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  #61  
Old 09-11-2008, 05:23 AM
JetA4GA JetA4GA is offline
 
Join Date: Aug 2008
Location: Ontario, Canada
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My understanding is that yes the air loads are dependent on your EAS, but the higher is your TAS the higher the disturnavce frequency your airframe is exposed to and therefore the closer you get to its natural frequency where you find flutter.

FG
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  #62  
Old 09-11-2008, 06:06 PM
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rvbuilder2002 rvbuilder2002 is offline
 
Join Date: Jul 2005
Location: Hubbard Oregon
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Quote:
Originally Posted by rbibb View Post
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.....
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
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Hubbard, Oregon
RV-6A (aka "Junkyard Special ")
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  #63  
Old 09-16-2008, 03:56 PM
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rv6ejguy rv6ejguy is offline
 
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It should be noted that not all aircraft have the Vne based on flutter margins. Air loads on the structure and windshield determine Vne for quite a number of aircraft and are therefore rated in IAS.
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Turbo Subaru EJ22, SDS EFI, Marcotte M-300, IVO, Shorai- RV6A C-GVZX flying from CYBW since 2003- 441.0 hrs. on the Hobbs,
RV10 95% built- Sold 2016
http://www.sdsefi.com/aircraft.html
http://sdsefi.com/cpi2.htm


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  #64  
Old 10-08-2008, 06:11 PM
delusional delusional is offline
 
Join Date: Oct 2008
Location: Boston area
Posts: 128
Question 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?
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  #65  
Old 10-08-2008, 08:50 PM
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rvbuilder2002 rvbuilder2002 is offline
 
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Quote:
Originally Posted by delusional View Post

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?

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.

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.
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Opinions, information and comments are my own unless stated otherwise. They do not necessarily represent the direction/opinions of my employer.

Scott McDaniels
Van's Aircraft Engineering Prototype Shop Manager
Hubbard, Oregon
RV-6A (aka "Junkyard Special ")
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  #66  
Old 01-21-2017, 08:45 AM
rongawer rongawer is offline
 
Join Date: Dec 2007
Location: Brentwood, CA
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Default 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.
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  #67  
Old 01-21-2017, 11:26 AM
bhughes bhughes is offline
 
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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)

Last edited by bhughes : 01-21-2017 at 11:37 AM.
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  #68  
Old 01-21-2017, 11:43 AM
Kyle Boatright Kyle Boatright is offline
 
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Location: Atlanta, GA
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Quote:
Originally Posted by bhughes View Post
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)
I'd love to hear more about your Renesis installation.
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  #69  
Old 01-21-2017, 10:58 PM
N427EF N427EF is offline
 
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Quote:
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.
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.

Quote:
Love the 93 oct pump gas even with 10% ethanol.
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.
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  #70  
Old 01-22-2017, 05:56 AM
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rzbill rzbill is offline
 
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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.
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