Fatal - TangoGyro Tango2 N8680G, near Melrose, Florida, USA 30 JUL 2022

Philbennett

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Well it seems like there are a couple of different reasons

1) AutoGyro. A structural design issue between hub bar and blade

2) AirCopter. Same. Both these are copies of each other

3) Trendak. It’s an AirCopter rotor as well

4) TAG. It was a obstruction and quality control issue where balancing rods were not properly secured and came out

5) Tango. It’s a structural design issue I suspect

6).ELA. I am not quite sure why but I have seen a few composite blades with cracks starting

I decided to go with Averso because Dominator did not at the time have appropriate blades for a 2 seater. Averso in my research had a lot of rotors out since 2004 and there were no reports of in flight failures or cracking and generally no negatives I could find. I did not want to get into figuring out how to manufacture the rotors when there was plenty else to figure out.

I know that Averso was of the opinion that AutoGyro 2400 hours lufe for their rotors was not appropriate given Averso rotors are about 20 pounds heavier because of having that much more metal and structure and they are lower.
I hear you and the 1-6 list isn't great. Add to that the design change that allowed pre-rotation to +++++ and one wonders how these things get approved quickly the level of testing and the knowledge that exists over seeing all of this... I wonder if the Accident branch conversation thread has been something like this:-

"Hey why did that rotor come off??"
"Well it was over loaded"
"Hmm lets do some tests"
"Hang on lets see how our testing relates to the design / approval documentation and the compliance documentation"
"Hang on who signs this off?"
"Hello regulator, who signed this off and with what credentials?"
[Silence]
"Lets dig a bit deeper"
[Regulator points to manufacturer, who points to regulator, who don't like the Accident Branch critique...regulator and Accident Branch get the port out over coffee and cigars]
"We can't have an Accident report that says we don't know what we are doing..."
"OK its agreed"
[Final report - "Gyro crash inconclusive..."]
Later...
"Hello Accident Branch"
"Yes"
"We have another accident"
 

Abid

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I hear you and the 1-6 list isn't great. Add to that the design change that allowed pre-rotation to +++++ and one wonders how these things get approved quickly the level of testing and the knowledge that exists over seeing all of this... I wonder if the Accident branch conversation thread has been something like this:-

"Hey why did that rotor come off??"
"Well it was over loaded"
"Hmm lets do some tests"
"Hang on lets see how our testing relates to the design / approval documentation and the compliance documentation"
"Hang on who signs this off?"
"Hello regulator, who signed this off and with what credentials?"
[Silence]
"Lets dig a bit deeper"
[Regulator points to manufacturer, who points to regulator, who don't like the Accident Branch critique...regulator and Accident Branch get the port out over coffee and cigars]
"We can't have an Accident report that says we don't know what we are doing..."
"OK its agreed"
[Final report - "Gyro crash inconclusive..."]
Later...
"Hello Accident Branch"
"Yes"
"We have another accident"

Well, that was kind of funny in a way but there is probably an element of truth to that.
More than likely theoretical fatigue calculations do not take into account real life flying that some people do. The small flapping incidents they have and because these are recreational flying machines, many people don't care much about reporting or doing proper inspections if nothing was clearly looking damaged, but the metal has been damaged and now prone to pre-mature fatigue. Hence a certain amount of real-life fudge factor is necessary just not so much that the aircraft becomes a tank because tanks do not fly.

I think the new king of yours may be feeling a little bit out of place too for now.
I have heard a lawyer in Pakistan has filed a petition with the high court there to get the Koh-i-Noor (the crown jewel 105+ karat diamond) worth $400 million back from him, now that the Queen has passed away to Punjab from where it was taken from its original owner under duress.
 

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Philbennett

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The inconvenient truth about rotor data is that somethings are known - for example the Cranfield study and their view upon the number of cycles along with whatever rationale drove the 100hr inspection of the rotor bolts following the German accident. Lets hope future publications are the full findings not some edited version because of egos at the regulator or the commercials of a manufacturer.

I'm not sure if he'd want the $400m to fund more places for terrorist to hide in or the crown to acknowledge their achievements. You may know there is much in all of our various countries past not to be proud of, raking it up becomes a race to the bottom.
 

Abid

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The inconvenient truth about rotor data is that somethings are known - for example the Cranfield study and their view upon the number of cycles along with whatever rationale drove the 100hr inspection of the rotor bolts following the German accident. Lets hope future publications are the full findings not some edited version because of egos at the regulator or the commercials of a manufacturer.

I'm not sure if he'd want the $400m to fund more places for terrorist to hide in or the crown to acknowledge their achievements. You may know there is much in all of our various countries past not to be proud of, raking it up becomes a race to the bottom.
Well, we don’t really know that is what happened but if they did edit the findings from university, that’s pretty bad. I would surely hope not. But regulators do make mistakes. FAA allowing a single AoA sensor input controlling pitching attitude of 737 Max was a huge blunder because they allowed internal DOA to approve things at Boeing. They need a waking up from time to time.

I don’t think the family asking for their ancestors property back has anything to do with hiding any terrorists. They want to donate it to the people affected by flooding there where 20 million people have lost everything and become homeless. It would not be waste.
 

Abid

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And then there's Magni:

The Magni composite rotors avoid the traditional fatigue-life issues of many rotors. There are Magni rotor blade assemblies that have flown in excess of 3000 hours – most of those in rugged training hours with students. There have never been any reported rotor failures or even structural cracks with Magni rotors – other than obvious rotor strikes with hard objects. Magni does, however, require replacement of rotor blades at 2500 operational hours. This is mostly so that the factory can evaluate such high time rotors to see if there are any issues developing, and to eventually determine if the 2500 hour lifetime limit can be extended.

Full composite material construction is a major reason for the long, trouble-free life of Magni rotor blades. But the Magni hub-bar attachment, with large lateral bolts rather than vertical bolting, avoids top side and bottom side stressor points at the bolt holes and hub-bar tips that would focus the fatigue stress at those most critically stressed root attachments points. With the high stress concentration points unavoidable with common vertical attachment bolts and holes, extruded spars and even full extrusions may be prone to stress fatigue cracks at or near these stressor points – often difficult to observe internally. Magni simply avoids all of these issues with use of a full carbon-fiber spar and fiberglass construction.

The Magni rotor spar consists of a large number of unidirectional carbon-fiber strips, routed tip to root through a rounded window in a massive, aluminum attachment hub block at the root of each blade. The horizontal configuration attachment bolts – two very large bolts that sandwich the aluminum attachment hub between the hub bar's steel plates – avoid the stressor points created by vertical bolt holes and the tip of the hub bar on standard-configuration rotors.

Magni is the only producer that uses this entire rotor and hub-bar configuration. As far as we know, there have been no normal-use failures of Magni rotors or hub bars in the [30+] years that this design has been in operation. Even a popular fiberglass rotor blade that employed an aluminum spar and standard vertical blade attachment bolts had severely limited life and experienced numerous cracking issues.
If there is one issue that really takes the fun out of flying, it is probably having doubts about the structure and reliability of the rotor!

– Greg Gremminger

Tyger
I would be careful touting this composite is king stuff. Composite structures mean a lot of human element and we all know how that can slip. TAG was composite, ELA rotors are composite and they have both had some serious QA and procedural issues. One place where you cannot have issues in a gyroplane. In fact composite rotor failures in the last 10 years have killed more people than extruded Aluminum ones. One has to keep that factual stat in mind.

As long as human element is so deeply involved, there will always be a chance of a slip forever. Constant vigilance and serious supervision against it is the only solution.

I do not understand the the point about hub bar attachment stressor points. That is not true. When you properly torque the fasteners, the whole system acts as one. Think of the prop hub holding prop blades. You can only get away using M8 or AN5 bolts because things are torqued properly, otherwise those bolts have no chance. The unidirectional composite spar is good, I agree. In AirCopter and earlier AutoGyro designs they had a transition point from a stiff sandwich to a soft extrusion very suddenly. Obviously does not take a rocket scientist to figure out why the cracks were found on the last clamping bolt point. AutoGyro improved that in next version but there still is a hard transfer. Their extrusion blades just have too little meat in them and the spar is not steel
 
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Andino

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I think the new king of yours may be feeling a little bit out of place too for now.
I have heard a lawyer in Pakistan has filed a petition with the high court there to get the Koh-i-Noor (the crown jewel 105+ karat diamond) worth $400 million back from him, now that the Queen has passed away to Punjab from where it was taken from its original owner under duress.
The Sikhs lost the Second Anglo-Sikh War in 1849, and the gemstone, at worst, was a spoil of war. Or, how far do you wish to go back? Didn't Nader Shah originally invade the Mughal Empire and loot the gemstone from Babur's Peacock Throne? And thereafter, didn't Ranjit Singh acquire the diamond from Shah Shujah Durrani under duress? Suggestion: get over it.

Besides, what has that diamond anything to do with this Tango2 crash? Was it not rather tacky to interject it here?
 

Andino

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[Final report - "Gyro crash inconclusive..."]
Or, pilot error flying beyond the envelope. Or, owner error due to poor maintenance. It still boggles me that the Cranfield report actually received some traction. We're overdue for its sequel.
 

Andino

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AutoGyro improved that in next version but there still is a hard transfer. Their extrusion blades just have too little meat in them and the spar is not steel
I wouldn't deem the Rotor System 2's skinny little aluminium tube a "spar." As you stated, there is still a "hard transfer" of forces. They merely "kicked the can down the road" for a few more hundred hours. It's their least worst rotor iteration.
 

Philbennett

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It still boggles me that the Cranfield report actually received some traction.
Why are you surprised that the Cranfield report received some traction? Isn't it one document that gives some colour on the blades? Yes agree it should have been expanded but I suspect it wasn't because it would bring the 2500hr life down... or potentially so. Even a move away from hours to take offs/landings.
 

Tyger

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Tyger
I would be careful touting this composite is king stuff. Composite structures mean a lot of human element and we all know how that can slip. TAG was composite, ELA rotors are composite and they have both had some serious QA and procedural issues. One place where you cannot have issues in a gyroplane. In fact composite rotor failures in the last 10 years have killed more people than extruded Aluminum ones. One has to keep that factual stat in mind.
As long as human element is so deeply involved, there will always be a chance of a slip forever. Constant vigilance and serious supervision against it is the only solution.
I do not understand the the point about hub bar attachment stressor points. That is not true. When you properly torque the fasteners, the whole system acts as one. Think of the prop hub holding prop blades. You can only get away using M8 or AN5 bolts because things are torqued properly, otherwise those bolts have no chance. The unidirectional composite spar is good, I agree. In AirCopter and earlier AutoGyro designs they had a transition point from a stiff sandwich to a soft extrusion very suddenly. Obviously does not take a rocket scientist to figure out why the cracks were found on the last clamping bolt point. AutoGyro improved that in next version but there still is a hard transfer. Their extrusion blades just have too little meat in them and the spar is not steel
I don't know what you mean by "be careful", exactly, and I was (indirectly) touting Magni rotors, not all composite blades. Obviously all composites (or extrudeds) are not created equal.
As far as the hub system, we can just let what Greg wrote be compared to what you have written, and let people decide for themselves. Hopefully folks will at least be more aware of just how different Magni's system is.
 

Abid

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I don't know what you mean by "be careful", exactly, and I was (indirectly) touting Magni rotors, not all composite blades. Obviously all composites (or extrudeds) are not created equal.
As far as the hub system, we can just let what Greg wrote be compared to what you have written, and let people decide for themselves. Hopefully folks will at least be more aware of just how different Magni's system is.

If Greg is saying the top to bottom bolt securing is what causes this cracking. That’s not technically correct. The transition from a hub that itself does not bend to a soft extrusion where all bending gets concentrated in this transition area is what causes the cracking. Having a better transition so bending is spread over a larger area would reduce the chances of this. Magni puts two bolts in shear and allows the blades to take bending which they do being composite quite well. In that sense he is correct. But his evaluation of top and bottom bolt stressors is not. The clamping of bolts itself isn’t the reason. The reason is improper concentrated transition. Those extruded blades need a bit more metal and a spar or loading element which is steel or similar electrically isolated from the Aluminum through a nonconductive structural glue.

Edit: I realized that you are focusing just on Magni. Magni has kept a clean record of QA in this. Absolutely
 
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Abid

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The Sikhs lost the Second Anglo-Sikh War in 1849, and the gemstone, at worst, was a spoil of war. Or, how far do you wish to go back? Didn't Nader Shah originally invade the Mughal Empire and loot the gemstone from Babur's Peacock Throne? And thereafter, didn't Ranjit Singh acquire the diamond from Shah Shujah Durrani under duress? Suggestion: get over it.

Besides, what has that diamond anything to do with this Tango2 crash? Was it not rather tacky to interject it here?

I see I touched a nerve in a couple of our British friends. I am long over it (like 32 years' worth over it). I don't think 1.7 billion people over there are. Art and heritage items of different places/cultures if taken out of those places under duress certainly do not belong in our Western museums and I am 100% sure that future generations of UK and others will realize that and make it right. It is a decision they have to arrive at themselves by thinking it through. But that is just a personal opinion and yes absolutely my bad in bringing that one liner up that riled you up so much. That topic does not belong here. My apologies and this would be the last call
 

Philbennett

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I see I touched a nerve in a couple of our British friends. I am long over it (like 32 years' worth over it). I don't think 1.7 billion people over there are. Art and heritage items of different places/cultures if taken out of those places under duress certainly do not belong in our Western museums and I am 100% sure that future generations of UK and others will realize that and make it right. It is a decision they have to arrive at themselves by thinking it through. But that is just a personal opinion and yes absolutely my bad in bringing that one liner up that riled you up so much. That topic does not belong here. My apologies and this would be the last call
Hey Abid - speaking for myself no nerves here and all is cool. I'm just saying that once you start digging around in the past it is seldom pretty. I think nations have enough problems dealing with the current events let alone trying to reconcile T-50, 100, 500, where do you draw the line??

Anyway I agree with Vance lets leave politics out of it we are likely not that far apart in our thinking.
 

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Hey Abid - speaking for myself no nerves here and all is cool. I'm just saying that once you start digging around in the past it is seldom pretty. I think nations have enough problems dealing with the current events let alone trying to reconcile T-50, 100, 500, where do you draw the line??

Anyway I agree with Vance lets leave politics out of it we are likely not that far apart in our thinking.

I agree
 

Abid

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I wouldn't deem the Rotor System 2's skinny little aluminium tube a "spar." As you stated, there is still a "hard transfer" of forces. They merely "kicked the can down the road" for a few more hundred hours. It's their least worst rotor iteration.

The main issue is the bending upward/downward cycle is being concentrated in one location too much. If it was spread over a bigger area, the fatigue life would improve greatly as the deflection would be much more spread out. This is a structural Mechanical Engineering problem. It does not require an aerospace degree. There are a few ways to do it but they will need to figure that out. I am curious of this talk of Cranfield study. Did the study demonstrate that fatigue life of rotor system 2 can be 2500 hours after this problem occurred in rotor system 1. Is that why you guys are bringing that up?
 
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Andino

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Why are you surprised that the Cranfield report received some traction? Isn't it one document that gives some colour on the blades? Yes agree it should have been expanded but I suspect it wasn't because it would bring the 2500hr life down... or potentially so. Even a move away from hours to take offs/landings.
Because it gave some colour on the blades is why I was surprised that the report received any traction.

The main issue is the bending upward/downward cycle is being concentrated in one location too much. If it was spread over a bigger area, the fatigue life would improve greatly as the deflection would be much more spread out. This is a structural Mechanical Engineering problem. It does not require an aerospace degree. There are a few ways to do it but they will need to figure that out. I am curious of this talk of Cranfield study. Did the study demonstrate that fatigue life of rotor system 2 can be 2500 hours after this problem occurred in rotor system 1. Is that why you guys are bringing that up?
The Cranfield report analysed Rotor System 1, the results of which fomented its replacement by the RS2. To my knowledge, there has been no similar analysis of the RS2, which is why I brought it up.
 

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In the discussion regarding rotor manufacturers there was no mention of sport copter blades. I was under the impression they have an excellent record. I need blades for the tango I'm rebuilding. So I'm reconsidering tango blades.
 

Philbennett

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I am curious of this talk of Cranfield study. Did the study demonstrate that fatigue life of rotor system 2 can be 2500 hours after this problem occurred in rotor system 1. Is that why you guys are bringing that up?
Sorry Abid for my part I missed this. The reason I mention is that the original RS1 in the first instance gave a life and service interval that the manufacturer and regulatory authority agreed upon one assumes by following the documentation and demonstrating an acceptable means of compliance etc. I am too lazy to look up the reference for RS1 but from memory it was either 2000 or 2500hrs.

Following on from that study - which was done on RS1 - the life was shortened in the UK to 700hrs. Now just for balance I myself flew at least 3 aircraft as an instructor with RS1 and the last one had +600hrs from my own flying / instructing before it was sold and with no failure or indeed issues. However I operated off a tarmac runway and as an instructor operating my own machine was flying essentially by the book. i.e. no fast taxi, no real hard landings, no hard life over rough grass strips and largely with me in the back to save the worst landings etc.

However given the problems that did occur with RS1 and the subsequent study finding the rationale to failure I do wonder if there was the same work done for RS2&3? After all the life of RS1 blades was more than halved which suggests [if nothing else] that the documentation and process that gave them the initial 2000 hours or more of life initially was very flawed.

I just wonder what the follow up to that was. It may have been extensive, but could also be zero.

What my own view is - and its reasonably thought through - is that recent accidents in Germany and UK have created new attention to rotor blades for this manufacturer except this time by the accident investigator. The German accident has significantly changed the inspection process for these rotors [again with such a change that one could question how the original regime was arrived at] and in the UK we have this outstanding report for a Cavalon fatal that, having gone through the process with the AAIB with a student who was sadly killed in one of my aircraft, given the timescales one wonders the sticking point of either investigation or debate because it is the oldest fatal accident still on the AAIB's book by circa 8months.

Current investigations

Statement

That an entire rotor head separates at altitude seems odd to this commentator as it must surely require a force that separates the head before the blades themselves are. If we see most accidents for rotary wing aircraft its very unusual for the blades to separate before the head does - unless there failure mode occurs first at the head - i.e. see the EC225 Norway accident.

One can be sure the issue will create debate because unless things are established beyond doubt the manufacturer will push back for the obvious reasons.
 
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