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R-22 ROTOR SEPARATION? Florida Photo

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R-22 ROTOR SEPARATION? Florida Photo

Old 4th Dec 2012, 10:25
  #21 (permalink)  
 
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...the eye witness in the video said "the white rotor popped off and flew up..."
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Old 4th Dec 2012, 10:53
  #22 (permalink)  
 
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Missed that

Thanks gB. I missed that. It does change my perception and increase my level of concern. I'm still not sure that loss of one rotor blade would lead to no fuselage damage and separation of the other rotor blade.

I just hope this is not yet another case of disbonding leading to blade failure and another loss of life. I'll wait for the initial report before further comments, but I have been waiting for three years for one airworthiness authority to release the report on the investigation I was involved in. It is so frustrating to sit aside and know of a significant issue but not being able to openly discuss it without the legal cover provided by the final report.I stress that my concerns may not be applicable in this case, and I certainly hope that is the case.

Regards

Blakmax
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Old 4th Dec 2012, 11:09
  #23 (permalink)  

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A truly tragic and horrific accident. It looks like a classic case of the "Jesus nut", or Robbo equivalent, failure.
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Old 4th Dec 2012, 11:53
  #24 (permalink)  
 
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I'm pretty much with you too M'hale as you would have seen. I'd be thoroughly cross examining historical flights pilots.

I checked the local WX but from here can't seem to go back further than the 1st but the photograph of the foliage and WX trends show nothing our of the ordinary at all, 5 to 10 knots fair etc.

I don't believe that a mast bump has to take out the tail boom and I agree with Blakmax that a bad flight condition on one blade could have imparted strong enough forces to cause the mast bump. Against that the eyewitness should have also said something like this, "even though we were seeing it what really got my attention was a really increasing swishing sound before the thing flew off"

The witness also said it "flew up" indicating an aerodynamic stability of some sort of the rotors, which wouldn't be the case with a major debond I don't think.

We had a '47 once with a mast cracked severely. It exhibited a very strong vibration and was cracked a third of the way around and nearly 1/8 inches wide at center of it.We put that down to constant over controlling, little or no corrosion evident from memory. The A/C was fitted with a no bar kit and the crack was just under the mast rod end clamps.

So I guess I am getting around to saying that if there was a pre-existing crack that it should have exhibited some form of vibe, but then again it could well have been very early stages. Another issue is the proximity of the ocean and whether there may have been advanced corrosion.

Certainly one blade off I think would take out either or both cab and tail boom in collateral damage.

The Aussie air force 205's from memory with their mast bumps years ago didn't have collateral damage, I could be wrong there.I used to know one of the eye witnesses to the second one and he didn't mention it.

Dennis, believe me you will need weightlessness to do damage; any sort of violent control inputs whilst you have positive pendular weight will just force the A/C to just follow the cyclic. A mate of mine and I were chewing this last night, his words were, 'You would have to think that after all the hundreds of thousands of hours of mug pilots and good mustering drivers that a simple problem like over controlling would have shown up yonks ago.'

Finally I will devoutly say that these things are not flimsy. Some of the components over the years have had their faults, the flimsy stainless steel skin on those blades being one, but they were only flimsy when idiots ran into things, quite solid enough to fly with and do all sorts of hard maneuvers with. Perhaps your engineer mate VF is talking about A/C that are flown over hours, if so it's non valid argument. Very many are over flown for sure.

These R22 A/C have had many beef up mods, 90% of which I am reliably informed emanate from North Queensland where they were consistently overflown.

So, Frank now has an aircraft design far superior than is needed should people fly according the 100 hour and AFM book.Lots of the blades failures have been shown to have just simply been so overweight so often that it is bleeding obvious someone will get hurt.

I've tried to hurt them often and toughest ride I have had for a long while was today, 42 degrees outside the moo cows being particularly not fond of such heat and some bloody cane toad had crawled into the machine some days ago while it sat outside with doors on, stink that bastard.

cheers tet

Last edited by topendtorque; 4th Dec 2012 at 11:54.
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Old 5th Dec 2012, 19:44
  #25 (permalink)  
 
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Originally Posted by mhale71 View Post
While i cant speak from experience myself i also would have thought mast bumping would come with tail and fuselage damage...
Hmmm, I'm not 100% sure but when I look at the picture closely I have the feeling that the cab might be missing at least partially.
Even if it was a doors off flight I seem unable to see the solid part of the cab that is normally underneath and a bit in front of the pylon.

Therfore I wouldn't rule out a classic mast bumping with severing the cab. In that case the tail boom might stay on unscathed. I'm pretty sure I remember cases before where that happened.
In that case we could only pretty much rule out LRRPM induced Mast Bumping because that usually blows the Rotor disc backwards leading to the Robbie- Cut.
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Old 8th Dec 2012, 16:00
  #26 (permalink)  
 
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Additional information here: Robinson R22 BETA II, N2626N: Accident occurred November 30, 2012 in Apollo Beach, Florida - Aviation News & Events

The helicopter was recovered from the bay 2 days later. The engine and rotor mast remained attached to the airframe. The rotor hub remained attached to the rotor mast; however, both spindle assemblies and their respective main rotor blades had separated from the hub and were not recovered. The tailboom separated about 6 feet from the transmission and the tailrotor remained with the tailboom. The rotor hub was retained for further examination and a further search for the main rotor blades was planned.
(bold mine)
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Old 10th Dec 2012, 02:25
  #27 (permalink)  
 
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Boy oh boy oh boy.

So much for witness statements.

We still don't know whether the spindles themselves or the hub failed, which I think I am right in saying would be first time ever for either and in either which way case I would say watch this space very closely or;
whether the spindle bearings failed in which case - I become mute.
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Old 10th Dec 2012, 04:31
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I am right in saying would be first time ever for either and in either which way case I would say watch this space very closely or; whether the spindle bearings failed in which case - I become mute.
Hmmm... I think you would be interested to read some of the initial comments to the request from the NTSB to ground the R-22 back in 1993..... They are all still there. I will leave it at that... Google is your friend.
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Old 10th Dec 2012, 11:51
  #29 (permalink)  
 
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The tail appears to be complete in the photo was it damaged by blade & broke on impact or did the water impact cause the break.
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Old 10th Dec 2012, 12:05
  #30 (permalink)  
 
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both spindle assemblies and their respective main rotor blades had separated from the hub
This what has got me? It seems quite clear and presumably written by a helicopter experienced person. It may be of course that it was the blades, outboard of the blade spindle housing which failed, which is where all other blade inboard failures have occurred. If it was a -2 blade and one failed, I guess it not unreasonable for the other to fail immediately given the massive torque spike. That is, if it already had a progressing fatigue crack.

I note in this link where there is an analysis of similar failures done by OZ ATSB that on none of the Aircraft mentioned did they carry out an inspection of the second blade to see whether there was evidence of fatigue crack commencement.

Except for the first, which was a -1, the rest are -2.

Thanks Gordy for this one which I think is the one you refer to, with 31 accidents. All appear to relate to being either mast bumping or low RRPM causing blade stall, or unexplained M/R divergence.

I still cannot find evidence of either hub, spindle or spindle bearing failure.

Cheers tet
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Old 10th Dec 2012, 14:30
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This is very interesting, we had a 22 Roll over in the hover about 3 years ago that appeared to throw a blade - it was thrown well clear of the wreckage with no bending or discernable damage, the mast sheared at the gearbox and then the mast wrapped under the machine causing a pre impact fire due to ruptured fuel tank (as the mast cut through it)
Fortunately both occupants escaped the wreckage , the pilot stated he didnt grab a skid (dynamic roll over) and the machine literally inverted itself very violently (both occupants lost their shoes)
We were convinced this was a blade separation (query bolt failure??) we recovered the blade with hardly and damage, the Hub broke in two and the bolt was no where to be found.
As a result everytime the blades come off the machine we now replace with new bolts (never did like the 'stretching' idea.)
The local FSDO felt there was some mileage in the blade seperation idea but the NTSB had no appetite to investigate further due to there being no injuries. We retained the hub and I still have it to this day.

Last edited by anti-talk; 10th Dec 2012 at 14:32.
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Old 10th Dec 2012, 22:09
  #32 (permalink)  
 
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Thanks, anti-talk, you have answered one query we all used to have that being, was there ever a chance of pilot survival in the neck area if one of a two blade system departed. Probably depend on a lot of factors though, actual cabin weight to help cancel reaction or whatever.

But regarding your hub, any chance of posting some photos of it?

NTSB had no appetite to investigate further due to there being no injuries.
Yes that is a galling issue, not just NTSB but it seems most all agencies have the same retardence of mind. It would be very wise to use their investigative resources in many areas. Too easy to cut back claiming their own financial resources limits, which of course means to fix it we need to go to the Ministers responsible, a tough task most places.
cheers tet..

Last edited by topendtorque; 10th Dec 2012 at 22:11.
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Old 11th Dec 2012, 09:37
  #33 (permalink)  
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Anti talk: can you pass on any photos of that head to Shawn, blacmax or me please?
AUS mustering: loads in the outback mustering are generally quite low, more concerned with the cycle records, given the value of S-N curves out at 10^7...

Photo of the descent show apparently that there has been a blade fuselage strike, the upper canopy area is missing, which is consistent with a loss of one blade and the track of the remaining blade. Following fuselage impact, that remaining blade is not going to be hanging around, so may not have hit the tail boom before departing fix.

Coning hinge... the tension on the coning hinge balance to the teetering hinge is important. If the blade starts flapping at the coning hinge instead of the teeter, it imposes very high strains on the blade, and a failure of the blade itself has been recorded in the UK (failed 3/4 through from TE in 20 minutes). Vibration is very high with such failures, no doubt that you are having a fun day. I have had a coning bearing eat itself in 5 minutes, and it was a rapidly decaying condition. I think the mfr would expect this to last longer in general, my event was a 44, and it was 5 minutes. On preflights, look for aluminium oxide (gray dust) around the teeter and coning bold spacer/washers.

Personally, have a query around the +ve delta3 configuration that occurs if the blade flaps at the coning hinge, but some very well respected aerodynamicists consider that not so unusual, gets my attention nonetheless.

RHC is a "finely" designed machine, much stronger than you would expect, and still a great machine to fly. It does get attention with the question of divergence from time to time. The concord event is probably the most perplexing case out there still on divergence.

Mast bumping is mainly a low g event; at low advance ratios, or hover, you may get a tail boom strike.. but I would be surprised if you get a mast bump straight off with rapid reversal of controls. (don't try this at home... :| ). The mast stops are very good indicators of contact from the inner land of the hub, the preflight of a RHC is worth every second. The rotor system is intolerant of abuse, but is able to still be flown within an impressive envelope with due care to the basic dynamics of a teetering head.

FDR

PS: the report will be very interesting to look at. The general modes of failure are pretty well established and the physical evidence will speak to the specific failure.

Last edited by fdr; 11th Dec 2012 at 09:48.
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Old 11th Dec 2012, 13:52
  #34 (permalink)  
 
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Next question for operators, how many Rotor Hubs are you getting back from RHC at 2200 hrs and how many are they are condemning.
Lets take a straw poll?
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Old 2nd Jan 2013, 08:13
  #35 (permalink)  
 
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The two main rotor blades from this fatal R22 accident still missing. Robinson offers reward for blades :

Robinson $2,000 reward

Last edited by HeliHenri; 2nd Jan 2013 at 08:15.
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Old 2nd Jan 2013, 08:51
  #36 (permalink)  
 
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Far be it for me to be cynical about this but does this equate to an equivalent value of $1000 per aircraft seat/passenger?

Does this value express Robinson's motivation to stimulate search incentive?

Does it also express their value of accident investigation?

Just asking.
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Old 2nd Jan 2013, 09:24
  #37 (permalink)  
 
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Dear oh dear.
Well this is what the preliminary report says
The rotor hub remained attached to the rotor mast; however, both spindle assemblies and their respective main rotor blades had separated from the hub and were not recovered
and, they are showing pictures of the bolt hardware.

Do we assume because of that the bolts intoto are missing? what is remaining? Any evidence of bolt breakage and twisting off of the hub? I don't have any idea how malleable the hub is and whether it could bend to accommodate such movement.

My gut feeling is that it would be extraordinary for the spindle hub-end to break before the retaining bolt, but I'll happily bow to wiser metallurgical heads.

A seaside residence and unchecked corrosion on steel bolts may have an answer, but gee whiz, surely not that bad and on both bolts????????.
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Old 9th Jan 2013, 03:42
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Here is a photo of one of the blades (can't find if this has been confirmed by NTSB). Note the big chunk out of the trailing edge near the trim tab. Spindle looks attached but hard to tell from this pic what part on that end might have failed.

From this site:TreasureWorks - Helicopter Blade Recovery - TreasureWorks Forum


Last edited by Matari; 9th Jan 2013 at 04:17.
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Old 9th Jan 2013, 06:54
  #39 (permalink)  
 
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Looks to me like there is a rather large part of the rotor hub still attached to that blade, including the blade bolt, or at least part of the bolt (to the left of the blade in the photo).

Edit: This is what I mean


Last edited by lelebebbel; 9th Jan 2013 at 07:11.
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Old 9th Jan 2013, 09:48
  #40 (permalink)  
 
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Trailing edge separation

Matari, I note the segment of blade held by the person in the picture. From initial observations I do not see any adhesive on the LE foaming adhesive bond surface. This means one of two things: 1. the adhesive was never bonded along that face or 2.(more probable) the failure was through the core. Closer investigation would tell the actual location of the failure.

Is that TE separation related to the crash? My initial thoughts are that it is not. The spar appears straight so that suggests that this blade has not impacted the cockpit or boom, which I would expect if a segment of blade had failed at the start of the crash. It is possible that the other blade has different damage patterns.

My suspicions fall on the close up discussed by leleb(etc.). If you look at the very left of the blurred image at the very end of the remaining structure, you will note that the left side appears bright, but the rest of the surface appears dull. Rapid fracture surfaces are usually brighter than regions where fatigue cracking has occurred. I stress that this is only a suspicion. Closer inspection would be required.

I'd love to make comments about the look on the guy's face but in respect to the deceased, it may not be appropriate to make light fun under the circumstances. RIP.

Regards

Blakmax

Last edited by blakmax; 9th Jan 2013 at 09:50.
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