Sikorsky S-76 down in the North Sea (Threads merged)
Thanks.
I have deleted my previous post to ensure that this subject matter is removed.
Just hoping to keep the thread and facts straight.
I personally feel that it is very important to ensure that anything that we discuss as fact, is indeed just that.
My sincere condolences to the families and colleagues affected by this tragic accident.
I have deleted my previous post to ensure that this subject matter is removed.
Just hoping to keep the thread and facts straight.
I personally feel that it is very important to ensure that anything that we discuss as fact, is indeed just that.
My sincere condolences to the families and colleagues affected by this tragic accident.
Iconoclast
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Facts. Whose facts.
To: Heliport
I made the statements about the blade failures based on the facts, as I knew them. These facts were published in Aviation Week and Space Technology and were also told to me by one of the trial lawyers involved in the litigation that followed the accidents. If these two sources did not repeat the facts either truthfully or correctly then my information is incorrect and I will admit that fact if in fact I am proven wrong.
[Edited:
* Inviting people to "ask Nick" questions in the present circumstances unfair. Nick cannot possibly be expected to answer questions on this thread.
* Claiming that because somebody hasn't answered a question to your satisfaction means they haven't got an answer, or the answer would be damaging to their company is silly. Rotorheads is the leading helicopter website, but it is not an official investigation.]
I would strongly suggest that you have Flying Lawyer who knows Nick to ask those questions etc
See my comments above.
If you have followed my various posts I have never offered my sympathy to the survivors of those individuals of the accidents discussed on these forums. It pains me deeply when people are killed in any type of aircraft accident however I do my damnedest to keep that from happening. My profile reads: Keeping crew and passengers safe. That says it all. If I have to use these forums to make people aware of problems that might manifest themselves then I will do that provided I am not censored.
I made the statements about the blade failures based on the facts, as I knew them. These facts were published in Aviation Week and Space Technology and were also told to me by one of the trial lawyers involved in the litigation that followed the accidents. If these two sources did not repeat the facts either truthfully or correctly then my information is incorrect and I will admit that fact if in fact I am proven wrong.
[Edited:
* Inviting people to "ask Nick" questions in the present circumstances unfair. Nick cannot possibly be expected to answer questions on this thread.
* Claiming that because somebody hasn't answered a question to your satisfaction means they haven't got an answer, or the answer would be damaging to their company is silly. Rotorheads is the leading helicopter website, but it is not an official investigation.]
I would strongly suggest that you have Flying Lawyer who knows Nick to ask those questions etc
See my comments above.
If you have followed my various posts I have never offered my sympathy to the survivors of those individuals of the accidents discussed on these forums. It pains me deeply when people are killed in any type of aircraft accident however I do my damnedest to keep that from happening. My profile reads: Keeping crew and passengers safe. That says it all. If I have to use these forums to make people aware of problems that might manifest themselves then I will do that provided I am not censored.
Last edited by Heliport; 28th Jul 2002 at 04:53.
I'm not trying to start a war here, so please let's drop the matter.
Any action taken by the moderator of this forum, was at my request. The "facts" in discussion are simply untrue. I know, because like everyone else operating S-76's we dealt with the issue when it arose (a long, long time ago).
With all respect Lu, I am not questioning your credentials, motivation or credibility. I am simply ensuring that any technical discussion be limited to the actual events, causes, findings and remedies. The facts that I am disputing are the experience I acquired whilst dealing directly with these original occurences a long time ago. So facts? Well my facts I guess!
The previous failures related to main rotor spindles. At no time were the blades implicated. There have been other blade issues, but unrelated to a failure of this type.
It is entirely inappropriate that any employee of Sikorsky (especially of the stature of the very identifiable poster here) would make any comment at this stage of ANY investigation, or be requested to respond by any of us here. Although immediate cause and mitigation may be defined, the completion of the investigation is a long way away and it is quite unreasonable to consider that anyone from Sikorsky would comment in any other manner than in an official capacity, (think litigation).
We are not going to solve this issue on this forum and should really consider the effects upon the families and colleagues affected by this, as well as individuals outside this sphere of operation who may not have the information to determine the veracity of the discussion.
Any action taken by the moderator of this forum, was at my request. The "facts" in discussion are simply untrue. I know, because like everyone else operating S-76's we dealt with the issue when it arose (a long, long time ago).
With all respect Lu, I am not questioning your credentials, motivation or credibility. I am simply ensuring that any technical discussion be limited to the actual events, causes, findings and remedies. The facts that I am disputing are the experience I acquired whilst dealing directly with these original occurences a long time ago. So facts? Well my facts I guess!
The previous failures related to main rotor spindles. At no time were the blades implicated. There have been other blade issues, but unrelated to a failure of this type.
It is entirely inappropriate that any employee of Sikorsky (especially of the stature of the very identifiable poster here) would make any comment at this stage of ANY investigation, or be requested to respond by any of us here. Although immediate cause and mitigation may be defined, the completion of the investigation is a long way away and it is quite unreasonable to consider that anyone from Sikorsky would comment in any other manner than in an official capacity, (think litigation).
We are not going to solve this issue on this forum and should really consider the effects upon the families and colleagues affected by this, as well as individuals outside this sphere of operation who may not have the information to determine the veracity of the discussion.
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Cyclic Hotline
Re "Any action taken by the moderator of this forum, was at my request."
That statement is open to misinterpretation. Just to avoid any possible misunderstanding: It's true you drew attention to Lu's post but I took action having read it myself and making my own judgment.
Lu
I stand by what I said in my previous post.
Heliport
Moderator
Re "Any action taken by the moderator of this forum, was at my request."
That statement is open to misinterpretation. Just to avoid any possible misunderstanding: It's true you drew attention to Lu's post but I took action having read it myself and making my own judgment.
Lu
I stand by what I said in my previous post.
Heliport
Moderator
Last edited by Heliport; 26th Jul 2002 at 08:07.
Iconoclast
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Titanium spar.
To: beanie
Let’s assume your are correct in stating that the spar is made of titanium alloy. If that were true the point of lightning attachment would have been seriously discolored.
Titanium has a strange property in that it will form colored oxides on the surface of the material when an electrical current is passed through it. The color can be varied with the increase or decrease in current level and all colors of the spectrum can be achieved with this variance. The voltage can vary from several volts to 50-100 volts in order to achieve the surface color change. If this relatively low voltage can effect the surface in forming the colored oxides then imagine what several million volts at very high amperage can do not only to the surface but the internal matrix as well.
Following the lightning strike, the blade was returned to the manufacturer for evaluation before it was returned to service. Currently the investigation team is gathering more information about the history of this blade. At this stage, there is no evidence to link the lightning strike to the fatigue failure, however, this is one of the variables still under active consideration.
Titanium has a strange property in that it will form colored oxides on the surface of the material when an electrical current is passed through it. The color can be varied with the increase or decrease in current level and all colors of the spectrum can be achieved with this variance. The voltage can vary from several volts to 50-100 volts in order to achieve the surface color change. If this relatively low voltage can effect the surface in forming the colored oxides then imagine what several million volts at very high amperage can do not only to the surface but the internal matrix as well.
Iconoclast
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Don't confuse me with facts.
To: widgeon
I lifted this off of the North Sea crash thread. I can’t answer your question in regards to the methodology of incorporating a secondary load path on the blade(s). My statements were based on the facts as presented to me. If you want to know ..... etc ask Nick.
See my comments above.
Titanium spar.
To: beanie
quote: Following the lightning strike, the blade was returned to the manufacturer for evaluation before it was returned to service. Currently the investigation team is gathering more information about the history of this blade. At this stage, there is no evidence to link the lightning strike to the fatigue failure, however, this is one of the variables still under active consideration.
Let’s assume your are correct in stating that the spar is made of titanium alloy. If that were true the point of lightning attachment would have been seriously discolored.
Titanium has a strange property in that it will form colored oxides on the surface of the material when an electrical current is passed through it. The color can be varied with the increase or decrease in current level and all colors of the spectrum can be achieved with this variance. The voltage can vary from several volts to 50-100 volts in order to achieve the surface color change. If this relatively low voltage can effect the surface in forming the colored oxides then imagine what several million volts at very high amperage can do not only to the surface but the internal matrix as well.
Note: There is a museum in either Spain or Portugal that is made of mainly Titanium alloy. If this museum is ever hit by lightning it will turn all colors of the rainbow.
I lifted this off of the North Sea crash thread. I can’t answer your question in regards to the methodology of incorporating a secondary load path on the blade(s). My statements were based on the facts as presented to me. If you want to know ..... etc ask Nick.
See my comments above.
Titanium spar.
To: beanie
quote: Following the lightning strike, the blade was returned to the manufacturer for evaluation before it was returned to service. Currently the investigation team is gathering more information about the history of this blade. At this stage, there is no evidence to link the lightning strike to the fatigue failure, however, this is one of the variables still under active consideration.
Let’s assume your are correct in stating that the spar is made of titanium alloy. If that were true the point of lightning attachment would have been seriously discolored.
Titanium has a strange property in that it will form colored oxides on the surface of the material when an electrical current is passed through it. The color can be varied with the increase or decrease in current level and all colors of the spectrum can be achieved with this variance. The voltage can vary from several volts to 50-100 volts in order to achieve the surface color change. If this relatively low voltage can effect the surface in forming the colored oxides then imagine what several million volts at very high amperage can do not only to the surface but the internal matrix as well.
Note: There is a museum in either Spain or Portugal that is made of mainly Titanium alloy. If this museum is ever hit by lightning it will turn all colors of the rainbow.
Last edited by Heliport; 28th Jul 2002 at 04:56.
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Extending somewhat on what Nigel has skirted.......in that due to the extreme vibrations, no call was possible....!!
Years ago [seems like yesterday].....I can remember a crew that had a Rotor Brake Quill on a B412 let go.
The vibration was so great that their Headsets "flew" off their heads....hence no Intercom or Radio available........great, right when you need both.
Perhaps a helmet thread .........who's game???
Years ago [seems like yesterday].....I can remember a crew that had a Rotor Brake Quill on a B412 let go.
The vibration was so great that their Headsets "flew" off their heads....hence no Intercom or Radio available........great, right when you need both.
Perhaps a helmet thread .........who's game???
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But if low voltages and amps can cause these oxides to form, surely the blade would have been rejected after being subjected to high volts, high amps in a lightning strike?
If such currents cause havoc with the titanium matrix, then I would expect the blade to have been scrapped. So either the damage, IF it occurred (as it's not clear from the AAIB findings just yet) was not apparent, or the check was not performed correctly, if I understand your statements correctly.
And as other operators have recently removed blades that have suffered lightning strikes in the past as a precautionary move, there must have been quite a number over the years that have been checked, found satisfactory and returned to service.
I cannot believe that if lightning had such damaging effects these blades would have been allowed back on aircraft. But then again, I may be proven wrong..
If such currents cause havoc with the titanium matrix, then I would expect the blade to have been scrapped. So either the damage, IF it occurred (as it's not clear from the AAIB findings just yet) was not apparent, or the check was not performed correctly, if I understand your statements correctly.
And as other operators have recently removed blades that have suffered lightning strikes in the past as a precautionary move, there must have been quite a number over the years that have been checked, found satisfactory and returned to service.
I cannot believe that if lightning had such damaging effects these blades would have been allowed back on aircraft. But then again, I may be proven wrong..
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About helmets, I've been told by a previous employer that pilots wearing helmets would scare the passengers into thinking that helicopter flying was a dangerous enterprise...
Sorry guys....but helmets would be totally useless in this event....when that blade let go....and the transmission left the aircraft with what was left of the bad blade and the other three blades.....head protection became a moot issue.
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In the ASB issued at the same time as the AAIB statement Sikorsky mention 8 blades that are known to have been involved in lightning strikes.
An amended version came out today stating that all blades involved in lightning strikes on the ground and in the air should be removed before the next flight.
An amended version came out today stating that all blades involved in lightning strikes on the ground and in the air should be removed before the next flight.
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Yes I understand the visual impact on passengers....also that this highly unique S76 accident was "unsurvivable'....AABI words.
But....Offshore crews do undertake HUET, wear Cold Water suits, wear lifejackets, have a beacon in their pocket, CVR, FDR, IHUMS, and so on and so on.........but the most basic of personal protection..........nope, it's to hard.....but to hard for all the wrong reasons.
Visors protect against birds.......Helmets provide a better Db noise reduction [important if you are having a busy week].......and your prime communication system will be there when you need it.........
Not to mention the better protection for yourself.....number "One".
Remember if you survive the initial or subsequent "Incident'.... then the rest on board have a far better chance as well......
I am as guilty as the rest....if I am rostered to an Onshore Base or task......sure my helmet is part of my basic kit and would'nt leave home without it.. [and passengers don't blink an eye]
But if the boss rosters me over water...."Old Faithful" stays in the cupboard.
Makes good sense.......Yuh!!
But....Offshore crews do undertake HUET, wear Cold Water suits, wear lifejackets, have a beacon in their pocket, CVR, FDR, IHUMS, and so on and so on.........but the most basic of personal protection..........nope, it's to hard.....but to hard for all the wrong reasons.
Visors protect against birds.......Helmets provide a better Db noise reduction [important if you are having a busy week].......and your prime communication system will be there when you need it.........
Not to mention the better protection for yourself.....number "One".
Remember if you survive the initial or subsequent "Incident'.... then the rest on board have a far better chance as well......
I am as guilty as the rest....if I am rostered to an Onshore Base or task......sure my helmet is part of my basic kit and would'nt leave home without it.. [and passengers don't blink an eye]
But if the boss rosters me over water...."Old Faithful" stays in the cupboard.
Makes good sense.......Yuh!!
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"It is entirely inappropriate that any employee of Sikorsky (especially of the stature of the very identifiable poster here) would make any comment at this stage of ANY investigation, or be requested to respond by any of us here.
Although immediate cause and mitigation may be defined, the completion of the investigation is a long way away and it is quite unreasonable to consider that anyone from Sikorsky would comment in any other manner than in an official capacity."
Although immediate cause and mitigation may be defined, the completion of the investigation is a long way away and it is quite unreasonable to consider that anyone from Sikorsky would comment in any other manner than in an official capacity."
The above is an excerpt from a post by Cyclic Hotline yesterday.
Lu
When we have experts of the calibre and standing of Nick Lappos prepared to give their time answering questions on the Rotorheads, it's unfair to abuse that generosity by asking questions which even indirectly relate to an investigation in which they or their company is involved. It is equally unfair to encourage others to do so.
Nick and I are friends and in regular contact, but I wouldn't think of trying to take advantage of that friendship by asking him any questions about this crash or anything which might be covered in the ongoing investigation - any more than he would ask me about an aviation case whilst the case is still current.
Surely that's just good manners, and respect for a friend?
Nick is a good friend and enormous asset to Rotorheads. Let's be sensible and respect his position.
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titanium properties
I’ve read in a variety of sources that the S76 (including the A model) does indeed have titanium spares in the rotor blades.
The following information was gleaned from a Titanium Industries website, where an association promotes the industrial use of titanium, and I’m posting this in case the lighting strike had anything to do with the metal fatigue the AAIB detected in the fractured rotor blade. The information on how to machine titanium and especially how to weld titanium was particularly interesting. The physical property discussion will be limited to only those properties that would be relevant in a lightning strike.
Titanium reacts strongly with normal air when heated, so arc welding requires a pure argon “air blanket”. An arc welded titanium structure shows colors if contamination develops. A “silver metallic” color means no contamination, a gold or straw color means some contamination, and a light or dark blue color means high levels of contamination (the blue colors also mean no structural soundness at all). Contamination can produce porosity, low-notch toughness value, and brittleness.
Titanium comes in 3 classes of alloys that include 2 normal lattice matrix classes, and a class with a mix of the 2 normal matrix. The first matrix is “hexagonal closed-packed” (HCP) lattice structure (also know as “alpha phase”). The second matrix is “body centered cubic” (BCC) lattice structure (also known as “beta phase”). Certain alloys stabilize the titanium to one matrix or the other within certain temperature ranges (“alpha phase” class alloys and “beta phase” class alloys) and some alloys stabilize a mixture of both (“alpha-beta phase” class alloys). Various heat treatings and “annealing” also help to stabilize the matrix of the various alloys.
Titanium can undergo a matrix transformation known as an “allotropic transformation”, that can convert the matrix from one lattice form to the other, when heated to certain temperatures (depending on the alloy). If I understand it correctly something like an “allotropic boundary” (my phrase) can form within a structure when titanium is “spot heated”, causing one lattice (or mixture) to exist on one side of the “boundary” and a different lattice to exist on the other side. This can be a source of structural weakness and/or brittleness.
Titanium is also a poor conductor of heat, which must be watched when welding it. This property allows hot spots to develop more easily within a structure.
All of this would be relevant to a lighting strike, because discoloration would indicate that atmospheric gases (namely oxygen and nitrogen) might have contaminated the metal if the lightning strike heated it. Also, the current from a lighting strike could cause local “hot spots” along a high amperage conduction path. If a matrix change occurred due to heating, the conduction path could possibly be a source for fatigue in the metal.
None of this will be relevant though, if a lighting strike had nothing to do with the fatigue that caused the fracture of this particular rotor blade.
The following information was gleaned from a Titanium Industries website, where an association promotes the industrial use of titanium, and I’m posting this in case the lighting strike had anything to do with the metal fatigue the AAIB detected in the fractured rotor blade. The information on how to machine titanium and especially how to weld titanium was particularly interesting. The physical property discussion will be limited to only those properties that would be relevant in a lightning strike.
Titanium reacts strongly with normal air when heated, so arc welding requires a pure argon “air blanket”. An arc welded titanium structure shows colors if contamination develops. A “silver metallic” color means no contamination, a gold or straw color means some contamination, and a light or dark blue color means high levels of contamination (the blue colors also mean no structural soundness at all). Contamination can produce porosity, low-notch toughness value, and brittleness.
Titanium comes in 3 classes of alloys that include 2 normal lattice matrix classes, and a class with a mix of the 2 normal matrix. The first matrix is “hexagonal closed-packed” (HCP) lattice structure (also know as “alpha phase”). The second matrix is “body centered cubic” (BCC) lattice structure (also known as “beta phase”). Certain alloys stabilize the titanium to one matrix or the other within certain temperature ranges (“alpha phase” class alloys and “beta phase” class alloys) and some alloys stabilize a mixture of both (“alpha-beta phase” class alloys). Various heat treatings and “annealing” also help to stabilize the matrix of the various alloys.
Titanium can undergo a matrix transformation known as an “allotropic transformation”, that can convert the matrix from one lattice form to the other, when heated to certain temperatures (depending on the alloy). If I understand it correctly something like an “allotropic boundary” (my phrase) can form within a structure when titanium is “spot heated”, causing one lattice (or mixture) to exist on one side of the “boundary” and a different lattice to exist on the other side. This can be a source of structural weakness and/or brittleness.
Titanium is also a poor conductor of heat, which must be watched when welding it. This property allows hot spots to develop more easily within a structure.
All of this would be relevant to a lighting strike, because discoloration would indicate that atmospheric gases (namely oxygen and nitrogen) might have contaminated the metal if the lightning strike heated it. Also, the current from a lighting strike could cause local “hot spots” along a high amperage conduction path. If a matrix change occurred due to heating, the conduction path could possibly be a source for fatigue in the metal.
None of this will be relevant though, if a lighting strike had nothing to do with the fatigue that caused the fracture of this particular rotor blade.
Last edited by Flight Safety; 27th Jul 2002 at 04:50.
I guess the supposition about the connection of a lightning strike and the subsequent blade failure (even if no connection is found)begs the question of just what kind of inspection is done? Is the Titanium spar exposed for its complete length....or just a small area around the actual point of strike? Also, would it not be considered prudent for an operator to scrap the blade subsequent to the blade being struck by lightning? I know in general experience, lots of damage can occur to metallic components that are not adequately bonded and thus allow arcing between adjacent metallic surfaces with different polarity or with poor bonding. Having seen a few lightning strikes to electrical circuits and metallic structures, the amount of damage is quite impressive, thus the thought of flying around with a set of rotor blades that had experienced a lightning strike more than feels me with concern. Just how far will an operator go to keep a part in service until its mandatory retirement life? I wonder if economic concerns might have influenced the decision to retain that particular blade in service rather than accept a financial loss and write off the blade? Are the other blades that have experienced lightning strikes now going to be retested or will the operators concerned merely remove them from service and scrap them as a good operating practice?
Lu,
Considering the situation.....If I were Nick Lappos....I would take a very real hiatus from this forum for quite a while. If any of his posts were to be misconstrued, misquoted, or in any way be thought improper, untimely, or remotely likely to cause Sikorsky a problem.....our dear friend would be in very hot and deep water with his superiors. Out of respect for Nick......lets give him a pass on any posts for a while.....hang out there in the ether Nick....and stay out of harm's way!
Considering the situation.....If I were Nick Lappos....I would take a very real hiatus from this forum for quite a while. If any of his posts were to be misconstrued, misquoted, or in any way be thought improper, untimely, or remotely likely to cause Sikorsky a problem.....our dear friend would be in very hot and deep water with his superiors. Out of respect for Nick......lets give him a pass on any posts for a while.....hang out there in the ether Nick....and stay out of harm's way!
vertalop I sit corrected 
We do indeed have two 212 s. 
I was thinking of the last job where we had 214's. Fortunately nobody has yet managed to drag me offshore on this job yet hence the mistook
I did point out that it was our operator that chose to ground the 76 rather than it being the CAA
Let's hope that the lessons learned from thei accident will bring about changes to the inspection procedures etc which will allow the 76 to restore it's good reputation.
We do indeed have two 212 s. I was thinking of the last job where we had 214's. Fortunately nobody has yet managed to drag me offshore on this job yet hence the mistook I did point out that it was our operator that chose to ground the 76 rather than it being the CAA
Let's hope that the lessons learned from thei accident will bring about changes to the inspection procedures etc which will allow the 76 to restore it's good reputation.