Aren't all V-speeds indicated rather than true?
Many aircraft Vnes are IAS but Vans are all TAS because of flutter concerns. This is the concern with turboed Vans designs.
Van's Air Force
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RV-10 with a Lycoming TNIO-390-X Turbo Engine
- Thread starter RV9AFlyer
- Start date
Many aircraft Vnes are IAS but Vans are all TAS because of flutter concerns. This is the concern with turboed Vans designs.
Turbos can be very reliable. There is almost no diesel applications left that do not include a turbo. Aircraft turbo-charging is closer related to diesel applications than racing car applications. Sub milisecond throttle response is not required so the turbine can be a larger diameter and therefore rotate at much more reasonable RPM's and allow dependability like diesel applications.
I have wondered if EGR could not be used effectively in aircraft. It would allow control of Turbine Inlet Temperature and allow continuous boost without worrying about detention as much. This is used in for this purpose in modern auto control systems.
Bob Parry
I have wondered if EGR could not be used effectively in aircraft. It would allow control of Turbine Inlet Temperature and allow continuous boost without worrying about detention as much. This is used in for this purpose in modern auto control systems.
Bob Parry
Turbos are very reliable these days, it is the control and exhaust systems that must be done right and often aren't.
Diesel turbos have an easy life from a temperature point of view due to the much lower EGTs however many Diesels run 20-45 psi (yes that's 70-120 inches hg Ab.) So they are generally spinning much faster.
Most gasoline engines in GA aircraft rarely run over 40-45 inches and that is only for takeoff. The only times the turbos are working hard is way up high (18,000 feet plus) where the pressure ratios and N1s get up there.
EGR is mostly used at part throttle conditions in automotive engines as it causes a substantial power loss at WOT. EGTs and turbine inlet temps are best controlled by proper spark timing and mixture via careful manual management or FADEC.
We do try to match relatively large turbine wheels and large turbine A/R ratio housings to get the least amount of backpressure and consequent charge dilution per unit torque delivered and match compressors carefully for the lowest compressor discharge temps at the typical mission altitudes and power settings.
For the Sport Class engines, much experimentation in the ADI areas has shown huge benefits.
Anybody knows if an GVT (Ground Vibration Test) has been performed on any RVs ?
If not, the cost could be distributed over a group (don't need many to bring the cost to low levels) of RVers that would want a certain configuration on a given RV Model; The unit cost for the GVT would then represent only a small amount of the turbocharged powerplant cost; This would also save a lot of electronic ink, and have the merit of providing real numbers not just "maybe I think that could be a problem".
Anyhow, consideration should be given to the new TIO-360-EXP: 185 HP @ 2700 RPM and 31.0 in Hg, Rated Power to FL250; It also has 8.5:1 pistons to retain as much SFC from the naturally aspirated IO-360 parallel valve 180 HP; Weighs around 350 lb complete except for the tail pipe.
If not, the cost could be distributed over a group (don't need many to bring the cost to low levels) of RVers that would want a certain configuration on a given RV Model; The unit cost for the GVT would then represent only a small amount of the turbocharged powerplant cost; This would also save a lot of electronic ink, and have the merit of providing real numbers not just "maybe I think that could be a problem".
Anyhow, consideration should be given to the new TIO-360-EXP: 185 HP @ 2700 RPM and 31.0 in Hg, Rated Power to FL250; It also has 8.5:1 pistons to retain as much SFC from the naturally aspirated IO-360 parallel valve 180 HP; Weighs around 350 lb complete except for the tail pipe.
If someone was to validate higher flutter margins through GVT or actual flight testing, that would clear the way for turbocharging the 10 and getting some better speeds up high. I know Van's might not like it but with the right testing, it would be nice to be able to get SR22T or Columbia speeds at least.
The new Mooney is really impressive and shows what decent turbocharging can do- it's faster than an old C90 King Air by a good amount.
The new Mooney is really impressive and shows what decent turbocharging can do- it's faster than an old C90 King Air by a good amount.
flyeyes
Well Known Member
Van's commisioned a GVT analysis of the RV-8 after the loss of N58RV about 10 years ago.
Clipped from the NTSB report:
If you care about resale value, you should buy a Bonanza. If you're building an expirimental, make it the way you want. That's why we do it. Go for it!!!
Make mine a TNIO 390
If you live in high mountainous terrain, the TNIO 390 would be the ticket. More hp than the 540 at the 10,000 runway DAs found in the summer in the west. Better climb (more power and less weight) that you need to get out of the high mountain valleys where climbs to 14k or more and wind related downdrafts are common. Still plenty of power for sea level takeoffs.
I know mine is a specialized application but I think not so uncommon based on the number of RVs I see in Colorado.
If you live in high mountainous terrain, the TNIO 390 would be the ticket. More hp than the 540 at the 10,000 runway DAs found in the summer in the west. Better climb (more power and less weight) that you need to get out of the high mountain valleys where climbs to 14k or more and wind related downdrafts are common. Still plenty of power for sea level takeoffs.
I know mine is a specialized application but I think not so uncommon based on the number of RVs I see in Colorado.
rbibb
Well Known Member
I'm no aerodynamacist but wouldn't it make sense to relate flutter to IAS? After all IAS is what the airframe "sees" in terms of the atmosphere as the ASI reads the guage pressure for the particular air conditions experienced at the time. Similar to how density altitude is what the airframe sees and determines lift produced at various angle of attacks, airspeeds, etc.
Of couse TAS and IAS are directly related - for one set of air pressures, temperatures, dew points, etc.....
Of couse TAS and IAS are directly related - for one set of air pressures, temperatures, dew points, etc.....
Most pilots think that indicated airspeed should be relevant to flutter resistance but the truth is, it is not (not directly anyway). This is not just for RV's, it is the case for all aircraft (though some have used indicated airspeed factored against density altitude for the pilot to determine if he is still in the safe zone).
The airspeed indicator measures dynamic pressure. This pressure directly corrects for stall speed at different density altitudes, etc. Knowing this, pilots often assume it would do the same for VNE as it correlates to flutter but it does not.
Flutter resistance is in part reliant on the pressure of the air flowing on the skin surface of a control surface to give it resistance to being displaced. This helps prevent the control surface from fluttering at its natural resonant freq.
If you are flying at a true airspeed higher than VNE, but at a low indicated airspeed (high altitude flight with a turbo), the high true airspeed gives you an even higher flow velocity over the surface of the control surface than is typical without a Turbo, but at a lower dynamic pressure (indicated airspeed) to help the surface resist flutter.
In this flight mode you are possibly much closer to flutter than you would be at lower altitude but indicating very near VNE.
VNE is the one flight dynamic that doesn't correlate directly to indicated airspeed. Some aircraft have charts to factor indicated indicated airspeed against density altitude (high altitude sailplane flight for example).
I think this is so misunderstood, because the aircraft most of us fly do not have the ability to fly at altitudes where it is an issue. The few general aviation aircraft that are capable, have likely been designed and tested specifically so that they have a safe margin from flutter in these conditions. RV's were not designed for high altitude nor have they been tested for it. Anyone flying at high TAS at high altitude in an RV is flying an experimental to the fullest meaning of the word. You may be ok, but you really have no way of knowing how close you are to the limit with out some very extensive and technical testing.
A good article for a more detailed description can be found here
http://www.vansaircraft.com/pdf/hp_limts.pdf
delusional
Well Known Member
can't let a sleeping dog...
So it sounds like the consensus is that the Lycoming 0-390 and it's four-cylinder relatives are potential candidates for the RV-10.
My question is this; Will the standard mount, cowl etc. work with the 0-390 or will some custom work be required? How about the spinner?
I'm thinking that the CG is not an issue since the battery can move forward if necessary.
What is to be gained? Payload! at 2700# and 210hp even with a fixed pitch prop takeoff performance should be at least as good as a Grumman Tiger, maybe better, based on very similar power and wing loading. But I figure I could save about 100# over a six cylinder.
Who cares? Really fat people, like me for example... Especially if I want to fit my lovely(and not real thin) wife and a couple fat friends. The extra 100# means I don't have to offload an hour of fuel. And I hadn't thought of the turbocharger... What do you figure that will cost in weight? But then you need oxygen, too, and so add some training for us lowlanders...
So, can anyone see any downside to this not mentioned above in this thread? And have I missed any other particularly pertinent threads on this question? And what would Van say?
So it sounds like the consensus is that the Lycoming 0-390 and it's four-cylinder relatives are potential candidates for the RV-10.
My question is this; Will the standard mount, cowl etc. work with the 0-390 or will some custom work be required? How about the spinner?
I'm thinking that the CG is not an issue since the battery can move forward if necessary.
What is to be gained? Payload! at 2700# and 210hp even with a fixed pitch prop takeoff performance should be at least as good as a Grumman Tiger, maybe better, based on very similar power and wing loading. But I figure I could save about 100# over a six cylinder.
Who cares? Really fat people, like me for example... Especially if I want to fit my lovely(and not real thin) wife and a couple fat friends. The extra 100# means I don't have to offload an hour of fuel. And I hadn't thought of the turbocharger... What do you figure that will cost in weight? But then you need oxygen, too, and so add some training for us lowlanders...
So, can anyone see any downside to this not mentioned above in this thread? And have I missed any other particularly pertinent threads on this question? And what would Van say?
Mount wouldn't work. Cowl might work (carb or fuel servo would be a lot further fwd and may not interface with induction scoop correctly). Spinner would work.
As for comparing to a Tiger...I have flown a tiger. It is not much of a 4 place (big adults) airplane anywhere other than the flat lands. At higher density altitudes I consider it at the most a three place or a two place and bags airplane. Particularly when comparing to teh performance that RV-10's typically get.
I agree that an RV-10 at full gross with 210 HP would be somewhat similar to a tiger in performance so with that being the case, why not just by a Tiger. You could save $60K or more, and a number of years of work. I realize there are other benefits to building, such as the use of all the great equipment not approved for certificated aircraft, a new airplane instead of well used, do your own maint., etc.; but if you really want an RV-10 for the same reason most people want one...for performance that you can't come even close too for the same dollar investment...then you need to build one with 260HP.
TNIO-390-X Price
Do you have a price for this setup? I like the idea of a turbonormalized system, or even Forced Aeromotives's supercharger, on a smaller engine. Let's face it, it's worked well for car manufacturers of recent years producing greater efficiency.
Using the 3% rule of thumb, an RV-10 with an IO-540 will have about 195hp with full throttle at 8,000 feet. So it stands to reason that an engine that can maintain that 200hp up into the teens will perform very well and provide the same climb rate consistently up to cruising altitude. The only way to get that is to either start of with a lot more horsepower (like the ACE 568 engine that is a bit of a firebreather at ~370hp) or go with turbonormalizing of some sort.
I'd be happy to see either methods work. Incidentally, that 200hp at 16,000 feet will get you more like 180 KTAS (208 SMPH), resulting in overall better economy and block times.
Do you have a price for this setup? I like the idea of a turbonormalized system, or even Forced Aeromotives's supercharger, on a smaller engine. Let's face it, it's worked well for car manufacturers of recent years producing greater efficiency.
Using the 3% rule of thumb, an RV-10 with an IO-540 will have about 195hp with full throttle at 8,000 feet. So it stands to reason that an engine that can maintain that 200hp up into the teens will perform very well and provide the same climb rate consistently up to cruising altitude. The only way to get that is to either start of with a lot more horsepower (like the ACE 568 engine that is a bit of a firebreather at ~370hp) or go with turbonormalizing of some sort.
I'd be happy to see either methods work. Incidentally, that 200hp at 16,000 feet will get you more like 180 KTAS (208 SMPH), resulting in overall better economy and block times.
I have 320 hrs on my super charged renesis. About 210-220 hp. Full fuel, two adults and baggage performance is close to vans 210 hp numbers. Add a passenger in 90F OAT and climb performance is poor but way better than a typical spam can. Love the 93 oct pump gas even with 10% ethanol.
RV10. N416AS. (Working on turbo swap)
RV10. N416AS. (Working on turbo swap)
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Kyle Boatright
Well Known Member
I'd love to hear more about your Renesis installation.
Are you proposing to run your 390 at 100% at all times?
Can't imagine that kind of engine treatment would result in trouble free operation to TBO.
A 540 running at 195 hp (75%) will go all day, every day and not be anywhere near operating limits.
I use the same kind of gas in my IO 540 and just like all the avgas burners, I run 170kts at 10,000 feet on 11GPH sipping 91Octane E10.
It's very hard to beat the IO-540.
rzbill
Well Known Member
My take on the turbo 210 vs NA 260 is that I would seriously consider it if my home base was at altitude. Back of the napkin calcs say the turbo 210 would lag in climb by roughly 500 fpm at sea level. This agrees with an earlier post relating the climb of an actual 210 hp installation.
Using US std atmosphere, the climb rates become equivalent at approx 6000 ft and the turbo leads above that.
So. The closer I lived to 6k, the more I would think about it.
In regards to cruise. If one decides to use 75% on the 210 turbo, 13000 ft is where the turbo catches the NA 260.
Doing my own FW Fwd including engine mount would not scare me off as long as one had a stock rv10 avaliable to measure to find the spinner position and angle relative to the airframe.
Using US std atmosphere, the climb rates become equivalent at approx 6000 ft and the turbo leads above that.
So. The closer I lived to 6k, the more I would think about it.
In regards to cruise. If one decides to use 75% on the 210 turbo, 13000 ft is where the turbo catches the NA 260.
Doing my own FW Fwd including engine mount would not scare me off as long as one had a stock rv10 avaliable to measure to find the spinner position and angle relative to the airframe.
