Turbocharged engine options for a 2 seater - what would you consider?

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TFF

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The Schneider Cup planes also had an almost unlimited runway being on water. They had time to get up to speed to where the props could get flying. Early Spits, Hurricanes , and Bf109s had to live with the hinderance; I don’t believe they ever fought with them. The DH 88 Comets were a handful. They had two speed props that could only change to full pitch after takeoff. They were a handful. Go around was almost impossible because of full pitch, and even the early spits and others had issues with this. It’s very hard to get a balance if the speed range is wide.
 

aeromomentum

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Some of the slightly earlier Schneider Trophy racers had lower power and about half the weight. For example the Curtis R3C-2 had 565 hp and a gross weight of 2737 lbs with a top speed of 245 mph done low. This is not all that far from current high performance EAB GA. Also keep in mind that the Curtis was biplane, had floats, lots of draggy wires and was 1920's technology.

The fixed pitch Hurricane Mk I is a fantastic example that a fixed pitch can work well. The top speed was over 300mph and had a ceiling over 30,000 feet. Keep in mind that they were not flat rating the engine and did not have the very wide power band.

Of course a CS prop will work better. But is it worth the cost and weight? If you are in a race or a dog fight and it makes the difference between wining or losing then of course it does. If you have a direct drive engine it may be worth it. But with an EAB GA aircraft with a flat rated wide power band engine that already has good takeoff, climb and cruise it may not be worth it but that is up to the owner/builder. For example if takeoff is 700 feet with CS props and 900 feet with FP. If climb is 1700 ft/min with CS and 1600 ft/min with FP. If cruise speed is about the same with both. The use of CS will reduce pay-load by about 30 lbs and increase cost about $12,000. These are comparative calculations for the Volato 400 but it has not yet been flown with the AM20T. We are working on it!
 

rv6ejguy

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The Hurricane Mk I with FP prop was no match for the BF109E-1 it was facing in France. An excellent account of what the RAF pilots went through in 1939-1940 can be found in Paul Richey's book "Fighter Pilot". The ROC offered by the FP prop always had them missing interceptions. He had the prop explode on one mission chasing a German fighter in a prolonged dive. They waited impatiently for the VP and CS props which were being churned out as quickly as possible once the Air Ministry realized how important these were to get on a more equal footing.

In any case, the OP stated he wants to have good TO and climb performance in the mountains. Sure you can install a 200hp engine and de-rate it with a FP prop to have adequate performance at low speed. FP is cheaper and lighter with less maintenance, trading off takeoff and climb performance. CS or VP props are certainly not worth it for everyone.

These are around $5500 Woodcomp - wooden propellers
These are around $3500 Ivoprop Corp. – Propeller Manufacturing

I'm using a 3 blade, 76 inch IVO Magnum with the high pitched blades. Even at max pitch, I cannot absorb climb power (35 inches) in level flight above about 12,000 feet without the rpm starting to creep up. I like to keep the RPMs down for better BSFC in cruise, hard to do that with FP.

I flown in plenty of RVs doing video shoots with both FP and CS props. The CS airplanes use about 50% less runway for takeoff and climb angle can be much steeper if you need to clear obstacles.

The FP prop doesn't give you any choices with MAP/RPM combinations in cruise. You have to close the throttle to reduce power. This increases pumping losses and increases BSFC. In serious cases at high altitude with a turbo, this could force the compressor near or into surge, increasing charge temperatures or causing real running problems.
 
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zolotiyeruki

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I'm curious to know if the Veloce 400 has flown at 18,000 feet yet with the AM20T and FP prop? What is the TO distance and ROC?
I'd love to hear an update as well. As of July at Airventure, they hadn't yet completed a 400 with an AM20T, but I believe they were working on it.
 

KeithO

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DUC are offering VP props for less than $10k provided that the gearbox has a hollow shaft to accept the actuator rod, which it appears has been planned for on Rotax models. They offer a constant speed option with an extra electronic instrument that adjusts pitch according to programmed rpm. These are very light composite props without the weight penalty usually associated with an MT or other. So, mr Kettering, please plan for the actuator rod and your product will be in a position to take advantage of the DUC VP propellers. Viking has already made the accommodation and for STOL applications the use of a VP prop obviously has a major impact both in terms of take off performance but also for cruise flight and slowing down for landing.
Variable Pitch Propeller — Viking & Valkyrie Power
 

Vigilant1

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The in-flight adjustable Ivoprop mentioned by Ross may be an attractive option for many. Source for below:

"Ultralight" (up to 100 HP).
Ranges 18-52" or
35" - 70"
Price
Weight
2 blade​
$1540​
7.5 lbs​
3 blade​
$1760​
9.5 lbs​
"Medium" (up to 150 HP)​
Range: 30" to 90"
2 blade​
$2720​
15.7 lb​
3 blade​
$3020​
19.2 lb​
Magnum (up to 700 HP)​
Ranges: 30" -90" or
45" to 105"
2 blade​
$3080​
24.2 lb​
3 blade​
$3466​
26.7 lb​
6 blade​
$4720​
45.7 lb​
Constant Speed governor (for above)
$350​

One thing I like about them is that the blades are rigidly mounted to the hub (the pitch changes via torsion of a metal rod inside the composite blade, which varies the twist of the blades.). So, no slop in that fitting to potentially contribute to TV/resonance issues. For those who may not have the resources for a multi-thousand hour test and validation program for their engine/PSRU/prop combination, eliminating risk where possible can be an important consideration.
 
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rv6ejguy

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My IVO has been totally reliable to date. I don't think it's the fastest prop in cruise but overall a better compromise than a FP on an automotive engine. Takeoff and climb is good.

I can't see one absorbing 700hp even with the 6 blade stacked version in aviation use but for the sub 200hp engines they seem to do the job.
 

rv7charlie

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For an alternate view, the IVOs I've worked with (admittedly a couple of decades ago) were most definitely *not* rigidly mounted to the hub. They had no drive lugs and the holes for the prop bolts make 'free fit' look tight. Obviously Ross and others using them on engines with gear reductions (much higher frequency torque pulses) are having ok luck with them, but do not consider one for a direct drive engine with any significant level of HP. The blades *will* move in the hub. IVO acknowledges this; they even refunded my money for the one I tried on a Lyc and quit selling them for Lycs. You can see the evidence for yourself in IVO's installation/maintenance instructions, where they have you put 'witness tape' across the gaps between the blades to monitor whether the blades are moving in the hub. This obviously means running a spinner is...problematic, if you intend to actually monitor for blade movement.

As to the pitch change mechanism, it's a clever solution to inexpensive pitch change, but the largest change in pitch happens at the tip, which is where you don't really want it to happen for an efficient blade shape. As speed increases, the 'twist' of the blade needs to increase, rather than decrease; the root needs to increase in pitch faster than the tip. edit: One byproduct of this poor pitch twist issue is cooling suffers, if you have typical cowl inlets. The under-pitched root starts blocking airflow into the cooling inlets as speed increases, due to it being under-pitched. This applies whether it's a Lyc or an alt engine with a reduction drive; one of the rotary guys had this issue.

Everything's a compromise, and in this case we're swapping efficiency for saving money & weight. Certainly worthwhile in some cases, but not the best solution.
 
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rv6ejguy

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For an alternate view, the IVOs I've worked with (admittedly a couple of decades ago) were most definitely *not* rigidly mounted to the hub. They had no drive lugs and the holes for the prop bolts make 'free fit' look tight. Obviously Ross and others using them on engines with gear reductions (much higher frequency torque pulses) are having ok luck with them, but do not consider one for a direct drive engine with any significant level of HP. The blades *will* move in the hub. IVO acknowledges this; they even refunded my money for the one I tried on a Lyc and quit selling them for Lycs. You can see the evidence for yourself in IVO's installation/maintenance instructions, where they have you put 'witness tape' across the gaps between the blades to monitor whether the blades are moving in the hub. This obviously means running a spinner is...problematic, if you intend to actually monitor for blade movement.

As to the pitch change mechanism, it's a clever solution to inexpensive pitch change, but the largest change in pitch happens at the tip, which is where you don't really want it to happen for an efficient blade shape. As speed increases, the 'twist' of the blade needs to increase, rather than decrease; the root needs to increase in pitch faster than the tip. edit: One byproduct of this poor pitch twist issue is cooling suffers, if you have typical cowl inlets. The under-pitched root starts blocking airflow into the cooling inlets as speed increases, due to it being under-pitched. This applies whether it's a Lyc or an alt engine with a reduction drive; one of the rotary guys had this issue.

Everything's a compromise, and in this case we're swapping efficiency for saving money & weight. Certainly worthwhile in some cases, but not the best solution.
IVO has had knurled drive plates for over 20 years now. Never had a blade move. None of my many customers using this prop have had a blade move on their auto conversions. Ancient history.

The shank of most FP and conventional props has a round or oval section near the root, not airfoil shaped so this portion can't produce any/ much thrust. The IVO is airfoil shaped there and can develop significant Delta P there, useful for ground cooling. I've measured it with manometers at about 3 inches H2O at 2000 rpm.

Most thrust on any prop in generated in the outer 2/3rds of the blade. The IVO may not have optimal AOA for takeoff or cruise in the outer portion of the blade but it's within a workable range. Still a much better choice for most turbocharged aircraft than a FP.

The IVO is light compared to something like an MT, about half the weight in fact, as I've owned both.

Yes, it's a compromise and I'd love to try an Airmaster but we balance cost, weight and performance against mission requirements here. Not the same for everyone. $9K for an MT at the time of my build wasn't in the cards nor could the extra weight be tolerated up front. The IVO was an easy choice for me and it's worked well for almost 20 years now.

IVO doesn't recommend their props for DD aero engines (Lycoming). My IVO allows takeoff in less than 500 feet, ROC of close to 1500 FPM and I've trued 181 knots at 15,000 feet.
 
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rv7charlie

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IVO has had knurled drive plates for over 20 years now. Never had a blade move. None of my many customers using this prop have had a blade move on their auto conversions. Ancient history.
Well aware, the one that I ran on my Lyc had knurled drive plates. And witness tapes were required. And the tapes broke. Repeatedly. And the knurls in the plates ate up the faces of the blades while they moved. And yes, the prop was torqued to IVO's specs, following IVO's proceedures. Repeatedly. Before IVO refunded my money. (I was lucky, both from a safety standpoint and financially.)

edit: And as I said, IVO quit selling the props to Lyc drivers. Has that changed?

The shank of most FP and conventional props has a round or oval section near the root, not airfoil shaped so this portion can't produce any/ much thrust. The IVO is airfoil shaped there and can develop significant Delta P there, useful for ground cooling. I've measured it with manometers at about 3 inches H2O at 2000 rpm.
The issue wasn't ground cooling; it was cooling at speed. At higher inflow speeds, the root area didn't have enough pitch, and became a blocking disc in front of the cooling inlets. Also a factor, no doubt, in the poor speed efficiency above about 150 kts.

I don't doubt it works for you (as I said in my earlier post), and that it's a clever, light, inexpensive option (as I said in the earlier post). I was just trying to give a heads-up to anyone considering them for direct drive engines.
 
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aeromomentum

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Well aware, the one that I ran on my Lyc had knurled drive plates. And witness tapes were required. And the tapes broke. Repeatedly. And the knurls in the plates ate up the faces of the blades while they moved. And yes, the prop was torqued to IVO's specs, following IVO's proceedures. Repeatedly. Before IVO refunded my money. (I was lucky, both from a safety standpoint and financially.)

edit: And as I said, IVO quit selling the props to Lyc drivers. Has that changed?


The issue wasn't ground cooling; it was cooling at speed. At higher inflow speeds, the root area didn't have enough pitch, and became a blocking disc in front of the cooling inlets. Also a factor, no doubt, in the poor speed efficiency above about 150 kts.

I don't doubt it works for you (as I said in my earlier post), and that it's a clever, light, inexpensive option (as I said in the earlier post). I was just trying to give a heads-up to anyone considering them for direct drive engines.
I had the exact same issues with using an IVO on a Lycoming on a KIS TR1. The IVO also did not perform as well (takeoff distance, climb and cruise) as the fixed pitch Sturba prop that I had re-contoured a little. Even better (again in takeoff distance, climb and cruise) than the Sturba was Prince and this prop was a little over pitched for optimum. The cruise speed was about 170 mph.

That is not to say that the IVO is not a great prop! Time and many other installations have proven it to be good. It was just not right for this application.
 

wsimpso1

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Well aware, the one that I ran on my Lyc had knurled drive plates. And witness tapes were required. And the tapes broke. Repeatedly. And the knurls in the plates ate up the faces of the blades while they moved. And yes, the prop was torqued to IVO's specs, following IVO's proceedures. Repeatedly. Before IVO refunded my money. (I was lucky, both from a safety standpoint and financially.)

edit: And as I said, IVO quit selling the props to Lyc drivers. Has that changed?


The issue wasn't ground cooling; it was cooling at speed. At higher inflow speeds, the root area didn't have enough pitch, and became a blocking disc in front of the cooling inlets. Also a factor, no doubt, in the poor speed efficiency above about 150 kts.

I don't doubt it works for you (as I said in my earlier post), and that it's a clever, light, inexpensive option (as I said in the earlier post). I was just trying to give a heads-up to anyone considering them for direct drive engines.
Hmm. In direct drive systems, the prop IS the flywheel and the prop sees all of the firing accelerations of the crank. If the IVO design can not handle direct drive firing accels, do not use it for direct drive engines. Do we have a broader sample of the IVO hub design being inadequate in direct drive systems?

The other side is auto conversions. Sure the crankshaft has firing accels. There is an elastic isolator after the flywheel and before the gear set. When properly designed, the prop hub sees much smaller accels from firing - on the order of 1-5% of what the Lycoming sees. This is ME340, a required class to recieve a BSME.

IVO props could be quite solid in geared/isolated systems.

Billski
 

rv6ejguy

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Well aware, the one that I ran on my Lyc had knurled drive plates. And witness tapes were required. And the tapes broke. Repeatedly. And the knurls in the plates ate up the faces of the blades while they moved. And yes, the prop was torqued to IVO's specs, following IVO's proceedures. Repeatedly. Before IVO refunded my money. (I was lucky, both from a safety standpoint and financially.)

edit: And as I said, IVO quit selling the props to Lyc drivers. Has that changed?


The issue wasn't ground cooling; it was cooling at speed. At higher inflow speeds, the root area didn't have enough pitch, and became a blocking disc in front of the cooling inlets. Also a factor, no doubt, in the poor speed efficiency above about 150 kts.

I don't doubt it works for you (as I said in my earlier post), and that it's a clever, light, inexpensive option (as I said in the earlier post). I was just trying to give a heads-up to anyone considering them for direct drive engines.
So why do you mention this at all? Far in the past, no longer valid. AFAIK IVO hasn't recommended their props for DD Lycomings for 20 years either so if you're considering one for that application, don't. IVO doesn't want to sell you one.

When my rads and oil cooler were located in the cheeks, no issue with cruise flight cooling nor do my customers using them have issues as you describe. Not something I've seen discussed by users anywhere either. Perhaps you had the low pitched version which isn't suitable for faster aircraft. The prop isn't a disc, not much solidarity there. My in-flight manometer studies don't support what you describe either and the width presented at the shank is the same as a typical metal FP prop used on Lycs- around 5 inches and with similar pitch at the root as well.

The OP wasn't considering a normally aspirated DD aero engine anyway...
 
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addaon

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Real-world experience is always valuable. It could certainly help someone looking at IVO (which is, after all, by far the lightest adjustable prop in its power range) to know limitations before trying to buy one needing to come up with a different plan then.

And if there’s one thing we know about HBA, it’s that each thread has a wealth of information, and each thread has a title, and once in a while they coincide.
 

rv6ejguy

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Real-world experience is always valuable.

And if there’s one thing we know about HBA, it’s that each thread has a wealth of information, and each thread has a title, and once in a while they coincide.
Agreed. I value the real world experience here a lot more than conjecture, unproven theories or feelings. What I don't get is folks saying something won't work well when someone else is already flying it, proving it does. This can apply to engines, props, electrical, aero or structural stuff. There's that old Chinese proverb...

Some people like to build it, fly it and prove it. Others enjoy the speculative part much more it seems.

Facts matter in the case of props here. IVO makes multiple models in both ground adjustable and in-flight adjustable plus different blade types. Some are not well suited to certain applications or aircraft. The IVO isn't the most efficient overall in my experience but is one of the least expensive and lightest VP props out there. That fits the bill for many.
 
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addaon

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Yeah. Honestly, I read the original post we’re discussing not as “don’t use Ivo”, but rather as “Ivo won’t sell props for direct drive; I learned that the hard way so you won’t have to, so now you know early.”

I’ve looked at Ivo a lot for my projects, and the weight is just incredibly appealing; and I get that there are cases where it’s the right option. But knowing the trade-offs — some of which are just basic trade offs of it /being/ so light, not about the design details — is valuable.
 

rv6ejguy

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In my dealings with IVO, responses were quick, service good. They've sold thousands of props and have been around for over 30 years. That's all good in my book. This morning, I emailed them a question and they responded in 4 minutes, confirming that they don't sell props for Lycomings.

There are some new VP/ electric CS options coming out now which is great but none are anywhere close to the IVO price point and there have been plenty of props come out with shank, hub and blade issues and even catastrophic failures plus some of these companies disappeared quickly, leaving customers stranded with no support.
 
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