to figure it all out. Help please :confused:
I really like the 180hp c/s fuel injected engine. Love the look of the James Cowl, and I wanna do some light aerobatics.

So if I go with Vans IO-360-M1B for 180hp/CS prop. Looking at James Cowl I'm forced to go with the long cowl. Which means I need an extended hub prop.

Question is: Is the Hartzell G2YR/N7605W-2X approved for light aerobatics? Does WW or MT offer any extended hub props that will work? (This info is crazy hard to figure out going off their websites)

Darn James long cowl dilemma:mad:
 
I was watching this thread hoping someone smarter than I would chime in. Well that didn't happen, so here I am.

It really depends on how you define "light aerobatics". Any maneuvers that approach 0g or go negative will introduce air pockets in the prop control engine oil. This will cause problems for the governor to control propeller RPM. Non-aerobatic props use oil pressure to coarsen the blades, so that pocket of air will make the RPM increase uncontrolled. It's likely an insignificant increase before oil is restored and RPM brought back in line. However, it could potentially cause an overspeed that means prop and/or engine teardown.

Prop extensions put more load on the crankshaft. It's a short lever exaggerating any maneuvering and gyroscopic loads.

Positive, low G maneuvers, it sounds okay. Inverted flight, high G or gyroscopic maneuvers might cause problems. No inverted snap rolls with your setup :D

Now we wait for someone smarter to prove me wrong
 
Ok, Copy that. Thank you David.
I definitely want to fly inverted at some point, so yeah that's going to be important. (I have flop tubes in both tanks and plan on an inverted oil system). I don't plan on anything more advanced than loops and rolls. No aerobatic tumbles or any Gary Ward stuff for me :p
I suspect I may need to shy away from the James cowl to open up my options a bit for an aerobatic propeller. I suppose with the 'standard' setup I'm bound to find a prop that will fit my mission. Finding basic info on a propeller is not easy and its very cryptic for a newbie to RV's.
 
Post 11 contains a lot of helpful information, although limited to one prop manufacturer.

MT is another option to explore. Not sure what offerings Hartzel has available for aerobatic operation propellors, I'm sure there's something.
 
Ok, Copy that. Thank you David.
I definitely want to fly inverted at some point, so yeah that's going to be important. (I have flop tubes in both tanks and plan on an inverted oil system). I don't plan on anything more advanced than loops and rolls. No aerobatic tumbles or any Gary Ward stuff for me :p
I suspect I may need to shy away from the James cowl to open up my options a bit for an aerobatic propeller. I suppose with the 'standard' setup I'm bound to find a prop that will fit my mission. Finding basic info on a propeller is not easy and its very cryptic for a newbie to RV's.

I think Ron’s post (22) has part of your answer. People fly more severe stuff then you describe with regular props all the time. They might not always be within the manufactures recommended operating range neither do they need to be on an experimental. As Ron pointed out that doesn’t seem to be an issue in particular if you consider what people do with their engines/props on Pits or Onedesigns.

So at this point its up to your risk appetite vs checkbook size.

Oliver
 
Give this thread a read through. It's an overspeed event at near Vne. A bit extra money on an aerobatic style prop is good insurance.

https://vansairforce.net/community/showthread.php?t=35265

Yep. The prop on my Rocket went flat at cruise speed due to a failed governor. RPM went to 3800+ and only came down when the airspeed bled off. The transient torsional resonance could be felt and heard - and was strong enough to break the safety wire on the prop bolts and back 4 of them out. Also broke the crank counterweight ears.

No ignition system is going to prevent overspeed if the airspeed is high enough to drive the propeller.
 
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