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Turboprop 10?

"...You get little to no warning and it's usually it happens very fast..."

Yep, and in a divergent mode, the next thing that happens is a flight control failure and then, well, you get the picture...:eek:

I would take a "double gyro failure" any time over the loss of a control surface...

I'll say it again, flutter is nothing to mess with and the TLAR approach when dealing with it is likely to end up...not so good...
 
To answer questions and clear some misunderstandings; Yes VNE in the RV10 is 230 MPH ( INDICATED ) is the key word here!! Remember as Alt goes up indicated A/S goes down because thinner air. Just as the Citation's I fly the VNE is 267 KTS but at 35K the indicated is about 180, true is 390 !!! As with the Citation, the RV10 with a turbine WILL bust VNE below a certain Alt.

This statement does not clear up a misunderstanding, it actually causes more.
It can not be said as a general statement that applies to all aircraft.
Please read the document linked to from THIS post at the beginning of this thread.
 
I swore I would not get drawn into this again, but I cannot help myself....

Indicated airspeed (IAS) is not a real speed, but a parameter defined as True Air speed (TAS) times the square root of the normalized (that is, divided by sea level air density) air density. One can always solve this definition for either the TAS or the density, and substitute the result in an equation. For some equations, in particular the lift of a wing and the parasitic drag, which in general depend on TAS and density, such a substitution results in a fortuitous cancelation: the density disappears, and only IAS is left. Of course the lift still depends on density, it's just "hidden" inside the definition of IAS.

Now for aeroelastic flutter, the situation is much more complicated. Many modes of vibration are possible, with different dependencies on TAS and density. Making a substitution of IAS (and density) for TAS does not, in general, result in any fortuitous complete disappearance of one of the other variables. But if we know the functional form of the flutter equation for any given mode, then the following statements are ALL TRUE:
1. In general, the onset of flutter depends on density and TAS.
2. In general, the onset of flutter depends on density and IAS.
3. In general, the onset of flutter depends on IAS and TAS (this is awkward to use, but is nonetheless true).

Now this is awkward, so the next logical question is:
1. Can I look at all densities from sea level to the maximum operating altitude of an airplane, and specify a single TAS which, if not exceeded, will be safe? The answer is YES.
2. Can I look at all densities from sea level to the maximum operating altitude of an airplane, and specify a single IAS which, if not exceeded, will be safe? The answer is YES.

What do the FARs say for normally certified aircraft? The answer is option (2), the manufacturer is to specify a single IAS which is safe at all altitudes the plane is certified to operate;OR, a chart of density (expressed in density altitude) and IAS which is not to be exceeded must be placarded.
The reason for specifying IAS to be used is clear: that information is readily available in every airplane. The FAA does not think it reasonable that pilots be expected to pull out an E6B and spin the wheel, prior to every descent during which high speeds may be encountered. I note that the vast majority of certified aircraft meet this requirement without resorting to placards.

What about E-AB aircraft? Well, as usual, it is up to the builder, not Vans, to determine safe limits. But finding Vne requires dangerous testing, or very sophisticated analysis, not available to the majority of builders, so most use Vans' numbers. I note that Vans is under no obligation whatsoever to furnish these numbers, and I am grateful that as a responsible manufacturer he has chosen to spin test, load test, etc. his kits. However, I do find it strange and very inconvenient that (at least per a single article written by Ken and since referenced many times) he has claimed a single TAS number. This is contrary to what is done on every certified aircraft, and therefore is bound to cause confusion. It is also dangerous, because the average pilot does not think that way. Ken's article about turbocharging is a red-herring. In my plans-built 10 I certainly cannot exceed 200 KTAS at 18,000'. BUT, I can easily nose it over to come down, and watch the airspeed creep a bit into the yellow (not red) arc. But wait! I just exceeded 200 KTAS! At the published service ceiling of 22,000' I can do this while still within the green arc on the airspeed indicator. Do we really expect those with steam panels to be wheeling away on their E6Bs, prior to commencing a descent? I am sure more than one RV pilot has exceeded the red line if it is a TAS number because they were unaware of this "not the usual" stating of Vne. I really wish Van would release all his test data, and be more forthcoming of what combination of airspeeds and densities are considered safe, and what are not, and find a way to express them consistent with the FARs for certified aircraft - just because that's what pilots are use to using.

In the mean time, as always, E-AB builders are themselves responsible for setting safe limits; hopefully those who wish to expand the envelope will have the means and skills necessary to insure they do so safely.
 
"...and find a way to express them consistent with the FARs for certified aircraft - just because that's what pilots are use to using..."

Agreed.

Don't you think, though, that one of the reasons he listed it as TAS is because he KNEW that as EABs, we would WANT to stick bigger and more powerful engines on this airframe, and fly it at high altitudes and suck on O2?

Although it is inconsistent with what almost everyone is familiar with, it does tend to keep a conservative performance margin, even if you hang that 1000hp TPE 331 on the nose...:D
 
"...and find a way to express them consistent with the FARs for certified aircraft - just because that's what pilots are use to using..."

Agreed.

Don't you think, though, that one of the reasons he listed it as TAS is because he KNEW that as EABs, we would WANT to stick bigger and more powerful engines on this airframe, and fly it at high altitudes and suck on O2?

Although it is inconsistent with what almost everyone is familiar with, it does tend to keep a conservative performance margin, even if you hang that 1000hp TPE 331 on the nose...:D

I certainly agree, the whole point of Ken's article is to discourage higher than recommended engines. But again, that is a red-herring in this discussion. Nearly every RV is capable of climbing to high altitudes where IAS and TAS are significantly different; then diving at red line (IAS) speeds. (By the way, in the side bar to Ken's article it was emphasized how much he exceeded Vne in TAS, but hardly mentioned that he was right at, or over, Vne in IAS, too!) My real worry here is aimed more at second and subsequent owners. Unless they frequent VAF or similar places, they are completely in the dark on this issue, and most will simply assume that Vne in their newly acquired airplane is the same as in every airplane they have flown before - a red line in IAS on their indicated airspeed gauge. Many will not hesitate to run the airspeed well into the yellow on smooth air descents. After all, that's what they've been taught, all their flying life.
 
To all, as I stated in my next post #46:
I do stand corrected as for Van's using TAS as VNE limit not IAS as with all certified aircraft. But as I have stated, speed / performance is NOT factor in my decision to use a Turbine.
Rocketman1988: Thank you for your post, I very, very much do respect Van's VNE and will not go beyond it. (Speed is NOT the reason for this install) And I wholeheartedly agree The experimental community does NOT need any more accidents! I cringe when I hear of an experimental accident, for the family and because as we all know in this small community, it tarnishes its view in the un-informed public eye.
Sig600, I am an experienced pilot, I have flt time in T34C, FA18's, Kingair B200,
Citation 501's and Citation 550's and RV's. And a 25 yr experienced A&P mech.
And a Citation VERY MUCH CAN exceed VNE and will do it straight and level below 180. The Commander 690 accident has no bearing on this topic.
Everything I am doing in regards to this install is for reliability and safety in mind. My build partner's God-father is a NASA aeronautical engineer and is helping us with all engineering data.
 
"...Thank you for your post, I very, very much do respect Van's VNE and will not go beyond it. (Speed is NOT the reason for this install)..."

Cool! I wish I could also go the turboprop route but the cash for the turboprop will be going to a couple of well known Universities...
 
Thanks

I swore I would not get drawn into this again, but I cannot help myself....

We like it when you do get involved.
Involvement is why we have such a lively forum.:)
 
OK - here's the thing.

The US experimental rules allow you guys to put in whatever engine you wish without any testing or justification. Without wishing to be rude, the US way is "bigger is better". 180hp RV-9s, 320hp RV-10s etc etc. None of the VANS aircraft need more than the recommended max - although I am certain lots of people will now write in and justify their huge engines!

All VANS are trying to do is to moderate things and try and quantify the dangers and issues involved with putting in an unnecessarily large engine.

And before anyone says it, yes - I know - that's why it's called experimental......
 
OK - here's the thing.

The US experimental rules allow you guys to put in whatever engine you wish without any testing or justification. Without wishing to be rude, the US way is "bigger is better". 180hp RV-9s, 320hp RV-10s etc etc. None of the VANS aircraft need more than the recommended max - although I am certain lots of people will now write in and justify their huge engines!

All VANS are trying to do is to moderate things and try and quantify the dangers and issues involved with putting in an unnecessarily large engine.

And before anyone says it, yes - I know - that's why it's called experimental......

What? 180 HP RV-9 is not a big engine. Now, putting an IO-540 in a -9 would be something! BTW, a -9 with an O-360 will not hit Vne unless there is some serious speed mods done to it.
 
What? 180 HP RV-9 is not a big engine. Now, putting an IO-540 in a -9 would be something! BTW, a -9 with an O-360 will not hit Vne unless there is some serious speed mods done to it.

The recommendation of nothing bigger than an O-320 for the RV-9 has nothing to do with VNE.

It is a function of VNO, and to some degreeVH, VMO.

VNO on an RV-9 can be easily exceeded in level flight with a 180 HP engine.
 
OK - here's the thing.

The US experimental rules allow you guys to put in whatever engine you wish without any testing or justification. Without wishing to be rude, the US way is "bigger is better". 180hp RV-9s, 320hp RV-10s etc etc. None of the VANS aircraft need more than the recommended max - although I am certain lots of people will now write in and justify their huge engines!

All VANS are trying to do is to moderate things and try and quantify the dangers and issues involved with putting in an unnecessarily large engine.

And before anyone says it, yes - I know - that's why it's called experimental......
And we still, in some remote corners of the United States, enjoy the God given right to choose as we wish what means in which to pursue happiness. Even if it doesn't conform to the "world's standards".
 
I swore I would not get drawn into this again, but I cannot help myself....

Please get involved more often. That post should be a sticky somewhere on the forum, or a front page article. Most informative safety-related post i've read here in at least a month.
 
Careful, Vne is based on TAS not IAS

I'm interested in this as a second option to the IO-540. At the rate that 540s are getting hard to find used and the higher and higher cost of new ones, this could be a doable project if reliability and compatability proves they are on par. Not to mention the fuel issue and price of 100LL (and/or replacement later on). This is what experimental aviation is all about! I'll put oxygen in my plane anyway, be happy to get up to 18K and do 200knts IAS but 300knts GS!!!

Vne is generally limited by flutter which is a function of fluid speed over the lifting surface. IAS is base on the pressure generated on the lifting surface and/or the pitot hole. Structures can flutter well below the published Vne TAS when IAS is uncorrected for density altitude. I had the same idea until I did some reading.
 
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