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Rv-10 Vne ?

Bob Martin

Well Known Member
I'm curious about the -10's VNE
I don't see it published in the performance info on the main Van's Site.
I'm sure it is listed somewhere, but figured some of you guys knew it already.
I have a -6 now and I'm contemplating the -10 and was wondering.
The spread from the top of the yellow to the VNE in the -6 is so small we have to throttle back on descents .....I was also reading about the HR3 the cruise was about 260 but the VNE was about 350....big spread
I understand the -6 and the HR3 are sport planes and the -10 has a different mission profile but I'm still curious.
Thanks,
Bob Martin RV-6
 
I haven't checked it yet, but the pictures on Van's web page looks like about 230mph.
Mel...DAR
 
Killer Item................

I bought my completed RV-10 about eleven years ago. While I was getting up to speed, learning as much as I could about the airplane I found the VNE question for the RV-10 to be a point of contention. When I read the POH's that various pilots had posted, I noticed a very serious flaw. Some of these pilots were using 200 Knots INDICATED airspeed as the VNE and some were using 200 TRUE. Well folks, there is a huge difference between the two. I upgraded my panel to an all Garmin panel that shows speeds, temps and just about anything else in any format that you want. Anyone that is using 200 INDICATED as a VNE is playing with fire! The RV-10 in a descent will easily get up to 200 TRUE in a matter of seconds depending how far you are coming down from. I don't mean from the flight levels, I am talking about as low as 9,000 feet. Indicated lags True by a large margin and it could be deadly. I called Van's about this and asked why it was True vs Indicated. I was told that it was too complicated to explain but they would send me an article that does. They did and the reason is flight control flutter. I have been trying to spread the word over the last ten years with limited results. I am going to put the link to the article that Van's sent me into this thread. I hope that I can insert it OK and that you will be able to get to the article. This is a killer item that most RV-10 pilots don't even know about!

http://www.australianflying.com.au/news/vne-and-flutter-explained
 
The spread from the top of the yellow to the VNE in the -6 is so small
6

Uh, you mean, like zero?

As others have indicated Vans official position - though not well publicized - is that Vne is given to us as a True Airspeed. Since this is different from normally certificated planes, it is confusing to many. I wish Vans was a little more forthcoming about what was or was not actually tested, at what speeds (true or indicated, etc.)
 
I wish Vans was a little more forthcoming about what was or was not actually tested, at what speeds (true or indicated, etc.)

The problem with that is that you'll immediately see a whole host of other questions right on top of that, from builders wanting to "hop up" their airplane. "What was the weakest structural member?" "Where did you see vibration and at what speed?" "How should I strengthen that piece?" "If I change the CG, can I go faster?" stuff like that.

That will explode exponentially in questions and workload for Vans if they ever start down that rabbit trail - and it also opens Vans up to liability when things go wrong, because "Vans said to do that!"

The way it stands today, YOU are the manufacturer, YOU are responsible for the flight and testing, and if YOU break it, YOU own both pieces.

You won't ever see Vans disclose their testing details. There is zero benefit for Vans to letting us peek behind the curtain, and there is significant liability in doing so. The margins in the airplane belong to the Vans engineers and test pilots, and we will, in all likelihood, never have access to them.
 
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Bob,
I agree with you!
Luckily I learned about the TAS/VNE, here from others.
But how many new buyers never learn.
I do understand it is the pilots responsibility to understand his aircraft, but this info almost seems hidden.
Maybe we should create a placard for the panel??
 
Bob,
I agree with you!
Luckily I learned about the TAS/VNE, here from others.

Maybe we should create a placard for the panel??

In point of fact this is exactly what the FARs require for normally certified airplanes (but not EAB): If Vne cannot be stated as a single CAS number, then there must be a placard that states various values of Vne in IAS as a function of altitude.
Most of the current EFIS units can be configured to place a red line on the airspeed tape at the calculated IAS where the IAS equals Vne in TAS, under the current conditions.

Vans, are you reading this? You need only look back two posts to see the confusion that exists. I would think it would be in the corporate self-interest to make this (Vans’ position) as clear as possible.
 
The issue of Van's Aircraft redefining Vne many years ago as TAS instead of IAS and not notifying pilots and builders is a long-standing one. Van's has been terribly remiss (negligent?) by not issuing a Service Bulletin or Service Letter addressing this critical safety-of-flight information change that would have officially alerted pilots and builders of the change.

Van's did issue an SL for the RV-14s, but not the older RV models, and the info is included in the POH's for the RV-12s.

For those that don't have EFIS' that allow you to put in Vne in terms of TAS, here's your sign.
The left table applies to RV-4, RV-6/-6A, and RV-9/-9A, and the right table applies to RV-7/-7A, RV-8/-8A, and RV-10:

i-wLv7VKD-M.jpg


(Use this information at your own risk.)
 
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Van's has been terribly remiss (negligent?) by not issuing a Service Bulletin or Service Letter addressing this critical safety-of-flight information change that would have officially alerted pilots and builders of the change.

And this is exactly why Vans doesn't want to talk about it - because people are way too loose with words like "negligent" and "liable".

Van's is not the manufacturer of the airplane - the builder is. That is the critical distinction between Certificated and E-AB. All it would take is ONE successful lawsuit against a company like Vans for the entire EAB industry to implode and disappear. You want certainty and guarantees? Go buy a Cessna.
 
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The problem is most certified light aircraft use IAS. The decision on a manufacturer using IAS verses TAS comes down to which occurs first in the operating envelope, flutter or structural failure. If flutter comes first you use TAS. If it’s structural failure IAS. Some aircraft use a composite. IAS below a certain altitude and TAS above that altitude. I believe Vans originally used IAS but switched to TAS as builders mounted ever bigger engines and the operating envelope expanded outside of what vans envisioned.
 
The problem is most certified light aircraft use IAS. The decision on a manufacturer using IAS verses TAS comes down to which occurs first in the operating envelope, flutter or structural failure. If flutter comes first you use TAS. If it’s structural failure IAS. Some aircraft use a composite. IAS below a certain altitude and TAS above that altitude. I believe Vans originally used IAS but switched to TAS as builders mounted ever bigger engines and the operating envelope expanded outside of what vans envisioned.

This is incorrect. Part 23 for certificated aircraft mandates CAS numbers (but allows a placard of IAS vs Altitude if one single CAS doesn’t work).
 
VNE should always be True. It is a measure of how fast the airflow is over the control surfaces. At sea level and low altitudes the difference is not so big but even at 8 or 9 thousand 200 ias could be 225 tas.
Flutter will very possibly kill you.
 
Flying with no data to please the lawyers?

So, are the guys that race these things having a lot of probs with flutter?

If so, lets hear it. Aren't they racing up in the high 200's I suspect that the relatively short winged RV's would have very good flutter margin at Q limit red line. and, therefore be OK flutter wise with indicated air speed much higher than red line or altitudes well into the high teens or twenties . I don't like the boogeyman tone of all of this. These things should be known.

Over 50 years ago, I test flew the original Stevens Acro carefully and incrementally to 250 or so. No flutter. I remember canopy or cowl failure was more of a concern. And that is strictly dynamic pressure, Q, as measured by IAS.

I think safety concerns re flutter will be best served by emphasizing the importance of control surface balance as well as knowing the calculated flutter and divergent speeds and some shared vibration test data. Airplane builder Cessna knows these things. I think RV builders should as well.

As it stands, it seems RV flutter speeds are a secret or unknown. Therefore, for safety, flutter speed must be assumed to be true air speed red line at sea level, with IAS max decreasing with altitude. I suspect this flutter dominated red line may be an unnecessary operational burden. but research would have to be applied to relieve that assumption.

Maybe the racers could help. In any event, a research minded builder who's heart was set on a turbo intercooled '10 cruising at 190kt IAS @ 24k ft. could do some high altitude shaker tests for the community.

Ron
 
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Many of them do mods to their airplanes (and test them - key part there) for additional flutter margin at higher speeds. They are, quite literally, test pilots when they do these things.

Some have not tested. Some have tested poorly. Some have found the limits. I've watched it happen a couple of times, it's not pretty.

At Reno, it truly is "Survival of the Fittest". Darwin rules there.
 
Van's is not the manufacturer of the airplane - the builder is. That is the critical distinction between Certificated and E-AB. All it would take is ONE successful lawsuit against a company like Vans for the entire EAB industry to implode and disappear. You want certainty and guarantees? Go buy a Cessna.

When it comes to items like Vne and some other design limits, I disagree. The RVs are kit-built airplanes designed by Van's Aircraft. A minuscule number of builders (maybe none) have the knowledge and/or capability to do comprehensive flutter analyses, conduct a ground vibration test, and conduct flight flutter tests on their completed airplanes to understand where the flutter boundaries are, and thus set Vne appropriately. Maybe some folks racing their RVs at Reno have done some work along those lines, but only Van's has done the work and have the knowledge about their designs necessary to set Vne.

Van's has now acknowledged that Vne should be in terms of TAS for the RVs (and it was many years ago that they did). But they have never officially communicated that critical safety-of-flight information to builders and pilots, so most do not know of this limitation. Therein lies the rub.
 
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VNE should always be True. It is a measure of how fast the airflow is over the control surfaces. At sea level and low altitudes the difference is not so big but even at 8 or 9 thousand 200 ias could be 225 tas.
Flutter will very possibly kill you.

No, Vne does not always need to be stated in terms of TAS to ensure that the airplane has adequate flutter margins up to it's Absolute Ceiling.

It's the responsibility of the designer/manufacturer to set 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 (i.e., IAS/CAS up to a certain altitude, and then a constant TAS above that).

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.
 
This is incorrect. Part 23 for certificated aircraft mandates CAS numbers (but allows a placard of IAS vs Altitude if one single CAS doesn’t work).

I just used IAS to keep it simple. The difference between CAS and IAS at speeds where flutter is a issue is usually under two knots. Below is a basic explanation. Where there can be a bigger difference is near stall speed.


Under what conditions are IAS and CAS approximately the same? At cruise and higher airspeeds.
 
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VNE should always be True. It is a measure of how fast the airflow is over the control surfaces. At sea level and low altitudes the difference is not so big but even at 8 or 9 thousand 200 ias could be 225 tas.
Flutter will very possibly kill you.

VNE does not need to be and often is not true airspeed. If the aircraft can fly throughout its flight envelope with out getting into a flutter regime it can be set to IAS.
 
Harmon Rockets with a modified RV4 tail set the VNE at 239kts or 275MPH. I set my F1 up at 225 Kts true airspeed for a greater margin. The F1 does have some additional mods to the tail beyond the Harmon skin change.

According to the owner of Harmon Rocket, LLC., he supplies parts to convert the RV-4, home-built kit, offered by Van's Aircraft, Inc., to a Harmon Rocket. The airplane modification kit was structurally tested through dive tests. The flight testing of the Harmon Rocket II consisted of flutter testing up to 300 miles per hour (mph), stability testing on the ailerons and elevators, g-load testing to 6 positive, and aerobatics training that included loops, rolls, and spins. No drawings were created for the tests. The single change made to the empennage section was an increase in the metal skin thickness from 0.016 to 0.020 inches.
 
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So...

"...No drawings were created for the tests..."

It would be unwise to generalize a series of undocumented "tests" on one airframe...

Point is, if you follow the kit designer's recommendations, you can be reasonably certain that you will not have any flutter issues.

If you choose to exceed those recommendations, you are not necessarily going to crash and burn but you ARE a test pilot, and there IS an increased and real chance of flutter.

Your choice, as this is experimental aviation but know that if you do get into a divergent flutter mode, it isn't going to matter how good of a pilot you think you are...
 
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