Blakmax, agree with your assessment.

Here's what we know so far:

1. One blade impacted the cabin, but probably not the blade shown here.
2. The clean 'cut' of the honeycomb on this blade looks more like structural failure vs. impact damage.
3. The spindle remained attached to the blade root.
4. There appears to be mechanical failure of the coning hinge attach point to the M/R blade, but that could be due to water impact (just guessing here of course).
5. So, possible failure of M/R blade honeycomb resulting in impact of second blade with cabin and possibly tailboom, liberation of the blade due to imbalance and structural failure, loss of aircraft control and impact with water.

The second blade will be interesting to see. The treasure hunter shown has probably already found it.

RIP, sad story.

Coning bolt failure,piece of hub trailing side,tusk on spindle bent inboard, No leadind edge damage, outer bits of honeycome & skin ? cleaved out by the other blade before it also launched from the mast?,need to see the whole batch of pieces to the cause,Spindle crack AD with the fiddling of the suspected parts contribute for the bolt failure?

I don't agree with Matari's depth of knowledge.

To me the cabin and bubble did still look in one piece and the tail boom if broken prior to water entry can easily be explained by immediate engine over speed causing whirl mode in the T/R drive shaft and breaking the tail boom right where they said it was broken. That is easy to see, have a look inside the tail boom, there will be evidence of the out of balance shaft. hitting it, bearing hangers torn off etc.

I don't agree that one blade hit the other, a) there is no pictorial evidence so far and b) that would also have meant at least half a turn after one departed with the consequent out of balance effects, not yet visible in the cabin photograph..

The thing that is really striking to me at the moment is that the threaded end of the blade bolt appears to be visible (under the rope).
If that is the case why did the nut detach and leave the rest of the hub behind - or elsewhere?

I cannot see the thread sufficiently to gauge its integrity.

Were both bolts over stretched at some assembly in the past causing damage to the threads, does or can the procedure of stretching leave the threads, hanging on the edge?

That may be a plausible explanation of both bolts at once?? It may explain why when the blade in the picture departed it did so rearwards until the nut less bolt cleared the other side of the hub, then it simply broke off the hub portion - still attached - because of rearwards leverage.

See that sort of thing in machinery all the time.

I sincerely hope they can find the other blade it should be easier now, but they might need a few more dollars to help.

Is anyone close by that can report on that?

tet.

Someone should have given me a tune up, if it is the bolt that I refer to of course it would have to be the nut in the left hand side of the photograph and presumably the trailing edge as the bolt is supposed to be installed with head on the leading edge and which looks totally different from the other end in view.

Meaning if it is the bolt the head of it is missing??.

Nut ,piece of hub,pitch link,mostly intact blade,a wipe mark next to the drain plug,chunk of blade gone, tip at the very end looks like a good dent, How deep was the water? did blade drop in the water & hit the bottom of the sea?
strange. over streched bolt? head scraching continues.

topendtorque,

My depth of knowledge on the R22 is very limited, and my knowledge of this puzzling accident even more so. I'm just speculating, not knowing any more than anybody else here. I really hope they find the second blade and some answers, pronto. Every R22 driver out there deserves a fast and thorough investigation.

Bolt Failure
 

Just to throw something else in to the pot..

We had an R44 Raven II that fortunately whilst sat in the hangar and not flying suffered a Blade Bolt Failure!

We returned to the machine after it had sat for a weekend to find a thrust washer sitting on the hangar floor! The full horror then dawned as you looked up to see one of the main Blade bolts sticking out from the Hub. If this had failed in flight and not whilst sat with the full weight of the blade on the droop stop I am sure the bolt would have totally departed from the aircraft along with the blade etc and you can imagine the rest....

The bolt was sent to our local CAA for inspection who then sent it to the FAA via Robinson, the opinion in the end was that it was a one off caused by Hydrogen enbritellment of the bolt and was not considered to warrant further investigation. The bolt had a total time of 80 hours from new.

I appreciate this was on an R44 not an R22 but the bolts must go through a similar manufacturing process??

I can email pictures if you PM with an email address me as I cannot seem to get them to insert to this post.

Helichoppers: this is so freaking scarey! What is more scarey is that neither the FAA or the CAA mandated for a supplier check on QA or a mandatory change to another supplier. Do you mean to tell me, you simply replaced the suspect bolt with another from stores and went flying!!!!!!:mad:

TC
Best post i have seen from you;) It is at this point one wonders what is the point of The CAA. 3 years ago whilst engineers doing an exhaust valve guide check discovered 1 collet missing and only half the other one, ie valve about to drop into engine. On futher investigation engine overhaul shop had put wrong valve into engine. Spoke to CAA who were not interested, at that point I gave up with the system:ugh:

The bolts are usually made in batches if one failed due to hydrgen embrittelment I would check the whole batch. The post treament bake process may have been missed.

Bolt Failure
 

Would be very interested in further info re the embrittled bolt (pictures), Im convinced our accident was bolt failure but no one seems to want to investigate it!
Fortunately the machine was in the hover when it 'appeared' to throw a blade and no one was killed.
We now as company policy regularly replace the blade bolts and NEVER re use them.
As an operator with 14 RHC aircraft I really would like to know the bolts are good!!!

We have maintenance schedules, manuals to tell us exactly how to do things, every item has to be made, tested, approved, with a paper trail, APs are certified & the FAA CAA say not a problem regarding a bolt that fell to pieces, makes me feel really safe in the knowledge that the regulators are on top of problems, surely at least the batch should be recalled at no cost to owners then an in depth examination made of both the batch & the manufacturing process\ facility.

TC

The aircraft was grounded pending investigation, once all the relevant authorities were satisfied we changed all the bolts and nuts for new ones, and the aircraft has flown without a problem since. We suggested that a recall was carried out on the bolts of that batch and that as a matter of safety the ones in service were replaced or inspected, that fell on deaf ears! what more can you do if the authorities and manufacturer wont do anything?

We were told there had never been any reported incidents of bolt failure but it appear there is more coming out in to the open.

HC

Sorry for my last post I forgot the rules, it is all ways the owners problem never the regulators or manufacturers, perish the thought, I wonder what the response would have been if it had happened in flight, another low G accident I suspect.
anti-talk
Was your bolt broken or damage to great to access initial failure glad it turned out not to bad.
Any official report done?

Yep NTSB investigated by 'telephone' as no one was hurt :ugh:
Bolt was never recovered but the hub was scored on the inside and subsequently fractured, have the hub (well not the part that would have had the bolt attached). Whats left of it that is!
The guys were incredibly lucky as they were in the hover, the rotation was so violent they both lost thier shoes in the impact.

I had understood that once these bolts had been subjected to appropriate torque they should not be re-used. Was I wrong in that belief?

Yes John you are, however we DO NOT re use them as a matter of internal policy

Just had a conversation with a friend who works part time in our industry and as a quality auditor for a large utility company. They have had a major issue with hydrogen embritlement in bolts holding gas pipes together !
They are having to withdraw bolts as some fail on torque up, some at a few days some at a few months. When i told him the story of bolt failure and it being a one off the response was initially stunned silence followed by " the quality control of the bolt manufacture has failed in which case the whole batch of bolts that that bolt came from will be affected, at the very least someone needs to get into the manufacturer to check on the process "
Best of luck if you fly one of frank's products :uhoh: At this point I dont know why I bother to have a Safety management system for my company when the manufacturer/ competent authority ( perhaps that shold be incompetent authority) obviously isnt interested in safety:eek:or shold that be :ugh:

When installing the procedure is to "stretch" the bolts to between .015" and .017". The manual carries a warning that overstretched bolts can lead to a catastrophic failure.

Indeed. Especially IF the bolts were more brittle and thus less malleable than usual.

Either checking or withdrawing a batch would be far cheaper than a game of chance.

That is just scary, beyond words.

Russian Roulette anyone? :ugh:

Russian Roulette anyone!
 

Russian Roulette with one round in a pistol I guess.
Not a Revolver!