TAG crash

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Tyger

Active Member
The investigator said that all gyros with the folding-mast option have been grounded for several months, but that's what they were flying...
 

Kolibri

FW and Gyros
My sincere condolences.

This is apparently the second time the 2-piece mast bracket broke in flight.


201902 TAG crash-1.png
TAG 2-piece mast-e.png
TAG 2-piece mast-f.jpg
 

twistair

Living in the Skies
Hundreds of RAF-2000 and Calidus, dozens of SparrowHawks etc flew and fly with 2-piece masts without single problem in this joint. "It's broken because it had a 2-piece mast" sounds at least unwise. We need more data about this particular broken joint to make assumptions/conlusions.
 

Jean Claude

Junior Member
The inclination of the mast towards the front generates a very large bending stress on the mast. Misunderstanding of the efforts generated in the two flanks. Mechanical stress exacerbated by two idiot holes .
 

Tyger

Active Member
twistair;n1141925 said:
Hundreds of RAF-2000 and Calidus, dozens of SparrowHawks etc flew and fly with 2-piece masts without single problem in this joint. "It's broken because it had a 2-piece mast" sounds at least unwise. We need more data about this particular broken joint to make assumptions/conlusions.
This looks like a pretty different design from those typical two-piece (non-"folding") masts that you mentioned. As Jean Claude said, it looks like there would be a lot of stress just about at the spot where it broke.
 

twistair

Living in the Skies
Tyger;n1141933 said:
This looks like a pretty different design from those typical two-piece (non-"folding") masts that you mentioned. As Jean Claude said, it looks like there would be a lot of stress just about at the spot where it broke.
I probably missed something but I didn't see any direct evidence/testimony that this broken place was the cause of the crash and not post-crash break. Ten years ago I had a crash (costly lessons!) in an MTOsport loosing an airspeed at low altitude and flopping it vertically from few meters. Its mast has broken on impact and completely separated.

If only I had no witnesses anybody could tell that the broken mast could be the reason for this crash. Later I saw some more such MTOsport post-crash masts broken at the exactly same point - where lower double part of the mast becomes single tube. The unnecessary welding line across this single tube is another idiot decision (almost quoting JC).
Next thing is that this part of the mast is easy to make design stress load calculation - if you know material and more or less actual dimensions. Let's just try to find more data to make any conclusions. I believe ASRA stuff is well enough experienced and educated to provide thourough technical investigation. Bad thing is that we never see their findings published. That aggrieves.
 
twistair;n1141935 said:
I probably missed something but I didn't see any direct evidence/testimony that this broken place was the cause of the crash and not post-crash break.
If you watch the video the rotor appears undamaged indicating it separated before the impact.

A few years ago we had a gyro lose it's entire rotor in flight, the main body crashed and was destroyed while the rotor auto rotated to the ground almost completely intact.
 

Kolibri

FW and Gyros
"It's broken because it had a 2-piece mast" sounds at least unwise.
twistair, had I actually written that, it would have been unwise.
But I didn't write that, did I?
Rather:
"This is apparently the second time the [TAG] 2-piece mast bracket broke in flight."


Hundreds of RAF-2000 and Calidus, dozens of SparrowHawks etc flew and fly with 2-piece masts without single problem in this joint.
I'm not blaming 2-piece masts in general.
However, something is wrong with the TAG design there.
Jean-Claude instantly pointed to the obviously bad orientation of the
"two idiot holes".

Also, there are several grades of titanium, and, as I understand it, the TAG gyro is made in China from Chinese materials.
Quality control would be paramount.



If only I had no witnesses anybody could tell that the broken mast could be the reason for this crash.
Well, watch the news video and catch the part about rotor separation.
And, as Alan pointed out, the rotor had no rotational impact damage typical of gyro crashes, but seemed to have autorotated down on its own.

ASRA did ground all the 2-piece mast TAG gyros.
That grounding was
"still in effect " at the time of this crash, according to ASRA Alan Wardell.
I hope that other affected TAG owners will comply until this is sorted out and fixed.

Regards,
Kolibri
 

thomasant

Member
So sad that such an accident had to happen. Sincere condolences.

Some years ago there was a very informative thread about aluminum vs steel vs titanium. The takeaway from that thread for me was that while titanium is lighter and stronger than steel or aluminum for the same weight, it is also more brittle comparatively. I'm thinking that the 2 per rev vibration may impose stresses on the mast that cause the metal to eventually give way. The video shows a fairly clean break at the junction plates, with blades intact.

I'm attaching a picture of my aircraft in the accident that I had in December, where the folding mast made of stainless steel actually made the mast fold without breaking on the impact of the high inertia rotors striking the ground. As can be seen, the side plates, also made of stainless steel, bent and distorted, but did not separate. I believe if my mast were made of a single piece, the impact forces could have caused even more damage due to the energy being passed on to the main keel structures. Folding mast 1.JPG

IMHO, I feel steel (Chromoly or Stainless) as being the most forgiving considering the stresses imposed at the mast. Maybe the engineers can clarify.
 

fara

AR-1 gyro manufacturer
This photo shows current version of our AR-1 folding mast after a wire strike where wires got wrapped around and pulled backwards while gyroplane went forwards and crashed nose first (pilot got electrocuted and blacked out on the way down). Gyroplane then flipped over rotors striking the ground. This is the end result. The plates bent backwards like a Banana. Top of the mast is shown to the left in the picture. This newer version of folding mast is a bit different than first iteration and plates are longer than what Antony had in his. Thankfully pilot gained consciousness and walked away from the wreck and later taken to the hospital to get checked out.
I am not sure what TAG folding mast accident cause or analysis is and I do not want to jump to conclusions but there is a reason why the plates would shear and that reason has to be methodically found.
 

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loftus

Active Member
I am trying to understand; did the rotor separate with the top half of the mast, or did it separate first and then the mast break on impact. Not sure if any of the pictures I can see clarify that. Oh, OK, video seems to clarify that it separated before impact- wow!!!! I would love to know what TAG are doing to rectify the problem.
 

twistair

Living in the Skies
loftus;n1141975 said:
I am trying to understand; did the rotor separate with the top half of the mast, or did it separate first and then the mast break on impact.
I'd rather like to find if the mast broke and this caused the crash or something else went wrong and caused mast break and separation.
 

Kolibri

FW and Gyros
I'm glad that both AR-1 pilots were able to walk away from their crashes, although in my opinion a mere two incidents are not enough to conclude anything,
positive or negative, about the AR-1 mast design. The damage to both seems rather fluky, probably due to the random nature of impacts.

Gyro incidents, regardless of manufacturer, sadden me. We must all do what we can to make them rare.

Regards,
Kolibri
 

fara

AR-1 gyro manufacturer
Kolibri;n1142002 said:
I'm glad that both AR-1 pilots were able to walk away from their crashes, although in my opinion a mere two incidents are not enough to conclude anything,
positive or negative, about the AR-1 mast design. The damage to both seems rather fluky, probably due to the random nature of impacts.

Gyro incidents, regardless of manufacturer, sadden me. We must all do what we can to make them rare.

Regards,
Kolibri
Of course. We need to wait for 100 crashes in AR-1 before saying that it may have some considered engineered crashworthiness points :).
So in your engineering qualified opinion the mast design of AR-1 folding mast is not capable of taking a rotor hit to the ground hit and deforming without breaking?
Why? Is it because its using Stainless Steel?

Only one was an AR-1. The other was an Apollo but we adapted AR-1 folding mast to it because the owner is a long time customer and a friend of ours.
 

Kolibri

FW and Gyros
fara, I doubt that any gyro mfg. would need 98 additional similar mechanical failures to draw some conclusions.

I am not an engineer. You are not a rated gyro pilot.

I didn't bring up the AR-1, but responded very neutrally to those who did.
This thread is about the TAG gyro crashes, not the AR-1 or even 2-piece gyro masts in general.
Shall we stay on subject?

Thanks,
Kolibri
 

thomasant

Member
The discussion did come up about two piece masts and their inherent safety as compared to single masts, that's why I chimed in as a survivor of an accident.
 

Kolibri

FW and Gyros
Some years ago there was a very informative thread about aluminum vs steel vs titanium.
The takeaway from that thread for me was that while titanium is lighter and stronger than steel or aluminum for the same weight, it is also more brittle comparatively.
Probably time to revisit that thread. Please post a link to it, thanks.
 

fara

AR-1 gyro manufacturer
Kolibri;n1142007 said:
fara, I doubt that any gyro mfg. would need 98 additional similar mechanical failures to draw some conclusions.

I am not an engineer. You are not a rated gyro pilot.

I didn't bring up the AR-1, but responded very neutrally to those who did.
This thread is about the TAG gyro crashes, not the AR-1 or even 2-piece gyro masts in general.
Shall we stay on subject?

Thanks,
Kolibri
Kolibri. You are not an engineer but you feel very qualified to make technical assessments and your assessments and opinions based on those assessments tend to favor one gyroplane manufacturer and even an idiot with half an eye can see through that and of course you know everything already and are always right. What's there to discuss.
I only said something about AR-1 because Tony talked about his experience and there was a second experience with similar mast as well. The bottom line is ASRA has grounded "only" TAG folding mast gyroplanes in Australia, not all models with folding mast.
 
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