Sikorsky S-76 down in the North Sea (Threads merged)
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Flyer43,
"talking with the benefit of hindsight" You are missing my point. The point is that BECAUSE the cause was still unknown, people were talking unknown riscs in operating the A/C when it could very well have been a problem common to more S76s but just happened to rear its ugly head on VX. I was taught to assume the worst and cater for that in order not to get caught out.
I'm still not convinced that the type should not have been grounded until proven safe simply for commercial reasons. There are lots of reasons for not flying that are happily accepted because the riscs are obvious, e.g. icing, fog etc. On those occasions the clients will have to make different arrangements, so they could have made them in this case as well.
Again, I stress the fact that I am not bashing anyone, I just want to learn from this discussion. If we learn from this tragedy we may be able to prevent another.
And I DO intend to fly it as soon as it's cleared.
"talking with the benefit of hindsight" You are missing my point. The point is that BECAUSE the cause was still unknown, people were talking unknown riscs in operating the A/C when it could very well have been a problem common to more S76s but just happened to rear its ugly head on VX. I was taught to assume the worst and cater for that in order not to get caught out.
I'm still not convinced that the type should not have been grounded until proven safe simply for commercial reasons. There are lots of reasons for not flying that are happily accepted because the riscs are obvious, e.g. icing, fog etc. On those occasions the clients will have to make different arrangements, so they could have made them in this case as well.
Again, I stress the fact that I am not bashing anyone, I just want to learn from this discussion. If we learn from this tragedy we may be able to prevent another.
And I DO intend to fly it as soon as it's cleared.
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S76Heavy
Thanks for that. I wasn't getting at you, just trying to suggest other ways of looking at things.
As far as I understand it, most decent operators who continued flying the S76 since the accident instigated rigorous inspections of major rotating parts prior to continuing flying. However, as stated before, just how much do you need to check to ensure an aircraft type is safe to continue flying, unless you actually know the cause of any accidents. Maybe they were right, maybe not. At least they did put some controls in place, if only for mitigations sake......
Thanks for that. I wasn't getting at you, just trying to suggest other ways of looking at things.
As far as I understand it, most decent operators who continued flying the S76 since the accident instigated rigorous inspections of major rotating parts prior to continuing flying. However, as stated before, just how much do you need to check to ensure an aircraft type is safe to continue flying, unless you actually know the cause of any accidents. Maybe they were right, maybe not. At least they did put some controls in place, if only for mitigations sake......
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Flyer43,
I did appreciate your comments, I just thought that you might have misunderstood mine.
We as a RW community should learn all the lessons from this tragedy and I feel there is a need to define what actions are to be taken after an accident and on what grounds.
By your taking part in the discussion perhaps something better may evolve, so thanks for the input.
So how do other pilots feel about the need for grounding their type after an initially unexplained accident?
I did appreciate your comments, I just thought that you might have misunderstood mine.
We as a RW community should learn all the lessons from this tragedy and I feel there is a need to define what actions are to be taken after an accident and on what grounds.
By your taking part in the discussion perhaps something better may evolve, so thanks for the input.
So how do other pilots feel about the need for grounding their type after an initially unexplained accident?
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I don't agree with grounding unless a very clear reason for doing so can be established.
If a type is grounded, and then nothing conclusive is found, what justification can there be for ungrounding?
This terrible accident will prove (I believe) to be one of these "millions to one" chances. It is always a chain of events and circumstances which lead to an accident, break the chain and it doesn't happen.
The S76 has accumulated many hours of safe operation and it is unlikely that whatever "failure" caused this accident is a problem generic to the whole S76 fleet.
LE
If a type is grounded, and then nothing conclusive is found, what justification can there be for ungrounding?
This terrible accident will prove (I believe) to be one of these "millions to one" chances. It is always a chain of events and circumstances which lead to an accident, break the chain and it doesn't happen.
The S76 has accumulated many hours of safe operation and it is unlikely that whatever "failure" caused this accident is a problem generic to the whole S76 fleet.
LE
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From the BBC:
Wednesday, 24 July, 2002, 15:10 GMT 16:10 UK
Rotor blade blamed for crash
A broken rotor blade was the most likely cause of a fatal helicopter crash in the North Sea.
Eleven men died when the Sikorsky S-76 crashed off the coast of Norfolk last Tuesday.
Air accident investigators say evidence from the wreckage suggests that one of the main rotor blades broke off during the flight between offshore rigs.
Ten bodies have been recovered, while the search for the remaining missing person was called off on Tuesday.
More soon.
Wednesday, 24 July, 2002, 15:10 GMT 16:10 UK
Rotor blade blamed for crash
A broken rotor blade was the most likely cause of a fatal helicopter crash in the North Sea.
Eleven men died when the Sikorsky S-76 crashed off the coast of Norfolk last Tuesday.
Air accident investigators say evidence from the wreckage suggests that one of the main rotor blades broke off during the flight between offshore rigs.
Ten bodies have been recovered, while the search for the remaining missing person was called off on Tuesday.
More soon.
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S76 Blade Loss
This isn't the first time a UK registered S76 has lost a blade in flight. Did not a Bristows machine crash onland somewhere near Peterhead some years back after loosing a blade in flight?
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S76 Blade Failure......
If the BBC is an "Official" source, then the cause of this accident seems to be a detached blade in flight.
Firstly, I am relieved that it seems no engineer or the flightcrew will have to wear the responsiblitity.......[for once].
However a blade just does'nt detach without a cause.......someone or some system will have to explain their actions as the investigation unfolds.
"On condition" blades do "crack" from time to time..[I personally know of two in Oz]......but none involving the spar.
It will be interesting to see what the "Igor" team do now!!
Having a lot of time and respect for this aircraft and its systems.......I have always felt uneasy about increasing the Nr from 100% to 107% with the same drive train........same basic A model components with extra stress.
Not saying this is a direct cause......just a concern that has been lurking in the back of my mind since the A+ and A++ became a reality.......
Firstly, I am relieved that it seems no engineer or the flightcrew will have to wear the responsiblitity.......[for once].
However a blade just does'nt detach without a cause.......someone or some system will have to explain their actions as the investigation unfolds.
"On condition" blades do "crack" from time to time..[I personally know of two in Oz]......but none involving the spar.
It will be interesting to see what the "Igor" team do now!!
Having a lot of time and respect for this aircraft and its systems.......I have always felt uneasy about increasing the Nr from 100% to 107% with the same drive train........same basic A model components with extra stress.
Not saying this is a direct cause......just a concern that has been lurking in the back of my mind since the A+ and A++ became a reality.......
There was a media report [BBC radio this week] that confirmed the blade failure 'theory' and added that the AAIB were looking at a possible link between an instance of lightning strike damage suffered by the lost airframe and the failure.
I guess that forming a conclusive link will take a while.
I guess that forming a conclusive link will take a while.
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A blade breaking off makes a lot of sense and explains why the crew had no time to make a radio call or do anything that could have possibly saved them.
Broken spindles caused the first 2 crashes about 24 years ago. The first in South America with 14 killed and the second a Bristow machine doing a NDB approach at Longside with 4 killed. That problem was fixed, so at least it's a new problem. Still incredibly tragic for all involved.
Broken spindles caused the first 2 crashes about 24 years ago. The first in South America with 14 killed and the second a Bristow machine doing a NDB approach at Longside with 4 killed. That problem was fixed, so at least it's a new problem. Still incredibly tragic for all involved.
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About 2 years ago Aero Contractors Nigeria (Schreiner) had a large portion of the trailing edge detach from the inboard section of a main rotor blade of an S76B in flight. The crew only noticed a small increase in vibration at the time, but when they shut down after landing on a drill ship they discovered a large section missing and only the main spar there. I believe that it was due to a manufacturing defect of a batch of blades, and all blades from that batch were grounded until repair teams were sent out to apply a strengthening patch to them.
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Sikorsky have put out an ASB (Alert Service Bulletin) that blades which have been involved in lightning strikes should be removed before the next flight.
The AAIB have stated that there is no evidence at this stage to link the lightning strike, and the spar failure, but it is one of the variables under 'active consideration'.
The AAIB have stated that there is no evidence at this stage to link the lightning strike, and the spar failure, but it is one of the variables under 'active consideration'.
Shining Example, apparently...
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The AAIB preliminary statement in full:
"The Air Accident Investigation Branch of the Department for Transport has recovered more than 90% of the structure of the Sikorsky S-76A which crashed into the North Sea near the 'Santa Fe Monarch' offshore installation. The remains of the helicopter were recovered by divers working from the 'Diving Support Vessel 'Mayo'. The main debris field was approximately 180 metres long, 30 metres wide and some 40 metres below the sea surface.
The wreckage was transferred from the 'Mayo' to a smaller vessel on Saturday evening and brought ashore at Great Yarmouth during the morning of Sunday 21 July. It was then transferred by road to the AAIB's facility near Aldershot, Hampshire where the vital components were examined by investigators from the AAIB, the National Transportation Safety Board (NTSB) of the USA, the Federal Aviation Authority (FAA) of the USA, the aircraft manufacturer and the operator. In the same time scale, the combined flight data and cockpit voice recorder data were analysed by AAIB staff.
The flight and acoustic data show no signs of any significant abnormality until some minutes after the helicopter had left the 'Clipper' platform for the 10 minute flight to the 'Monarch' platform. During this short flight, the pilots discussed a small increase in vibration but this increase appears to be so slight as to give them no cause for concern. A few minutes later a catastrophic event occurred during the early stages of the helicopter's approach to land on the Monarch platform. The helicopter was in level flight at approximately 400 feet height and at a speed of some 100 knots. The data recorder ceased operating at this event and the eye witness evidence is still being collated and analysed to determine the final flight path. The accident was not survivable.
Amongst the wreckage were two items of major significance. Firstly, three of the main rotor blades exhibited only superficial damage whereas the fourth was fractured at a position approximately six feet from the blade root. The missing blade section was not recovered from the main debris field and the team are now confident that it lies elsewhere. The second significant clue was the condition of the main rotor gearbox. The casing had fractured and there was visible evidence that the gearbox together with the rotor head had broken away from the fuselage mountings.
The fractured blade was taken to a specialist metallurgical facility where the fracture surface was cleaned and prepared for metallurgical analysis. Preliminary results were inconclusive but on Tuesday, evidence of fatigue was found that enabled the investigation team to conclude that the blade fracture had initiated the catastrophic event. The gearbox had separated from its mountings due to the severe imbalance created by the separated blade section.
At this stage, there are a number of variables that are being evaluated to determine the likely origin of the fatigue. One variable may be related to a lightning strike suffered by the subject blade in 1999 but there are other variables under active consideration.
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.
At 1600 hrs on Tuesday 23rd July the FAA and the United Kingdom's CAA were made aware of these findings. The FAA is the regulatory body which issued the original type certificate for the American built helicopter; the CAA is the regulatory body which issues airworthiness certificates for aircraft registered in the United Kingdom. Both regulatory bodies are now considering what safety action might be appropriate.
At this stage of the investigation, there is no evidence of any flight crew or line maintenance malpractice. The investigation team is now focussed on the reasons for the blade fracture, particularly the origin of the fatigue. This information may take some time to establish but it will be crucial information required by the aircraft manufacturer and the regulatory bodies in deciding the most appropriate safety action.
Any future statements issued by or on behalf of the AAIB will be through the Department for Transport's Press Office."
"The Air Accident Investigation Branch of the Department for Transport has recovered more than 90% of the structure of the Sikorsky S-76A which crashed into the North Sea near the 'Santa Fe Monarch' offshore installation. The remains of the helicopter were recovered by divers working from the 'Diving Support Vessel 'Mayo'. The main debris field was approximately 180 metres long, 30 metres wide and some 40 metres below the sea surface.
The wreckage was transferred from the 'Mayo' to a smaller vessel on Saturday evening and brought ashore at Great Yarmouth during the morning of Sunday 21 July. It was then transferred by road to the AAIB's facility near Aldershot, Hampshire where the vital components were examined by investigators from the AAIB, the National Transportation Safety Board (NTSB) of the USA, the Federal Aviation Authority (FAA) of the USA, the aircraft manufacturer and the operator. In the same time scale, the combined flight data and cockpit voice recorder data were analysed by AAIB staff.
The flight and acoustic data show no signs of any significant abnormality until some minutes after the helicopter had left the 'Clipper' platform for the 10 minute flight to the 'Monarch' platform. During this short flight, the pilots discussed a small increase in vibration but this increase appears to be so slight as to give them no cause for concern. A few minutes later a catastrophic event occurred during the early stages of the helicopter's approach to land on the Monarch platform. The helicopter was in level flight at approximately 400 feet height and at a speed of some 100 knots. The data recorder ceased operating at this event and the eye witness evidence is still being collated and analysed to determine the final flight path. The accident was not survivable.
Amongst the wreckage were two items of major significance. Firstly, three of the main rotor blades exhibited only superficial damage whereas the fourth was fractured at a position approximately six feet from the blade root. The missing blade section was not recovered from the main debris field and the team are now confident that it lies elsewhere. The second significant clue was the condition of the main rotor gearbox. The casing had fractured and there was visible evidence that the gearbox together with the rotor head had broken away from the fuselage mountings.
The fractured blade was taken to a specialist metallurgical facility where the fracture surface was cleaned and prepared for metallurgical analysis. Preliminary results were inconclusive but on Tuesday, evidence of fatigue was found that enabled the investigation team to conclude that the blade fracture had initiated the catastrophic event. The gearbox had separated from its mountings due to the severe imbalance created by the separated blade section.
At this stage, there are a number of variables that are being evaluated to determine the likely origin of the fatigue. One variable may be related to a lightning strike suffered by the subject blade in 1999 but there are other variables under active consideration.
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.
At 1600 hrs on Tuesday 23rd July the FAA and the United Kingdom's CAA were made aware of these findings. The FAA is the regulatory body which issued the original type certificate for the American built helicopter; the CAA is the regulatory body which issues airworthiness certificates for aircraft registered in the United Kingdom. Both regulatory bodies are now considering what safety action might be appropriate.
At this stage of the investigation, there is no evidence of any flight crew or line maintenance malpractice. The investigation team is now focussed on the reasons for the blade fracture, particularly the origin of the fatigue. This information may take some time to establish but it will be crucial information required by the aircraft manufacturer and the regulatory bodies in deciding the most appropriate safety action.
Any future statements issued by or on behalf of the AAIB will be through the Department for Transport's Press Office."
Last edited by Heliport; 27th Jul 2002 at 19:45.
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construction info ....
as background info could someone tell me a bit about the construction of the Blade in question, materials, dimensions etc ...... how much would a replacement blade be valued at ....... how sophisticated is the Vibration monitoring and reporting system/guidance to the crew?
Iconoclast
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Reliable sources say....
To: Cyclic Hotline
What you say about spindle failures may be totally correct.
......................................
......................................
............................................
Now maybe I got it wrong .............................
I really do not know because I have no drawings or pictures relative to the construction of the S-76 rotorhead.
Lu
I've deleted your earlier post, and edited this one.
I'm also - that you could possibly think it appropriate to make such serious allegations. When challenged, it turns out you haven't got a shred of evidence to support your allegations.
Not only is it irresponsible, but it damages your own credibility as a contributor to discussions.
Please think before you hit the 'submit' button.
Heliport
Moderator
What you say about spindle failures may be totally correct.
......................................
......................................
............................................
Now maybe I got it wrong .............................
I really do not know because I have no drawings or pictures relative to the construction of the S-76 rotorhead.
Lu
I've deleted your earlier post, and edited this one.
I'm also
- that you could possibly think it appropriate to make such serious allegations. When challenged, it turns out you haven't got a shred of evidence to support your allegations.Not only is it irresponsible, but it damages your own credibility as a contributor to discussions.
Please think before you hit the 'submit' button.
Heliport
Moderator
Last edited by Heliport; 26th Jul 2002 at 07:56.