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RV-3 fatality

Has this ever happened to an RV before (wing folding in straight & level)??

It happened to a Zenith Zodiac earlier this year, Zenith's utter silence on the matter sealing my decision to build an RV...
 
mdredmond said:
Has this ever happened to an RV before (wing folding in straight & level)??

I think that the Van's demonstrator RV8 had a wing fold up, but I don't believe anybody ever figured out for sure why. I think most figure that it was due to somebody overstressing the airframe by cranking back too hard, but since the aircraft has no data recorder, you can't know for sure. They subsequently stress tested the b-jeebers out of the wing design (very publicly, to their credit) and it passed with flying colors.
 
szicree said:
I think that the Van's demonstrator RV8 had a wing fold up, but I don't believe anybody ever figured out for sure why. I think most figure that it was due to somebody overstressing the airframe by cranking back too hard, but since the aircraft has no data recorder, you can't know for sure. They subsequently stress tested the b-jeebers out of the wing design (very publicly, to their credit) and it passed with flying colors.

I found that accident . The probable cause was:

"The intentional or unintentional sudden application of aft elevator control by an undetermined aircraft occupant that exceeded the design stress limits of the aircraft. The aircraft gross weight, which exceeded the maximum allowable for aerobatics, and airspeed, which exceeded the maximum maneuvering speed for the weight, were factors in this accident."

So pilot error on that one. That's no surprise...
 
mdredmond said:
I found that accident . The probable cause was:

"The intentional or unintentional sudden application of aft elevator control by an undetermined aircraft occupant that exceeded the design stress limits of the aircraft. The aircraft gross weight, which exceeded the maximum allowable for aerobatics, and airspeed, which exceeded the maximum maneuvering speed for the weight, were factors in this accident."

So pilot error on that one. That's no surprise...

Made me think how much we might be at the mercy of our passenger - if they unexpectedly grab the stick and yank back. Perhaps add a glass rod which connects the stick base and the stick. They yank back too hard and (snap!) stick comes off in their hand.
 
Wing failures on RV-3s

mdredmond said:
Has this ever happened to an RV before (wing folding in straight & level)??

It happened to a Zenith Zodiac earlier this year, Zenith's utter silence on the matter sealing my decision to build an RV...

There were four or five wing failures in early RV-3s that lead to fatalities; some historical information on those failures can be found here: http://www.romeolima.com/RV3works/Info/info.htm#WingSparBackground

I seem to recall someone on the Matronics Zenith forum (if I recall correctly; it may have been a Yahoo forum) saying Zenith did respond to the report of that failure to the extent that Zenith said they were waiting for more facts from the NTSB. Which seems reasonable to me since one failure does not make a trend.

When you compare the number of past fatalities due to wing failures in RVs versus Zenith aircraft relative to the guesstimated flight hours in each fleet, I suspect neither one comes out as being more prone to this type of structural failure than the other. When you consider other suspected systemic issues with either line of aircraft (nose gear failures on RVs, canopies failures on Zenith 601s come to mind from my past reading) I think they tend to balance out and both companies do try to address them when they suspect a design problem.
 
I have a buddy building a 601XL. He called the factory regarding the fatal accident mentioned on this post.
The 601 failure was due to the plane being assembled at the airport...and the pilot using non graded bolts to attach the wings to the fuselage. I would not consider that a design flaw. Ivan/Sugar Land, Texas.
 
szicree said:
I think that the Van's demonstrator RV8 had a wing fold up, but I don't believe anybody ever figured out for sure why. I think most figure that it was due to somebody overstressing the airframe by cranking back too hard, but since the aircraft has no data recorder, you can't know for sure. They subsequently stress tested the b-jeebers out of the wing design (very publicly, to their credit) and it passed with flying colors.
I'm sorry to jump in here, but you're posting some awfully subjective comments. 1. The -8 wing failure *was* due to overstress caused by pilot error (probably the passenger over pulling). It's definite and well documented. 2. Van's subsequent static loading of the -8 wing passed. I would hardly say Van's tested the b-jeepers out of it. It just passed. 3. Do some very basic investigation and read the NTSB report. There was a witness who's comments supported the scenario of overload. Also, the failed components indicated pure overload failure.

I have heard (but not seen myself) that the -8 spar has been subsequently redesigned (extended spar doubler) - which is a good thing. It was comparatively weak at the aileron/flap intersection with a wing skin junction and a spar doubler terminating at the same span location.

Condolences to the family and friends of the lost -3 pilot.
 
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Low Pass said:
The -8 wing failure *was* due to overstress caused by pilot error (probably the passenger over pulling). It's definite and well documented.

I stand corrected. Can you tell me where I can find the documentation of the over pull?
 
I read all that stuff years ago when it happened and I also talked to folks at Van's back then. As I said in my original post, most people (myself included) believe that it was an overpull; however, there are those who disagree with that judgement. The NTSB report cites an overpull as the "probable" cause, so I don't see how we can rightly use a term like "definite". Further, if it was "definitely" caused by a pilot error, then why spend all that time and money to stress test the wing? The fact is nobody can know for sure what happened cuz they weren't there. Having read everything I can about it, I'm pretty sure they got it right, but I also know that smart people get things like this wrong sometimes.
 
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Actually Steve, I agree with you. I believe that "definite" will never be proven but the "probable" is the most likely. And the metallurgist has a "definite" opinion that it was overstressed. I can't argue with that part.

Actually, when I read these posts it peaked my curiousity and I went back and reread the reports. It takes me back to that sick feeling I had after the accident just days after sitting in N58RV and taking photos with the RV grin firmly in place.
 
RVWanabe said:
I have a buddy building a 601XL. He called the factory regarding the fatal accident mentioned on this post.
The 601 failure was due to the plane being assembled at the airport...and the pilot using non graded bolts to attach the wings to the fuselage. I would not consider that a design flaw. Ivan/Sugar Land, Texas.

That would 'splain it... So I can't attach my wings with Home Depot bolts?? Why, they're only 78 cents each...
 
szicree said:
... The NTSB report cites an overpull as the "probable" cause, so I don't see how we can rightly use a term like "definite". Further, if it was "definitely" caused by a pilot error, then why spend all that time and money to stress test the wing?...
Two reasons come to mind. First, Van lost a friend and co-worker in that accident and if I were him, I would want to know what caused the wing to come off. Was it an engineering error, construction error, what?

Second, Vans had a lot of time and money in the "new" RV-8 and its wing design. The stress testing they performed, the openness in which they preformed it and published the results helped keep the business afloat.

As for the test, Vans bought a set of wings from a builder who lost interest in building and used those wings for the test. The thinking was that user built wings might not be as strong as a pair built in Vans' shop. Turns out they were much stronger than Vans' ultimate (yield) design load calculations. Unfortunetly I don't remember the exact number.
 
N941WR said:
Two reasons come to mind. First, Van lost a friend and co-worker in that accident and if I were him, I would want to know what caused the wing to come off. Was it an engineering error, construction error, what?

Second, Vans had a lot of time and money in the "new" RV-8 and its wing design. The stress testing they performed, the openness in which they preformed it and published the results helped keep the business afloat.

I also heard that there was at least one law suit due to the accident. If I were being sued, I would test and prove there was nothing wrong with the design.

Karl
 
N941WR said:
Two reasons come to mind. First, Van lost a friend and co-worker in that accident and if I were him, I would want to know what caused the wing to come off. Was it an engineering error, construction error, what?

Second, Vans had a lot of time and money in the "new" RV-8 and its wing design. The stress testing they performed, the openness in which they preformed it and published the results helped keep the business afloat.

As for the test, Vans bought a set of wings from a builder who lost interest in building and used those wings for the test. The thinking was that user built wings might not be as strong as a pair built in Vans' shop. Turns out they were much stronger than Vans' ultimate (yield) design load calculations. Unfortunetly I don't remember the exact number.

Bill,
The wing's upper skin wrinkled at 9.2 Gs. The wing never completely failed, but the test was stopped at that point, as it showed that the wing had entered the "plastic" state. As I recall, (I'm going from memory here) the engine monitor showed that the aircraft was straight and level at approximately 1000 ft AGL. Speed was approx 190 mph. Va for the RV8 is 142 mph. The aircraft was also loaded beyond the 1550 pound aerobatic gross weight. The aircraft then executed a sharp climb.
The metalurgist stated that the wing spar failure was an ACUTE event. This means that there was no prior fatique or damage to the metal. The failure was a current, sudden event.
The person in the rear seat was a personal friend of the Vans employee who was the pilot. The GIB was a professional crop duster pilot. Given the these facts and knowing that the pilot was aware of the 8's limitations, you can see how it is ASSumed that the over G was executed by the GIB.
Charlie Kuss
 
An ex Zodiac builder speaks

mdredmond said:
Has this ever happened to an RV before (wing folding in straight & level)??

It happened to a Zenith Zodiac earlier this year, Zenith's utter silence on the matter sealing my decision to build an RV...


I can't fault your decision to build an RV but having built and flown the zodiac for 7 years I can tell you its a pretty stout little airplane. What you forgot to mention was the wing folded right after it was bolted on the airplane by the new owner. The airplane was taking a brief check out flight after re mounting the wings. The airplane had flown perfectly well before.

I don't have the exact facts but it is highly likely the new owner left the nuts off the spar bolts or left bolts out.

Hardly the airplane's fault.

I would have liked to see a response from Zenair as well though.

Frank
 
Light stick and passenger

szicree said:
Having read everything I can about it, I'm pretty sure they got it right, but I also know that smart people get things like this wrong sometimes.
Steve buddy, I have about a grand of time in RV-4's, just be careful, when you have a passenger the stick forces get very very very light. I had flown quite a bit solo acro in the dash 4. I remember the first time I did my normal 3 g pull-up with a passenger, I over shot quite a bit, say 4.5 g. Also landing you can't flare too much, you almost hold forward stick to keep the tail off, depending on speed. My RV-4 was at the fwd CG limit solo BTW. Just be careful.

I only mention this to you because of the factory RV-8 accident we are discussing. There is no doubt they where over acro gross weight and that one guy had little or no RV-8 experience. Both being former or current Ag pilots, I am sure the passenger was use to higher stick forces. Although I don't know who was actually flying at the time of the accident I could see the light stick force catching them by surprise, and since the the pilot trusted the passenger, who was a buddy, he might have been less vigulant. I know I was surprised when I first flew my RV-4 two up. A RV-4 and guess the RV-8 are two different planes solo v. dual.

Again the RV-4 stick gets real light with aft CG. I am sure the RV-8 is the same. It is so easy for a passenger to yank on the stick at high speed and remove the wings. Key of course is doing maneuvers at or below maneuvering speed. There was another near miss in a RV-4 when a passenger, the pilot assumed the passenger knew what to do since he was a real Acro Pro? The passenger preceded to do a Split-S from near cruise speed. They pulled out well over 9 g's and past Vne. There where permanent wrinkles. With that said, I think the RV-4/6 had wings might have a slight edge with greater structural margin than the newer design RV-7/RV-8, which are strong enough but not over built. Lesson is just don't let anyone play with your stick.
 
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That's why I took the rudder pedals and stick out of the back seat of my Rocket. I had dual controls on my RV-6 and my son's friend had us upside down at 1600' in a hearbeat thinking he was flying his computer.

If I can't see them, they aren't touching the controls.
 
First of all, just to clarify, I have no axe to grind - just a little hangar talk here...

As an engineer, I get razzed by friends, coworkers and family for never really committing 100% to any judgement or expectation. At work I've been asked, "Why did the compressor fail?" "Well, I can say with 95% certainty that the blah, blah, blah...."

Later on, inevitably, operations would ask, "Will the repaired compressor work?" "Well, we believe it will." "Bryan, can't you ever just say yes or no?!" "No." :D

Why did the wing fail on N58RV? God is the only one who knows with 100% certainty. I believe (having reasonable knowledge of the physics, materials and structure) with 99+% certainty that the wing failed due to overload.

The metallurgical exam showed no fatigue, pre-existing damage, corrosion and that the material met spec. These results are conclusive to me with 99++% certainty. Plus all the other circumstantial info... Just curious, but what else could it have been?

And, yes, the RV-8 stick forces get a lot lighter with a someone in the back. After letting an "F-16 pilot colonel" fly from the backseat of my RV once (can you say holy cr@p!), I never let a new pilot fly without me encircling the front stick with both my hands. This way I can grab my stick ;) within a fraction of a second, and they can't move it more than a 1/2 inch or so.

...up to about 8 cents now, I believe
 
Bryan and GMC,

You guys nailed it. I was also stunned at how pitch sensitive my -8 becomes with a typically sized GIB. (Typical these days being over 200 lbs.) On one flight I was into the overhead break and used my typical pull to put on 2-3G's to get down to flap speed. Man 'o man...I think I hit 4G before I unloaded. I swear I hardly moved the stick at all, just the usual "suggestion of pressure" so typical with these lovely airplanes. On landing, the airplane does settle nicely into approach speed with little nose up trim if any, and seems to land better than I can while solo. So, I kinda like having extra weight aft for landing but for maneuvering above Va, the pax doesn't get the stick. It stays clipped into position on the seat back where it normally rides 99.9% of the time.

I seldom allow anyone to fly from the back seat anymore and, oddly enough, most pax don't even care to. I had a high-time pilot GIB once pull waaay too much on the stick and I learned that day to NEVER ASSume that the guy/gal knows how sensitive the airplane has become with their biomass on board. I don't care who they are, how many hours they have, or what kind of a/c they have flown. Nothing flies like an RV. Dontcha love it? :)
 
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