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Why not a TSIO 540

Nathan Moon

I'm New Here
Just wondering if anyone has done this. With O2 and cruise in the teens I would think that you could get speeds approaching 190 knonts true.
 
Because no one makes a TSIO-540...


Ohhhh you meant a TIO-540. Like a Mooney Bravo engine? Other than Van's utter hate for anything complex (TURBO??? OMG complexity!!) It's probably work OK. Of course, all the usual naysayers will cut in now. Also consider the setup from a T-182 (235HP) or a Turbonormalized IO-390 as options...
 
Dont need the 'T'

Nathan Moon said:
Just wondering if anyone has done this. With O2 and cruise in the teens I would think that you could get speeds approaching 190 knonts true.

You dont need the "t" to make 190TKAS+ in the teens.
 
MCA said:
Who makes a turbonormalized IO-390?

Turbonormalizing just means you take a normally aspirated engine and add a turbo system that keeps the manifold pressure a sea level up to it's critical altitude. Tornado Alley Turbo makes STC'd turbonormalizing kits for certificated aircraft, you could buy the same components that the C-177RG kit has (IO-360 A1B6) for the IO-390.

http://www.taturbo.com/
 
The article the last poster references has to do with flutter at altitude. In a nutshell, Vne is based on true airspeed, not indicated airspeed. Your indicated airspeed is about 2% low for each 1000 feet of altitude. Go up 12K feet at full throttle and put the plane in a 1000ft/min descent and you will exceed Vne and risk control surface flutter. (In the article that's what happened to the author). Potential catastrophic failure. Now put a turbo on, at 12K instead of the MP of 18-19 inches with a normally aspirated engine, you are now getting up to 30 inches! You may be at Vne in cruise, put it in a dive and OMG!

And have you seen how tight the IO-540 is? There may be more room if you go with a 360 or 390 with a turbo. But you will have to give up take off power going with the smaller engine. It's true that at altitude you will have the power of the IO-540 with a TIO smaller engine. The only other debate is fuel economy. From what I have read a IO-540 producing X HP uses about the same amount of gas as a TIO-360 producing X HP, it's just a bit heavier.
 
Turbo in an RV-10

O.K., I can understand the concern about putting too much stress on a light RV airframe by pushing it past the Vne. And you do mention a 1000 foot per minute dive. Then you go to the manifold pressure and IAS and TAS.

My questions are these: Resolved: a 1000/min. dive will put an RV past it's Vne, but what does manifold pressure have to do with anything? Don't forget, the 7 & 8 are already rated for 200 H.P. so I don't see why a dive at one manifold pressure should be different than another as far as surface flutter is concerned. As for IAS, TAS: I plan an RV with a full glass cockpit, why would I worry about inaccuracies or conversion calculations for steam gages?

The turbo-normalized engine is to get me in and out of mountain valleys briskly and also allow me to cruise at altitude with 55-60% power. It has nothing to do with dives or loops which I can just as easily perform without a turbo. I think that VANS is worried that pilots will take their aircraft past Vne in straight and level flight and that an RV is just not designed for that kind of stress. I believe a prudent pilot can manage that risk.

As I have been unable to find a suitable alternative for the kind of mountain flying I like to do, so the TNIO 390X it will have to be. I very much hope I'm right.

Richard Vidaurri
You seem to be arguing from the point of view of a 2 place RV.
Otherwise, I would ask if you have ever flown an RV10. With the 260 hp IO540 you are talking 1500-1800 fpm climbs, and you want more?
Apparently you think you will be able to have an accurate TAS displayed.
If you want to bet your life on it, be my guest.
Problem is you don't really know the design Vne vs the flutter margin, especially if you choose to ignore Ken Krueger's article, so you don't really know what your never exceed speed really is.
Keep in mind that jets with glass cockpits still use a barber pole to depict a max operating speed that changes with altitude. Basically with the RV-10, if you achieve more power than the normally aspirated 260 will at altitudes over 10,000 you will have no flutter margin. Or, you want 300 hp so that you can throttle back to 195, to somehow get better efficiency than running the stock engine at 75%? Good luck with that.
 
Since each airplane is unique and not built to a type certificate it could be argued the flutter margins for each airplane are unknown. A conservative number provided by Vans is a nice thing to follow. Possibly prevents stumbling into the unknown, maybe.

Out of the approaching 6,000 RV's out there I'm not aware of any losses to flutter. Who wants to be the first? I'm aware of one RV that exceeded 325 mph true (don't ask). Did not explode, but perhaps another one would. That's about what it amounts to, flutter, explode, like the shuttle with plasma burning into the wing. Drama, yes, but the point is don't build a plane that can easily go there. You might not do it but the next owner very well could.
 
I'm thinking that Van's has tested his airframes to +10% over the stated Vne. Of course your particular airframe may not exhibit the same margins.

Richard's intent was to cruise at 55-60% power at high altitude, little different than than say 75% at 8500 feet or so.

You won't be climbing at 1500 fpm in an atmo 540 RV10 at 12000 feet at gross.

I'm wondering how many posting here have hit a real downer in the mountains? Climb performance can save your life here.

You don't need glass to tell you TAS either, just buy the ASI with the temp and altitude scale you can adjust to read TAS right there. If you can't do this, then certainly don't fly a turbocharged RV.
 
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When I mentioned manifold pressure at altitude I was stating that you could have a MUCH higher MP at 12K with a turbo than a normally aspirated. That directly translates to higher TAS, very easily getting you over Vne if put in a 1000ft/min dive. The only advantage I see is if you were up at that altitude and you hit a very heavy downdraft that you needed the 1500ft/min climb rate at 12K that a TIO-540 would give. Everything else about it would be negative, initial cost, increased maintainence, reduced TBO, and good luck trying to stuff it into the cowling. If you put a TIO-390 you might be losing the increased climb an IO-540 would give at sea level take offs, a much more likely scenario. A 310 HP IO-540 would give you more HP at altitude with less of the turbo negatives. The cheapest alternative for the need for the only occaisional increase in HP at altitude would be a NxO (nitrous) system, relatively cheap and you'll see a **** of a boost only when needed!
 
Topic drift outside RV-10

My post would have made much more sense had I clarified that I was interested in an RV-7A or 8A. I've never even seen an RV-10. Personally, I'm not certain I'll be able to have an accurate TAS but Insight Avionics says I will - so I'll be your guest.


But all is well. After much discussion and research I have concluded that the RV is just not the plane for what I want to do. I love it and I wish I could afford two aircraft but I can't.

So there.



Best,

Richard Vidaurri

Yes, the failure to communicate is right. :( You are on the RV-10 list. The RV-10 is a 4 place, non-aerobatic design using a 260 hp IO540. The topic was a turbocharged IO540 or TIO540.
So all of your post was a non-sequitor. All of Vans designs have exceptional climb performance with normally aspirated engines.
Perhaps you would be happier with a Harmon Rocket or equivalent?
 
On the Vans site there is small piece about 60 RV-6s that they sold to the Nigerian Air Force. These are now that branch's primary trainer for it's pilots.

But how did he do it? Doesn't it seem to you impractical to train jet pilots in an airplane that has such a narrow Vne margin? He talks about making some aerodynamic alterations but doesn't say what those were. Do you have any idea? Does anyone?

Best,

Richard

Van's sold kits to another company that under contract built them for the Nigerian Air Force so Van's was just a parts supplier.

The airplanes are a primary trainer as you said which means that are teh very first airplane that the students ever fly. Primary trainers don't have to fly at jet speeds. Cubs, Champs, and even C-172's have been used as primary trainers for military pilots in the past.
 
This makes sense but maybe they did something else. Somewhere on these forums a pilot was saying that he thought counter-balancing the rudder on an RV would improve the Vne margin. Any thoughts on this?
I think I would build the aircraft as designed by Van, and remain within his recommended Vne.

Flutter has caught a lot of very experienced people by surprise in the past, as it is very difficult to predict.

Case study: Back in the 1980s, Boeing got caught by surprise by flutter on the prototype of the E-6 TACAMO aircraft, which was a modification of the 707. They had vertical tail flutter, and lost about half of the vertical tail surfaces, but managed to get back to the airport. I would assume that Boeing then did a big flutter investigation, including ground vibration testing. They fixed the aircraft, repeated the flutter test, and lost half the vertical tail again.

If a company with all the resources of Boeing can't reliably predict flutter margins, I wouldn't put too much weight on the opinion of some random guy on the web about the effect on flutter margin of some mod.
 
Yeah, I visited with a guy...

....last Friday (near Beaufort, S.C.) who experienced flutter and total wing disintegration on his Cassutt, back in the late 60's. His name...a well known Nick Jones of F-1 fame and early PRPA member with several speed records to his credit in his White Lightning.

He was making the required test flight, pulling 6 g's and then diving it to 10% above max straighline WOT speed when the ailerons fluttered and the wooden, mahogany skinned wing disintegrated. He bailed out and lived but it was close, very close since his 'chute didn't get a full canopy 'til near the tops of powerlines:eek:

Be safe,
 
I can see that there are good reasons to stay within the design parameters of the RV (-7A in my instance), but what then does Van do about aerobatics -especially loops?

Thanks,

Richard

Richard,

The manual recommends starting a loop from between 140 and 190 MPH, coming down the back side, you will be much slower than those speeds, so the trick is to pull the power off when going over the top as you come down the back side. When done correctly, you should not exceed VNE.

Here are the VNE numbers, in MPH, from my manual:
RV-4: 210
RV-6: 210
RV-7/8: 230
RV-9: 210

Section 15 of your builder's manual includes info on aerobatics.

Then again, don't take acro advice from a guy flying an RV-9.
(Before anyone asks, no, I have not looped my -9.)
 
I don't think its VNE you need to worry about...

My concern would not be the VNE of the aircraft, but the health of the occupants. A turbo normalised RV would easily climb to FL25 in around 10-15 minutes. At that climb rate you will probably get the bends unless you purge the nitrogen from your body by inhaling pure oxygen prior to flight etc,

As others have pointed out the turbo should not be an issue with VNE as long as you or your EFIS can calculate TAS correctly. An RV with normally aspirated Lycoming will easily exceed VNE on descent with power on so I don't see a major safety issue.

Regards
Richard

RV7A
 
Interesting

I have assumed that with a simple Dynon spitting out your TAS then you could just fly off of that number at altiude. I.e for the 7 at least simply don't exceed 200kts, If its starts to get bumpy reduce MP to 160.

I.e this is now a moot point..add as much power as you want at any alttude, just keep an eye on TAS.

Make sense?

Frank
 
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And make sure your TAS is actually your TAS.......... as I have found out, static is not always STATIC.......... 10-20 knots is a big deal in these cases!
 
While you have all been discussing the numbers and such, the first thing that ran to my mind was the fit of such an engine. I was just looking over the TEO540 at Lycoming's booth. I think the turbo is pretty much the same as the TIO540, and so you'd have a lump on the left side of your cowl plus some possible interference with the engine mount. The TEO is worse because you have some stuff on the accessory side to clear around the mount (plus a remote controller package that would have to go on one side of the firewall or another - I had already lost interest at that point and didn't stick around for details). So, I just don't see that all the extra effort would be worth it.
 
The article the last poster references has to do with flutter at altitude. In a nutshell, Vne is based on true airspeed, not indicated airspeed. Your indicated airspeed is about 2% low for each 1000 feet of altitude. Go up 12K feet at full throttle and put the plane in a 1000ft/min descent and you will exceed Vne and risk control surface flutter. (In the article that's what happened to the author). Potential catastrophic failure. Now put a turbo on, at 12K instead of the MP of 18-19 inches with a normally aspirated engine, you are now getting up to 30 inches! You may be at Vne in cruise, put it in a dive and OMG!

And have you seen how tight the IO-540 is? There may be more room if you go with a 360 or 390 with a turbo. But you will have to give up take off power going with the smaller engine. It's true that at altitude you will have the power of the IO-540 with a TIO smaller engine. The only other debate is fuel economy. From what I have read a IO-540 producing X HP uses about the same amount of gas as a TIO-360 producing X HP, it's just a bit heavier.

Vne in any aircraft except Van's apparently is IAS. IAS is what the airframe "sees", and there is no way that a certified manufacturer would specify calculated TAS as a Vspeed. I doubt the FAA would certify it as such.
 
Vne in any aircraft except Van's apparently is IAS.

Vne IS defined in terms of TAS (or combination of IAS and TAS) for a couple of certificated airplanes and most modern sailplanes to ensure that adequate flutter margins exist throughout the normal operating envelope. Instead of using a constant TAS Vne, some manufacturers define a decreasing IAS Vne with increasing altitude, basically mimicking the constant TAS value.

IAS is what the airframe "sees"...

For structural design speeds and most performance speeds that is correct, but not for flutter.

The conservative approach for flutter is to assume a constant TAS limit when the critical flutter mode(s) are either not known or not well understood. Some flutter modes have flutter speeds that follow a TAS line with increasing altitude. An example of these are the so-called "explosive" flutter modes, where there is a large decrease in aeroelastic damping for a small increase in airspeed. "Aeroelastic" damping is Structural Damping plus Aerodynamic Damping. Structural Damping is usually a constant, the value of which depends on the construction design and materials used in the structure.

Other flutter modes follow the so-called "half and half" speed line with increasing altitude, roughly midway between EAS (CAS/IAS for us non-Mach challenged RV's) and TAS. An example of these would be the so-called "hump" flutter modes, where there is a small decrease in aeroelastic damping for a large increase in airspeed. It is called a "hump" mode because it looks like a hump when plotted on an Airspeed vs Damping plot.

And some flutter modes follow more of an EAS line with increasing altitude.

The designer/manufacturer sets Vne to insure that the airplane will be flutter free and that proper margins of damping exist to Vne (with some margin) up to the Absolute Ceiling of the airplane. And that is whether Vne is stated as a constant IAS/CAS, constant TAS, or a combination of both. Also, just because a designer/manufacturer sets Vne as a constant IAS or constant CAS doesn't mean they have not taken flutter into account. It means that they just set Vne in terms of a constant IAS/CAS number that ensures that flutter will not occur within the operating envelope of the airplane.
 
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Vne IS defined in terms of TAS (or combination of IAS and TAS) for a couple of certificated airplanes and most modern sailplanes to ensure that adequate flutter margins exist throughout the normal operating envelope. Instead of using a constant TAS Vne, some manufacturers define a decreasing IAS Vne with increasing altitude, basically mimicking the constant TAS value.
.

What certified (GA) aircraft have ANY Vspeeds in TAS? I have never seen one. I am not absolutely sure they do not exist, but I have never seen one. Obviously I have not seen every aircraft.

I understand that it is a conservative approach.

I was merely responding to the statement that Vne IS a TAS measurement. AFAIK, only in Van's
 
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What certified (GA) aircraft have ANY Vspeeds in TAS? I have never seen one. I am not absolutely sure they do not exist, but I have never seen one. Obviously I have not seen every aircraft.

I understand that it is a conservative approach.

I was merely responding to the statement that Vne IS a TAS measurement. AFAIK, only in Van's

You are correct: type certificated aircraft are required by part 23 to specify limiting speeds in IAS, presumably because many such aircraft have no direct display of TAS. However, the manufacturer may placard the aircraft with different limits in IAS as a function of altitude - which may be essentially the same as a single TAS number! Staying out of flutter trouble can be complicated. I personally wish Vans had followed part 23 here (which they are not legally obligated to do) and published an IAS vs Altitude chart for Vne, just to avoid all these posts.
 
Here's your chart:

i-t32pVQR-M.jpg
 
You are correct: type certificated aircraft are required by part 23 to specify limiting speeds in IAS, presumably because many such aircraft have no direct display of TAS. However, the manufacturer may placard the aircraft with different limits in IAS as a function of altitude - which may be essentially the same as a single TAS number! Staying out of flutter trouble can be complicated. I personally wish Vans had followed part 23 here (which they are not legally obligated to do) and published an IAS vs Altitude chart for Vne, just to avoid all these posts.

THe manufacturer can placard many things. I have never seen a placard indicating a reduction in Vne with altitude. The only Vne I have EVER seen in any GA aircraft is the little red spot on the ASI. Can you provide an example?
 
THe manufacturer can placard many things. I have never seen a placard indicating a reduction in Vne with altitude. The only Vne I have EVER seen in any GA aircraft is the little red spot on the ASI. Can you provide an example?

A Cirrus SR22T has a Vne of 205 KIAS below 17,500 feet, decreasing linearly to 175 KIAS at 25,000 feet. There is a cockpit placard for this.

The Columbia 400 / Cessna TTX has a Vne of 235 KIAS, minus 5 knots per 1000 feet above 12,000 feet pressure altitude. It's been a while since I've flown one, but I seem to recall a cockpit placard in addition to the limitation in the POH.

And of course various helicopters have Vne speeds that similarly vary with altitude, but that's due to aerodynamic phenomena not applicable to airplanes!
 
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THe manufacturer can placard many things. I have never seen a placard indicating a reduction in Vne with altitude. The only Vne I have EVER seen in any GA aircraft is the little red spot on the ASI. Can you provide an example?

It's very common on turbocharged piston GA airplanes. Turbines too for that matter, but they generally have a 2nd needle on the ASI that's known as a barber pole that decreases with altitude.
 
And of course various helicopters have Vne speeds that similarly vary with altitude, but that's due to aerodynamic phenomena not applicable to airplanes!


I believe it’s due to the TAS of the retreating blade and retreating blade stall, right?

Plus the various keys and turbo props that have a moving barber pole that comes down with altitude.. it’s very short sighted for someone to say that Vans are the only planes that have a TAS limitations.
 
Vne in any aircraft except Van's apparently is IAS. IAS is what the airframe "sees", and there is no way that a certified manufacturer would specify calculated TAS as a Vspeed. I doubt the FAA would certify it as such.

To put it simply if flutter is not an issue within the design limits of the aircraft at a desired max IAS speed you can use IAS. If testing shows an airframe has sufficient strength at 175 Knots and no occurrences of flutter to the surface ceiling of the aircraft at 175 KIAS then there is no need for true airspeed use.
Now put a bigger engine or a turbo on it and fly it to a higher altitude. The airframe will still have the strength required for air loads but might have a flutter issue at those altitudes with the higher TAS. In this case you need to use TAS as the max. Some higher performance GA aircraft continue to use IAS but require IAS Airspeed reductions as the aircraft climbs. Essentially a poor man’s TAS limit.
 
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