EC225 crash near Bergen, Norway April 2016

[squib66]

n305fa

I advance no theory. Mitchaa commented on a difference in recollection between operator and EC in 2009.

Undisputed facts are that in that case the operator did not follow the MM instructions for debris on the epicyclic magnetic chip detector, did not follow the written EDR process and continued to fly the aircraft after the debris having misidentified ferrous debris as non-ferrous.

So undisputed in fact that the FAI concluded:

Bond’s maintenance and inspection failures, which it readily admitted, were
• A failure to follow the correct task in the aircraft maintenance manual on the discovery of a metal particle, or “chip”, on G-REDL’s epicyclic chip detector on 25 March 2009, which would have resulted in the removal of the epicyclic module and an examination of the magnets on the separator plates;
• A failure to ensure that communications with the manufacturer of the helicopter on 25 March 2009 were done in accordance with the recognised procedures, with the result that misunderstandings arose between the parties, which contributed to the failure by Bond to perform the correct task;
• A failure to identify the nature of the substance of the metal particle when on 25 March 2009 performing a specified task in the aircraft maintenance manual and in doing so might have lost the opportunity to avoid the consequences of its failure to perform the correct task.

The AAIB did in fact determine that the debris, and failure to recognise it as a sign of degradation of the epicyclic gears (p112 of the 115 page report which you are now selectively quoting), was contributory.

However, there is no actual evidence to suggest the discussions of 25 March 2009 are relevant to LN-OJF, though I can see how it might suit some people.

[riff_raff]

Originally Posted by AW009

The line between genius and insanity is a very fine one. But out of my technical view, the „suspension bar solution“ of (SUPER) PUMA - as realized by AS/ECF/AHF - might be genius, but is'nt at all ingenious

This brings up an interesting point. There was some discussion of design issues with the H-60/S-76/S-92 main rotor drivetrain. One thing I would point out is a fundamental difference between the design of the main gearbox structural attachments of the H-60/S-76/S-92 versus the EC225 in terms of fault tolerance. The Sikorsky design transfers rotor loads to the airframe using the gearbox housing, while the EC design transfers most rotor loads to the airframe using a set of struts. Both Sikorsky's stressed housing and EC's strut arrangements are attached to the airframe at three locations, and failure of just one of the three attachments would likely be catastrophic. If you take a close look at the picture of an S-92 main gearbox below, you'll note that the airframe attachment uses two bolts at each location, which provides single fault tolerance capability for this flight critical fastener function. The single clevis pin used at each end of the EC225's struts has no fault tolerance capability.

It might be possible to make the EC225 strut arrangement fault tolerant if two independent struts could be used at each of the three attachments, where one strut is capable of continuing safe operation in the event the other strut fails (assuming of course the kinematics of the system can be made to work properly).

[Satcomm]

Rif raff, Sikorsky uses 4 points of attachment for their "stressed" gearbox. Also, the S92 is on phase 3 of it main gearbox. There have been failures (cracks found) of mounting feet and in fact are still quite closely monitored by HUMS. Not much point in have 2 bolts when the entire foot is detached from the gearbox. Seems they have finally nailed it now though and luckily there were no accidents in the process, no more cracked feet, however, I believe there have been a couple frame issues since.

Every manufacture out there could make a helicopter that would never fail, problem is it would never get off the ground. Hey why not throw an extra motor in, then we would never have to worry about single engine performance either.

[jimf671]

Originally Posted by riff_raff

... ... the airframe attachment uses two bolts at each location, which provides single fault tolerance capability for this flight critical fastener function. The single clevis pin used at each end of the EC225's struts has no fault tolerance capability.

I am not sure it works quite like that. For one thing, we've been told there are two retaining pins on the end of the clevis. For another, we already know that bolts in the MGB assembly have not been Sikorsky's strongest suit.

[Lonewolf_50]

@jimf671
Comment deleted, Satcomm caught my thinking about the wrong bolts.

[Satcomm]

Lonewolf, I think Jimf671 was referring to the S92 AD asking operators to check the main gearbox mounting bolts. Here is the reason copied from the AD.

"The FAA received a report of a failure of a main transmission mounting bolt, detected during routine maintenance inspection. Undetected bolt failure could result in loss of support of the main transmission, and subsequent loss of control of the helicopter."

AKA: gearbox detaching from airframe with rotohead attached ... Same undesired result.

The oil filter studs were a totally different issue.

The main gearbox mounting feet with the "2 bolt redunanticy" were also responsible for several ADs. 2 bolts in a single foot is not really redundanticy, when the foot breaks off you just have 2 useless bolts in the frame rather then 1.

[buzz66]

L & L1 good to go
EC225 no good and now L2 no good.

Pretty hard story to sell if you ask me!

Are the SUS Bars and Gearbox's that much different between lets say an L1 and an L2? I would think not.

Is it because an L2 and 225 are heavier?

Is it just Risk tolerance?

Is there a "b Omega" issue they are not talking about?

Is it because of the Articulated Head design?

Explain why if Airbus suspect a Sus Bar failure would the L and L1 be allowed to fly and the L2 and 225 not?

[Noiseboy]

With the shaft breaks, AH said it was a bad batch, which it was due to moisture retained after manufacture, they modified the plug to prevent this from happening. They were absolutely correct in their initial statement.

The second break of the same part was due to the build up of the 'mud' as they called it, which also contained moisture, this was an old part, almost through its second life, and the presence of the mud introduced corrosion that the original design testing had not taken into account.

It was the operators and oil industry who brought in outside agencies to verify AH conclusions which they agreed were correct, and in hindsight the prolonged grounding was not necessary since both cracks could be explained and avoided, this then led to an L2 making an approach to Sumburgh the next year. That should have been a 225, which either would have been direct to ABZ or the aircraft would have done what the PNF failed to do and stop the aircraft flying into the water.

I'm not advocating blind faith in AH, but the way the story is told in previous posts is not accurate, and given that AH designed and manufactures these things, and will have been involved in every failure of these things, they will have the most data to come to conclusions more quickly.

[Apate]

I think Airbus should be praised for finding the root cause so quickly. What a shame the AIBN and AAIB, Norwegian and UK CAA are all taking SOOOOO long to come to a similar conclusion

[riff_raff]

Originally Posted by Satcomm

2 bolts in a single foot is not really redundanticy, when the foot breaks off you just have 2 useless bolts in the frame rather then 1.

That's not correct. What I stated is that having two bolts at each attachment, where one bolt would be capable of providing continued safe operation should the other bolt fail, provides single fault tolerance for the fastener function. In terms of fault tolerance, this is considered independent from a failure of the associated housing structure. Two bolts are used at each flight critical attachment because failure of one bolt is considered to be a possible event, while structural failure of the housing is considered to be an extremely improbable event.

[RVDT]

is considered to be an extremely improbable event

Which Sikorsky had no problem convincing the FAA of until...........................

[birmingham]

When more than 100 people were killed on Piper Alpha there was a massive HSE revolution. It changed the perception of acceptable risk in the NS for ever. That's the way it is in the oil business - my opinion or anyone else's can only be that.

This very unfortunate run for the Puma will have the same effect in Helicopter operations. People who think this is just another inevitable fatal accident are missing the point. The passengers aren't really interested in the fact that this latest incident was or was not caused by planet gear failure, suspension bars, bevel gear, vortex loss of control or anything else. They simply will not tolerate 5 hull losses in seven years. A line has been crossed. If you don't get that then you don't get NS HSE culture.

The pax know helicopter accidents are inevitable, they also know many good men and women already dedicate themselves to helicopter safey. But they will require, and will get a further step up in safer flying. So at least one good thing will come out of this tragedy.

[HeliComparator]

Originally Posted by birmingham

...They simply will not tolerate 5 hull losses in seven years. A line has been crossed. If you don't get that then you don't get NS HSE culture.

So is NS HSE culture based on hard science and fact, or on emotion and hysteria? If based on hard science and fact "it" will be aware that dumping a well tried and tested family of helicopters, for unknown and barely tested new models, cannot be considered a safe thing to do for with ABSOLUTE CERTAINTY the new models will contain some "gotchas" just as the previous generation did (S92, EC225, AW139 etc). So do tell us, is NS HSE culture really so ignorant and stupid as to want to promote dumping the existing fleets and replacing with brand new types?


Personally I would rather continue with well used fleets whose bugs have nearly all been identified and fixed, rather than starting the process all over again with the sure knowledge that there will be near misses at best, fatal accidents more likely, as the new fleet's bugs are ironed out.


Of course what is at the bottom of this is that current certification standards are not fit for purpose. Far too bureaucratic and lacking in good engineering practice (common sense if you like) with far to many design points dismissible by playing the "extremely remote" card when there is zero evidence that such a failure will be extremely remote. And anyway, with a large fleet flying a lot of hours, it is by definition only a matter of time before "extremely remote" events happen.


Let us remember how probability works. If an event is 1 in a million it doesn't mean it will happen on the 1 millionth time. It might never happen in the lifetime of the product. Or it might happen on the first time. So the certification standards consider catastrophic failure inevitable (given enough exposure) and therefore the loss of the odd human acceptable.

[HeliComparator]

Originally Posted by Apate

I think Airbus should be praised for finding the root cause so quickly. What a shame the AIBN and AAIB, Norwegian and UK CAA are all taking SOOOOO long to come to a similar conclusion

Could you explain why EASA are happy to allow the EC225 to continue to fly?


I suggest that UKCAA and NCAA are taking a pragmatic line that avoids confrontations with the workforce etc, and of course on an individual basis is probably a consequence of that worst of civil service diseases - arse covering.

[birmingham]

Helicomparator;

You asked ...

"So is NS HSE culture based on hard science and fact, or on emotion and hysteria?"

All four play a part as does corporate attitudes, media pressures and trades unions.

Hard facts are only part of the process.

[HeliComparator]

Originally Posted by birmingham

Helicomparator;

You asked ...

"So is NS HSE culture based on hard science and fact, or on emotion and hysteria?"

All four play a part as does corporate attitudes, media pressures and trades unions.

Hard facts are only part of the process.

In that case I suggest it's a seriously flawed process if its aim is to optimise safety.

[birmingham]

Flawed certainly but by no means ineffective. A lot of the response to Piper Alpha was emotional even hysterical but it undoubtedly made the industry safer, faster. We both agree that the helicopter industry's certification system is not without its own flaws.

The E&P industry is well used to external pressures, often emotional, unreasonable, even hysterical. But the likes of Statoil and Norske Shell don't simply dismiss it as irrational. They have come to understand the damage it can do, so listen, learn and respond and it has made them better organisations for it.

A big chunk of the workforce is spooked, this will need to be addressed not just explained away.

[jimf671]

As someone who has spent several decades trying TRYING to teach the British how to use nuts and bolts, I have been concerned about both of the fastener problems that have been highlighted on the S-92 box.

The oil filter stud problem indicated a very poor decision about materials.

I am aware of the main gearbox mounting bolt problem but I don't know any of the detail. I would be grateful if someone can direct me to documents with more detail about that failure.

[PlasticCabDriver]

Originally Posted by HeliComparator

Could you explain why EASA are happy to allow the EC225 to continue to fly?

Presumably for the same reason that EASA haven't grounded all the A320s or EC145s recently. EASA will ground a type when they have a reason to do so, not when they don't have a reason not to.

If EASA grounded all the 225s and then subsequently the investigation into LN-OJF cannot come up with a definitive answer, do we then leave all those dozens and dozens of 225s to rot over one mystery incident? Very hard to undo a grounding without a good reason why.

3 weeks ago an EC225 crashed killing everyone on board for an as yet unknown reason.
5 days ago an A320 crashed killing everyone on board for an as yet unknown reason.

How many offshore workers have since flown out of/back to Aberdeen on A320s without a murmur?

Ask them to get on a 225: "no chance"!

[Jdbelo]

The AIBN has initiated an extensive investigation and a massive search for components from the helicopter both on land and in the sea. Most of the wreckage is retrieved from the sea and is already the subject of examinations.

Latest update: 23.05.2016