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difference?

So does flying with your feet on the rudder pedals vs with your feet off the pedals, make a difference in rudder flutter margin?

Do the flutter test pilots do the testing with their feet on the pedals, and do we all fly around with our feet off the pedals???

Seems like feet on the pedals would be more effective than more counterbalance weight.
 
rockwoodrv9 said:
Would it be as simple as producing a skin that folds at the edge rather than being riveted? How about a piece of .062 or even thinner bent to scab on over the trailing edge?
Click to expand...

Don't know about an aluminum design Rock, and I don't know that a carbon part could even be made that would be 1. equal aerodynamically, 2. lower in mass, 3. stiffer in every mode, and 4. lighter in overall weight and 5. shorter CG with the same balance mass of the 6/7/8/9. Pretty tall order.

Based on Lancair rudder construction, it appears possible, but by an expert.

The Vne for the 7 is quite a bit higher than the 9 already, so I think you have a better margin staying within the 9 limits. With the 7 the only model having so many inflight structural failures (what ever the reason) and the 9 having none, you should sleep well.
 
rockwoodrv9 said:
I'm looking for a way to strengthen the zipper. If I took a 4" piece of .062, bent it to about 160 degrees (not sure if that is the correct bend) and then epoxy or rivet to the trailing edge?
Click to expand...

It would move the rudder CG rearward, which is probably a very bad idea.
 
Pilots

Isn't the simplest solution for pilots to respect Vne and Vno (and a couple of other design limit numbers)?
 
Why not use a different rivet on the trailing edge? Un-zipping may be only on the shop end? That the side of the rivet process that depends on the builder to "get it right" with mushroom the shop end? Do not know?

rockwoodrv9 said:
I understand the reason. Shipping for all the tail kits that go out is big too. Im looking for a way to strengthen the zipper. If I took a 4" piece of .062, bent it to about 160 degrees (not sure if that is the correct bend) and then epoxy or rivet to the trailing edge? That would strengthen it considerably and maybe help with AV type wind damage too.

I flew today and on my walk around, I tried flexing the rudder like it would in the wind. It feels pretty solid, but I can see how a wind gust could weaken it and after several smacks, I could see it weakening. I imagine flutter do the same thing in seconds.
Click to expand...
 
rv8ch said:
Sorry - could not resist.

View attachment 29715
Click to expand...

You hit the nail on the head here Mickey.

While thousands of -7s have accumulated millions of flight hours safely, seems some people want to make unvalidated changes to the airplane because some folks had the airplane come apart well over Vne.

I'd feel better leaving it up to Van's to design and test a solution to increase flutter margin- if justified at all.

Of course anyone can make a mod and test it themselves if they want to play test pilot and flirt with flutter.
 
If I want to go that fast, I'll do it in an airframe designed for it. The RV's are terrific all-around airplanes but they are not intended for 250+ knots.
 
Ha if I want to go fast I get in my 2017 Nissan 370Z. I really hauls &##&.
We did custom exhaust and an Inteck tune on it, 6 speeds of gears and good tires etc. This little car is one tough ride. Haven't broken it yet.
You get a real feeling of fast (and somewhat dangerous) when you are spinning around in circles and smoke going everywhere. Or careening around a corner, ETC
Fly an airplane 200 knots and no big deal. I stay within my planes build specs.
My three cents worth of fun Art
 
For those who may not have read the following about why the RV7 rudder was changed, here's the scoop from the 'Man'.
Personally, I've decided to go back to the 'original' smaller rudder.

https://www.vansaircraft.com/wp-content/uploads/2002/06/sb02-6-1.pdf

CONCLUSION:
Flown within the recommended limitations of Section 15 of the Construction Manual, either the original or the enlarged RV-7 rudder will provide adequate authority for spin recovery. The substitution of an RV-9 rudder on an RV-7 improved spin recovery. With the larger rudder, the RV-7 will have better spin recovery from whatever flight condition the pilot may encounter
 
Barnaby Wainfan

I really enjoy the Wainfan articles in Kitplanes. The current online issue the subject is vertical tails. Following Wainfan's logic the RV6 and RV7 would have much improved spin recovery if the rudder chord were wider at the bottom and narrower at the top. Apparently only the 6 and 7 really need better spin recovery.
The new Zealand report is very interesting. Non aerobatic pilot, did not like aerobatics but managed to break the airplane. NZ has an aerobatic rating and the pilot was not rated.
 
Snowflake said:
Posts like this worry me. The point of the counterbalance is to balance the rudder, just like the elevators.
Click to expand...

Really? What about the ailerons? They have counterbalances but are not 100% balanced.

Not all surfaces are designed to be 100% counter balanced.

Skylor
 
Test Pilot

Z-EDD said:
Would adding more lead improve the flutter margins? I don't know, but I'm not going to go into test pilot mode to find out.
Click to expand...

Good call! Additional counterbalance weight at the rudder tip could quite possibly have negative consequences on the resonant frequency of the entire rudder/vertical stabilizer system. What "seems" like a good thing could really be a bad thing!

Skylor
 
Test Pilot Mode

If you built an EAB and flew the entire phase one, certifying documentation as required-exactly what mode were you in if not test pilot mode?
To the letter of FAA requirements for EAB the airplane must be tested at least to Vne and some would argue to 110% of Vne.
The Atlantic city accident has strong evidence of gross overspeed, far in excess of Vne. In some of the other accidents such evidence is not very strong. In the Utah accident the NTSB was uncertain which of two ground tracks was the accident airplane. The Washington accident was a vertical event according to witnesses. Most of the airplane was not recovered from the water.
 
And from the New Zealand accident report...

"Anecdotal evidence from individuals who knew the pilot, indicated that the pilot liked to fly “around the clouds”. On the day before the accident flight, the pilot had conducted a local flight in ZK-DVS, to the north-west of Whangarei. During this flight, the pilot climbed the aircraft to an altitude of approximately 6,000ft. On the accident flight the pilot climbed the aircraft to an altitude of approximately 4,500ft. On both days cloud layers were reported to be either at or below these altitudes (refer environmental factors section).
In addition to holding a private pilot licence - Aeroplane (PPL-A), the pilot also held an airline transport pilot licence - Helicopter (ATPL - H), with an instrument rating. Thus, the pilot would have received training and operational experience in IMC during his piloting career.
Although the pilot held an instrument rating, research has shown that the effects of spatial disorientation associated with an inadvertent IMC encounter, can still impact the performance of instrument rated pilots.3
The safety investigation could not conclusively determine if the aircraft inadvertently entered cloud. If, however, an inadvertent IMC encounter did occur, it is possible the pilot experienced the effects of spatial disorientation, leading to the aircraft entering an unusual attitude."

Bearing in mind these are slippery aircraft unlike some aircraft that are very draggy. Get these noses down too long and quickly find yourself in trouble. Respecting VNE, VA, training and flying within your ability level are the keys here. There have been many safe hours flown in RV's worldwide. If you are a low time private pilot consider advanced training of how to get out of something if you get into it and more importantly how not to get into it in the first place.
I, like many here fly commercially and have over 20000 hours but I'm going to get trained on my RV 7 when its built by an experienced RV pilot and approach it with the same professionalism I do in my day job. One ex colleague does flight testing for BFR's now and its surprising to hear some don't even know how to do a weight and balance on their aircraft.

I went to take a C172 for a weekend and needed to get current....maybe 10 or 15 years since i flew the last lighty. The young instructor said to me I wont do to much as you are very experienced....I said yes I am....on airliners....not 172's so you do what you need to ensure I'm safe. the first landing I think I rounded at 50 feet and couldn't find the ground....lol. My point is...even for fun you have to approach flying seriously to be safe and these accidents point to not design faults but pilot error.
 
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BillL said:
This is speculation and should be removed.
Click to expand...

Thanks Bill I edited my opinion on what caused this accident however reiterate this information comes from the official report. whatever happened he got to 244 knots and if you read the report these snapshots are taken 5 seconds apart so the speed may have even been higher than that.

also from the report...."The safety investigation could not conclusively determine if the aircraft inadvertently entered cloud. If, however, an inadvertent IMC encounter did occur, it is possible the pilot experienced the effects of spatial disorientation, leading to the aircraft entering an unusual attitude". so that is speculation only on my part...rightly or wrongly....simply my opinion...I had a student once put me in a 90 degree angle of bank over a VOR in an Arrow.....its always a possibility.

also the report detailed his experience on the sikorsky heli he operated and the recovery from an unusual attitude is different than for a fixed wing...namely reducing the power in a fixed wing versus increasing power in a heli....and possibly resulting in a time delay reducing power with increasing airspeed in a high angle of bank nose low situation.

Whatever happened the point is looking at the data and the report rudder flutter was the cause from overspeeding the aircraft. They even show other breakup rudders and they all seem to show the same damage...broken in the middle and unzipped....all caused by flutter. (and high speed events)

hey Im just keen on learning everything possible....because i dont want it to happen to me.
 
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RV-4 wing separation

Roadjunkie1 said:
There was a post a while ago, possibly referring to a Kitplanes article, about the most common cause of RV-4 wings parting company with the airplane. As I remember, it was pilots newly acquiring an RV-4, not builders, that would execute a fast low pass with a zooming pull-up. Easy to overstress any airplane. The RV series is very responsive without being twitchy but even SMALL stick inputs can results in LARGE changes in attitude. Pull the stick back half an inch at cruise and see how fast you are suddenly at another altitude. .
Click to expand...

Too my knowledge there has never been a in flight wing separation in an RV-4. If you have an actual incident I would be very interested in hearing about it.

Duff
 
Wing Separation

In some of the RV7 reports the breakup starts with the failure of the vertical tail, followed by the horizontal tail, then the wing(s) The NZ report clearly states rudder flutter.
So yes, the wings failed, probably a result of G forces far beyond the design strength. Probably a G load similar to what Van discusses in "Aerobatic Epistle".
Once again-the Washington accident-most of the airplane was never recovered so no sequence of events in the NTSB final.
 
RV4

A search using RV-4 wings folded will confirm that at that time there had never been a structural failure of an RV-4. I believe that remains correct.
That misconception likely came from confusing an early RV8 wing failure with the RV4.
 
Limitations

Flying within published limits is a very admirable goal.
When I was instructing aerobatics full time in the Pitts S2B, T34, Stearman and Sukhoi SU29 I would always try to provide time for a short chat with a new trainee beyond the standard briefing.
An older gentleman showed up. What do you fly? RV6. Do you have any aerobatic experience? "Well I was trying to do rolls in the RV and I got confused and stopped the roll inverted and pulled. How fast did you get. Almost 300 but the worst part was I almost hit the ground.
I do not recall a discussion of G load. The point is the pilot and the airplane survived. All indications are that he would have survived in a RV4. But likely not in a RV7.
I have some very strong opinions on how this should be remedied but I will bite my tongue for now.
I am motivated by a number of reasons. Very high on the list is that I exchanged a series of emails with the pilot who died in the Atlantic City area crash. I wonder if I missed an opportunity to try and talk him out of "teaching himself rolls".
I detest seeing the words aerobatics, homebuilt and structural failure and fatal all in the same paragraph.
 
Holy COW

jrs14855 said:
An older gentleman showed up. What do you fly? RV6. Do you have any aerobatic experience? "Well I was trying to do rolls in the RV and I got confused and stopped the roll inverted and pulled. How fast did you get. Almost 300 but the worst part was I almost hit the ground.
I do not recall a discussion of G load. The point is the pilot and the airplane survived. :eek::eek::eek: All indications are that he would have survived in a RV4. But likely not in a RV7.
.
Click to expand...

Makes my hair stand up! I'll bet he was pulling as Terra Firma started to get closer. I'd love to have seen the G-meter if he had one.....:eek:

This is also a primer for training in recovery from unusual attitudes as well, not just aerobatics. There is a difference and some people really don't have any interest in doing aerobatics but would benefit from unusual attitude recovery. This gentleman might have been an example.

The -4 is one of the easiest airplanes to roll. It can be done feet on the floor. It is much tidier with some rudder input. I don't think I've ever been "confused" as to where I was in a roll. But I have seen this and other airplanes in some unusual attitudes. Situational awareness training......:eek::(:eek:

I hope he went right out and bought some lottery tickets.......:rolleyes:
 
""Well I was trying to do rolls in the RV and I got confused and stopped the roll inverted and pulled. How fast did you get. Almost 300 but the worst part was I almost hit the ground. "

The planes may change but the behavior stays the same.

Prospective purchaser of a T-18 reached out at the top of a roll during a "test flight."

The normally straight center section now had a dihedral, and other permanent wrinkles.

John Thorp calculated, from the "set," that the airframe "saw" 11.3Gs in the extraction.

These are pretty tough birds!
 
jrs14855 said:
How fast did you get. Almost 300 but the worst part was I almost hit the ground.
Click to expand...

All of this is extremely interesting to me. From the Canadian report regarding Vans flight testing, ”The kit manufacture had conducted flight testing of the RV-7A prototype. No indications of flutter were encountered at a speed of 217 knots. Additional theoretical flutter analysis was done where the flutter speed was calculated to be 300 knots for the baseline design.”

I guess you just never know. Perfect case in point…the year 1955, the Douglas A-4 Skyhawk had been demonstrated to be flutter-free up to 600 knots. Then one day, nine months into the flight test program, Douglas test pilot Bob Rahn was returning from a test flight when, at 450 knots, 10,000’, he hit some turbulence from some clouds and all heck broke loose. He had severe rudder flutter that scared the Be-Jesus out of him. Douglas had to completely re-engineer the rudder due to this. Bob was very confused since he had encountered flutter 150 knots below what they thought to be flutter-free.
 
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Walt,
I built and installed the 8 rudder for my 7A back in 2012 after flying with the big rudder 4 years.

I decided to do it after reading about some failures of the big rudder.
I was afraid I might accidentally exceed VNE one day and wanted all the "cushion" I could get...

You'll love the 8 rudder! It's like power steering!

I laid both rudders across a chair to show the size difference. See photo link below. Hope it works.

Mark

https://photos.app.goo.gl/EVa17ojicECaNpA78



Walt said:
For those who may not have read the following about why the RV7 rudder was changed, here's the scoop from the 'Man'.
Personally, I've decided to go back to the 'original' smaller rudder.

https://www.vansaircraft.com/wp-content/uploads/2002/06/sb02-6-1.pdf

CONCLUSION:
Flown within the recommended limitations of Section 15 of the Construction Manual, either the original or the enlarged RV-7 rudder will provide adequate authority for spin recovery. The substitution of an RV-9 rudder on an RV-7 improved spin recovery. With the larger rudder, the RV-7 will have better spin recovery from whatever flight condition the pilot may encounter
Click to expand...
 
Flutter

Around 20 years ago I was talking to a guy at Van Nuys about racing airplanes. After some lengthy discussions he said "would you care to join us for a bowl of soup". I was baffled by the us but we went to a diner near the airport and got a big table. One at a time some retired gentlemen came in and I was introduced to them All VERY well known names from Lockheed and Reno Air Races. Back at the airport with the guy who was C130, we went to a cold t hangar and saw his homebuilt project and his V tail Bonanza. When the conversation turned to the Bonanza he made the statement "no one fully understands the flutter issue with the V tail." They had concluded that one extra rivet near the trailing edge could cause flutter.
One of the most memorable days of my life.
 
Mark Burns said:
Walt,
I built and installed the 8 rudder for my 7A back in 2012 after flying with the big rudder 4 years.

I decided to do it after reading about some failures of the big rudder.
I was afraid I might accidentally exceed VNE one day and wanted all the "cushion" I could get...

You'll love the 8 rudder! It's like power steering!

I laid both rudders across a chair to show the size difference. See photo link below. Hope it works.

Mark

https://photos.app.goo.gl/EVa17ojicECaNpA78
Click to expand...
Thanks Mark, almost done, just gotta finish the installation of the vertical cap then test flight and over to paint shop.
Been meaning to do this for years, seeing all the broken rudders at Osh gave me the extra incentive I needed.
 
swift12 said:
Thanks Bill I edited my opinion on what caused this accident however reiterate this information comes from the official report. whatever happened he got to 244 knots and if you read the report these snapshots are taken 5 seconds apart so the speed may have even been higher than that.

also from the report...."The safety investigation could not conclusively determine if the aircraft inadvertently entered cloud. If, however, an inadvertent IMC encounter did occur, it is possible the pilot experienced the effects of spatial disorientation, leading to the aircraft entering an unusual attitude". so that is speculation only on my part...rightly or wrongly....simply my opinion...I had a student once put me in a 90 degree angle of bank over a VOR in an Arrow.....its always a possibility.

also the report detailed his experience on the sikorsky heli he operated and the recovery from an unusual attitude is different than for a fixed wing...namely reducing the power in a fixed wing versus increasing power in a heli....and possibly resulting in a time delay reducing power with increasing airspeed in a high angle of bank nose low situation.

Whatever happened the point is looking at the data and the report rudder flutter was the cause from overspeeding the aircraft. They even show other breakup rudders and they all seem to show the same damage...broken in the middle and unzipped....all caused by flutter. (and high speed events)

hey Im just keen on learning everything possible....because i dont want it to happen to me.
Click to expand...

Thanks, I followed this accident as I had talked to Dean several times before the accident. My son self-toured NZ and Dean was kind to give him a north end tour. My son was impressed with his methodical approach to safety. Noted the 244kts, too much for what ever reason.

I am certainly interested in learning, including that we may speculate after a report is out.(thanks DanH!) A new arena!! Although my intended learning is all in the technical arena. Numbers numbers numbers.

The 9 (7tall) rudder compared to the 8 (7short) is 11% heavier, CG is 27% farther from the spar, and area is 30% greater with a .016 skin vs .020. Both have the same counterweight, giving the 8 a better balance percent. It really should not surprise anyone that the it would improve flutter margin. We get reminded every 12-18 months of this.

Fly safe.
 
jrs14855 said:
In some of the RV7 reports the breakup starts with the failure of the vertical tail, followed by the horizontal tail, then the wing(s) The NZ report clearly states rudder flutter.
So yes, the wings failed, probably a result of G forces far beyond the design strength. Probably a G load similar to what Van discusses in "Aerobatic Epistle".
Click to expand...

When the horizontal tail (or most of it) leaves with the vertical fin, the fuselage pitches sharply nose down, and the subsequent wing failure is the result of negative loading...it folds downward.
 
Could someone share the correct part number for the appropriate vertical stab fibreglas tip to install on an RV7 to match the RV8 rudder?

Picture downloaded from Mark Burns' post above:

RV8 (short 7) rudder mounted on RV7 vertical stab.jpg

Thanks,

Mike
 
BillL said:
Thanks, I followed this accident as I had talked to Dean several times before the accident. My son self-toured NZ and Dean was kind to give him a north end tour. My son was impressed with his methodical approach to safety. Noted the 244kts, too much for what ever reason.

I am certainly interested in learning, including that we may speculate after a report is out.(thanks DanH!) A new arena!! Although my intended learning is all in the technical arena. Numbers numbers numbers.

The 9 (7tall) rudder compared to the 8 (7short) is 11% heavier, CG is 27% farther from the spar, and area is 30% greater with a .016 skin vs .020. Both have the same counterweight, giving the 8 a better balance percent. It really should not surprise anyone that the it would improve flutter margin. We get reminded every 12-18 months of this.

Fly safe.
Click to expand...

All good Bill….as I say to my colleagues it’s not who’s right it’s what’s right….and can we learn anything from it. Interesting about the numbers on the rudders. Reading a lot of this stuff makes me keen on investigating it further throughout my build and perhaps looking at an 8 rudder instead. I won’t be doing any low level aeros and don’t enjoy spinning. it seems to me the 8’s haven’t had these failures….mmmm
 
skylor said:
Really? What about the ailerons? They have counterbalances but are not 100% balanced.
Click to expand...
Yes, but they are also used differently... The aileron is designed to carry an aerodynamic load during flight... The rudder is essentially intended to float in trail most of the time until it's needed.

Of course, that said, the elevators are intended to carry a load full time as well, and they are balanced... So... Hmm.

Good call! Additional counterbalance weight at the rudder tip could quite possibly have negative consequences on the resonant frequency of the entire rudder/vertical stabilizer system. What "seems" like a good thing could really be a bad thing!
Click to expand...
This is very true as well, and I wouldn't suggest changing what Van's recommends. I haven't read that part of the build manual, it just seemed to me that if the control was going to be balanced, that it would make sense that it be balanced, not "partly balanced." I admit it's been a while since I studied control surface design, I may be forgetting something fundamental.

Does the build manual say to build the rudder first, or the elevators? Could it be that the manual goes into detail on the elevators, and then later when building the rudder it assumes you know all about balancing from doing the elevators and don't need a refresher?
 
RV8JD said:
… in-flight breakup of an RV-7 (N731RV; Arlington, AZ; 6/27/2017)…Contributing to the accident was an inflight collision with a bird."[/INDENT][/I]
Click to expand...

Yeah, this accident has been discussed on here before. I agree with others that it’s doubtful a “rock pigeon” brought down this RV. The NTSB does mention: “It is possible that the pilot made an evasive maneuver before or during impact with the bird, that in combination, resulted in an overstress structural failure of the, vertical stabilizer and rudder”.
I agree.
 
Snowflake said:
Yes, but they are also used differently... The aileron is designed to carry an aerodynamic load during flight... The rudder is essentially intended to float in trail most of the time until it's needed.

Of course, that said, the elevators are intended to carry a load full time as well, and they are balanced... So... Hmm.


This is very true as well, and I wouldn't suggest changing what Van's recommends. I haven't read that part of the build manual, it just seemed to me that if the control was going to be balanced, that it would make sense that it be balanced, not "partly balanced." I admit it's been a while since I studied control surface design, I may be forgetting something fundamental.

Does the build manual say to build the rudder first, or the elevators? Could it be that the manual goes into detail on the elevators, and then later when building the rudder it assumes you know all about balancing from doing the elevators and don't need a refresher?
Click to expand...

I have just re-read the instructions for the RV-7 empennage. Note these instructions were updated at the time of the HS service bulletin in 2014 and are in the newer “check box” format and rather more detailed than the old instructions, which I don’t have access to right now. Construction of the rudder is detailed before the elevators and contains no reference to balancing. Elevator construction is last in the sequence and has 2 references to balancing. In the pre- amble it is mentioned that the elevators are balanced control surfaces. Under “finishing the elevators” it is stated to conduct final balancing after the elevators are finished and painted, and the preferred method is to leave the counterweights slightly heavy and then balance by drilling small holes on the inner face of the counterweight.

So no mention of balancing the rudder, followed by considerable detail on balancing the elevators. For whatever reason the designer never intended the rudder to be fully balanced.
 
Z-EDD said:
... For whatever reason the designer never intended the rudder to be fully balanced.
Click to expand...

Which is completely reasonable. The paper that has been referenced a couple of times in this thread talks about this - it's not always desirable to have the CG on the hinge line.
 
Z-EDD said:
For whatever reason the designer never intended the rudder to be fully balanced.
Click to expand...
Until someone from Van's weighs (sorry) in on this I don't think we can conclude what the designer's intent was. We can only conclude that instructions for balancing were not included in the manual... And I think most of us would agree that not everything is in the manual.

rv8ch said:
The paper that has been referenced a couple of times in this thread talks about this - it's not always desirable to have the CG on the hinge line.
Click to expand...
This is true. Different aircraft with different configurations will have different margins for flutter and different control harmonization and feel. But I would have expected that two control surfaces that are so similar in configuration (Elevator and Rudder on an RV) and used in the same performance envelope would have similar requirements for balancing.

But, there are differences, elevator is pushrod controlled and is usually under load, rudder is cable controlled and usually floating, etc. etc. It would be great if someone from Van's could comment on this but given the litigious society we live in I can understand why they don't.

At the end of the day I don't think it's been shown that an RV-7/7A operated within the published design/performance envelope is at any risk.
 
Snowflake said:
At the end of the day I don't think it's been shown that an RV-7/7A operated within the published design/performance envelope is at any risk.
Click to expand...

Agree. If there was a systemic fault here, dozens or hundreds of 7s would have crashed by now, given the thousands flying.
 
Snowflake said:
At the end of the day I don't think it's been shown that an RV-7/7A operated within the published design/performance envelope is at any risk.
Click to expand...

No one disagrees.

Trouble is, despite good intentions, sometimes they get outside the envelope. The plain truth is everyone makes a mistake from time to time.

BTW, I met a fella at OSH with an RV-7 rudder installed on his beautiful new RV-8. He said he thought it would give him more control authority.
 
rv6ejguy said:
If there was a systemic fault here….
Click to expand...

Arguably if flown within limits, there is nothing unsafe about the -9 rudder on the -7. But as Dan pointed out and we all know…we all make mistakes. In the last 15 yrs, every single catastrophic RV rudder flutter failure has been a -7 with the -9 rudder. Not the RV-3. Not the RV-4. Not the RV-6, not the RV-8.

Makes one think…hmmm.
 
DanH said:
No one disagrees.

Trouble is, despite good intentions, sometimes they get outside the envelope. The plain truth is everyone makes a mistake from time to time.
Click to expand...

So if you "beef up" the design, however you do it, and enlarge the envelope, won't you still have the problem of people making mistakes and exceeding it?

How far do you go to ensure that no pilot ever violates a design constraint?
 
Accident Record

What I can find:
RV4 structural failures zero
RV6 structural failures-one that was called a RV6 but was not built to plans. Modified RV3 wings among other poor choices. Continental six cylinder engine.
There are 4's and 6's that have been intentionally operated in excess of Vne, primarily for racing.
Racing at Reno is very likely to mean moderate turbulence, sometimes severe.
Many would contend that operation in moderate or greater turbulence should be limited to Va, which at Reno means one should not even bother starting the race.
 
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