another look at the AutoGyro MTOsport crash of 11 September 2016 in Germany (D-MDOZ)

[Kolibri]

It appears to me that the engineers at AutoGyro did not correctly anticipate the loads from the customer use for rotor system one and field experience motivated a redesign of the blade grips.

As far as I know no one was hurt using the first rotor system.

You live in a fantasy world if you imagine that everything is engineered correctly when it leaves the factory in any industry.

No, Vance, my "fantasy world" is that something is first overbuilt, for safety and long service life, and field experience later illuminates
where weight and expense may be reduced without unwisely compromising strength.

AutoGyro (and ELA, etc.), on the other hand, underbuilds from the start, and field experience soon mandates that they add strength.

For life-risky aviation, that's the wrong way to do it.

 

[Vance]

No, Vance, my "fantasy world" is that something is first overbuilt, for safety and long service life, and field experience later illuminates
where weight and expense may be reduced without unwisely compromising strength.

AutoGyro (and ELA, etc.), on the other hand, underbuilds from the start, and field experience soon mandates that they add strength.

For life-risky aviation, that's the wrong way to do it.

Your fantasy world has never been how aviation works Kolibri.

Airworthiness directives exist because all the manufactures in aviation have engineers who make mistakes.

It looks like you will need to scrap your RAF 2000.

 

[Kolibri]

Airworthiness directives exist because all the manufactures in aviation have engineers who make mistakes.

I believe, in this case, you're conflating mere human error with incompetence and ignorance.

Your fantasy world has never been how aviation works Kolibri.

It is with the one gyroplane kit mfg. that I've full faith in. They overbuild from the start.

A decade ago they could have jumped on the Rotax 912 2-seat bandwagon, but they did not believe 100hp was sufficient for
a gryo's gross weight providing their level of safety and robustness.

Of course, that didn't stop others from building flimsy machines which effectively "time out" in less than 1000 hours.

It looks like you will need to scrap your RAF 2000.

Regarding its trim, upper mast, rotorhead, hub bar, and blades . . . that's exactly what I did. :whoo:
I removed it, replaced it all in my $11,000 upgrade, and refused to sell off the OEM parts.

Most of the remaining RAF parts one can generally live with if on a <$40,000 budget.

 

[WaspAir]

Vance, a "fantasy world" for me is one in which the unqualified follow a chain of unsupported assumptions (peppered with a series of likely, could be, might have, and the like) in the total absence of data to reach an alarming conclusion un-endorsed by any responsible authority, full of what sounds like engineering requirements but which in fact are unfounded, unrealistic, and arbitrary expectations. Inasmuch as even a stopped clock is right twice a day, there could in theory be disasters ahead, but that's hardly a solid basis for making decisions. This stuff is like fan fiction for the NTSB.

 

[Vance]

I admire you skill with the language J.R.

To get so much thought in three sentences is quite an achievement.

I realize there is no penetrating Kolibri's alternate reality.

I post because I have seen the effect such fear mongering has on the less informed and don't want to leave his delusional babbling unchallenged.

 

[Jazzenjohn]

I like the discussions where there is an open minded search for the truth above the discussions where people just want to win the argument.

 

[Kolibri]

I realize there is no penetrating Kolibri's alternate reality

Oh, and with what logical argument, Vance?

Your 1000% overstatement of what costs a currently available and long proven rotor which lasts many thousands of hours of hard flying without failing?
Your helmet-through-the-prop theory with not only only no evidence (i.e., impact damage), but countering evidence (location found near end of debris trail)?
Your "AutoGyro-merely-made-a-mistake" apologetics for their unacceptably delicate and dangerous first rotor system which was on its way to in-flight failures?
That more frequent inspections of AutoGyro RS2 blades will . . . decrease safety?

And you accuse me of "delusional babbling"?

I post because I have seen the effect such fear mongering has on the less informed and don't want to leave his delusional babbling unchallenged.

"And this award goes to St. Vance, for saving aviation from Kolibri! "

Had I or others posted about the first examples of cracking RS1 blades, you'd have been pompously belittling that, too.


__________

the total absence of data to reach an alarming conclusion

Oh, sorry, WaspAir, I thought you were referring to the BfU's report, which didn't even remark on the nature of the blade tearing pattern,
and offered no evidence for rotor rpm decay.

of what sounds like engineering requirements but which in fact are unfounded, unrealistic, and arbitrary expectations

And in your fantasy world, hundreds of gyro pilots do not fly on exactly such a quality rotor right now.
As if I'm demanding some unreasonable level of strength and safety. Well, I've been flying on mine for 3 years.

Also, Magni owners seem to have no rotor failure issues.


__________
AutoGyro doesn't make a trustworthy rotor. They don't know how.
However, they certainly know how to self-congratulate their German selves:

AutoGyro – Quality and Expertise

The German art of engineering, combined with an unparalleled world-wide distribution network provides you with absolute confidence and freedom to explore the skies.

Our fleet of up to 3,000 aircraft around the globe is testament to our commitment to quality and innovation, making us the world’s favourite gyroplane by far.

Designed and produced in Germany, with multiple international design awards, our team of more than 100 highly qualified and professional technicians, engineers and designers, is dedicated to providing the best aircraft possible without compromising on quality or indeed our engineering heritage.

Even as late as 2011, AG's persistent vibration issues complained about in the USA were due to the factory not delivering matching blades.

They still have square-cornered hub bar/straps clamped on the blades. Real genius there not to round off those ends to disperse the load.
That's some impressive "engineering heritage".




Want to see some real engineering in comparison?
Here is the blade strap of a Hughes 269; note the smooth taper and rounded ends, plus full surface contact (no gaping holes) with the blade:



Here's a RotorWay replacement blade, with proper stress relief and load transfer:




Neither did ELA know how to make a trustworthy rotor or hub bar (e.g., the departing blade in Poland).
They finally and mercifully ditched their own junk part for something better from an outside supplier.

Even if D-MDOZ's blade did not first fatigue fail, I'm this side of aghast that working professionals in the gyro world believe it acceptable that
a rotor blade can be so weak that even striking its model airplane-glued tail might break the blade off at its root.

The individual in the crowd who pointed out that the emperor had no clothes was neither Phd nor court anointed.
It was a child who simply spoke the truth.

To the non-jeering audience members here, have you noticed that people like Vance cannot fairly concede any point of mine?
When I politely (yet soundly) counter his position, does he maturely admit it? No.
Instead, he trots out his tired old shopworn insults of "fantasy" and "delusional" while simultaneously accusing AutoGyro owners of such
mechanical incompetence that they cannot be trusted to inspect their rotor blades twice as often as the schedule.

I'll take this abuse from "professionals" if my posts can awake even one fellow gyro pilot to a possibly looming safety issue.

Please vigilantly check your blades for wear, stretching, and cracking.
Meanwhile, have a nice weekend!

Kolibri

 

[PJB]

Standby Kolibri i asked you several days ago to present the FAA regulations for blades and the published material from other makers that show how their design is so much better and their proof of lifing. So far i can only reply "nothing heard"......

 

[Kevin_Richey]

Edited: (Sorry, I inadvertently posted a question for WaspAir RE: the A&S 18As here in this thread, instead of over there in the current thread on them)

 

[HighAltitude]

Kolibri, please start over.

You started this theory last October and yet you are still all over the place and this latest effort is still incoherent. First, you throw out a failure due to a crack through the last bolt hole. You back it up with one "failure" (not knowing how the blade separated) at the bolt hole and a string of photos that failed between 2 inches and 4 inches past the last bolt hole. You even provided a photo of an obvious cutaway of a blade. the band saw marks of each piece are blatantly obvious! (the right photo with a red circle at the bolt hole)

Now after 4 pages of posts, you are zeroing in on the clamping parts design with a few insults about how a glued tail section is "model airplane glued". Wow, that is funny coming from a person who cheers for Sport Copter and their glued blades. But I digress. No AG blades have cracked or failed at the very edge of the hub bar. None. Does a crack across the bolt hole cause the blade to break 2 to 4 inches away? Do posts of rolled over gyros have ANY relationship to a crack in the 6th bolt? No, and no.

I also find i comical that you also post multiple photos of the other blade still attached. If I follow your "logic", that blade is the one that chopped off the tail. It has severe damage and it bent all to hell but it didn't fail at the hub. It was clearly hit by the prop, it clearly fell from the sky attached, and it clearly did not fail. It is part of the same roughly treated high time gyro. I try really hard to follow along but you own photo evidence doesn't match your written narrative. Do you realize that you are providing photos that refute what you write?

So Koibri please clarify which of the three theories you want to run with so we can get back to the topic. And while you're at it, let us know who you are so those of us can thank you for saving us and give you "a case of beer" as a reward. I can't do that if I don't know who I am looking for. Its time to come out of your shadow. You can't insult "professionals" without sharing your credentials that makes your opinions more weighted than the experience of the #1 gyro manufacturer in the world. I might be the first to ask for your credentials, but I am certainly not the first to question them. Why not come out of the closet so we all can give you the credit and respect that you so desperately seek.

 

[Kolibri]

and a string of photos that failed between 2 inches and 4 inches past the last bolt hole.

High Altitude, you're missing something there.
The failure seems to have begun inside the doubler at the outboard bolt hole, continued past the doubler along the blade's internal rib, and in one case then tore off laterally from there.

You even provided a photo of an obvious cutaway of a blade. the band saw marks of each piece are blatantly obvious! (the right photo with a red circle at the bolt hole)

That photo of some parts was included merely to show the construction of the blade and doubler, and where the outboard retaining bolt would be.
If the doubler shows "band saw marks" then that's it came from the factory. Nobody cut it later.

that is funny coming from a person who cheers for Sport Copter and their glued blades.

That's quite a false comparison, as Sport Copter uses the Boeing spec 555 aerospace epoxy (Hysol) which makes a bond stronger than the parent material.
They've never had a bonding failure, even in the worst of impacts.

The AutoGyro horizontal stabilizer, however, often enough breaks apart along its bond seam, separating the upper and lower halves.

I also find i comical that you also post multiple photos of the other blade still attached. If I follow your "logic", that blade is the one that chopped off the tail.

No, I've never said that, for I don't believe that.
It is not the one which chopped off the tail, for it hasn't that kind of impact damage on the end of the leading edge.
Its bent damage appears to be from the ground impact while attached to the rotorhead/mast/gyro, including a "spike" impact with the rudder guide axle.

I try really hard to follow along but you own photo evidence doesn't match your written narrative.
Do you realize that you are providing photos that refute what you write?

You've misinterpreted. See above.

Now after 4 pages of posts, you are zeroing in on the clamping parts design

Yes, as further evidence of a poor design.
I am not, as you seemed to mis-infer, claiming that D-MDOZ failed at the edge of the doubler.
It didn't have to, as cracking inside the doubler at the bolt hole was sufficient.


_____________
Regarding my "credentials" I should think that the objective intelligence of a gyro pilot/owner would be enough.
This is within the orbit of many here, however, I probably cannot help those with a vested interest in maintaining the fiction that AutoGyro makes a robust 2500 hour rotor.
This group would likely include many/most gyro CFIs (who often train in AG machines) and nearly every AutoGyro owner.

Now, for the rest of us, let's recap.

Let's go back to the BfU report and rotor rpm decay and blade flap. Let's, arguendo, assume that is exactly what happened.
That said, there still remains the troubling nature of the blade tear. The doubler tells the tale.

The white circles show the topside blade surface fretting and compression of the doubler during coning moments.
The red arrows portray the violent blade bending and breaking of the doubler.
The yellow arrow shows the probable last tear direction during detachment.
(Notice the longitudinal tear as the squished blade was bent around the doubler trailing edge behind the front -- the blade's last fulcrum before tearing off.)





A solely centrifugal separation would not have bent down and broken the doubler.

Hitting the tail would not have bent down and broken the doubler.

While rotor flap would have presented very strong downward bending moments, shouldn't that be survivable?
Many RS2 bladed gyros have experienced a low rotor rpm takeoff and subsequent flapping, yet did not break (though I'll wager they were compromised),
However, D-MDOZ's blade failed during rotor flap.

My gyro rotor mantra -- and I see no reason why it shouldn't be everyone's mantra -- is this: its parts should be strong enough to withstand blade flap.

D-MDOZ, however, I believe had been sufficiently weakened by its 1073 landings over 333 hours.
Some faulty material may have contributed to the weakness.

So, to summarize, that blade should not have broken off.
Not from rotor flap, and not even from striking the tail.
That it did should alarm every AutoGyro owner, especially because the tear obviously began at the historic cracking locus of RS1.

My hypothesis merely extends in logical progression the working/weakened undesired "hinge" at the bolt hole, and postulates that as it began to
fail and tear it produced the (singular) blade flap which struck the tail.

But one needn't go that far to honestly suspect that even if blade flap occurred first (from, say, bad piloting), and not as a cause of a tearing blade,
the simple fact that the blade tore at all as it clearly did is grounds for increased caution.

Regards,
Kolibri

 

[Kolibri]

Something that I couldn't make out in the torn blade root photo was the "stepped" hole behind the outboard bolt.
I just learned from an August 2011 engineering report that RS2 has an aluminum 6005A-T6 "sleeve, bonded inside the blade in the region of the bolt holes . . . with a wall section of 3mm".
It is termed "reinforcing tube" with part #BT3893.





In their goal of strengthening the RS2 blade over the RS1, the top and bottom web thickness was increased from 4mm to 5.5mm.
So, versus the RS1, the RS2 blade at the bolt holes is 3mm thicker, with an additional 6mm of 6005A-T6 in the sleeve.

And yet it broke.

I would be surprised if mere rotor flap, or even striking the tail, would be sufficient to break a non-compromised RS2 rotor.

Thus, I continue to suspect that -- despite the less rigid scalloped hub bar with 2.85° of coning -- the RS2 blades continue to flex and weaken at the outboard bolt holes.

Regards,
Kolibri

 

[Vance]

In my opinion based on reading his posts Kolibri knows very little about engineering or manufacturing and is condemning a rotor system he doesn't understand simply because of things unrelated to the function of the rotor system.

Every indication is that the new rotor system is working just fine.

A team of people who know a lot more about engineering and accident investigation than I ever will and have resources for analysis carefully looked at this accident and did not identify the rotor system as contributory.

Showing unrelated pictures, assigning irrelevant meaning and repeating assertions does not make them correct.

I will continue to fly and recommend AutoGyro products and continue to perform the maintenance and inspection procedures called out in the very thorough documentation available on line.

Based on my experience I feel AutoGyro products are sufficiently robust to outlast most owners' interest in gyroplanes if they are maintained as prescribed in the documentation.

They appear to be holding their value well indicating to me that they function well in the gyroplane world.

I have seen AutoGyro GMBH gyroplanes used for training (hard usage) with over 700 hours on them that look and function like new.

I have seen AutoGyro products that were not well maintained that I would not fly. It is to AutoGyro GMBH’s credit that there are not more accidents due to poor maintenance.

 

[Steve_UK]

At the recent Aero 2019 trade show held at Fredrichshafen, Germany Auto-Gyro displayed several brand new production gyros, the current production base line is

D-MCAU Cavalon serial number #398

D-MTOJ MTOsport serial number #1744

No shortage of takers.

 

[Kolibri]

A team of people who know a lot more about engineering and accident investigation than I ever will and have resources for analysis carefully looked at this accident and did not identify the rotor system as contributory.

The BfU report did not at all mention any material analysis of the torn blade root, probably because none was conducted.
Rather, they implicitly alluded to rotor rpm decay and subsequent rotor flap as the possible cause of the tail strike.

Even if that were true, it still doesn't justify a blade separating like that.
This is what AutoGyro apologists like you refuse to admit.

I have seen AutoGyro GMBH gyroplanes used for training (hard usage) with over 700 hours on them that look and function like new.

Maybe so, but you've not seen any of them even close to the alleged 2500 hours of rotor service life.
Or even half that. Those RS2 owners with 1250+ hours are welcome to post hi-res photos of their blade bolt holes.

Based on my experience I feel AutoGyro products are sufficiently robust to outlast most owners' interest in gyroplanes if they are maintained as prescribed in the documentation.

LOL, yes, I agree! That seems to be exactly what AutoGyro banks on.
Low time products for even lower time users.


_________

No shortage of takers.

Sure, Steve, but so what?
Sales are not ipso facto of superior strength or safety.

The discontinued V-tail Beechcraft Bonanza is a classic case in point.
Its inherent structural weakness caused some 200 in-flight failures.
This was vigorously denied by Beechcraft and their fans, until a dogged researcher successfully made his case.

Regards,
Kolibri

 

[Kolibri]

A team of people who know a lot more about engineering and accident investigation than I ever will and have resources for analysis carefully looked at this accident and did not identify the rotor system as contributory.

The BfU report did not at all mention any material analysis of the torn blade root, probably because none was conducted.
Rather, they implicitly alluded to rotor rpm decay and subsequent rotor flap as the possible cause of the tail strike.

Even if that were true, it still doesn't justify a blade separating like that.
This is what AutoGyro apologists like you refuse to admit.

I have seen AutoGyro GMBH gyroplanes used for training (hard usage) with over 700 hours on them that look and function like new.

Maybe so, but you've not seen any of them even close to the alleged 2500 hours of rotor service life.
Or even half that. Those RS2 owners with 1000+ hours are welcome to post hi-res photos of their blade bolt holes.

Based on my experience I feel AutoGyro products are sufficiently robust to outlast most owners' interest in gyroplanes if they are maintained as prescribed in the documentation.

LOL, yes, I agree! That seems to be exactly what AutoGyro banks on.
Low time products for even lower time users.

Every indication is that the new rotor system is working just fine.

So, Vance, you're actually going to assert that the RS2 separation in D-MDOZ connotes a rotor system that is "working just fine"?
Really?


_________

No shortage of takers.

Sure, Steve, but so what?
Such sales are no guarantee of superior strength or safety.
They certainly do not betoken an engineering sophisticated customer profile.

The discontinued V-tail Beechcraft Bonanza is a classic case in point.
Its inherent structural weakness caused some 200 in-flight failures.
This was vigorously denied by Beechcraft (which blamed the pilots), until a dogged aviation consumer magazine successfully made their case.

The V-tail Bonanza came under close scrutiny in the mid-1980s following a series of in-flight breakups. Several airworthiness directives were issued and a special study was done by the FAA and the Department of Transportation, which resulted in a stabilizer reinforcement kit at the root of the V-tail. After the installation of the kit, the in-flight breakups decreased dramatically.

______________
Using the two engineering reports comparing tensile loads between RS1 and RS2, I compiled a side-by-side table.
(Since AutoGyro CFIs and owners no doubt have their own report copies, my work can be scrutinized for accuracy.)



In all categories but "blade hole tensile stress" the RS2 has less reserve strength factor than the RS1.
Without the BT3893 "reinforcing tube" it would have been 0,829x (vs. 1.288x with the tube).

Regarding "blade section tensile stress" the RS2 data ignores the "benefit of [BT3893 reinforcing tube]".

But, as the RS2 structural report qualifies, the tensile data "neglects bending stress" (which is covered in other reports).

One may wonder why include tube, instead of simply adding that 6mm increase of section to the top and bottom blade webs.
The RS2 webs were increased to 5.5mm (from the RS1 4mm), and I suspect that 8.5mm webs were not possible to extrude in 6005A-T6 in conjunction with the very thin skins of the trailing 50% of the profile. Material flow rates would be excessively disparate.

Hence, the only way to reinforce that bending area of the blade was to insert a tube.

But why use such a thin walled tube made of aluminum? Why not a heavier wall, or even steel?
Probably to keep the chord balance at or under ~30%.

Those are my thoughts on the tensile reports. The bending stress data will be more relevant.

Regards,
Kolibri

 

[Vance]

The BfU report did not at all mention any material analysis of the torn blade root, probably because none was conducted.
Rather, they implicitly alluded to rotor rpm decay and subsequent rotor flap as the possible cause of the tail strike.

Even if that were true, it still doesn't justify a blade separating like that.
This is what AutoGyro apologists like you refuse to admit.



Maybe so, but you've not seen any of them even close to the alleged 2500 hours of rotor service life.
Or even half that. Those RS2 owners with 1000+ hours are welcome to post hi-res photos of their blade bolt holes.



LOL, yes, I agree! That seems to be exactly what AutoGyro banks on.
Low time products for even lower time users.


_________

Sure, Steve, but so what?
Such sales are no guarantee of superior strength or safety.
They certainly do not betoken an engineering sophisticated customer profile.

The discontinued V-tail Beechcraft Bonanza is a classic case in point.
Its inherent structural weakness caused some 200 in-flight failures.
This was vigorously denied by Beechcraft (which blamed the pilots), until a dogged aviation consumer magazine successfully made their case.




______________
Using the two engineering reports comparing tensile loads between RS1 and RS2, I compiled a side-by-side table.
(Since AutoGyro CFIs and owners no doubt have their own report copies, my work can be scrutinized for accuracy.)





In all categories but "blade hole tensile stress" the RS2 has less reserve strength factor than the RS1.
Without the BT3893 "reinforcing sleeve" it would have been 0,829x (vs. 1.288x with the sleeve).

Regarding "blade section tensile stress" the RS2 data ignores the "benefit of [BT3893 reinforcing sleeve]".

But, as the RS2 structural report qualifies, the tensile data "neglects bending stress" (which is covered in other reports).

One may wonder why include sleeve, instead of simply adding that 6mm increase of section to the top and bottom blade webs.
The RS2 webs were increased to 5.5mm (from the RS1 4mm), and I suspect that 8.5mm webs were not possible to extrude in 6005A-T6 in conjunction with the very thin skins of the trailing 50% of the profile. Hence, the only way to reinforce that bending area was to insert the sleeve.

Then why use such a thin walled sleeve made of aluminum? Probably to keep the chord balance at or under ~30%.

Those are my thoughts on the tensile data. The bending stress data will be more relevant.

Regards,
Kolibri

In my opinion the strength of the blades on D-MDOZ did not affect the safety of the flight.

In my opinion the BFU investigators did not do materials analysis because they understand that rotor blades are not expected to survive impact at flight RPM.

The sky is not falling because AutoGyro GMBH may not be right about the blades going to 2,500 hours. AutoGyro GMBH mandates inspections to recognize problems before they become flight critical.

AutoGyro rotor blades are inexpensive to replace so even if they don’t go for 2,500 hours it does not significantly add to the cost of operation of AutoGyro gyroplanes.

With a little more research on the Bonanza V tail story you might have learned: "In virtually all the structure-related accidents the airplane was flown outside the envelope. Often as not this was the result of the pilot losing control." According to Air Facts Journal; they are not the only ones with this opinion.

There has not been a series of crashes because of the AutoGyro rotor system and in the case of D-MDOZ in my opinion the gyroplane was flown outside the envelope.

Just because you don't understand why the rotor system works doesn't indicate there is a problem to me.

 

[Kolibri]

"In virtually all the structure-related accidents the airplane was flown outside the envelope. Often as not this was the result of the pilot losing control."

Funny how the FAA AD on strengthening the parts seemed to cause the pilots to fly inside the envelope. <rolling eyes>

The sky is not falling because AutoGyro GMBH may not be right about the blades going to 2,500 hours.

No, but it would definitely call B.S. on their service life projection and thus design.
As I earlier wrote, such a high and even number smacks more of marketing than engineering.

In my opinion the BFU investigators did not do materials analysis because they understand that rotor blades are not expected to survive impact at flight RPM.

Where did the BfU report state that the tail was struck at flight rrpm?
If anything, they implied sufficient rotor rpm decay to have caused the flapping itself.

AutoGyro rotor blades are inexpensive to replace so even if they don’t go for 2,500 hours it does not significantly add to the cost of operation of AutoGyro gyroplanes.

$4,800 (the last figure I've seen) is inexpensive?

There has not been a series of crashes because of the AutoGyro rotor system

No, not to date, but there have been enough blade breakages from <flight rrpm to strongly suggest that the parts are not robust.
If there is one system in a gyro that I'd insist were "hell-for-stout" it would be the rotor system.

and in the case of D-MDOZ in my opinion the gyroplane was flown outside the envelope.

Based upon what evidence?
I've read the report carefully, and I read German. I saw nothing that would indicate that.

Regards,
Kolibri

 

[Vance]

I feel it is safe to say on a cost per hour basis $4,800 for blades in inexpensive even if they only make 1,500 flight hours that is $3.20 per hour and for most gyroplane enthusiasts thirty years of flying.

In my opinion based on my experience the rotor striking the tail is not a part of the normal flight envelope.

In my opinion a rotor blade breaking in a crash is not indicative it will break in flight.

I feel that the AutoGyro rotor system is well proven.

 

[Kolibri]

even if they only make 1,500 flight hours

If I purchased a gyro which was alleged to have a 2500 hour rotor life, I'd be less than thrilled that it needed replacing at 60% of that,
regardless of the $3.20/hour cost (vs. $1.92). I'd feel that I had been "sold to" by hucksters.

In my opinion based on my experience the rotor striking the tail is not a part of the normal flight envelope.

Of course not. But what made a blade strike the tail at all? Unloading the rotor to cause rrpm decay?
There is no evidence that the pilot made such an error, especially from where the ground witness saw him fairly high above (nonturbulent) terrain.

In my opinion a rotor blade breaking in a crash is not indicative it will break in flight.

Perhaps not, but the odds increase that it could, or even will, break in flight.

The energy transmitted to gyro blades by the strongest of gusts and convection and turbulence pales in comparison to the violence of a ground impact.
Conversely, rotor blades which remain intact throughout all variants of crashes can be assured never to break in flight.
That's the sort of confidence I prefer in my blades.

I feel that the AutoGyro rotor system is well proven.

You'd have said such about RS1 until 2010.
Using your 50 hour/year operation figure, the oldest of RS2 blades (since 2011) have only about 400 hours.
I.e., it's too early to make such a blanket proclamation of "well proven".

_______
I feel that D-MDOZ was the "first canary in the mineshaft" with its 333 hours and 1073 landings.

For those who are comfortable and competent doing their own basic gyro maintenance, I would urge 50 hour inspections of the rotor blade holes.
For the average owner, that's only once a year vs. every two years.

I'd think that an annual condition inspection c/should include this, anyway, so Vance's "removing the blades more often than the recommended inspections
for cracks is going to lead to more safety issues than simply following the factory recommendations for inspection" was baseless.

Meanwhile, try not to overstress your AG blades with excessive coning. Make gentle roundouts and flares.
Go slowly over rough ground (and with the rotor lock off, holding the cyclic in hand).
Perhaps support the blades in hangar.
Such has no downside, and can only help extend rotor life.

Safe flying,
Kolibri