Veloce 600, 6 seat pressurized twin auto-converted engines.

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Vigilant1

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Mark, I'm sure you are looking for the next project. ;) I'd nominate a "value leader" little brother to the Veloce 600 ("Veloce 400?'" "Veloce Lite"?) Seating for 2+1, useful load approx 800 lbs (so, room for 300 lbs of fuel (50 gal)), two NA AM13s driving fixed pitch props fixed gear, no pressurization, but same basic layout as the Veloce 600. The FP props will need to be sufficiently flat pitched so they can work for SE climb at relatively low speed, and this will limit top speed (and save about $15k+). No need for retractable gear, and I'll bet it would still do 180+ KIAS at a low GPH, with enough fuel for serious cross country travel. This capitalizes on the low initial cost and good BSFC of the AM13 and AM15 engines.
 
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Voidhawk9

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You may want to look on their website, your suggestions already exist, or pretty close to them.
 

Alessandre

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I think the veloce 400 is already flying for long time, I think since 2010 with the old name of the Volato 400, I remember of this airplane from Brazil airshows, great airplane.
 

lelievre12

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Turbocharging 'auto' engines at 35,000 is certainly non-trivial.

As a start, it's not possible to use Avgas at above 22,000 feet easily as its Reid vapor pressure range is only 5.5 to 7 psi. At 35,000 feet, standard pressure is only 3.5 psi so all your Avgas just boiled out of the tank and turned to vapor. Even at 22,000, any kind of suction in the injection system will lead to vapor lock. Of course, Mogas is far worse with vapor pressure ranges of 8 to 14 psi and correspondingly far lower usable altitudes. Even sillier to propose Mogas at 35K.

It is possible to pressurize fuel tanks and feed lines however the challenge is immense once fuel enters the hot engine bay. Heat increases vapor pressure and tries to boil the fuel. For this reason, vaned fuel pumps in certified TIO/TSIO constant pressure fuel systems return large amounts of fuel to the tank as bubbles. The fuel being sucked from the tank mostly arrives at the pump as vapor. They are therefore specially designed to cope with fuel volatility without cavitating as their prime function. Auto systems are not designed with as much attention to this issue.

Beyond the fuel, another issue at 35K is with the turbos. The high pressure ratios needed to maintain elevated boost levels needed in 'auto' engines will require compound turbocharging unless supercharged. This inevitably leads to highly elevated exhaust back pressure and EGT with a myriad of issues thereafter. The most glaring is that exhaust guide lubrication is compromised by high pressure/temperature exhaust gases escaping up the exhaust guide towards the lower pressure of the cylinder head and crankcase. Even synthetic lubrication is vaporised at these temperatures and so the guide becomes unlubricated and the valve wears quickly and/or sticks. Valve failures are a number one killer of certified engines at altitude unless run well ROP in order so that unburnt fuel lubricates valves and compensates for the missing oil. LOP is simply not possible as there is no unburnt fuel to assist the guides. Of course none of these issues were contemplated by the auto engine designers whom had sea level in mind. Strike two.

I could go on and on, however I'm with RV6EJGUY on this one. Better to claim more modest numbers and start simple than make extravagant claims from the starting block. 35K is simply dreaming. Not a single certified Avgas engine currently available that could operate at that altitude. Jet-A rules up there as it's vapor pressure is dramatically lower at only 0.125psi.
 
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Marc Zeitlin

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As a start, it's not possible to use Avgas at above 22,000 feet easily as its Reid vapor pressure range is only 5.5 to 7 psi...
Not arguing with this, because I know exactly zippo about the subject, but it does bring up the question of how Jim Price and others have set altitude records in gasoline powered aircraft, to 35K and above? How did they get the fuel systems to work? Jim's plane was a pretty much dead stock Long-EZ - no pressurization of the fuel system, or anything fancy like that.

I also have customers that have flown their bone stock COZY III's above 22K ft. for substantial distances, so temperatures will have equilibrated - how come that worked?
 

tspear

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@lelievre12

I think you should tell all the Aerostar owners they are flying impossible airplanes.
I normally flew between 25 and 28K in pressurized comfort with twin Lycomings powered by twin turbos on each engine. They were single stage turbos, and maintained full 42in of MAP to the mid 20s. I also would run LOP, and I know a lot of Aerostar owners who have been running LOP for over a decade and have wonderfully clean engines to show for it.

Tim
 

Vigilant1

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At least one factor: The fuel in the tanks does cool with altitude, reducing volatility. Obviously, there are a lot of factors that affect how quickly that happens.

FWIW, Reid Vapor Pressure is computed at 100F.
 
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rv6ejguy

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Turbocharging 'auto' engines at 35,000 is certainly non-trivial.

As a start, it's not possible to use Avgas at above 22,000 feet easily as its Reid vapor pressure range is only 5.5 to 7 psi. At 35,000 feet, standard pressure is only 3.5 psi so all your Avgas just boiled out of the tank and turned to vapor. Even at 22,000, any kind of suction in the injection system will lead to vapor lock. Of course, Mogas is far worse with vapor pressure ranges of 8 to 14 psi and correspondingly far lower usable altitudes. Even sillier to propose Mogas at 35K.

It is possible to pressurize fuel tanks and feed lines however the challenge is immense once fuel enters the hot engine bay. Heat increases vapor pressure and tries to boil the fuel. For this reason, vaned fuel pumps in certified TIO/TSIO constant pressure fuel systems return large amounts of fuel to the tank as bubbles. The fuel being sucked from the tank mostly arrives at the pump as vapor. They are therefore specially designed to cope with fuel volatility without cavitating as their prime function. Auto systems are not designed with as much attention to this issue.

Beyond the fuel, another issue at 35K is with the turbos. The high pressure ratios needed to maintain elevated boost levels needed in 'auto' engines will require compound turbocharging unless supercharged. This inevitably leads to highly elevated exhaust back pressure and EGT with a myriad of issues thereafter. The most glaring is that exhaust guide lubrication is compromised by high pressure/temperature exhaust gases escaping up the exhaust guide towards the lower pressure of the cylinder head and crankcase. Even synthetic lubrication is vaporised at these temperatures and so the guide becomes unlubricated and the valve wears quickly and/or sticks. Valve failures are a number one killer of certified engines at altitude unless run well ROP in order so that unburnt fuel lubricates valves and compensates for the missing oil. LOP is simply not possible as there is no unburnt fuel to assist the guides. Of course none of these issues were contemplated by the auto engine designers whom had sea level in mind. Strike two.

I could go on and on, however I'm with RV6EJGUY on this one. Better to claim more modest numbers and start simple than make extravagant claims from the starting block. 35K is simply dreaming. Not a single certified Avgas engine currently available that could operate at that altitude. Jet-A rules up there as it's vapor pressure is dramatically lower at only 0.125psi.
Where do I start here?

Geez I've flown PA-31Ps at 22,000- 24,000 feet lots, years back. The 100LL worked just fine. I have multiple customers flying turbocharged Experimentals at up to 25,000 as well. Have customers flying Mogas up to 20,000 feet.

Geared auto engines don't need anywhere near the PRs that diesels require. I only use 32-35 inches for takeoff. Most are running less than 40 inches. This gets you up past altitudes where cannula don't work so well. 35,000 feet is a different story however. You'll need a pressure mask or pressurization up there and 2 stage turbos. You won't be using mogas up there.

Flown my friend's 340s up high and LOP. He's had it for years, RAM engines, works fine.

TAT recommends LOP for their turbo IO-550s. Pressure guide lube is the answer here and it works. Lots of folks flying their certified turbos engines LOP with no issues.
 

lelievre12

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Not arguing with this, because I know exactly zippo about the subject, but it does bring up the question of how Jim Price and others have set altitude records in gasoline powered aircraft, to 35K and above? How did they get the fuel systems to work? Jim's plane was a pretty much dead stock Long-EZ - no pressurization of the fuel system, or anything fancy like that.

I also have customers that have flown their bone stock COZY III's above 22K ft. for substantial distances, so temperatures will have equilibrated - how come that worked?
Certified airframe/engines deal with Avgas vapor pressure limitations by pressurizing the fuel tank (usually with ram air) and sometimes by using a belly mounted settling tank where return fuel is mixed with fresh fuel from the wing. However the 'main' item that keeps them running (at least in IO or TSIO) is a vaned fuel pump designed to push bubbles out and back to the return tank. The pump has a vapor ejector which fires a jet of unmetered pressurized fuel past the top of the pump inlet chamber and back to the settling tank. Fuel vapor is swept along with the jet. Most of the pump output is dedicated to this returning of fuel and bubbles to the belly tank and not actually pumping fuel to the engine. Here is a typical IO/TSIO pump cross section showing the entire upper section dedicated to vapor elimination.



Fuel Pump CHamber.JPG

All of these 'tricks' allow certified aircraft (including Aerostar) to reach up towards 30,000 feet in their certification. However every POH I have seen still has procedures to deal with hot day vapor issues in these planes. And nobody is certified with Avgas to 35K.

This is because the problems simply get too hard when your Avgas fuel vapor pressure is 7 PSIA and at 35K the outside air is only 3.5 PSIA. That's a big shortfall. Were you to try it, you'd need positive tank pressurization (not just ram air) and elevated pressure in the fuel suction system.

It is possible to do it, for example by using a submersible injection pump mounted inside the fuel tank and I have seen this method in some conversions (eg Viking) but with no attention paid to tank pressurization or vapor extraction.

The point is simply that these problems are not trivial and simply making a claim that we are "going to 35K" without a lot of careful work is doomed simply to vapor lock and engine failure. Certainly a superficial comparison of adapted sea level auto electronic fuel injection to certified aviation injection systems ignores the point completely.
 
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blane.c

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Normal cruise in DC-4 and DC-6 is on the engine driven fuel pumps which shows the lowest pressure on the fuel pressure gage. Prior to normal cruise is a purge period which agitates the fuel in the tanks with the two speed fuel boost pump located in the fuel tank on low, the low setting registers a higher fuel pressure than that of the engine driven pump alone. Depending on the outside air temperature difference at take-off and at cruise altitude and according to the little chart/graph a time is determined as to how long to leave the boost pumps on agitating the fuel before turning them off. When it is time to turn off the boost pump, fuel pressure is closely monitored for any drop in pressure below the engine driven pump pressure and any fluctuation would be cause for the boost pump to be turned back on for at least another 20 minutes.

I have turned the boost pump back on many times as the result of a sag in normal engine driven pump pressure indicated gas bubbles remained in the fuel. This wasn't at altitudes like those being discussed, we went to 17,000ft once in the entire time I flew transports and though we flew at 15,000ft on some routes lower altitudes were more common. It wasn't unusual to leave boost pumps on for an hour or more after reaching cruise altitude before being able to turn them off successfully in the summer.
 

PMD

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...when looking at many other aircraft like the Piaggio Avanti in side view and most business jets in both plan and side view, the Veloce 600 has less sail area in front of the CG.
I assume you mean proportionally relative to area? Also assume you mean aerodynamic equivalent rather than physical cross section.

Let me congratulate you for having the stones to even THINK of taking on this project, never mind actually trying to DO it. Also, would like to strongly endorse your choice of layout. There are several reasons an Avanti does as well as it does and the Otto Celera has headed down a similar path.

It might be a bit early to ask this, but from the rendering the front row seats not only have the best view, but seem to be at a station where there is not a lot of width. How do front row occupants gain access to their position?

Finally, another vote to think seriously about the smaller, non-pressurized version. A lot fewer big problems to solve. The 1 + 2 seating suggested might be a challenge to the "normal" layout of side-by-side up front (as this would preclude the training market IMHO).
 

PMD

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Certified airframe/engines deal with Avgas vapor pressure limitations by pressurizing the fuel tank (usually with ram air)

The point is simply that these problems are not trivial and simply making a claim that we are "going to 35K" without a lot of careful work is doomed simply to vapor lock and engine failure. Certainly a superficial comparison of adapted sea level auto electronic fuel injection to certified aviation injection systems ignores the point completely.
As someone who deals daily with dissolved gasses, gas/liquid emulsions (and water-in-oil) you have answered many questions that I would have asked if we were having this discussion.

Of course, the best solution is to feed your 35k recip a diet of Jet A and/or ULSD.
 

rv6ejguy

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Lelievre12- A tank vented to dynamic pressure would only be subject to an extra 1/2 psi at 220 kts. at 25,000 feet.

I am wondering how Flyin' Tiger made it to 47,000 feet with an SI engine? Straight from Bruce Bohannon this morning-
"yes, 100LL only. We were in the marketing business and had to move the plane around the country for show and tell. It was set up for “pump gas” for that reason. Tanks were vented like any other RV, just tubing pointed into the wind."
BB

This kinda shoots your dire predictions to smithereens... Real world trumps conjecture every time. The vapor pressure of gasoline is radically different at the low temps typical at high altitudes. Obviously it's not getting vapor into it as you assert.

Here's a screenshot from one of my customers flying at a DA of 21,200 feet on Mogas:

greg.png

Our standard Lycoming EFI system with floor mounted fuel pumps.
 
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PMD

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I am wondering how Flyin' Tiger made it to 47,000 feet with an SI engine? Straight from Bruce Bohannon this morning-
"yes, 100LL only.

Our standard Lycoming EFI system with floor mounted fuel pumps.
Of course, you make some extremely valid points, but I would like to be able to reduce this to some hard numbers. Yes the RVP of light distillates drops with temperature, but the bulk mass of fuel in a tank does not follow the air temp all that quickly. I have never been past the upper teens in 80/87 or 100LL and then never with a temp probe in a fuel tank, so can't really add any first or second hand experience. On top of that 47k is a LOT more than 30k home of the 702P community (that I have also heard are running LOP now instead of pouring gallons of excess fuel at their poor, long suffering Lycs). Even 21k on pump mogas is quite an eye opener.
 

rv6ejguy

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Of course, the best solution is to feed your 35k recip a diet of Jet A and/or ULSD.
The main problem with this on recips is that Jet A gells at -40C and Diesel at -8 to -40C depending on composition and additives so you'd have to heat it in the tanks up there. It might be challenging to divert enough heat from the coolant to do that. The good thing is that could potentially cut cooling drag. Ambient temp at 35K on a standard day is -65F.

Secondly, the pressure ratios (around 10) required by a CI engine up there also require a 2 stage turbo system and with that higher drag from the massive intercoolers required.
 
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rv6ejguy

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Of course, you make some extremely valid points, but I would like to be able to reduce this to some hard numbers. Yes the RVP of light distillates drops with temperature, but the bulk mass of fuel in a tank does not follow the air temp all that quickly. I have never been past the upper teens in 80/87 or 100LL and then never with a temp probe in a fuel tank, so can't really add any first or second hand experience. On top of that 47k is a LOT more than 30k home of the 702P community (that I have also heard are running LOP now instead of pouring gallons of excess fuel at their poor, long suffering Lycs). Even 21k on pump mogas is quite an eye opener.
I always like to provide real world examples in my debates and videos. That tends to shut down most (but not all) naysayers fairly quickly.

Chinese proverb: "Man who say it cannot be done should not interrupt the man doing it."

Most current turbocharged GA aircraft are effectively limited to around 25,000 to 28,000 feet for a variety of reasons. 35K is in a bit different realm and not so easy. We'll have to watch Mark's progress on this very cool project.
 
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rv6ejguy

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This chart shows the relationship of vapor pressure with temperature and why Lelievre12's assertion is not valid unless the fuel is over 55F or so:

vapor.png
 
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