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EC225 crash near Bergen, Norway April 2016

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EC225 crash near Bergen, Norway April 2016

Old 22nd Jun 2016, 17:02
  #1381 (permalink)  
 
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AW, in post 1389 are you saying/implying that the same gearbox manufacturer makes both the engine/prop box on the A400 and the main box on the 225?
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Old 22nd Jun 2016, 17:22
  #1382 (permalink)  
 
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John Dixson: Sorry, but this is very right, very well proofed and system immanent.

Last edited by AW009; 23rd Jun 2016 at 03:51. Reason: Mistake
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Old 22nd Jun 2016, 17:57
  #1383 (permalink)  
 
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AW009 I think your point is entirely valid. EADS is suffering badly from these issues and the problem has reached the point where the engineering needed to resolve them may no longer be commercially viable. The 400 has reduction gearbox issues and the C130J doesn't. Both the S92 and EC255 have had reduction gearbox issues but the EC225's appear overwhelming. Unfortunately even if this accident enquiry decides that the suspension bar failed initiating the tragedy, the discovery of more fatigue issues with the planetary is a massive blow. Also if we are making automotive comparisons the;"it's too complicated - you laymen don't understand it's just the way it is, s*** happens" response is reminiscent of British Leyland in the 1970s (and we know what happened to them).BTW I am a fan of many EADS products especially the A320/330s that I have had a lot of time in, but we need to address reality here; Look who makes the Mini Cooper now!

So while allegedly off subject - anyone else worry that geared-fan engines for the A3** and B737-* NEOs may bring unwanted complexity to what are currently astonishingly safe and reliable aircraft, after all, these puma gearbox problems also appeared relatively late in the life of a successful design?

Last edited by birmingham; 22nd Jun 2016 at 18:30.
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Old 22nd Jun 2016, 23:53
  #1384 (permalink)  
 
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Surely from here Oil Company's will start with the basics.

1. He who has the best Gearbox run dry times (no cheating e.g. Glycol)
2. Best Single Engine performance

The AW189 does over 60 mins with no Glycol, now that's a Gearbox!
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Old 23rd Jun 2016, 01:00
  #1385 (permalink)  
 
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Buzz

And the Bell 429 4 hours.
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Old 23rd Jun 2016, 09:38
  #1386 (permalink)  
 
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Buzz

The AW189 does over 60 mins with no Glycol, now that's a Gearbox!
Yes, but its a shame that the airframe is having trouble coping with it and the fuel capacity and burn restrict range.

Run dry, run wet, glycol or no run dry, down here in Oz, we need 92s (and 225s) to fly the long haul routes.
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Old 23rd Jun 2016, 11:20
  #1387 (permalink)  
 
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AW do make good gearboxes. Having toured the factory at Vergiate on a couple of occasions I have to say their transmission workshop is very impressive. The EH101 MGB is a beast!
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Old 23rd Jun 2016, 11:56
  #1388 (permalink)  
 
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And the Bell 429 4 hours
It looks a little too much, at what torque level?
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Old 23rd Jun 2016, 12:09
  #1389 (permalink)  
 
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Originally Posted by birmingham View Post
... ... reminiscent of British Leyland in the 1970s (and we know what happened to them). ... ...
Ouch. With a handle like birmingham, presumably you can recall the Lord Stokes one about not being in the business of making cars for the secondhand market. But they were always rubbish at cars. Trucks and industrial machinery were what they were good at. That is where there truly is a comparison with the Super Puma. Just as the 225 is an upgrade of the 330, in the UK, a very large proportion of the trucks delivering your internet shopping are an upgrade of 70s and 80s Leylands with DAF written on the front. The Sud Aviation stuff has Airbus written on it but it's not helping at the moment.
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Old 23rd Jun 2016, 12:12
  #1390 (permalink)  
 
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Originally Posted by msbbarratt View Post
This info on steels, bearings, etc. is excellent.

But isn't it time for a reality check? It seems clear that the combined talent of the design authority, crash investigators, regulators and operator maintenance staff is unable to fully understand or control what is happening to these aircraft. Whatever it is that we know about materials, operating conditions, wear rates, etc, that knowledge is inadequate in this case.

I know that the aviation sector is generally run with great maturity and care by all those involved, and takes pride in knowing all aspects of aircraft behaviour and how to operate safely.

However for this type they imposed a regime of intensive examination after every flight, after a few other accidents occurred. To me that sounds like "we don't really, truly know what's happening, so we'll sample the gearbox condition at every opportunity and maybe find out". In retrospect that's probably going to look like a bad idea.

The most important part of the investigation will be its focus on how it came to this.
I think you are right

to me it's both a technical and a cultural problem,
combined with a control authority regime that is reactive.

In other countries outside Europe, there is much more focus
on precaution to fault modes. Not only on aircraft as well as in other businesses, simply because the culture/law systems allows to put the responsibility on the manufacturer alone.
For sure it creates an environment of political correctness that is not always
smooth and easy to work with, but if it avoids accidents it´s worth it.

It induces also serious research on government funded platform, that
has absolutely no comparison elsewhere.
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Old 23rd Jun 2016, 12:47
  #1391 (permalink)  
 
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In other countries outside Europe, there is much more focus on precaution to fault modes.
Having worked in SE Asia and N America, as well as having a good grasp on what happens in S America and Africa, I have to say I have no idea what you're talking about!!

If anything Europe is over regulated.

Do you wish to provide examples to support your statement?
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Old 24th Jun 2016, 06:43
  #1392 (permalink)  
 
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Here's something interesting to consider regarding the level of technology used to design the typical main rotor gearbox. Take the example of the AS332 MRGB failure in April 2009. The gearbox was designed prior to 1993. And the accident investigation was performed in 2011, around two decades later. If you take a look at the very sophisticated finite element fracture analysis study work described in the 2011 accident report, you'd appreciate that this level of analysis capability was far more advanced than what was available to the gearbox designers in 1993.

The various types of failure modes and the fundamental process behind each one, have been understood by gearbox designers for many years. But remember that the gearbox conforms to a design that was certified many years ago, and represented the acceptable level of safety and reliability required by government regulations.
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Old 25th Jun 2016, 14:10
  #1393 (permalink)  
 
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Lightbulb Times are gone


Looking back at 1993 as @riff_raff did, the Super Puma family has a lot of ‘constructive gray areas’ that never have been really ‘rayed’ with reference to the current certification criteria and to a present state of technique and science.
To summarize:


• E.g.: Rotor suspension by 3 suspension bars instead of 4 or 5 (redundancy & harmonics) and also ‘zero# redundancy by the discontinuous rotor mast and by an extensive ‘de-axation / outlining’ between bevel gear and upper ‘rotor shaft bearing’ in the conical housing?

• Suspicious fixing and securing of the suspension bars with bolts, Nappy Pins (Fokkernadeln) and Washer (not chamfered)?

• The ring gears of the planetary gear modules are simultaneously with the outer housing structure of the MRGB (compare PGB of TP400D6)?

•The inner parts of satellite mesh gear wheels are direct possession of outer bearing races of the roller bearings?

No continuous rotor mast with axial and radial bearings at highest and lowest end and not non-positive to the bottom of MRGB, thus the forces and moments can not transferred direct via the bedplate of MRGB into the transmission and engine deck of the cell. Compare S61 SEA KING (https://www.youtube.com/watch?v=F9wnzBaE24s) and S60B SEAHAWK = S92 SUPER HAWK (http://aasf1-ny.org/4-Standards/Docu...r%20System.pdf, there D6 & D7))?!

•The bevel gear butt with welded shaft, might be of similar resistance to torsion-, shearing- and tensile forces as tp)?

• Etc., etc., ….

Times are gone for (Super) Puma!

Therefore AIRBUS should better clean his mess, instead of a permanently creating knocking sayings and new excuses. This is pure reality – absolutely no bashing - and seems identical also to other AC types of AIRBUS (e.g. NH90 and AS400M having a state of technology and a certification base of the 90th).

In military aviations AS/EADS/ABH always had been a ‘purveyor to H.M.’, but in professional commercial aviations being a market leader, finds its end in reliabilty, in operational and technical flight safety and not only in terms of economic and defense politicaly utilitarian national and subjective yardsticks.

That is a fact the French quys in their ’laissez faire’ never have understood and now they have to pay the bill in an international ’hardball scenario’ of lessee and lessors. The next fate of ABH will be to become a central ‘Second Hand Shop’ for PUMA and this might become a very large one, if ABH wouldn’t change its philosophy fundamentally.

Last edited by AW009; 26th Jun 2016 at 08:05. Reason: Format
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Old 27th Jun 2016, 14:48
  #1394 (permalink)  
 
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Originally Posted by riff_raff View Post
Here's something interesting to consider regarding the level of technology used to design the typical main rotor gearbox. Take the example of the AS332 MRGB failure in April 2009. The gearbox was designed prior to 1993. And the accident investigation was performed in 2011, around two decades later. If you take a look at the very sophisticated finite element fracture analysis study work described in the 2011 accident report, you'd appreciate that this level of analysis capability was far more advanced than what was available to the gearbox designers in 1993.

The various types of failure modes and the fundamental process behind each one, have been understood by gearbox designers for many years. But remember that the gearbox conforms to a design that was certified many years ago, and represented the acceptable level of safety and reliability required by government regulations.
Whilst it may well be that the gearbox conforms to a design certified several years ago it should also be remembered that following two bevel gear shaft failures, both resulting in precautionary ditchings with no serious injury, Airbus Helicopters extensively re-designed that shaft and these have now been retro-fitted into all of the offshore fleet.

So it would appear there is a precedent at AH for today’s analytical methods to be used to analyse stress distribution in older components and to redesign them and have them approved against (original?) certification requirements.

The big question is, did AH make any design changes to the 2nd stage planet gears following the 2009 accident and AAIB Safety Recommendation 2009-075 to “review the design, operational life and inspection processes of the planet gears” ? The TBO for the epicyclic module appears to have remained at 2000FH.

Last edited by Concentric; 27th Jun 2016 at 18:43.
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Old 28th Jun 2016, 02:25
  #1395 (permalink)  
 
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AW009-Minor point regarding your linked .pdf ... it is explicitly for the UH-60A Black hawk, not a Seahawk and not an S-92. (Seahawk is SH-60B, albeit derived from the S-70/Blackhawk basic design. It has more in common (IDGB and carrier assembly) with UH-60L than the A. Your larger point is taken and understood if we read = (which is "equals") to be read like "very similar; based on the same design philosophy." Your pointing to those illustrations for an example of a kind of design works well to illustrate your point.
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Old 28th Jun 2016, 14:11
  #1396 (permalink)  
 
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‘zero# redundancy by the discontinuous rotor mast and by an extensive ‘de-axation / outlining’ between bevel gear and upper ‘rotor shaft bearing’ in the conical housing?
AW009, I looked at the plans and I do not understand where you see a misalignment ?
As for the rotor mast, I do not see what you mean by "discontinuous" ?

(I am not a neophyte but you may know more than I do)
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Old 28th Jun 2016, 18:45
  #1397 (permalink)  
 
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New investigation update released by AIBN

A new update has been released pointing towards the failure of the second stage planet gear as being the most probable cause of the accident

http://www.aibn.no/Aviation/Investig...-File&attach=1
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Old 28th Jun 2016, 19:09
  #1398 (permalink)  
 
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From the report:

"Main Gearbox history: The main gearbox (MGB) was received from Airbus Helicopters after modification, inspection and repair before it was installed in LN-OJF 15 January 2016. At the time of installation, the MGB had accumulated 1 080 hrs since new. At the time of the accident, it had accumulated approximately 1 340 hrs since new."


"Examinations of these parts show that one of the fracture surfaces can be described as being close to 100% fatigue."


" It is considered unlikely that this fatigue crack propagated as a consequence of a structural break-up of another component."


"Even though some differences are observed when comparing the LN-OJF accident with the G-REDL accident, the fatigue fractured planet gears, however, show clear similarities."


"The AIBN is aware that the gearbox was involved in a road accident in 2015. The gearbox was inspected, repaired and released for flight by the manufacturer before it was installed in LN-OJF in January 2016. Whether there is a link between this event and the initiation and growth of a fatigue fracture, is being investigated."

"AIBN will also look into the follow-up of safety recommendations issued after the Super Puma accident in Scotland in 2009 (https://www.gov.uk/aaib-reports/2-2011-aerospatiale-eurocopteras332-l2-super-puma-g-redl-1-april-2009)."

The last statement is very interesting. Does anyone know if all the safety recommendations have been satisfactory actioned and closed? To my knowledge, they did not change the design, and the monitoring systems have remained the same after the 2009 accident.
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Old 28th Jun 2016, 19:34
  #1399 (permalink)  
 
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I guess the response to the safety recommendations are in one of the AAIB annual reports
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Old 28th Jun 2016, 20:08
  #1400 (permalink)  
 
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Originally Posted by Pi1ot View Post

"AIBN will also look into the follow-up of safety recommendations issued after the Super Puma accident in Scotland in 2009 (https://www.gov.uk/aaib-reports/2-2011-aerospatiale-eurocopteras332-l2-super-puma-g-redl-1-april-2009)."

The last statement is very interesting. Does anyone know if all the safety recommendations have been satisfactory actioned and closed? To my knowledge, they did not change the design, and the monitoring systems have remained the same after the 2009 accident.
Not only the design of planetary gearing and monitoring systems but also Safety Recommendations 2011-045 and 2011-046 concerning the use of g-switches which can lead to the premature removal of power to CVFDR systems. I do not think the cessation of recording on the 2009 accident has actually been satisfactorily explained.
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