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

Vance

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Kolibri;n1144132 said:
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.


Safe flying,
Kolibri[/COLOR]

Inappropriate control inputs are what make a rotor strike a tail on a gyroplane.
 

Vance

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Kolibri;n1144132 said:
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.


Safe flying,
Kolibri[/COLOR]

In my opinion this is more baseless conjecture.
 

Vance

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Kolibri;n1144132 said:
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".

_______


Safe flying,
Kolibri

This is typical of your baseless conjecture and pretending people said something they did not. Average is not highest.

Fifty hours a year is the average flight time for all experimental amateur built aircraft.

Many AutoGyro products are used for training and fly four to six hundred hours a year and yet there still has been nothing more catastrophic than cracks in the bolt holes.
 

Vance

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Kolibri;n1144132 said:
_______
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 "[/COLOR]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

Inspecting the blades using new hardware and a calibrated torque wrench is probably not going to hurt anything. Reusing the hardware or not torqueing the bolts to the correct value is in my opinion a bad idea and it is my observation it is common practice.

Take flying advice from Kolibri for what it is worth with his limited experience and demonstrated lack of knowledge.
 

Kolibri

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Inspecting the blades using new hardware and a calibrated torque wrench is probably not going to hurt anything.
Reusing the hardware or not torqueing the bolts to the correct value is in my opinion a bad idea
I should think that goes without saying . . . or should.

Average is not highest.

Fifty hours a year is the average flight time for all experimental amateur built aircraft.
Of course average is not highest.
My point (I thought) was clear: the average RS2 bladed gyro has, at most, about 400 hours.


Many AutoGyro products are used for training and fly four to six hundred hours a year and yet there still has been nothing more catastrophic than cracks in the bolt holes.
So, the RS2 blade bolt holes have been cracking in higher hour machines, but this is not catastrophic because the cracks are detected during regular 100 hour inspections?

Call me old-fashioned, but routine blade bolt hole cracking is not acceptable, especially in the allegedly improved RS2.


Take flying advice from Kolibri for what it is worth with his limited experience and demonstrated lack of knowledge.
Heh, well, what little I do know is sufficient to urge caution here.
True ignorance, however, wouldn't do even that.

Regards,
Kolibri
 

Vance

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Many AutoGyro products are used for training and fly four to six hundred hours a year and yet there still has been nothing more catastrophic than cracks in the bolt holes.

Kolibri;n1144145 said:
So, the RS2 blade bolt holes have been cracking in higher hour machines, but this is not catastrophic because the cracks are detected during regular 100 hour inspections?

Call me old-fashioned, but routine blade bolt hole cracking is not acceptable, especially in the allegedly improved RS2.



Regards,
Kolibri[/COLOR]

What evidence do you have that the RS2 blade bolt holes have been cracking in higher hour machines Kolibri?

Pretending that is what I wrote is typical of your distorted thought process and why most people don't respond to your posts on The Rotary Wing Forum.

As far as I know there has been nothing beyond cracks in the holes of high time first rotor system.

I am not aware of any cracks found in high time RS2 on AutoGyro products.

It appears to me the weakness is in your thought process and not the rotor system on AutoGyro products.
 

Kolibri

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Many AutoGyro products are used for training and fly four to six hundred hours a year and yet there still has been nothing more catastrophic than cracks in the bolt holes.
As far as I know there has been nothing beyond cracks in the holes of high time first rotor system.
Then you should have written the former sentence with more clarity, Vance.
The goal of clear composition is that the text cannot be read any other way than how the writer intended.
While your writing has improved over the years, it still contains the odd and confusing phrasing, QED.


___________
The RS2 is hollow inside the clamped areas, and the doubler forms a poor contact zone.
There is no root pad, thus the clamped load is not properly spread out.
The blade continues to bend and work laterally at the outer bolt hole, and blade fatigue is only forestalled somewhat by the scalloped hub bar and increased coning angle.

Nobody here has expressed any faith of RS2 lasting to its advertised 2500 hours, including you.

I suspect that owners of high time RS2 AutoGyros would be reluctant to publicly admit that they've found bolt hole cracking.

Regards,
Kolibri
 

Vance

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I write to the level of comprehension of most of the readers of the Rotary Wing Forum.

Some apparently get left behind.

It appears to me you don't understand how a bridge works Kolibri and you imagine solid is always better.

Solid is not necessary for structural integrity.

The blade grip system on AutoGyro has an appropriate contact area that works just fine.

I am willing to bet my life on the AutoGyro rotor system. That would suggest to most people I have faith in the system.

I carry out inspections as prescribed in the excellent AutoGyro GMBH documentation.

I suspect most gyroplane pilots would let people know when they find something that is not airworthy.

I let people know when my Sport Rotors were no longer airworthy at around 1,500 flight hours and nine years.

I did not sell them to someone else.

I let people know when I found problems with a Cavalon.

I don't sell AutoGyro GMBH products and I don't sell for Sport Copter.

I let people know when I found a problem on an American Ranger despite it being my favorite currently produced gyroplane.

I feel pre-flight inspections and annual condition inspections are important and I spend time teaching that.

I feel based on my study of NTSB reports; learning to fly a gyroplane well is the most important thing to mitigate the risk of flying.

People who are driven by fear and ignorance should probably find a different hobby instead of inventing things to be afraid of and trying to scare other people.
 

Kolibri

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I let people know when my Sport Rotors were no longer airworthy at around 1,500 flight hours and nine years.
It's a pity that you left the reason for that unstated (corrosion from your salt air) while mentioning ~1500 hours (as such could be misconstrued as having meaning about service life).
(There are ways to nearly totally inhibit salt air corrosion of aluminum, but you apparently were unaware of them.)



It appears to me you don't understand how a bridge works Kolibri and you imagine solid is always better.

Solid is not necessary for structural integrity.
Then you're wrong about me there. Yes, I know that bridges are bolted (for movement), not welded.

I made the point that the RS2 blade load is not properly distributed.
Their flexing hub bar was a step in the right direction, but the bending stress remains concentrated at the outboard bolt holes.
I suspect that time will tell.

What remains interesting is how you stubbornly resist trying to explain how a flapping low rpm rotor can be excused for breaking off after striking the tail.
Your (second) set of Sport Rotors would not ever detach like that, but somehow that is no indicator to you of superior strength.
No offense, but talk about a distorted thought process.

Regards,
Kolibri
 

Kolibri

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I am willing to bet my life on the AutoGyro rotor system.
Heck, Vance, what rotor system wouldn't you fly on?
You even dismissed objections to the RAF's crack-prone <2004 hub bar.



I let people know when my Sport Rotors were no longer airworthy at around 1,500 flight hours and nine years.
It's a pity that you left the reason for that unstated (corrosion from your salt air) while mentioning ~1500 hours (as such could be misconstrued as having meaning about service life).
(There are ways to nearly totally inhibit salt air corrosion of aluminum, but you apparently were unaware of them.)



It appears to me you don't understand how a bridge works Kolibri and you imagine solid is always better.

Solid is not necessary for structural integrity.
Then you're wrong about me there. Yes, I know that bridges are bolted (for movement), not welded.

I made the point that the RS2 blade load is not properly distributed.
Their flexing hub bar was a step in the right direction, but the bending stress remains concentrated at the outer bolt holes.
Before crack initiation and propagation, material can first be weakened in an area.
There are numerous examples of <flight rrpm tip-overs where an RS2 blade broke off at its outer bolt hole.
That clearly suggests the weakest area along the span.
A metallurgical study of such broken parts would show if this area had been working internally before the crash.

What remains interesting is how you stubbornly resist trying to explain how a flapping low rpm rotor can be excused for breaking off after striking the tail.
Your (second) set of Sport Rotors would not ever detach like that, but somehow that's no indicator to you of superior strength.
Yet you accuse me of a "
distorted thought process"?

Here's a formula for a safe and robust gyro rotor:
Blades with high strength in the root, attached to rounded end blade straps with radiused edges, on a strong yet sufficiently flexible hub bar.

The poor design of RS2 should be obvious simply from the straight edged doubler, with hard/sharp corners pressing on the blade.


RS2 square doubler corners.png


Talk about a recipe for stress risers.
Yet AutoGyro GmbH touts its "
German heritage of engineering" as if they were the Mercedes-Benz of gyros.

Regards,
Kolibri
 

j bird

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Here we go again!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!:Cry:
 

WaspAir

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Shhhhh !! You'll only encourage him. If past is prologue, the last word here will be claimed in green type, and each black type entry only prolongs the process.
 

Kolibri

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Sure, WaspAir, tell us all how the photo I just posted is representative of a well-designed gyro rotor.

Or, will you merely suggest yet another tune to whistle past that graveyard?
 

Kolibri

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The new ELA at least has the rounded blade straps and stepped blade roots done nicely.
Such is apparently beneath or beyond AutoGyro.


TAG hub bar plates.png
 
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Kolibri

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After discussing this crash and the RS2 sleeved blade root with an expert in the field, I've a sub-hypothesis to pose.

To wit: that the blade flexing and working at the outboard bolt hole first broke off the end of the 14mm O.D. 3mm wall aluminum sleeve.

In fact, it seems logical to assume that the sleeve and entire blade root did not necessarily break off simultaneously.
The inner portion (the sleeve) probably broke before the outer portion (the blade).

Not being restricted to move, that broken ring of 6000 series aluminum could have been flung by centripetal force within
the blade's longitudinal hole, lodging at the end cap.

For now, I'll call it 1" long, but it could have been a bit more, or less. Such a severed ring would weigh 0.0157 lbs. (7.121400209 grams).


weight of AutoGyro RS2 broken 1 inch sleeve.png


+/- 7 grams is a lot of weight in rotor blade balancing. I've flown in a gyro which had highly objectionable vibration being less than 3 grams out of balance.

Now, this 7.1 grams suddenly moving full outboard would not be as violent as adding the same weight, since the internally broken blade weighs the same
but the longitudinal center of mass has been lengthened, nonetheless creating an imbalance with the opposite blade -- and a severe one.

This would more quickly fail an already compromised blade at the bolt hole. While progressive, it may have all happened within just a few seconds.
Or, if the sleeve took a while to migrate outwards, several minutes (with a pilot perplexing vibration which got worse and worse).

That the blade broke in flight before striking the tail is a hypothesis. I've not proven this, however, what has been shown repeatedly is that the RS2 blade is
weakest at the outer bolt hole, and apparently too weak to tolerate impact energies which do not sever other gyro blades (most notably, Magni and Sport Copter).

Even Trixy, Xenon, and RAF blades don't snap off at the root during mere taxi tip-overs. Why do Auto-Gyros?

I suggest some serious scrutiny of the RS2 engineering.

Regards,
Kolibri
 
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Kolibri

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RS2 blade sleeve.png

From AutoGyro's own engineering diagram, with my red-marked outboard piece which may have independently broken off.
Since the bolt hole centers are 1.875", the end piece is about 76.6% as long, or an estimated 1.44" (36.5mm) -- vs. my earlier guess of 1" (25.4mm).

Thus, it would weigh an estimated 10.2 grams (vs. only 7.1 grams).
RS2 blade sleeve.png
 
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