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

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nicknack

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Hmm, maybe I should widen this sucker up...
View attachment 114808
Is this something that’s in development? Any more information?
FYI, our program is starting with a proof of concept fixed gear and non pressurized version. Only after this as flown and completed a real test program will we add retracts and pressurization.
Glad to hear of a very measured/methodical development plan. Sure it will not be the fastest way to the end product, having real proven performance at every stage of development is far more important to overall success.
 

TarDevil

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The Twin Velocity appealed to me a lot, even though it's a canard. This airplane, if it comes close to performance specs, is better.

But... it remains one of those "Lottery Dreams."
 

aeromomentum

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Mark, thank you for your comments. You don't come across as defensive at all, just answered each point made. :)

Can you say what MAP and rpm is required to make 65% power?

If you can make this all happen, your next problem will be making enough of them!
Based on calculation and similar to what has been observed in testing, about 29 inhg and about 5800 to make about 170hp. This assumes about FAA standard day at sea-level and is also about what the non turbo version does on a SAE standard day installed in a car with emission controls, etc. The non turbo version has half a point higher compression.

I hope so!
 

rv6ejguy

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Based on calculation and similar to what has been observed in testing, about 29 inhg and about 5800 to make about 170hp. This assumes about FAA standard day at sea-level and is also about what the non turbo version does on a SAE standard day installed in a car with emission controls, etc. The non turbo version has half a point higher compression.

You'd run at 5800rpm in cruise? I'd expect around 4000-4500 rpm and 35-38 inches MAP for less stress, better VE and BSFC. That means pressure ratios of 5 to 5.4 at 35K. I'm not aware of any turbos which reach these PRs and if they did, compressor efficiencies would be pretty low up there and the surge margin would be pretty low as well.
 

Vigilant1

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The 1020 ft/min single engine climb is what I calculated. The two engine rate of climb should be about 2850 ft/min. I think the 2285 was a typo.
Mark, thanks for the clarification. With a clean design and adequate span, 55hp seems reasonable.
Yes, there is less asymmetrical thrust than conventional light twins due to reduced prop spacing.
With the listed stall speed and the relatively closely spaced props, it seems it would be practical to achieve a VMC that is lower than VS1 (via mild engine canting off centerline, sufficient rudder authority, etc). In my opinion, that would go a long way to improve the engine-out safety of any twin design.
 

aeromomentum

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Mark, thanks for the clarification. With a clean design and adequate span, 55hp seems reasonable.

With the listed stall speed and the relatively closely spaced props, it seems it would be practical to achieve a VMC that is lower than VS1 (via mild engine canting off centerline, sufficient rudder authority, etc). In my opinion, that would go a long way to improve the engine-out safety of any twin design.
Yes, one of the design ideas was to make Vmc lower than Vs1 even lightly loaded. Mainly by rudder authority.
 

aeromomentum

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You'd run at 5800rpm in cruise? I'd expect around 4000-4500 rpm and 35-38 inches MAP for less stress, better VE and BSFC. That means pressure ratios of 5 to 5.4 at 35K. I'm not aware of any turbos which reach these PRs and if they did, compressor efficiencies would be pretty low up there and the surge margin would be pretty low as well.
I think you answered your own question. Yes, we would get slightly better VE and BSFC at a lower RPM. But the BMEP would be higher and it would require higher pressure ratios. I am also not aware of any turbos that efficiently reach these pressure ratios. So we use a little less manifold pressure and a little higher RPM and we can get better turbo efficiency without the need for the higher pressure ratio. You are correct that surge margin becomes an issue at altitude and higher pressure ratios.

So like anything in the world, the RPM, power and pressure ratio are compromises. We chose a higher RPM so the other 2 would work.

Also keep in mind that even with the 5800rpm at cruise the total piston travel over 2000 hours is still well less than that of this engine in a car over it's normal lifetime.
 

rv6ejguy

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169hp and 66lbs./hr (11 gph) equates to .39 BSFC. I can't see how that will happen at 5800 rpm with this engine. The VE has dropped up there and the frictional losses are much higher there than at say 4000-4500. I certainly don't operate my turbo engine like this as the fuel burn goes sky high. Tried that once for a speed run at 16,000 feet.
 

blane.c

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In the round motor world of my experience we cruised with two inches more than the abbreviated RPM so 2000 RPM 22 inches, 2200RPM 24 inches we were taught not to be square and especially not to be under square. We were taught that if the pressure was insufficient the rings would float and the upper ring lands would break off the pistons, damaged pistons were brought to class for us to look at. So obviously there is not a direct correlation between an engine with a RPM basically double as for sure 5800RPM and 60 inches is a bit unrealistic on the one hand but it seems to me that there has to be a correlation between a faster turning engine and manifold pressure that makes more sense to me on the other hand.

PS, I remember there also being a discussion about insufficient manifold pressure allowing the propeller to walk as well which put additional strain on a list of other components.
 
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Island_flyer

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I love the visibility, especially for the front seat occupants. Forward, up, and down. Easy to enjoy the scenery in cruise, as well as seeing other aircraft in the traffic pattern. Entry and exit for the pilot(s) might be a squeeze, though I managed it in the Partenavia P.68C for years. If there’s no center pedestal in the way it should be OK.
 

aeromomentum

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169hp and 66lbs./hr (11 gph) equates to .39 BSFC. I can't see how that will happen at 5800 rpm with this engine. The VE has dropped up there and the frictional losses are much higher there than at say 4000-4500. I certainly don't operate my turbo engine like this as the fuel burn goes sky high. Tried that once for a speed run at 16,000 feet.
The SFC map I was provided is in metric units and this is not exactly on a contour but interpolating and converting it is showing about .39. Best is shown at .37 but we can not practically operate in that area. In any case at least for this engine and at these power and RPM levels the fuel burn is not greatly increased. Increase the RPM to 7000 or the BMEP substantially and then the fuel burn does increase substantially. That being said, we are not using the factory system so their maps and numbers do not directly apply even if they help us know what should be possible.

If you want to see what you can do with the tuning of this engine and also the numbers you can produce with your system I will ship an engine to you next week. I would love to use your engine management system. I think many pilots would more confidant with your system set up with your expertise and experience.
 

rv6ejguy

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The SFC map I was provided is in metric units and this is not exactly on a contour but interpolating and converting it is showing about .39. Best is shown at .37 but we can not practically operate in that area. In any case at least for this engine and at these power and RPM levels the fuel burn is not greatly increased. Increase the RPM to 7000 or the BMEP substantially and then the fuel burn does increase substantially. That being said, we are not using the factory system so their maps and numbers do not directly apply even if they help us know what should be possible.

If you want to see what you can do with the tuning of this engine and also the numbers you can produce with your system I will ship an engine to you next week. I would love to use your engine management system. I think many pilots would more confidant with your system set up with your expertise and experience.

I haven't seen any SI turbo auto engine which can do .37-.39 BSFC at 5800 rpm with these CRs but perhaps I'm behind the times. Maybe at 50% power and half that rpm. I see nothing special with this engine, pretty standard 86 X 86mm, 2L , 4 valve engine.

I'd love to run this engine on my test stand but have zero time for this sort of fun any more unfortunately. Already working 60 hour weeks trying to keep up with a 10 week order backlog.
 
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aeromomentum

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Looks like large sail area in front of the cg. How did the RC model fly on one engine?
Yes it does. But using three methods including CFD it does not appear to be an issue all the way to 90 degrees. We have not yet built an RC model and due to the power to weight/size ratio of a model this is less likely to be an issue on an RC model even if it is in fuel scale. While it also concerns me when looking at the drawings, the numbers show plenty of margin. Also 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.
 

BBerson

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My first design was a twin pusher. Of course, it was overweight, underpowered and had severe aft cg with both engines on the back. And it was a one seater. The aft cg contributed to yaw instability with the increased forward sail area and less aft. Yes, the Avanti looks odd, but that canard must allow a more forward cg. The business jets look odd also, but the engines are closer to center.
And many of those jets get ventral fins added after testing. I would add some extra vertical area just to be sure. There might be something that can't be simulated.
 

Vigilant1

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Yes, one of the design ideas was to make Vmc lower than Vs1 even lightly loaded. Mainly by rudder authority.
Great, I hope that works out. If Vmc can be kept below Vs1 even with the dead prop unfeathered (i.e. no "dead engine" appraisal and emergency action required by the pilot, the plane can be flown down to Vs1 if both throttles (incl dead engine) are just pushed to the firewall and rudder used naturally to manage yaw), it will add a lot of safety.
 
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