225 cleared to fly in UK & Norway

[TUPE]

Super Puma 225 helicopters, which were grounded after a crash in Norway, are to fly over the North Sea again.
The UK Civil Aviation Authority (CAA) and the Norwegian authorities have allowed flights to resume if operators meet new safety conditions.
These include more frequent inspections and earlier replacement of components.
A crash involving the helicopter off the coast of Norway killed 13 people, including Iain Stewart from Aberdeenshire, in April 2016.
CAA head of airworthiness John McColl said: "This is not a decision we have taken lightly. It has only been made after receiving extensive information from the Norwegian accident investigators and being satisfied with the subsequent changes introduced by Airbus Helicopters through detailed assessment and analysis.
"The safety of those who travel on offshore helicopter flights is a key priority for both the UK and Norwegian aviation authorities.
"We would not have made this decision unless we were convinced that the changes to the helicopters and their maintenance restore the required airworthiness standards."
The CAA said that helicopters will not begin flying immediately. A plan of checks, modifications and inspections needs to be undertaken before any flights take place.
These include:
Change in the design by removal of the components that were susceptible to premature deterioration
Earlier replacement of component
Design change to introduce an improved maintenance inspection method to detect any deterioration at an early stage
More frequent inspections
Reduction in the thresholds for rejecting components based upon early signs of any deterioration
Mr McColl added: "We continue to work with the helicopter operators, the offshore industries, international regulators, unions and pilot representatives to enhance offshore safety standards still further and all these parties are actively involved in ongoing discussions."
Les Linklater, executive director of the offshore industry safety group Step Change in Safety, said: "At this time, there is an ongoing Airbus survey for pilots and passengers regarding these specific helicopters' flight safety and comfort, which was issued just one week ago. It's our understanding that this survey still has a further three weeks to run.
"Given the importance of the workforce's opinion regarding this highly emotive subject we do not feel it's appropriate to make any further comment until Airbus has gathered, and shared, the survey's results and can demonstrate how they intend to address any concerns raised by the workforce.
"We would encourage all members of the workforce to participate and have their voices heard."


Norway crash helicopter type cleared to fly - BBC News (http://www.bbc.co.uk/news/uk-scotland-north-east-orkney-shetland-40538083)

[cyclic]

Has anyone seen the survey yet? It was going to workers and pilots apparently.

[helicrazi]

Has anyone seen the survey yet? It was going to workers and pilots apparently.

Its on the O&G people website under the news section, and on the airbus website or here:

Airbus Helicopters Survey ? Outreach to oil and gas workers (http://www.airbushelicopterssurvey.com/)

[etudiant]

The survey studiously avoids any controversial topics.
The nearest it comes to intersecting the real world is when it lists the 4 corrective actions taken wrt the gear box and asks whether the respondent was aware of them.
Possibly the meat is the questions whether the opinion of the employer, the union, the pilot or the fellow workers are very important in deciding to use the aircraft.

[birmingham]

"We would not have made this decision unless we were convinced that the changes to the helicopters and their maintenance restore the required airworthiness standards."

The measures don't seem all that different to what was proposed when the European regulator approved flying 225s some months back. So it would help if some of the detailed analysis could be published. If we accept (and I do) that the regulators are independent, ignoring any political or commercial pressure; then, presumably, the detailed analysis has been based on examining the condition of a large number of both types of epicyclic used in the 225. Is it the case that the results of such a study have "convinced that the changes to the helicopters and their maintenance restore the required airworthiness standards"? While I am sure it will be discussed in the final report, some details of this analysis would help support the decision to go flying. The problem Unite, the pax, operators etc. have, is that unless they have seen the details, all they do know for sure is; (1) this issue has killed twice and (2) both these regulators got the decision wrong once before.

[Mee3]

(1) this issue has killed twice
You made an assumption that many experts tried hard to proof to exist.

So far the so called solution had been introducing more idiot proof maintenance and has no impact to the design a part from adding an extra mag plug.

If politic has no place in the final report, it will be very interesting to see how they turn the "findings" early in the preliminary report into a non issue.

[havick]

Isn't this all moot given that everyone has moved on from the 225 (almost everyone anyway)?

[birmingham]

Isn't this all moot given that everyone has moved on from the 225 (almost everyone anyway)?

Well it is in the sense that even if it had been possible to find an absolutely definitive failure mode and remove it, the H225 or any other heavy for that matter, would still struggle. The market for that class of a/c in the E&P sector has certainly peaked. The S92 has gained share since the accident but, otherwise we would be seeing quite a few of those permanently withdrawn too.

The accident, the oil slump and the maturity of the North Sea have created something of a perfect storm here.

I think the future for these types is largely a military one.

[jimf671]

Those who have 'moved on' are in serious danger of the numbers coming back and biting them in the ar5e.

That's partly because the numbers tell us that a highly popular type that does a huge proportion of the work and goes that long without a fatality is ground-breaking. It's also because there are competitor types out there that have been involved in hundreds or thousands of fatalities.

[KiwiNedNZ]

It's also because there are competitor types out there that have been involved in hundreds or thousands of fatalities.

Seriously ??? Care to share which type has killed hundreds or thousands of people ????

[P3 Bellows]

Jim..........

I have told you a million times........... stop exaggerating :rolleyes:

[havick]

Those who have 'moved on' are in serious danger of the numbers coming back and biting them in the ar5e.

That's partly because the numbers tell us that a highly popular type that does a huge proportion of the work and goes that long without a fatality is ground-breaking. It's also because there are competitor types out there that have been involved in hundreds or thousands of fatalities.

Can you point to any evidence to support your claims?

[helicrazi]

There is a gap still in the North Sea for the 225 but it would be hard to convince customers to contract it.

The range.

Did the 225's have to make stops (or be positioned) out of Sumburgh to reach some of the further afield platforms?

What is it the 225 can do that the 92 can't? Is that important for the customer? If so, then we may well see a return to Aberdeen with the 225. After all, it's actually quite a nice aircraft and it does it job well (Disregarding the one in a million type freak accident)

If it happened again though even after all these additional safeguards, can you imagine the subsequent fall out.

What is it the 225 can do that the 92 can't?

I'm biting my tongue at that one...

[rrekn]

The 225 had more pax/payload over longer distances than the 92 (in part due to the external fuel tanks rather than the 92s internal ones). It was also about $5-7m cheaper to purchase, which resulted in lower costs to the operators and customers.


But like many had said about, moot point now. No major operator will use them for O&G work again.

[jimf671]

... that the 92 can't?

Not shake your teeth out?
Not deafen the Captain?
Range-Payload?
Autopilot?
Escape windows?
Float?
MGB run dry time?
...

[Twist & Shout]

Return to service.
I enjoyed flying the EC225. I hope I'm never asked to fly one^again.

I've seen nothing to suggest Airbus knows why* the failures that saw the rotor system detach, occurred. How can they seriously claim to have mitigated the risk of another rotor detachment causing the death of all on board?

^ or an AS332L2 with the same failure history.
* My understanding- they know what failed, not why.

V the S92
I'm amazed the payload/range debate is not settled.
I'm unfamiliar with the S92, but used to fly an EC225 on a contract which also had S92s. On occasions, we couldn't carry the required payload, and the S92 could. Some conditions must favour one machine. From memory, it was the high ambient temp that was a major factor in the S92s advantage in that relatively long range OS operation.

[SASless]

Reminds me of the Comet-Boeing 707 situation in a way.

A couple of Comets made like their namesake and it got grounded....in the meanwhile the 707 was out there flying and gaining buyers/Users.

When the problems got sorted on the Comet it was simply too late for it to recover its place in the World Market.

[henra]

Seriously ??? Care to share which type has killed hundreds or thousands of people ????


In all fairness he is maybe slightly exaggerating but not much:

S-61:
Civil: >181 Fatalities
Incl. Mil: >458 Fatalities
S-76:
>181 Fatalities


P.S.:
I don't have the figures for the Mi-8 but that will be easily in the Thousands.

[loop swing]

The 225 had more pax/payload over longer distances than the 92 (in part due to the external fuel tanks rather than the 92s internal ones). It was also about $5-7m cheaper to purchase, which resulted in lower costs to the operators and customers.


But like many had said about, moot point now. No major operator will use them for O&G work again.

Your fuel tank placement is incorrect.
92 has external tanks in the sponsons.
225 has internal tanks circa 4000lbs plus and additional 500lbs in each sponson. Same fuel uplift in both machines

[212man]

Your fuel tank placement is incorrect.
92 has external tanks in the sponsons.
225 has internal tanks circa 4000lbs plus and additional 500lbs in each sponson. Same fuel uplift in both machines

I think what he meant was that for the S92 to compete on range, it requires the internal fuel tanks in the cabin which then reduces the space available for the pax. I'm pretty sure he knows about the sponson tanks......

[jimf671]

In all fairness he is maybe slightly exaggerating but not much:

S-61:
Civil: >181 Fatalities
Incl. Mil: >458 Fatalities
S-76:
>181 Fatalities


P.S.:
I don't have the figures for the Mi-8 but that will be easily in the Thousands.


No exaggeration required at all. I lost count on the Mi-8 family around 2700 and estimate the total must be between 5k and 10k (in RECORDED accidents).

Around 12000 built across many decades though.

[birmingham]

From this week's Flight International ....

While expressing “deep regret” for the 2016 accident, Airbus Helicopters says it welcomes the lifting of the flight ban, but adds: “We understand that this will not necessarily result in immediate passenger flights as there is a lot of work to be done to restore confidence in the aircraft.”

Interesting statement especially with the sudden interest in surveying the users.

There comes a time in the life of all helicopter projects where for a variety of reasons the manufacturer decides to call it a day. I can see why it was necessary for AH to take this to the point where their machine was cleared to fly. Whether there is a commercial case for doing much more beyond that is something AH must have considered. It is a very different market now to when the H225 and indeed S92 were launched.

[Concentric]

There must have been some very major development between 28 June (https://www.flightglobal.com/news/articles/uk-caa-sees-no-prospect-of-quick-return-for-grounded-438857/) when the CAA released a statement that it had "no immediate plans to lift the restriction" and 7 July (http://www.caa.co.uk/News/Restrictions-on-H225LP-and-AS332L2-Super-Puma-helicopters-to-be-lifted(1)/) when they stated “The UK and Norwegian aviation authorities have today set out plans for the lifting of operating restrictions on H225LP and AS332L2 helicopters”.

That would appear to be a very short time in which to make, test, verify and document any technical discovery.

It is said however that a week is a long time in Politics.

[rotor-rooter]

Originally Posted by henra View Post
In all fairness he is maybe slightly exaggerating but not much:

S-61:
Civil: >181 Fatalities
Incl. Mil: >458 Fatalities
S-76:
>181 Fatalities


P.S.:
I don't have the figures for the Mi-8 but that will be easily in the Thousands.

No exaggeration required at all. I lost count on the Mi-8 family around 2700 and estimate the total must be between 5k and 10k (in RECORDED accidents).

Around 12000 built across many decades though.

It would perhaps be very interesting and enlightening to see the same numbers for the entire Puma/Super Puma family. And then perhaps to equate all these numbers into a reasonable analysis of fleet size and hours flown. Anyone? Or are we all just satisfied with half an answer and a pretty meaningless statistic?

[Fareastdriver]

numbers for the entire Puma/Super Puma family

670/890 in 2014. I couldn't tell you how many they have killed through mechanical reasons.

[Lonewolf_50]

Fareastdriver: Do you mean that through 2014, from birth, Puma/Super Puma have contributed to 890 fatalities? I find it hard to believe that in one year that many people lost it in that model/family.

[riff_raff]

Reminds me of the Comet-Boeing 707 situation in a way.

You make a somewhat relevant point here. Except I would compare this EC225 helicopter problem to that experienced with the horizontal tail surface actuator jack screws on some MD-80 commercial aircraft (http://lessonslearned.faa.gov/ll_main.cfm?TabID=2&LLID=23&LLTypeID=2). Basically a combination of design and maintenance issues occurring at just the right time to cause a catastrophic failure.

Lessons learned, right?

[Fareastdriver]

I didn't write that very well. That was the production figures up to 2014.

From 1971 I can remember eight fatal write-offs. Three of them mechanical, the others mishandling.

[Twist & Shout]

You make a somewhat relevant point here. Except I would compare this EC225 helicopter problem to that experienced with the horizontal tail surface actuator jack screws on some MD-80 commercial aircraft (http://lessonslearned.faa.gov/ll_main.cfm?TabID=2&LLID=23&LLTypeID=2). Basically a combination of design and maintenance issues occurring at just the right time to cause a catastrophic failure.

Lessons learned, right?

The difference between those two fixed wing examples and the L2/225 failures is that the reason for the fixed wing failures was determined and rectified.

[loop swing]

I think what he meant was that for the S92 to compete on range, it requires the internal fuel tanks in the cabin which then reduces the space available for the pax. I'm pretty sure he knows about the sponson tanks......

Re-reading original post, I see that now :ok:

After reading comments from the not-so-informed on social media regarding all things rotary, you can forgive me for wanting to clarify!

[helicrazi]

Finally some common sense

BP will not reintroduce fatal crash helicopter - BBC News (http://www.bbc.co.uk/news/uk-scotland-north-east-orkney-shetland-40567877)

[jimf671]

It would perhaps be very interesting and enlightening to see the same numbers for the entire Puma/Super Puma family. And then perhaps to equate all these numbers into a reasonable analysis of fleet size and hours flown. Anyone? Or are we all just satisfied with half an answer and a pretty meaningless statistic?


I don't have the figures with me but the pattern for the majority of large types is that across a few decades if you put 1000 helicopters out there working then they will typically have hundreds of accidents and one or two hundred people might die in those accidents. Some more, some less. Generally, the more military stuff they do and the more they operate in poorly regulated territories, the more people die.

What seems pretty clear is that the S-92 and H225 stand out from their parents (S-70/H-60 and AS332), and the rest, in their low rate of mishap and fatality so far. Anything that fails to acknowledge that is regrettable.

We can hope the H175 and AW189 will make a further 'step change in safety'.

I have not looked at any numbers separating Mi-171 from the 8 and 17. That might be pretty interesting.

[finalchecksplease]

Finally some common sense

BP will not reintroduce fatal crash helicopter - BBC News (http://www.bbc.co.uk/news/uk-scotland-north-east-orkney-shetland-40567877)

But when you click on that link just below the headline it says:BP will not use the Super Puma 225 and L2 helicopters until the root cause of last year's fatal crash is known.

Once that is established and the other oil companies start using the EC225 the economics will come into play and they will follow. Everybody knows the EC225 gives better payloads / range in most cases so the operating cost will be lower and this bottom line is what the beancounters are interested in.

[helicrazi]

But when you click on that link just below the headline it says:

Once that is established and the other oil companies start using the EC225 the economics will come into play and they will follow. Everybody knows the EC225 gives better payloads / range in most cases so the operating cost will be lower and this bottom line is what the beancounters are interested in.

Quite possibly, but I think what most have the issue with is the 'smoke and mirrors' and the ban being uplifted without understanding the root cause which is exactly what has happened. Im not getting into the S92 vs H225 argument because for me it isn't about that, its about yet again the aircraft being brought back into service without knowing what actually caused it. Putting chip detectors in place and reducing TBO and increasing inspections is simply not good enough. Stick a plaster on it, it will be fine, and if its not we will catch it in time. yeh right :ugh:

BP for me have taken the right decision, review the evidence when we understand what caused it. Only then can a proper informed decision be made.

[terminus mos]

Once that is established and the other oil companies start using the EC225 the economics will come into play and they will follow. Everybody knows the EC225 gives better payloads / range in most cases so the operating cost will be lower and this bottom line is what the beancounters are interested in.

I think that the 175 / 189 will fill the medium range market at a lower seat mile cost. The S-92 will continue to fill the longer range heavy requirement as it now does reliably. Contrary to what many think, the workforce does have a voice and won't welcome the 225 back if the stats are true. The return of the 225 is potentially therefore commercially irrelevant. Even if it came back at half price, which oil company aviation department is going to take the cost vs safety risk?

[finalchecksplease]

I think that the 175 / 189 will fill the medium range market at a lower seat mile cost. The S-92 will continue to fill the longer range heavy requirement as it now does reliably. Contrary to what many think, the workforce does have a voice and won't welcome the 225 back if the stats are true. The return of the 225 is potentially therefore commercially irrelevant. Even if it came back at half price, which oil company aviation department is going to take the cost vs safety risk?

You might be right on all the above except when you say the offshore workforce has a voice in the UK sector. They do and stick together on the Norwegian side (still working 2 on -4 week off roster) but sadly not to the same extend on the UK side (same goes for the pilots & engineers).

The future will tell if the 225 will return or not, I think it might (but it will take some time) because sadly money talks.:ugh::ugh:

[sinnon7]

Shell and other supermajors say ‘no plans’ for return of Super Pumas


https://www.energyvoice.com/oilandgas/north-sea/144381/shell-supermajors-no-plans-return-super-pumas/

[rotor-rooter]

Last month, Petronas and it's contract partners issued a 90 day termination notice for the utilization of their 225 contract with MHS. This one does specifically identify ExxonMobil as terminating their utilization of the type on this contract.

Petronas' partners want to terminate MHS Aviation's helicopter service too | The Edge Markets (http://www.theedgemarkets.com/article/petronas-partners-want-terminate-mhs-aviations-helicopter-service-too)

[Sky Sports]

People keep speculating on whether the 225 will 'come back'.
Let's not forget that, in other parts of the world and with other operators, it never went away!

[rotor-rooter]

Could you be so kind to remind us of the Operators and Fleet sizes that continued to operate?

[Sky Sports]

Air forces.

[UKpaxman]

Surely once the pax lose faith in the aircraft to the extent seen in the N Sea it's effectively finished for the scheduled work? i know the chinook was a very different aircraft to the other aircraft in service at the time, and it didn't have many fans before the sumburgh incident, but aren't there parallels here where pax no longer want to fly in the 225 - despite it continuing service elsewhere and in the military - as did the chinook.

[terminus mos]

Air forces

That would be the 725 then and doesn't count in the context of this thread. Military is not engaged in passenger carrying public transport long range high utilisation operations.

[212man]

That would be the 725 then and doesn't count in the context of this thread. Military is not engaged in passenger carrying public transport long range high utilisation operations.
That would be the H225M then - do keep up;-)

[terminus mos]

That would be the H225M then - do keep up;-)

Ah yes, it would be now I suppose. But a new badge maketh not a new helicopter.

[Self loading bear]

I am very well aware of the differences in operating and maintenance between civil offshore and military operations.
But if the military type would loose a head, I think it would be eagerly included in the Safety statistics by the criticasters of the mother type.
(Not that I am a fan of the type).
Are all losses of the military type been clearified?
I recall the loss of a Spanish one above sea off the Canary Islands?

SLB

[etudiant]

Surely the way to resolve this issue is by running the power train under sustained stress.

The 225 gear box has a graceless failure mechanism which was unexpected.
That should be reproducible, given all the clues we have. Running the system full out for 6 months would be ample to hit all the life limits afaik.
What has been learned from such efforts or has nothing such been attempted?

[Mee3]

I am very well aware of the differences in operating and maintenance between civil offshore and military operations.
But if the military type would loose a head, I think it would be eagerly included in the Safety statistics by the criticasters of the mother type.
(Not that I am a fan of the type).
Are all losses of the military type been clearified?
I recall the loss of a Spanish one above sea off the Canary Islands?

SLB
Nope. Almost never.

Unless it crashed, caused life or injury, or the assets itself is new or damn expensive.
"little incident" like inflight flame out, hydraulic leaking, undercarriage collapsed, almost but did not shake off the rotor head due to loose blade pin, window panel falling off, hot start without cranking, APU on when cowling slided back, TR cowling inflight dangling, slice the wheels half while landing with brakes on, glycol injection due to"pressing the wrong button", OEI take-off... unless it is officially reported to OEM, OEM cannot use it in their statistic, at least not the ones published.

[Concentric]

Surely the way to resolve this issue is by running the power train under sustained stress.

The 225 gear box has a graceless failure mechanism which was unexpected.
That should be reproducible, given all the clues we have. Running the system full out for 6 months would be ample to hit all the life limits afaik.
What has been learned from such efforts or has nothing such been attempted?
Whilst some testing is appropriate and I would hope has been undertaken, I think just running the power train under sustained stress alone might not be the way to replicate the conditions that led to either of the 2 planet gear/bearing premature failures occurring. There are probably many H225 and L2 MGBs that have reached their full service life limit on planet gears without incident.

What you might have to start with is introducing a deliberate surface imperfection, then run the bearing under typical service conditions and examine it at periodical intervals to monitor the growth of any cracks and/or spalling. All that will tell you of course is the rate of growth, not what caused the process to begin by creating the initial imperfection.

This paper (http://evolution.skf.com/the-progression-of-surface-rolling-contact-fatigue-damage-of-rolling-bearings/)describes such a test programme by a well known bearing manufacturer. It also describes the different spalling growth behaviour of ball bearings to roller bearings. The planet gear spherical bearings would approximate to the ball bearing behaviour. Unfortunately the paper only tests a setup where the indentation exceeds the Hertzian width in the rolling direction. It would be interesting to find any testing where the indentation is smaller than say the Hertzian width at typical mid-flight loading.

In my opinion the key area to be investigated is how micro-pits came to be created on the outer raceway. Was it corrosion due to moisture? Was it indentation from fine (or not so fine) metallic particles suspended in the lubricant? Was it a failure of the lubricant to provide or maintain an elastohydrodynamic film between roller and raceway? Was it related to long-term storage rather than operation?

You are correct that the 225 gearbox has a graceless failure mechanism. Part of that is due to the architecture, which Airbus may be unable to change due to certification limitations.

[Pablo332]

Anyone know of a 225 out there at the moment flying on contract?

[212man]

Anyone know of a 225 out there at the moment flying on contract?
Out where? I believe there are at least two in Vietnam that have never stopped.

[RVDT]

In my opinion the key area to be investigated is how micro-pits came to be created on the outer raceway. Was it corrosion due to moisture? Was it indentation from fine (or not so fine) metallic particles suspended in the lubricant? Was it a failure of the lubricant to provide or maintain an elastohydrodynamic film between roller and raceway? Was it related to long-term storage rather than operation?

How many different lubricants are approved for this gearbox?

Perception of "better" is open to interpretation.

From the same manufacturer an example is on some (not all) of the AS350 series you have the option of using a range of mineral and synthetic oils.

All are "approved" yet in this particular case experience dictates that the use of mineral oil will get you much better service life from gearbox components come overhaul.

The difference in the lubricant and their characteristics do have significant effect on all the points that Concentric quotes.

In years past many manufacturers used turbine oils in their main gearboxes. Mostly that has all changed as it worked but not that well in hindsight.

There are much better options available today. More common these days are synthetic industrial or agricultural lubricants and in a lot of cases automatic transmission fluids.

[Concentric]

RVDT,

I have been wondering the same since reading your post (http://www.pprune.org/3429369-post425.html) from 10 years ago.

I do think the lubricant is a very important and possibly overlooked part of this puzzle. The ‘Full Flow Magnetic PLUG’ as Airbus is calling their newfangled magnetic particle ‘detector’ sounds to me like it is in fact more of a Full Flow Magnetic FILTER. These are common enough in terrestrial engineering and manufacturers claim they can remove particles down to sub-micron level.

Despite all the gearbox issues Airbus have had over recent years with the 225 and L2 I am curious as to why they never improved the oil filtration but stuck with a 25 micron traditional filter. As most people on here will be aware, the Sikorsky S-92A has always had 3 micron filtration (while it remained attached, that is) and 3, 5 or 10 micron filtration is now pretty common on industrial transmissions.

Is the introduction by Airbus of what is effectively a fine magnetic filter actually recognition that they needed to purify the oil to a better quality to reduce the risk or rate of micro-pitting, which appears to lie at the root of the bearing failure? It might be embarrassing for them to call it a 'filter' for a couple of reasons including the wording of existing certification that is based on 'detection' of spalled particles. Prevention is always better than cure (or even just detection). Would that have convinced the UK and Norwegian regulators?

The revelation (AIBN report 1.6.9) that 44% of particles in Airbus' spalling test programme were found still in the gearbox must raise questions as to the drainage and internal flow patterns within the casing and/or whether those 44% of particles were finer than 25 microns and were being re-circulated through the filter. If the flow pattern to the lube oil pickup is not ‘full flow’ then the effectiveness of the new ‘FFMP’ or magnetic filter is questionable.

An interesting paragraph (1.18.3) of the AAIB report 2-2011 on G-REDL relates to later findings of particles on another aircraft G-REDN, particularly the 2011 discovery. Quite why, after identifying a particle as 16NCD13 steel, that aircraft was authorised to fly under ‘close monitoring’ for 25 FH then resumed routine flight for a further 87 FH is something that today might be considered unwise. But that isn’t my main point. It is that after finding some particles on the main module MCD, removal of the sump plate found more which were not captured by the MCD. Disassembly of the MGB then recovered "numerous" other metallic particles which had come from a 2nd stage planet gear, and notably silica.

Those findings suggest that not only were the MCDs quite ineffective but that numerous particles were not being flushed down to the sump or picked up by the lube pump (at least not the main lube pump, the one that feeds the 25 micron filter and this new FFMP).

If Airbus is installing this magnetic filter to enhance the existing filter then they ought to look at the internal flow streams within the MGB casing. They previously improved jetting of the vertical shaft bore but the whole gearbox really needs to be looked at for flushing effectiveness, perhaps even off-line flushing on the ground.

They should also remember that silica is not magnetic but it is actually harder than bearing steel (http://www.machinerylubrication.com/Read/30095/hard-particle-contamination). I would not be surprised if the filter pore size is reduced sometime soon as an ‘unrelated’ enhancement.


In other news… whilst everyone’s attention has been on the lifting of the H225 ban by CAA and CAA(N) on 7th July 2017, Airbus and EASA have recalled planet gears of 2 types for the Dauphin family (SA365, AS365 and EC155) according to AD 2017-0116 (https://ad.easa.europa.eu/page-2/) dated 5th July 2017 citing similar differences in contact stress to the H225 findings. Whatever next?

[Mee3]

findings of particles on another aircraft G-REDN, particularly the 2011 discovery. Quite why, after identifying a particle as 16NCD13 steel, that aircraft was authorised to fly under ‘close monitoring’ for 25 FH then resumed routine flight for a further 87 FH is something that today might be considered unwise...

In other news… whilst everyone’s attention has been on the lifting of the H225 ban by CAA and CAA(N) on 7th July 2017, Airbus and EASA have recalled planet gears of 2 types for the Dauphin family (SA365, AS365 and EC155) according to AD 2017-0116 (https://ad.easa.europa.eu/page-2/) dated 5th July 2017 citing similar differences in contact stress to the H225 findings. Whatever next?
Regardless of what and how much it was retained in the gearbox, chipping criteria is based on calculation and backed by statistical data. Same goes to damage tolerance on the gearbox. Silica related to 2nd stage gear however, is new to many including me. Can you elaborate more?

Dauphin bearing recall is an AH initiative. If anything is to take away from it, is that they are obviously singling out OEMs. The bearing and gear are totally different from puma. Unlike Puma, dauphin never had the power to hurt the its MGB, It's said in a way that AH might not take my good intention gracefully.

[Concentric]

Regardless of what and how much it was retained in the gearbox, chipping criteria is based on calculation and backed by statistical data. Same goes to damage tolerance on the gearbox. Silica related to 2nd stage gear however, is new to many including me. Can you elaborate more?
Obviously there should be no silica inside the gearbox. If it does get in there as contamination during gearbox module or mast installation, or during lubricant filling, its hardness might be a factor in starting the creation of micro-pits by causing surface asperities. Is it an Airbus requirement for lubricant to be pre-filtered and piped into the MGB or is it just poured? Is the air breather protected?

The statistical data is:
G-REDL, one chip detected, misinterpreted, catastrophic failure.
G-REDN, several chips detected, one confirmed as 16NCD13, aircraft allowed to fly, numerous more chips detected, planet gear spalled (669FH).
LN-OJF, zero chips detected, catastrophic failure.
What calculations can you perform on that?

If chips have previously been found to be left in the casing and on the sump plate without being detected, how can Airbus be sure the main lube pump sitting higher off the sump will pick them up and deliver them to this FFMP? The standby pump would be more likely to pick them up but that flow will not pass a detector. That is why I think this modification is more about filtering oil that is then delivered to the planetary spray nozzles than detecting macro particles after spalling.

[helicrazi]

Obviously there should be no silica inside the gearbox. If it does get in there as contamination during gearbox module or mast installation, or during lubricant filling, its hardness might be a factor in starting the creation of micro-pits by causing surface asperities. Is it an Airbus requirement for lubricant to be pre-filtered and piped into the MGB or is it just poured? Is the air breather protected?

The statistical data is:
G-REDL, one chip detected, misinterpreted, catastrophic failure.
G-REDN, several chips detected, one confirmed as 16NCD13, aircraft allowed to fly, numerous more chips detected, planet gear spalled (669FH).
LN-OJF, zero chips detected, catastrophic failure.
What calculations can you perform on that?

If chips have previously been found to be left in the casing and on the sump plate without being detected, how can Airbus be sure the main lube pump sitting higher off the sump will pick them up and deliver them to this FFMP? The standby pump would be more likely to pick them up but that flow will not pass a detector. That is why I think this modification is more about filtering oil that is then delivered to the planetary spray nozzles than detecting macro particles after spalling.

Maybe a stupid question but what is the TBO on the planet gear as in the case of REDN which effectively failed at 669FH, or is it more a case of the whole gear box not an individual component?

Your last paragraph I completely agree with, and brings me back to the 'smoke and mirrors' comment I made earlier, this FFMP sounds a looks good, which in effect I think its :mad: useless

[Mee3]

The statistical data is:
G-REDL, one chip detected, misinterpreted, catastrophic failure.
G-REDN, several chips detected, one confirmed as 16NCD13, aircraft allowed to fly, numerous more chips detected, planet gear spalled (669FH).
LN-OJF, zero chips detected, catastrophic failure.
What calculations can you perform on that?

There you completely missed the point and cherry picky what you would like to hear.
And some fact:
REDL did have just one chip.
REDN had numerous chip after "close monitoring" and still flying, nuff said. and I would appreciate if you would quote the conclusion in the report as well.
OJF, until the norwegian can explain why did they drawn up conclusion before they have a clue and been taking hindsight finding like opening christmas present is beyond me.

BTW, rarely seen a gearbox could survive the heavy hover after initial finding. But in the money world, even a rock fell off is acceptable.

[SimonK]

Imho I'd be amazed if it returned to the North Sea in any shape or form. The only industry people I've spoken to who think it should and could come back seem to be 99% Airbus personnel or the odd die hard 225 pilot. The loss of confidence in the 225 in the offshore workers is a done thing, it's happened and it ain't coming back. I get that the 225 was a very capable aircraft and better in some ways than the S92, but the confidence has gone. Etched forever in the brain when you think of the 225 is that horrible shot of the windmilling rotor head falling down to the ground. It's finished guys.

[Concentric]

OJF, until the norwegian can explain why did they drawn up conclusion before they have a clue and been taking hindsight finding like opening christmas present is beyond me.

BTW, rarely seen a gearbox could survive the heavy hover after initial finding. But in the money world, even a rock fell off is acceptable.
I am afraid you have got me there.:rolleyes::confused:

[Variable Load]

Mee3's message sounds like something Google translate might generate? If however he's a native English speaker, then :eek::eek::eek:

[RVDT]

Concentric,

Further to my previous about the different oils - when using "mineral" oils the service period of flight hours and calendar period is much shorter.

That could easily contribute to a large proportion of the better result.

WRT your comments about "silica" - could it be something as simple as a poor vent on the gearbox allowing it to enter from just airborne debris? Dumber things have happened, wood for trees etc.

I did point out and demonstrate to a certain associated manufacturer how water was getting in to their gearbox which resulted in numerous changes to the venting and fixed the issue.

The unusual thing was that if you had any experience with older aircraft and different manufacturers the fix was obvious! No need to re-invent the wheel!

[terminus mos]

It's finished guys.

There is also at least one larger influential operator actively working with Airbus to bring the 225 back to commercial service.

[Twist & Shout]

There is also at least one larger influential operator actively working with Airbus to bring the 225 back to commercial service.

Can you imagine the consequences of another one shedding the rotor system?
1 is bad luck, 2 is negligence, 3 would be a lawyers wet dream.

[havick]

There is also at least one larger influential operator actively working with Airbus to bring the 225 back to commercial service.

I could see them being used in the utility world for fire work where paying public aren't sitting in the back, with no one else wanting the airframes acquisition should be a fraction of their original value.

[birmingham]

There is also at least one larger influential operator actively working with Airbus to bring the 225 back to commercial service.

Operators can only bring them back if they have customers.
I really can't see any significant N/S oilco dare to specify the 225.
That shot of the rotorless Bergen a/c haunts the industry like the shots of Piper Alpha.
Oil Cos like to think of themselves as Gung Ho cost cutting warriors. The reality is that when it comes to HSE they are a flock of corporate sheep. It's dead Jim!

[Sky Sports]

Why do people think the 225 only operates in the North Sea?

Before the grounding, what percentage of the worldwide fleet, including the military machines, were actually operating there?

[helicrazi]

We don't think that, what we know is that the main 2 countries that operated them in the north Sea, grounded them, the rest of the world carried on as normal (after a short while) rightly or wrongly.

[S92PAX]

There is also at least one larger influential operator actively working with Airbus to bring the 225 back to commercial service.

Of course they will try. They are tied into multi million pound leases/purchases and can't afford to abandon these aircraft.
What they obviously don't realise is the strength of feeling against flying in them again.
After the first incident I was one of quite a large number that refused to fly in them. For this we were treated to a day at Bristows being shown how good they were and the extensive checks and maintenance that would prevent it happening again. What are they going to do with us now?

[industry insider]

There is no commercial imperative to bring the 225 back into service, North Sea or internationally. There is no shortage of S-92 capacity to fill the heavy requirement and Super Mediums are increasingly filling intermediate requirements.

Bringing a 225 on contract would probably displace a 92 or 189 /139 which are all cheaper to operate anyway. The 225 has always been more $ hourly than the 92 and with changing MGBs every 1000 hours will only be more expensive again. So, as an operator, one would really have to want to rather than need to bring it back.

We have all been told that this is the most scrutinised MGB ever, 3 or 4 times now. This time I don't believe it and I won't be putting any passengers in it.

[riff_raff]

In years past many manufacturers used turbine oils in their main gearboxes. Mostly that has all changed as it worked but not that well in hindsight.

There are much better options available today. More common these days are synthetic industrial or agricultural lubricants and in a lot of cases automatic transmission fluids.

In the US, most newer rotorcraft gearboxes use a dedicated transmission oil like DOD-PRF-85734 or a commercial equivalent, rather than turbine engine oils like MIL-PRF-7808. DOD-PRF-85734 transmission oil is a synthetic base lubricant that is hard on some materials and finishes. So one consider with using this oil is ensuring all elastomer seals and coatings are chemically compatible.

[Concentric]

In the US, most newer rotorcraft gearboxes use a dedicated transmission oil like DOD-PRF-85734 or a commercial equivalent, rather than turbine engine oils like MIL-PRF-7808. DOD-PRF-85734 transmission oil is a synthetic base lubricant that is hard on some materials and finishes. So one consider with using this oil is ensuring all elastomer seals and coatings are chemically compatible.
Would that include the Sikorsky S-92A tailrotor drive I wonder?

[rotor-rooter]

What became of the AS332L/L1 fleet? These helicopters dominated the marketplace and then just seem to have vanished completely. Between the L/L1/L2 and 225 all disappearing, this must have a major impact on Airbus revenues?

[Sky Sports]

this must have a major impact on Airbus revenues?

New 225 bookings for the North Sea sector started to dry up a couple of years ago, well before the grounding. Airbus forecasts for the 225 predicted the majority of business would come from the military, and so it was proven. The grounding in some sectors, has had a slight impact on revenue.

[terminus mos]

The 225 effectively replaced the L / L1 and even L2 in some areas. Faster, smoother, better payload and with new avionic technology, it made the L Series commercially obsolete. Many Ls ended up in the secondary market like the German Border Guard. Vector bought some I think. Some were canniblised for spares as support was becoming expensive and difficult. Some even went to the scrapyard. There was a brief resurrection when the 225 was grounded first time.

[Twist & Shout]

A few of the old buses are back flying contracts in Australia (and East Timor), since the demise of the 225

[birmingham]

New 225 bookings for the North Sea sector started to dry up a couple of years ago, well before the grounding. Airbus forecasts for the 225 predicted the majority of business would come from the military, and so it was proven. The grounding in some sectors, has had a slight impact on revenue.

As I have said many times before here I think the North Sea market is pretty much over for the 225, and not just because of the accident. The O&G market has been down longer than before and other than in the US is not showing much of an uptick.

The 225 (or rather its military versions) can certainly be re-engineered to have a bright military future and there are areas of the world where it can continue commercially.

The elephant in the room which is just not going away is doubt over the safety of the MGB. Nothing that has been said yet, is going to change that. However, there is nothing to stop AH setting out a radical re-engineering plan or, if/when it really knows, to explain exactly why this happened and a clear indication that that has been fully fixed.

[212man]

there is nothing to stop AH setting out a radical re-engineering plan

Apart from the X6 project....

[birmingham]

Apart from the X6 project....

that is still someway off but yes I agree they could just slow burn until then

[Mee3]

I am afraid you have got me there.:rolleyes::confused:
As I said, picking what you wish to hear does not change the fact. Report is coming soon and the conclusion is quite interesting.

[Fareastdriver]

I suppose they could make the top bearing housing and support lugs out of stainless steel with steel support tubes down the roof. At least the rotor should stay on should the upper planetary disassemble itself.

Whether you can control it is another matter.

[SASless]

The reality of what we are discussing here......we have had two occurrences like what the video of the shed rotor system slowly spinning on its way to earth and rising column of black smoke from the wreckage in the Bergen video shows.

Yet, today, there is no definitive explanation of exactly what caused the failures....we know pretty well HOW they happened...but not WHY they happened.

It might be that I missed the explanation in all of the posts in this thread that did clearly lay out the case of what actually caused the failures.

Lots of jabber about how to better monitor the MGB's for potential failures of the same sort, modifications of inspection schedules and component replacement, lots of testing of modified or different parts and components.....but no definitive statement of the exact root cause of the two failures.

Did I miss or over look it?

Am I the only one?

If that exact cause is not genuinely identified....should passengers and crew be flying in the aircraft?

[Fareastdriver]

If that exact cause is not genuinely identified....

The cause is that the orbital gear cannot contain a disassembling planetary gear. Containment is not new; I've flown helicopters with a containment ring around the turbines to stop them destroying the other engine and hydraulics.

The problem with the existing gearbox is that there is only one failure path; that goes and you are dead. It is IMHO impossible to guarantee that any gear assembly will last it's planned overhaul life however long you test it.

The 330 and 332 got away with it because the design of the gearbox had sufficient reserves. You pile in more torque and strain on affectively the same bottle then something has to go. I cannot see any other way than a complete redesign with multiple failure paths within the gearbox.

History may prove that this way will be the standard in the future.

[Geoffersincornwall]

My engineering colleagues have explained that this type of gear wheel is made of a steel that has rather a severe crack propagation characteristic and as such the failure mode is severe and is exacerbated by the lack of debris created during the failure process. This lack of debris leaves the airworthiness of the component design open to question as there is no effective way of preventing ultimate failure once cracks have appeared.

You may well ask how we progress from here. It rather looks as if the edge of the carpet has been raised and the offending question swept under it. A large notice stating DO NOT GO HERE has been stuck in the ground by the EASA lawyers who appear to have wagged at large and menacing finger at the brave chaps and chapesses in the UK and Norwegian CAA.

G

[SASless]

As I read it....Geoffers and Fareastdriver have arrived at two different causes already.

Both very experienced Pilots and professionals and each has carefully considered a lot of information about this.

We have had a lot of good discussion by some very sharp folks....but yet there is ambiguity when it comes to the actual mechanism of these two failures.....which I am not sure even AH really knows what is causing the failures.

Which is it.....wrong material that does not afford reasonable detection of a pending failure as Geoffer's Engineer buddies are saying or is it the Orbital Gear cannot contain a failing Planetary Gear as suggested by Fareastdriver?.

Or....is it something altogether different?

Is this apparent contradiction indicative of the problem confronting the Helicopter Industry, Operators, and Customers?

AH and the Authorities in conjunction with the Accident Investigators seem not to be able to explain this situation to the degree there is conformity of thought as to the actual root cause?

Until there is a definitive....proven....without any doubt....explanation....should the aircraft be certified by any authority as being safe for flight in general air transport operations carrying passengers?

[Twist & Shout]

Until there is a definitive....proven....without any doubt....explanation....should the aircraft be certified by any authority as being safe for flight in general air transport operations carrying passengers?

No.

It should be in the experimental category. With associated warnings and restrictions.

[Concentric]

As I read it....Geoffers and Fareastdriver have arrived at two different causes already.
Their individual explanations are not mutually exclusive but in fact describe different phases in the failure sequence. That sequence is something of a chain reaction that ought to have been prevented at any of a number of places. It wasn’t and that is a failure of the designers to consider the unthinkable.

[SASless]

Concentric,

Are you agreeing with my statement that the definitive cause has not been fully identified and all EVERYONE (including AH Engineers) is discussing are symptoms, responses, and assumptions resulting from that lack of certainty about what kicks off that sequence of events?

[Pittsextra]

We are running the risk of accepting the nonsense of ambiguous communication. Ever thought that it exists so as not to generate an instant set of questions from the final report?

[riff_raff]

My engineering colleagues have explained that this type of gear wheel is made of a steel that has rather a severe crack propagation characteristic and as such the failure mode is severe...

Geoffers - The planet gears in question were made from 16NCD13 double vacuum melt steel (AMS 6263) which is very high quality. You can find some data on the alloy here (https://www.cartech.com/globalassets/datasheet-pdfs/16ncd13.pdf). It has excellent fracture toughness and was a good material choice for this application.

Having said that, there is an interesting situation described in the AIBN report issued on April 28, 2017 regarding the fracture analysis work used to certify the gearbox design. If you read the report beginning with section 1.17.6.3, there is some discussion of revisions to EASA CS 29.571 Fatigue tolerance evaluation of metallic structures, and how this relates to the EC225 MRGB.

If you look at the CT scan image of the failed planet gear outer bearing race section shown in fig. 38 of the report, you'll see that there is a sub-surface fracture (highlighted in red) passing thru several spall locations just ahead of the final rim fracture. This sub-surface fracture runs at a shallow depth (~.012") and lies entirely within the carburized case thickness (~.050").

Then consider this part of the report:
"1.17.6.4 Assessment of the MGB against CS 29.571 - The AAIB investigation into the G-REDL accident found that the phenomenon of crack formation within the carburized layer of the outer planet gear race had not been considered during the design and certification of the AS 332 L2 and EC 225 LP epicyclic reduction gearbox module or the development of the approved maintenance program of the MGB.

The AAIB stated in the G-REDL report (on page 95) that “although the design satisfied the certification requirement in place at the time of certification”, and further “it would appear that if the current requirements [CS 29.571 issued in 2003] were applicable they may not have been met."

The report is saying that the original fracture analysis performed to certify the gearbox design did not take into account the particular type of failure that occurred in this case. This may not provide the complete explanation many are looking for as to why this unfortunate accident happened, but it helps clarify things quite a bit.

[Concentric]

Concentric,

Are you agreeing with my statement that the definitive cause has not been fully identified and all EVERYONE (including AH Engineers) is discussing are symptoms, responses, and assumptions resulting from that lack of certainty about what kicks off that sequence of events?
SASless,

Generally speaking, I am in agreement that the definitive cause (or ‘root cause’ as I would prefer to call it) has not yet been satisfactorily explained or reported. The regulators lifting the restrictions before the AIBN has reported seems to me like ‘putting the cart before the horse’. Hopefully since the ‘cart’ has already appeared, the ‘horse’ will not be too far behind. Mee3 claims inside knowledge that the report is coming soon. I can’t tell if that comes from the horse’s mouth though, given the apparent direction of travel.

What the other 2 posters described were both consequences and each was generally correct as such but neither is the absolute root cause. They were not quite adjacent ‘dominos’ in the failure sequence either but the speed with which the whole design came apart illustrates the vulnerability of the 1960’s era architecture of this MGB.

Those consequences illustrate the criticality of ensuring all possible failure modes of the planet gear/bearing are considered in its design and in particular fatigue tolerance, which leads into riff_raff’s excellent post above. One thing I would add to that is that the mechanical properties of the stock material can be considerably different to those of the finished heat treated component.

[Hompy]

No sharing of gearbox components with the Tiger is there?

": Absturz Kampfhubschrauber Tiger
Am 26. Juli 2017 gegen 14.20 Uhr Mitteleuropäischer Sommerzeit ist ein Kampfhubschrauber Tiger aus bislang ungeklärter Ursache circa 70 km nordöstlich von Gao in Mali abgestürzt. An Bord des Hubschraubers befanden sich zwei Besatzungsangehörige, die bei dem Absturz ums Leben gekommen sind. "

My two pence: I doubt I will be asked to but I will not be flying the 225 until I am clear the problem that caused the failure has been clearly identified and a redesign has been implemented rendering further failure of the same type impossible. More frequent inspection does not cut it for me.

[Geoffersincornwall]

riff raff - would it be true to say that the fracture toughness you refer to means that the fracture dynamics are somewhat rapid as a result?
G.

[rjsquirrel]

sasless said, "As I read it....Geoffers and Fareastdriver have arrived at two different causes already. Both very experienced Pilots and professionals and each has carefully considered a lot of information about this."

The amazing thing is that the Airbus VP of Sales told a group of Industry experts 8 weeks ago (HeliOffshore Conference) that the cause was shipping damage to the gearbox. He was so certain that he advocated a sensor in shipping containers that could tell of shipping abuse.
So, perhaps, Sasless, we have THREE different causes, and we put them in a hat and select the agreed upon one.

I choose what's behind door #4, unknown. http://www.pprune.org/forums/images/smilies2/eusa_wall.gif

[SASless]

I would suggest Door Four contains something lots of folks do not care to consider....that being the "root cause" is the basic design of the 225 MGB.

It is not capable of containing what should not be a catastrophic failure and fails in that regard due to its inability to transfer the load path to other parts of the gearbox following a failure within an individual module.

We know the existing detection and monitoring systems fail to give enough warning...so perhaps there must be a simpler explanation than what the Boffins are looking for.

The American MGB designs use "thru shafting" as a way of holding all the big pieces together unlike the AH 225 gearbox.

Or am I misunderstanding the various drawings I have been looking at?

Any of you design engineers able to help me with this?

[riff_raff]

riff raff - would it be true to say that the fracture toughness you refer to means that the fracture dynamics are somewhat rapid as a result?

Predicting propagation of a fracture within a metal structure is a fairly complicated task, mostly due to the wide range of variables involved. The fracture propagation analysis is intended to demonstrate that a worst case size/shape flaw in the part structure will not produce propagation of a fracture originating from this flaw that results in a catastrophic failure event.

The rate at which a fracture will propagate is greatly influenced by the stress levels at the fracture tip. The fracture will only propagate if the stress level at the crack tip exceed the local tensile strength of the material. The design of planets gears like the example discussed, having a very thin section rim and internal radial support provided by just a few rollers over a limited angular sector of the bearing, is very difficult to get right. If the planet's spherical roller bearing has excessive internal radial clearance, it can produce higher bending stresses in the gear rim than it was designed for.

[Concentric]

I would suggest Door Four contains something lots of folks do not care to consider....that being the "root cause" is the basic design of the 225 MGB.

It is not capable of containing what should not be a catastrophic failure and fails in that regard due to its inability to transfer the load path to other parts of the gearbox following a failure within an individual module.

We know the existing detection and monitoring systems fail to give enough warning...so perhaps there must be a simpler explanation than what the Boffins are looking for.

The American MGB designs use "thru shafting" as a way of holding all the big pieces together unlike the AH 225 gearbox.

Or am I misunderstanding the various drawings I have been looking at?

Any of you design engineers able to help me with this?
In Root Cause Analysis (https://en.wikipedia.org/wiki/Root_cause_analysis), the design features and detection or monitoring system failings you describe above would be regarded as causal factors but not the root cause. Those causal factors certainly affect the final outcome and ought to be identified at the design stage, at least in any new design and in Failure Mode Analysis.

The architectural differences compared to US-made MGBs you describe could make a significant difference in mast retention; however the containment requirements are different to those on a turbine which can be shut down. As you know, it is not enough to just retain the mast you also need rotor rpm and pitch control, probably with some hydraulics. Broken gears and other shrapnel rattling around in a gearbox with no quick escape path could jam or seize the drive or damage blades or dampers. Freewheels on the input side are designed to allow for an MGB to rotate faster than an engine, not slower, and there is no output freewheel allowing the rotor to maintain rpm in an auto with a seized gearbox. The ‘Lack of Lubrication’ thread gives a graphic account of a Huey with a seized MGB.

Having said that, I do think the Blackhawk and possibly the similar S-92A MGB architecture would be less likely to seize if a planet gear fractured, which I am not sure has ever happened.

The root cause is what caused the bearing to initiate a crack in the first instance but then propagate it in a manner that the designers had not expected, i.e. different to spalling, leading to catastrophic fracture.


There is a curious statement on Airbus' accident investigation status page (http://www.helicopters.airbus.com/website/en/ref/LN-OJF-Accident-Investigation-Status_395.html) that: "We understand the sequence of events that led to the fatigue fracture, but the exact cause is still being investigated." That might infer they think they know 'how' but do not yet know 'why'.

[albatross]

sasless said, "As I read it....Geoffers and Fareastdriver have arrived at two different causes already. Both very experienced Pilots and professionals and each has carefully considered a lot of information about this."

The amazing thing is that the Airbus VP of Sales told a group of Industry experts 8 weeks ago (HeliOffshore Conference) that the cause was shipping damage to the gearbox. He was so certain that he advocated a sensor in shipping containers that could tell of shipping abuse.
So, perhaps, Sasless, we have THREE different causes, and we put them in a hat and select the agreed upon one.

I choose what's behind door #4, unknown. http://www.pprune.org/forums/images/smilies2/eusa_wall.gif

Something like these? Impact Products | SpotSee (http://www.spotsee.io/impact)

Was not the gearbox returned to Airbus for overhaul after the transport accident in Australia?

Well at least he did not mention their..bad maintainance..re installation "missing pins" accusation.

[albatross]

German helicopter lost rotors before Mali crash - report | World | Reuters (http://af.reuters.com/article/worldNews/idAFKBN1AO2JH?feedType=RSS&feedName=worldNews&utm_source=feedburner&utm_medium=feed&utm_campaign=Feed%3A+reuters%2FAFRICAWorldNews+%28News+%2F+A FRICA+%2F+World+News%29&&rpc=401)

So is there any commonality between the Tiger and EC 225 rotor system/ gearbox? Question was asked in a previous post here but not answered.

[henra]

German helicopter lost rotors before Mali crash - report | World | Reuters (http://af.reuters.com/article/worldNews/idAFKBN1AO2JH?feedType=RSS&feedName=worldNews&utm_source=feedburner&utm_medium=feed&utm_campaign=Feed%3A+reuters%2FAFRICAWorldNews+%28News+%2F+A FRICA+%2F+World+News%29&&rpc=401)

So is there any commonality between the Tiger and EC 225 rotor system/ gearbox? Question was asked in a previous post here but not answered.



No.
And the word is the Tiger lost the Rotor blades not the entire head.
Looks more like too high rpm or (negative?) G- Overload.

[albatross]

Thanks for the reply.
I googled but was unable to find an answer.

[MightyGem]

The unions aren't happy:
https://www.energyvoice.com/oilandgas/north-sea/147637/breaking-unions-rebuff-attempts-reintroduce-super-pumas-north-sea/?utm_source=facebook

[Lonewolf_50]

And the word is the Tiger lost the Rotor blades not the entire head. That would make the Tiger accident more similar to the US Army Apache that was lost near Galveston last year, though in that case the root triggering cause of a blade letting go may be different. Only one blade needs to depart for the whole thing to go all wrong in fractions of a second.

[birmingham]

The unions aren't happy:
https://www.energyvoice.com/oilandgas/north-sea/147637/breaking-unions-rebuff-attempts-reintroduce-super-pumas-north-sea/?utm_source=facebook

It is clear that many operators are also keen to see the root cause of this accident - even in countries not so influenced by the opinions of North Sea workers here is the latest from Flight Global

https://www.flightglobal.com/news/articles/era-group-plays-down-swift-return-for-h225-helicopte-440147/

[rotor-rooter]

The actions so far, doesn't appear to have gained a lot of passenger confidence either.

Helicopter survey suggests '62% unlikely to fly in Super Pumas again' - BBC News (http://www.bbc.co.uk/news/uk-scotland-north-east-orkney-shetland-41199778)

[helicrazi]

Or pilot confidence

[birmingham]

Flight Global showing that the industry is still adopting a wait and see approach

https://www.flightglobal.com/news/articles/insight-from-flightglobal-offshore-oil-gas-suppor-441046/

Rare, possibly unique, for such an incident to be so thoroughly investigated, so much known, but unable to identify the absolute root cause more than a year on and after two events.

How much of the reticence do you think is down to weak demand and how much to safety worries?

[Cyclic Hotline]

Pull out all the stops?

Airbus boss flies in Super Puma in bid to demonstrate its safety - BBC News (http://www.bbc.com/news/uk-scotland-north-east-orkney-shetland-41482890)

[piperpa46]

I'd like to see the report stating the cause of the accident. There must be one since Airbus Helicopter has a full understanding of it.
And it doesn't really send a good signal when you won't answer questions:
Emerging from the helicopter, Airbus CEO Guillaume Faury made a statement but would not answer questions.

[Fareastdriver]

Airbus boss flies in Super Puma in bid to demonstrate its safety - BBC News

Maxwell went for a ride in a BV234 just after the Sumburgh crash 'to demonstrate its safety' It didn't stay on the North Sea very long.

[Self loading bear]

I see a good opportunity to test the effectivity of Airbus media campaign:

Have Airbus CEO Guillaume Faury picked up from his lawn by company H225 every morning for the daily ride into the office.
Let his wife wave him off.

Ask his wife how she feels:
- after 1 month
- after 3 months
- after a Year

SLB

[roundwego]

Maxwell went for a ride in a BV234 just after the Sumburgh crash 'to demonstrate its safety' It didn't stay on the North Sea very long.

The 234 remained operating for many years (9 if I remember correctly) in the North Sea after the Sumburgh crash. Helikopter Service in Norway operated them very successfully. It was economics and commercial requirements which took them off the North Sea eventually.

[nowherespecial]

SLB, that Sir is a bloody good idea!

[birmingham]

"Airbus said it has a full understanding of the cause of the crash and, after introducing a range of measures, is confident it could not be repeated".

Does this mean that Airbus has access to a draft of the final report? While I agree it is very clear what happened I haven't yet seen anything in the public domain that would lead me to conclude I had a full understanding of the cause of the crash.

[Twist & Shout]

Airbus have consistently treated the truth with disdain during these tragic events.
One of the low lights was claiming the Norway crash was a “mtce issue” within 24hrs of the multiple fatalities. (All but stating the pins were left out of the lift bars)
It would be an obvious act of naivety to believe anything that they say now, unfortunately.

[FloaterNorthWest]

https://www.oilandgaspeople.com/news/15251/exclusive-airbus-full-interview-on-super-puma-future/

[Apate]

Airbus have consistently treated the truth with disdain during these tragic events.
One of the low lights was claiming the Norway crash was a “mtce issue” within 24hrs of the multiple fatalities. (All but stating the pins were left out of the lift bars)
It would be an obvious act of naivety to believe anything that they say now, unfortunately.

Totally agree.

Airbus = :ugh::ugh::ugh:

[casper64]

Interesting video on Airbus website:
lInfo Centre - Airbus Helicopters (http://www.helicopters.airbus.com/website/en/ref/Info-Centre_393.html)

[EESDL]

Whilst reading the article did anyone else think of a government minister getting his daughter to eat a hamburger during the 'Mad cow' crisis?

[helicrazi]

There is an energy voice survey now being done asking if you would fly in one again,

after you click your decision it tells you the current polling results and how many have voted

Surprisingly at the moment, its 86% would fly in it again and 10% no, seems a bit different from the airbus poll

for you maths gurus, there are 2 other options to make up the remaining percentage. cant remember what they were, one was something about being happy with the s92 as replacement.

[Bing]

Whilst reading the article did anyone else think of a government minister getting his daughter to eat a hamburger during the 'Mad cow' crisis?

Oh no, there was actually a scientific case, at the time, that eating beef was a safe thing to do based on evidence. Whereas this seems to be based on reducing the gearbox life to 25% of what it's supposed to be based on crossing fingers.

[diginagain]

I see a good opportunity to test the effectivity of Airbus media campaign:

Have Airbus CEO Guillaume Faury picked up from his lawn by company H225 every morning for the daily ride into the office.
Let his wife wave him off.

Ask his wife how she feels:
- after 1 month
- after 3 months
- after a Year

SLB

Pack him in with 18 other blokes, dressed in a gimp suit and EBS/ lifejacket combo, and take the scenic route to work.

[419]

There is an energy voice survey now being done asking if you would fly in one again,

after you click your decision it tells you the current polling results and how many have voted

Surprisingly at the moment, its 86% would fly in it again and 10% no, seems a bit different from the airbus poll

Only my opinion but the reason for so many people being willing to fly in the 225 now could possibly be to do with the current state of the oil industry.

With so many oil workers and contractors losing their jobs and with little possibility of finding similar employment at the moment, maybe many of the people willing to fly in the 225 are simply agreeing to do so out of fear of losing their livelihood if they refused.
If people could walk out of a job and find another one shortly afterwards, the survey results may well be a lot different.

[Self loading bear]

Interesting video on Airbus website:
lInfo Centre - Airbus Helicopters (http://www.helicopters.airbus.com/website/en/ref/Info-Centre_393.html)

I have watched the video, indeed interesting. Outside the video they say that they know what happened but in the video they bet on 4 horses: different types bearings; better detection of smaller spalling particles; preventing or signalling shock loads when in transport and preventing dirt ingress while not mounted in aircraft.

All four good measures but they also cut TBO to a quarter and maintenance is limited to Airbus approved maintenance centers.
(Was this not always the case?)

This is only right if they would know and could prove that all these 3 or 4 cheese holes have lined up in this crash. (I.e. Dirt ingress has caused spalling on a previously shock loaded surface of a higher stressed bearing type)

But removal of the more vunerable bearing type is not the complete solution?

I am willing to give credits for the measures they have taken.
But I think they still not know precise.

The maintenance and inspections they have implemented will probably eliminate a sound business case for commercial use?
Perhaps somebody can give insight in what this means on Cost per seat Mile (not down to the penny but more or less relative to S92)

SLB

[Twist & Shout]

I have watched the video, indeed interesting. Outside the video they say that they know what happened but in the video they bet on 4 horses: different types bearings; better detection of smaller spalling particles; preventing or signalling shock loads when in transport and preventing dirt ingress while not mounted in aircraft.

All four good measures but they also cut TBO to a quarter and maintenance is limited to Airbus approved maintenance centers.
(Was this not always the case?)

This is only right if they would know and could prove that all these 3 or 4 cheese holes have lined up in this crash. (I.e. Dirt ingress has caused spalling on a previously shock loaded surface of a higher stressed bearing type)

But removal of the more vunerable bearing type is not the complete solution?

I am willing to give credits for the measures they have taken.
But I think they still not know precise.

The maintenance and inspections they have implemented will probably eliminate a sound business case for commercial use?
Perhaps somebody can give insight in what this means on Cost per seat Mile (not down to the penny but more or less relative to S92)

SLB

I’m only a simple ex EC225 driver, but how many of the “4 factors” were present in both fatal failures? The manufacturer of the bearing?

Is that a mirror, almost hidden by all this smoke?

[Concentric]

There is an energy voice survey now being done asking if you would fly in one again,

after you click your decision it tells you the current polling results and how many have voted

Surprisingly at the moment, its 86% would fly in it again and 10% no, seems a bit different from the airbus poll

for you maths gurus, there are 2 other options to make up the remaining percentage. cant remember what they were, one was something about being happy with the s92 as replacement.
You might want to take another look at the voting figures...
It doesn't take a maths guru to see that the voting trend is now more and more towards "No", currently 49% overall and that very few have been added to the "Yes" vote, currently 43% overall. In the last 24 hours the additional voting has been 71% "No" and 19% "Yes". Interestingly the Sikorsky popularity is climbing slowly so maybe the Airbus lobby had their say yesterday:=

[casper64]

It depends how you interpret the video...
THE cause of the crash was the minor spalling on the inside of the ring gear, this seems 100% certain. Now the question is: how did this spalling happen??? For this they made this huge fault tree analysis and came up with the following possible causes:
A: by intrusion of small particles
B: by shockload
C: by pressure of the roller bearings
D: by fatigue
E: a possible combination of the above.
To counter this they;
A: Reduced the risk of particles entering the gearbox by the additional covers and to perform the work only in certified maintenance centers.
B: To counter effect of shock loads they installed monitor sensors on transport cases, remove gearboxes with "incidents" from the fleet and have maintenance done in certified maintenance centers.
C: To counter the effect of the pressure of the rolling bearings they have removed the version with the generally higher pressure from the fleet, reduced lifetime of MGB.
D: To counter the effect of fatigue they have reduced lifetime on MGB, reduced stress with only allowing the better bearings.
E: To counter the risk of undetected spalling they raised inspection intervals and installed better chip detectors.

Now with all those measures in place I think they covered all most likely causes of the accident. Is it a 100% guarantee??? No, but we will never have a 100% certainty with mechanical things flying through the air... If you additionally add up the fact that these gearboxes also have 100 of thousands if not millions of hours of flighttime I think it is currently even safer than when putting in a brand new gearbox design as some have suggested. I would get on one without hesitation.

[etudiant]

As Twist and Shout points out, we have two very similar accidents and the bearings are the only obvious common element.
The discussion in this thread suggests that the internal component failure process may not produce significant particles before complete disintegration.
Passengers would be more confident in the fixes if the huge effort AH has put into analyzing these accidents had allowed them to reproduce the MGB failures that occurred. Without that, concern remains that the fixes are not addressing the problem.

[casper64]

As Twist and Shout points out, we have two very similar accidents and the bearings are the only obvious common element.
The discussion in this thread suggests that the internal component failure process may not produce significant particles before complete disintegration.
Passengers would be more confident in the fixes if the huge effort AH has put into analyzing these accidents had allowed them to reproduce the MGB failures that occurred. Without that, concern remains that the fixes are not addressing the problem.

I don't know if the other crashed aircraft had the same bearings, but in case it had, then this is taken care of by removing these bearings from service, as the other ones never had an issue. Additional safety on the MGBs that never had an issue in the first place, is then subsequently provided by increasing inspections, reducing lifetime and better chip detectors. This should take care of the problem... again, 100% guarantee? No. But if you want 100% one should just stay where humans belong: with 2 feet on the ground...

[henra]

Passengers would be more confident in the fixes if the huge effort AH has put into analyzing these accidents had allowed them to reproduce the MGB failures that occurred.

In a way, yes. On the other hand the fact that they couldn't reproduce it straight forward shows that it must be a very unlikely combination of factors. Now they eliminated or reduced multiple additional factors besides the obvious one (the Bearing manufacturer - seeing the different rollers in the video gave me shivers - how can so differently radiused rollers be equally suited to the same application?). Personally I would say with all these measures in place the next helicopter to lose an entire MGB will be a different Make/Model. Will it be economically viable? Well that is a good question.

[Twist & Shout]

In a way, yes. On the other hand the fact that they couldn't reproduce it straight forward shows that it must be a very unlikely combination of factors. Now they eliminated or reduced multiple additional factors besides the obvious one (the Bearing manufacturer - seeing the different rollers in the video gave me shivers - how can so differently radiused rollers be equally suited to the same application?). Personally I would say with all these measures in place the next helicopter to lose an entire MGB will be a different Make/Model. Will it be economically viable? Well that is a good question.

When combined with the low flying hrs the EC225 fleet is likely to accumulate in the foreseeable future, My personal opinion is the same as yours, well as far as another model goes anyway.

[casper64]

Now they eliminated or reduced multiple additional factors besides the obvious one (the Bearing manufacturer - seeing the different rollers in the video gave me shivers - how can so differently radiused rollers be equally suited to the same application?).

What do you mean? From what I have onderstood they have removed the "bad" bearing variant from the fleet? Totally agree with the last part, it was quite a big difference in radius!

[Noiseboy]

One point to note is that as well as removing any gearbox which has suffered impact from service, they also removed any having had a lightning strike.

The gearbox fitted in the L2 accident had sustained a lightning strike while fitted to a different airframe. Maybe they cannot categorically say it is the gear types because both gearboxes had encountered external factors which could contribute to the cause.

[SASless]

Bottom line....one more fatal occurrence and the Fat Lady will have sung.

[casper64]

Bottom line....one more fatal occurrence and the Fat Lady will have sung.

If it is not caused by pilot error or external factors but due to further technical reasons, even if not related to a gearbox but again something else: Yes absolutely.

[Twist & Shout]

Human nature (for most of us) means we tend to believe things we are told.
Otherwise everything breaks down.

The problem with people/companies that lie, is you can no longer believe anything they say.
Maybe AH had several transmissions fail during their attempts to replicate the catostrophic failure, and are simply lying about that too.

I have no knowledge to suggest this, just pointing out that once someone looks you in the eye and lies to you, it is foolish to ever believe anything they say again.

I won’t.

[henra]

One point to note is that as well as removing any gearbox which has suffered impact from service, they also removed any having had a lightning strike.

The gearbox fitted in the L2 accident had sustained a lightning strike while fitted to a different airframe. Maybe they cannot categorically say it is the gear types because both gearboxes had encountered external factors which could contribute to the cause.



It probably takes an external damage event (e.g. like lightning strike or transport damage) to trigger premature spalling and propagation of cracks. The design itself seems to be OK as long as no such premature initiation occurs (otherwise more H225/AS332 helicopters would have lost their gearboxes - they accumulated massive fleet hours without such occurrences). It appears that it is simply not very tolerant against such external influences. And the combination of that particular bearing type producing higher peak stresses in the outer race plus an external factor was apparently sufficient in two instances to trigger this premature cracking. The really unfortunate part is that this damage mechanism isn't really properly captured by HUMS&Co. That is what makes it so dangerous.

[henra]

Bottom line....one more fatal occurrence and the Fat Lady will have sung.

One more fatal accident caused by mechanical problems (not only Gearbox related) would indeed be the final nail in the coffin at least for civil ops.
That said with the current level of precautionary measures and low flying hours you will probably have to wait rather long for this.

[SASless]

One more fatal accident caused by mechanical problems (not only Gearbox related) would indeed be the final nail in the coffin at least for civil ops.
That said with the current level of precautionary measures and low flying hours you will probably have to wait rather long for this.

One would hope.....but if you understand Probability Theory the it could happen on the very first flight. It could be a fault not related to the current problem but cause the absolute end to the aircraft in civil service.

A question that does arise.....why no such failures in military aircraft.....or have there been some?

[S92PAX]

I don't know if the other crashed aircraft had the same bearings, but in case it had, then this is taken care of by removing these bearings from service, as the other ones never had an issue. Additional safety on the MGBs that never had an issue in the first place, is then subsequently provided by increasing inspections, reducing lifetime and better chip detectors. This should take care of the problem... again, 100% guarantee? No. But if you want 100% one should just stay where humans belong: with 2 feet on the ground...

I think this could be challenged. ERA stated in their briefing about they court claim against Airbus that they inspected the gearbox on their aircraft and found similar spalling on both types of bearing/gear. I think their is a lot more information to come out before a factual opinion can be formed.

[henra]

A question that does arise.....why no such failures in military aircraft.....or have there been some?



At least I'm not aware of any such occurrence in military use.
Would surely have come up by now.
So why not in the military?
- Luck?
- less intense utilisation?
- More frequent/intense inspections?
- No unfortunate combination of external event (Lightning strike, transport damage) with that same type of bearing?
- any combination thereof?
- other?


Good question.

[etudiant]

I think this could be challenged. ERA stated in their briefing about they court claim against Airbus that they inspected the gearbox on their aircraft and found similar spalling on both types of bearing/gear. I think their is a lot more information to come out before a factual opinion can be formed.




That is actually quite troublesome.
It suggests both these bearing versions are overstressed and that it was merely chance that caused two MGBs with the same kind of bearing to possibly be subjected to unusual stresses, via lightning strikes or road accidents.
If comparable spalling is indeed found in both bearing types, reliable failure warning becomes essential. Not sure how this could be achieved, possibly radioactive tracer material in the bearings might add sensitivity, perhaps enough to allow timely intervention.

[diginagain]

video - Airbus Helicopters (http://www.helicopters.airbus.com//website/en/ref/video_475.html)

[212man]

video - Airbus Helicopters (http://www.helicopters.airbus.com//website/en/ref/video_475.html)
See post #118

[Hompy]

Nice video, good narration and graphics. Big company big budget.

The problem is, Airbus Helicopters, you exposed us to your ‘company values’ after the crash when, in your desperation to keep the machine selling, you tried to blame innocent parties. Maybe it was sinister and deliberate, maybe it was just wishful thinking. It worked, for a very short time and even now your lies have not completely disappeared as those who lent on them are too stupid to let them go. The victims of your deception were offered no apology or compensation. The lies were concocted and propagated by your highest level managers and ‘best’ experts. Even the president of France got involved.

You need a new helicopter with a gearbox of more robust design. You also need a new management team and a new set of values, which you cannot buy from a marketing sub contractor. You need to go back to how you used to be.

[Self loading bear]

Airbus has mandated the replacement of the gears of the same supplier in the dauphin gearboxes. Good move but now there are problems supplying sufficiënt replacement parts. Potential grounding into 2019!

https://www.flightglobal.com/news/articles/gearbox-troubles-leave-some-dauphin-helicopters-grou-442356/

SLB

[Apate]

Nice video, good narration and graphics. Big company big budget.

The problem is, Airbus Helicopters, you exposed us to your ‘company values’ after the crash when, in your desperation to keep the machine selling, you tried to blame innocent parties. Maybe it was sinister and deliberate, maybe it was just wishful thinking. It worked, for a very short time and even now your lies have not completely disappeared as those who lent on them are too stupid to let them go. The victims of your deception were offered no apology or compensation. The lies were concocted and propagated by your highest level managers and ‘best’ experts. Even the president of France got involved.

You need a new helicopter with a gearbox of more robust design. You also need a new management team and a new set of values, which you cannot buy from a marketing sub contractor. You need to go back to how you used to be.

Great summation :ok::ok::ok:

[AnFI]

The multi engined helicopter is inherently more likely to have catestrophic failures of this kind.
This must be taken into account when weighing the upsides of engine redundancy.

(Anyone know why the BK117 fell out of the sky ? Gearbox also?)

Complexity is inherently more prone to several classes of failure (including pilot error)

[Geoffersincornwall]

AnFI - I suggest you read the detail behind this failure before trotting out your nonsense.

G.

[henra]

The multi engined helicopter is inherently more likely to have catestrophic failures of this kind.
This must be taken into account when weighing the upsides of engine redundancy.


Oh, How have I missed these stupid comments, free of any (meaningful) connection to the topic on hand.... :ugh:

Gearbox Failure of second stage Planetary gear has absolutely zero to do with the number of Donks all the way down the transmission chain.
Null, Nada, Zilch.

[AnFI]

Henra do you say that because the failure in this exceptionally complex gearbox was downstream of the gearing concerning combination of engines?
If so
I'm not sure in Nada is the right analysis. For example, if one gearbox has 400 tapered roller bearings and another has 10 then which one is more likely to experience a failure of a tapered roller bearing?
So regardless of the contention that this planet gear was working in an area that would be present if it were a single, it doesn't mean it's nada.
Not to mention that lower margins of critical components to carry spare engines is not neccessarily better.

What is the probability of executing a successful Engine Off Landing compared to the probability of executing a Rotor Head Off Landing ?
Pretty poor i'd say.

[GrayHorizonsHeli]

AnFI, i get your last statement....but I think in the middle ground you get really cloudy on the comparison. Im not sure if you're over thinking it or what.
More parts equals more possible problems, but when engineered to spread the loading, than more parts equals more reliability.

I'm not going to try and compare anything inside the gearbox to try and convince you, i'm simply going to use rope as an example and perhaps that simple comparison will suffice.

How strong is rope when there is 1 strand, versus rope with multiple strands?

[RVDT]

Simples - the one with the 10 bearings.

It would never be a safety issue as it would never actually fly.

Scalability laws? Velocity ratio? :D

[Kulwin Park]

So, after reading all these posts... Has any operator in the world started using the affected 225's again, or getting pilots current again to bring them back to operational standards????
Cheers, KP

[SASless]

AnFI - I suggest you read the detail behind this failure before trotting out your nonsense.

Geoffers scores a Hole in One!:ok:

[P2bleed]

So, after reading all these posts... Has any operator in the world started using the affected 225's again, or getting pilots current again to bring them back to operational standards????
Cheers, KP


Yes I believe COHC in China has for some time.

[212man]

Yes I believe COHC in China has for some time.

SFS in Vietnam never stopped. Heli-Union are busy promoting their SAR machine at trade shows right now: AFF AND SAR EUROPE 2017 - (http://www.heli-union.com/aff-sar-europe-2017/)

[gasax]

Well there is nothing like blind faith!

The fundamental problem here is that Airbus have not been able to duplicate the failure.

Instead they are relying on trying to use procedural barriers against potential failure causes. But the issue is that these are potential causes, not the definitive cause - which might be something new, but more likely is some threshold value being reached which means that instead of spalling the material cracks.

There was some interesting comment earlier on regarding better lubrication which might be an interesting route of investigation - suppressing surface damage whilst allowing crack initiation. But until Airbus can duplicate the problem, all of this is guesswork. Gearbox has fallen off a truck - don't let gearboxes fall off trucks, gearbox has x hours - don't let gearboxes accumulate x/4 hours and so on.

They might be the answer - alternatively they might just be garlic necklaces - incredibly effective in repelling vampires - and you know I've never been bitten by a vampire since I started wearing it!

[riff_raff]

gasax,

Your concern about AH not yet having established the root cause of this problem is valid. Unfortunately, it can be extremely difficult or even impossible to diagnose such problems with 100% certainty since there often can be a combination of factors that contribute to the failure, some of which may not be traceable.

The video describing corrective actions being implemented by AH in response to this problem was actually pretty good. However, one thing I noted was that some of the corrective actions are already standard procedure at other companies I have seen performing similar work. For example, more careful packaging and handling of critical components, better contamination control of the environment used for assembly, etc.

All of the corrective actions being implemented are good steps. But as you noted, it may never be established that they actually address the root cause of this problem.

[Geoffersincornwall]

The way I see it the cause of the failure was a fracture resulting from a source that did not produce detectable spalling. If the whole design philosophy of MGB's is dependent on the early detection of spalling to warn of impending failure then the fact that no spalling was detected (if it was ever produced??) then we are not in a very good place and gearbox designers must be quaking in their boots. Mind you as a non-engineer my poor opinion of using a gear wheel as the outer race may not count for much. What might count a little more is the fact that there were two 'qualities of gear wheel out there but no one outside AH appears to have known about that rather interesting and worrying fact.

G

[AnFI]

Geoffers: "the fact that there were two 'qualities of gear wheel out there"
Do you mean two different (conformal) Curvatures of Tapered roller bearing?

and

GreyHorizons: "How strong is rope when there is 1 strand, versus rope with multiple strands?"
I take your point about the spreading of load, but I'm not so sure it's as good an arguement as it sounds.
A bolt is (a bit) like a one strand cable. A rope made of strands, where every strand is near it limit, is obviously MORE dangerous, since the failure of any one strand will tip the others over their limit. OR imagine a rope where the failure of one strand leads to the failure of the whole crane. That is the parallel with this case.

The scaling point has some truth but the 400 single point failure items in a gearbox of this type should be taken seriously.

[riff_raff]

AnFI,

I did not read that the planet gear spherical roller bearings from the two suppliers actually had different "conformal curvatures" (or osculation ratios). What I recall was that they had different roller widths, different contact angles, different retainer designs, and different contact stress levels at similar analysis conditions.

[OnePerRev]

Interesting Video from Airbus showing the exact failure that many of us here zeroed in on from the first photos of the broken pinion. Alarming that blame is cast on handling damage. Spalls move away from dents and get bigger, further away. If it initiated at a dent, it would still be there. This was no dent and they know it. Further, although spalling is the initiating trigger, they neglect to discuss where the fatigue load comes from. The same fatigue load that caused multiple fractures I would suggest, perhaps not coincidentally 90 degrees apart. They probably do not understand the loads but here is another thought: On such a raceway, fatigue damage will very likely initiate sub-surface. the fatigue itself could cause a spall, not just the other way around. Which means propagation toward the teeth may already be underway by the time the spall forms, let alone gets big enough for particle detection. The problem: Both suppliers parts are subject to the load, and thus subject to the failure. Hopefully they guessed at a low enough life to preclude that. But all the same, is this a hope based argument rather than a data driven one? It would be a shame to see a third preventable event, when they should by rule understand the loads.

[etudiant]

Why would the regulators accept that handling damage argument if the evidence is not there?
If there is fatigue caused spalling, surely it should be possible to replicate the failure. We've had more than enough time to run a 10,000 hour test if needed.
Yet replication has not been achieved, which indicates that some aspect of the failure mechanism is still being overlooked.

[Twist & Shout]

Why would the regulators accept that handling damage argument if the evidence is not there?
If there is fatigue caused spalling, surely it should be possible to replicate the failure. We've had more than enough time to run a 10,000 hour test if needed.
Yet replication has not been achieved, which indicates that some aspect of the failure mechanism is still being overlooked.

AH are just using a scatter gun approach
They don’t claim both gearbox that failed fell off a truck.
Just trying to throw enough conjecture around that the fact that they do not know what caused the failure is overlooked. :ugh:

It’s the modern world: do something, to make everyone feel better, even if it wouldn’t have fixed the problem that caused the reaction in the first place.

After scum hijacked several airliners in flight, we were all forced to chain our helicopters up. (Fines issued for unlocked machines):yuk:

After a madman in Vegas shoots people from 450m away with an arsenal of modified automatic rifles, lever action shotguns are banned in QLD (with the Vegas atrocitie cited as the justification by the Premier):D

The rotor detaches from two similar AH machines. OH times are reduced even though there is no evidence this was the issue.

At least they did something :ugh::ugh::mad:

[birmingham]

An interesting and very slick film about a unique situation. Airbus have now removed the part involved in the two occurrences. Additionally, they have introduced new sensors and sensibly restricted operations to minimise the possibility of recurrence of any of the identified failure modes. Operators can go one step further of course; by not using the 225 at all they can guarantee no recurrence. However, even that will only eliminate the risk in the 225. MGB failure can happen in all helicopters not just Super Pumas; managed risk is part of every life in helicopter ops. But most take the view that in the current economic, HSE and industrial relations landscape, completely removing the 225 is their safest bet. Unless and until the actual failure mode can be identified and removed from the equation Super Puma ops are likely to remain a minority sport.

[Twist & Shout]

I know the “Super Puma” name is bandied around by the uniformed press.
This is a Professional Pilots forum.

Lets be clear L, L1 model Super Pumas are unaffected.
L2 Super Pumas, and EC225s share the gearbox design, that on two occasions, has catastrophically failed.

[Fareastdriver]

The problem is that the gearbox has had it's load lifting requirements expanded from 6,300 kg. from the original 330 A to 11,200 kg. in the same dimensional gearbox. You can only stuff new wine into old bottles so far.

[birmingham]

I know the “Super Puma” name is bandied around by the uniformed press.
This is a Professional Pilots forum.

Lets be clear L, L1 model Super Pumas are unaffected.
L2 Super Pumas, and EC225s share the gearbox design, that on two occasions, has catastrophically failed.

Apologies - but even to the familiar the endless branding and re-branding can confuse. I'm only discussing affected aircraft sometimes referred to as Super Puma Mk 2 i.e. AS332 L2 EC225 (or should that be EC225 L2?) or H225. Not being military I have no idea what MGB is fitted to the models formerly known as Super Pumas and branded since the 90s as AS532, Cougars, EC725M, Caracal, Super Cougars or H225M! I haven't included national military derivations (I think!) or locally built versions for the sake of sanity!

Can I safely assume that none of these military a/c are fitted with the problem box even the later model H225Ms?

[Twist & Shout]

Apologies - but even to the familiar the endless branding and re-branding can confuse. I'm only discussing affected aircraft sometimes referred to as Super Puma Mk 2 i.e. AS332 L2 EC225 (or should that be EC225 L2?) or H225. Not being military I have no idea what MGB is fitted to the models formerly known as Super Pumas and branded since the 90s as AS532, Cougars, EC725M, Caracal, Super Cougars or H225M! I haven't included national military derivations (I think!) or locally built versions for the sake of sanity!

Can I safely assume that none of these military a/c are fitted with the problem box even the later model H225Ms?

Can’t help you with the military models, but understand there is a military equivalent of the EC225, with the same problematic gearbox.

In Australia and nearby, AS332L and L1 are operating on oil and gas operations.
The clients, workers and pilots know the difference.

[212man]

p6rBeKRrnKU

Not sure I'd describe that as testing.....:confused:

[Apate]

Maybe it was a testing flight for the pilot, as all that hand flying be can hard to do when you are used to just pressing buttons ;)

The aircraft certainly wasn't tested! Perhaps the crew were scared something bad might happen :}

[etudiant]

Would it be pointless to run some of these gearboxes to destruction?
Documenting the failure paths in order to provide some improved understanding of these disasters. Perhaps we might even learn something new.

[obnoxio f*ckwit]

Looks like Vector in Gosport?

[riff_raff]

Would it be pointless to run some of these gearboxes to destruction?
Documenting the failure paths in order to provide some improved understanding of these disasters. Perhaps we might even learn something new.

Unfortunately, the type of testing you describe would not likely be helpful. What most people, including many engineers, don't understand is the fundamental purpose for conducting tests. In the aerospace industry, the primary reason for conducting tests is to validate design and analysis work. Normally, tests (qualification, acceptance, etc) are conducted under very tightly controlled conditions using a test article specifically constructed for the test procedure.

Consider what would be required to bench test say 5 EC225 main gearboxes to their service life limit. There is the huge cost to manufacture the gearbox test articles. There is the significant cost to operate the test stand for a couple thousand hours required for each test procedure. At something like 2000 hours per gearbox test, it would take over one year to complete the 5 tests operating non-stop.

[Concentric]

Would it be pointless to run some of these gearboxes to destruction?
Documenting the failure paths in order to provide some improved understanding of these disasters. Perhaps we might even learn something new.
Whilst the desire to recreate actual operating conditions inside a gearbox as faithfully as possible might at first suggest a whole-gearbox test, if that test were taken to failure it would not only be expensive and potentially hazardous but the inertia of the machinery would likely cause significant secondary and collateral damage that could obscure inspection of failed components, fracture surfaces and detection of certain compounds.

Since it is known exactly which component failed (the 2nd stage planet gear/bearing race) it is more scientific to conduct tests on examples of just that component in isolation and simulate the operating conditions.

A test rig used to examine propagation of rolling contact fatigue cracks in bearing steel is shown in this technical paper (http://www.sciencedirect.com/science/article/pii/S014211231630411X). Whilst that test rig is designed for external bearing surface test pieces (because it is easier, for one thing) it should be possible to design a rig to test internal surfaces too although space would be much more restrictive.

Rather than just testing to destruction, such a rig allows tests to be paused and the test piece removed for examination at intervals to measure and chart growth of the defect.

In the above test the focus is mainly on crack initiation at or close to the surface and is a result of cyclic contact stresses, often increased in magnitude (up to 4.76GPa) to accelerate the fatigue process. Whilst lubrication is provided in this test it is considered only at the surface.

There are many other technical papers available which investigate lubrication effects not only at the bearing surface but also with seeping into and pressurization inside a crack. This paper (http://www.sciencedirect.com/science/article/pii/S0043164816307293) (also available here (https://www.researchgate.net/publication/316562980_Influence_of_lubricant_formulation_on_rolling_cont act_fatigue_of_gears_-_interaction_of_lubricant_additives_with_fatigue_cracks)) compared different lubricant additives with the same synthetic base oil to investigate their effects on lubricant seepage into a developing crack. Not wishing to get too technical, it should be clear from a brief scan of these papers that the effect of a lubricant is far more complex than just some oily stuff that you either have in your gearbox and are OK with, or have lost and are (or very soon will be) in trouble without.

Lubricants work mechanically, hydraulically, thermodynamically and chemically. Lubrication is a science in itself and I find it very surprising that it receives little or no mention in investigation reports to date.

I previously queried whether a dramatic reduction in AH statistics of spalling or pitting circa 2009 may have been due to some change in lubrication/lubricants. Having since read up a little on tribology and the different effects of some lubricant additives on the surface (mostly beneficial) and inside cracks (sometimes detrimental) I would not be at all surprised if the next report investigates this area in considerable depth.

[etudiant]

Thank you, Concentric, for your insightful comment.
It makes sense to focus on the component that failed, rather than the entire assembly.
As you point out, that minimizes the cost and maximizes the test flexibility.

The possibility that a change in the lubricating compound helped suppress the failure symptoms in this design, although very plausible, is quite novel. How does the certification process deal with such a possibility?

[AnFI]

riff raff
just a hypothetical question
How many gearboxes would you have to run and for how long under what conditions
to demonstrate a catestrophic in service failure rate of < 10^-9 per hour?

etudiant "As you point out, that minimizes the cost and maximizes the test flexibility." minimising cost !

"focus on the component that failed, rather than the entire assembly."
so if you wanted 10^-9 for the gearbox and there are 20 planet gears then would they have to be better than 5x10^-11 /hr reliable eh?
how would anyone ever establish that? is it even possible?

what is the acceptable catestrophic failure rate for a gearbox? is there one?

[Apate]

AnFI, not only is your maths failing you (I see you've edited your post) but your English also needs improving.

Does anyone know what catestrophic (sic) means :E

[etudiant]

AnFi what are the alternatives?
AH currently has a multi billion dollar program near death. In that context, blowing up a hundred gear boxes would be a cheap solution, if it helped restore the type to market acceptance.
The logic for the planet gear reliability calculation is yours, but note that we had 2 catastrophic failures in about 2 million hours of operations iirc, so we are a long ways from 10 to the ninth.
I'm no regulator, but I'd think that the acceptable rate of catastrophic gear box failure is zero. I'd hope regulators would not be bamboozled by sweet talk about 9 sigma reliability. We don't tolerate aircraft whose wings fall off either.

[OnePerRev]

Testing is great. Challenge is "How" to test.
Interesting points by Concentric, but I fear that the focus on the spalling has led people to examine what we typically understand from spalling events on a bearing raceway, and that this event was NOT a typical spalling event due to ordinary Hertzian contact stress. Tell us more about the other fractures, and then we can talk about the likelihood of spall propagation to fatigue crack initiation and propagation happening on three separate regions at similar timelines. Maybe more likely that general rim fatigue began in multiple locations and the subsurface initiation produced a spall. Not the other way around.
So we rumor folks do not know the details of the ring stress loads on this planetary arrangement, maybe AH does but probably not. If you don't, then a test would also probably miss the load, and the test worthless in real benefit (Finding and correcting the problem). Most test stands lack something, even if just the ability to represent a larger load for test purposes. A piece-part test can do that, but then lacks the rest of the appropriate interface. A classic problem for engineers, not so easy.

[etudiant]

Gearboxes that transmit heavy loads are not new and neither are failures.
Here we have literally hundreds of specimens in all stages of life, from new to near retirement, so lots of specimens for analysis.
It seems pretty straightforward to establish a set of tear down baselines that evaluate the components and then to do some sustained torture testing. The testing obviously has to include appropriate loads. If there is need to create a new test stand and procedure, I'd think the AH team would be well advised to pioneer it.
Presumably the stresses within the gearbox were evaluated during the certification process. If not, one wonders what design and certification criteria are provided.

Hopefully this tragedy will eventually help remove some of the mysteries of gearbox design. That would be fitting monument to the crews and passengers whose lives were lost because of our ignorance.

[GrayHorizonsHeli]

"Here we have literally hundreds of specimens in all stages of life, from new to near retirement, so lots of specimens for analysis..."


by reducing the OH cycle, they have done this, although tragically late in this case.
I'm curious if the other manufacturers have used this an an opportunity to re-evaluate their own gears too. I'm not convinced that Airbus is the only one at risk here. Are the other makes and models ticking time bombs as well?

whatever went wrong, you can bet Airbus will solve it at some point. they are at least moving in the right direction in my opinion.
can the 225 model survive though? I'm skeptical but remain positive.

[EESDL]

.....and will anyone believe them when they say they have solved the issue?
Difficult to forget the Airbrush roadshow of 'smoke and mirrors' after the first separation.
They went to great lengths to convince the user that they had it sorted......

[Twist & Shout]

.....and will anyone believe them when they say they have solved the issue?
Difficult to forget the Airbrush roadshow of 'smoke and mirrors' after the first separation.
They went to great lengths to convince the user that they had it sorted......

“Fool me once, shame on you”
“Fool me twice, shame on me”

[etudiant]

I'm curious if the other manufacturers have used this an an opportunity to re-evaluate their own gears too. I'm not convinced that Airbus is the only one at risk here. Are the other makes and models ticking time bombs as well?

whatever went wrong, you can bet Airbus will solve it at some point. they are at least moving in the right direction in my opinion.
.

You raise an important point.
Gearboxes are a common concern and every propulsion manufacturer has the scars to show from it. So there is a basis for a more concerted attack on the problem.
In the turbine business, the USAF periodically funds new technology engine prototypes in order to advance the state of the art. Something similar seems warranted for gearboxes, because evidently our understanding of the technology involved is inadequate.

[Fareastdriver]

A common gearbox design of the Puma family is that the annular gear is part of the gearbox housing. This breaks, so does the gearbox, leading to the rotor assembly leaving the aircraft as the stabilising struts are not strong enough to retain it.

All gearboxes need to be redesigned so that there is a failure path which would stop at the annular gear. You will lose your drive but you are still alive and have some control over where the aircraft is going.

Should you lose the main drive in the gearbox in a Puma remember NOT to shut down the engines in the autorotation or you will lose your hydraulics and alternators. The electric pump cannot cope with the rotor control.

[bigglesbutler]

Should you lose the main drive in the gearbox in a Puma remember NOT to shut down the engines in the autorotation or you will lose your hydraulics and alternators. The electric pump cannot cope with the rotor control.

I hadn't thought of that but yes a good one to note, although I hope to never have to remember it IF I ever get to fly the 332/225 again.

Si

[riff_raff]

riff raff
just a hypothetical question
How many gearboxes would you have to run and for how long under what conditions to demonstrate a catestrophic in service failure rate of < 10^-9 per hour?
what is the acceptable catestrophic failure rate for a gearbox? is there one?

AnFI,

Sorry for the tardy response.

The answer to your first question is that for single path flight critical systems/components, an example of the FAA threshold for catastrophic failure events is "extremely improbable" as defined in AC 25.1309-1A section 7d (https://www.faa.gov/documentLibrary/media/Advisory_Circular/AC_25.1309-1A.pdf). Compliance with this requirement is normally demonstrated entirely by analysis, and the acceptable approach is described in section 8d of the document noted. To demonstrate by test that a complete main gearbox system has a catastrophic failure rate below the "extremely improbable" threshold of 1x10^-9/flight-hour, you would need to test a statistically relevant number of type-confoming gearboxes to their design TBO. And then calculate the failure rate based on the number of catastrophic failures and total accumulated test hours.

One thing you need to consider is the huge number of test hours that might be required to produce a valid result for a very high reliability rate. And each gearbox build would only provide maybe 2000 hrs of test, so you would need to test a very large number of gearboxes. There is some work being done on methods for accelerated life testing, like this example (http://www.ein.org.pl/sites/default/files/2012-02-02.pdf).

Regarding the speed/load conditions used for this type of test procedure they are defined by a "mission profile", which is a representation of the speed/load/time intervals during a typical flight cycle. You can read more about reliability testing in MIL-HDBK-781 (http://everyspec.com/MIL-HDBK/MIL-HDBK-0700-0799/download.php?spec=MIL_HDBK_781A.1933.pdf).

[rotor-rooter]

Following the recent loss of a 332L in Japan.

https://ad.easa.europa.eu/blob/EASA_AD_2017_0232_E.pdf/EAD_2017-0232-E_1

[birmingham]

Confirmation (as was pretty much understood) that this was not a similar incident to those discussed in this thread.

My understanding is that these machines have different MGBs and there have been no MGB incidents on AS 332 C, AS 332 C1, AS 332 L and AS 332 L1 machines that show similarities to the Norwegian 225 incident

[industry insider]

My understanding is that these machines have different MGBs and there have been no MGB incidents on AS 332 C, AS 332 C1, AS 332 L and AS 332 L1 machines that show similarities to the Norwegian 225 incident

But plenty of chips and MGB changes in 1982 when the type was introduced, 70 MGB changes in the first year of operation.

[HeliHenri]

.
Back to topic : https://www.verticalmag.com/press-releases/south-koreas-national-119-rescue-headquarters-acquires-two-h225-helicopters/


Second order of the SAR version in few months after the one from the Japan Coast Guard : Japan Coast Guard orders three additional H225 helicopters | Jane's 360 (http://www.janes.com/article/71634/japan-coast-guard-orders-three-additional-h225-helicopters)
.

[birmingham]

.
Back to topic : https://www.verticalmag.com/press-releases/south-koreas-national-119-rescue-headquarters-acquires-two-h225-helicopters/


Second order of the SAR version in few months after the one from the Japan Coast Guard : Japan Coast Guard orders three additional H225 helicopters | Jane's 360 (http://www.janes.com/article/71634/japan-coast-guard-orders-three-additional-h225-helicopters)
.

The 225 makes for an excellent SAR platform and the SAR variants are exceptional. The military will be able to live quite happily with the current operational restrictions. They have a very different risk profile to the commercial operators where the safety benefits of the new platform to the SAR mission outweigh lingering concerns over the MGB. I would also image they were cut a very decent deal. It is a good place to start rehabilitating the type's reputation. E&P operations are another matter.

[HeliHenri]

The military will be able to live quite happily with the current operational restrictions.

No military stuff in both cases here.

[birmingham]

No military stuff in both cases here.

I think that is splitting hairs to be honest. My point was that SAR (military, para military, contract or civilian) plus indeed many other military/para military operators will be much less concerned by the ops restrictions than E&P as your own post clearly demonstrates.

[MC5Wes]

Saw this video today.

https://m.youtube.com/watch?v=0ZbTN6pM2SE&feature=youtu.be

[SASless]

70 MGB changes in the first year of operation.

Then BHL reduced the Cruise Power Setting and amazing things happened!

[Twist & Shout]

70 MGB changes in the first year of operation.

Better than 2 rotor separations

[industry insider]

Then BHL reduced the Cruise Power Setting and amazing things happened!

The point being too much torque is bad for the box. Should have been a lesson for the 225.

[SASless]

But the 225 was the greatest thing since sliced bread according to some at Bristow....far better machine than the very inferior 92 as some told us at great length.

Brand loyalty is fine up to a point....then reality has to be considered.

Did Bristow Engineering not ever raise questions about the possibility of Gearbox issues in the 225 in light of the earlier problems or did they just enjoy the EC/AB Tea and Cookies and sign on the dotted line?

How did that turn out for them?

I mention BHL as they were the Operator with the largest fleet of EC/AB aircraft but the question applies to all of the Operators.

[Mee3]

But the 225 was the greatest thing since sliced bread according to some at Bristow....far better machine than the very inferior 92 as some told us at great length.

Brand loyalty is fine up to a point....then reality has to be considered.

Did Bristow Engineering not ever raise questions about the possibility of Gearbox issues in the 225 in light of the earlier problems or did they just enjoy the EC/AB Tea and Cookies and sign on the dotted line?

How did that turn out for them?

I mention BHL as they were the Operator with the largest fleet of EC/AB aircraft but the question applies to all of the Operators.
I don't think you know them well enough to quote them then dis them.

[SASless]

It does beg the question.....and remembering the two crashes were not Bristow machines. Were they doing something the other operators were not?

Perhaps you are not familiar with the history of discussions about the various merits of the 225 and 92 that went on here for years.

Thus, you might not t have the background to make the comment you just did.

[HeliComparator]

The point being too much torque is bad for the box. Should have been a lesson for the 225.


No, you have no evidence that reducing torque would have made any difference and one thing was certain, reducing cruise torque resulted in increased vibration. Not only obvious vibration from the rotor head, but vibration in the tail pylon are too. Vibration being a fairly destructive thing.


This idea was often mooted by folk with no technical knowledge but every time, EC (as they were then) said it was a bad idea.


Mind you, even at reduced cruise power it was still a lot smoother than an S92!

[HeliComparator]

But the 225 was the greatest thing since sliced bread according to some at Bristow....far better machine than the very inferior 92 as some told us at great length.

Brand loyalty is fine up to a point....then reality has to be considered.

Did Bristow Engineering not ever raise questions about the possibility of Gearbox issues in the 225 in light of the earlier problems or did they just enjoy the EC/AB Tea and Cookies and sign on the dotted line?

How did that turn out for them?

I mention BHL as they were the Operator with the largest fleet of EC/AB aircraft but the question applies to all of the Operators.

The 225 was the greatest thing since sliced bread according to virtually all the pilots (we did have one weird one who preferred the S92). Right up to the point, after 100s of thousands of hours, where one had a rotor head fall off. Yes that is a pretty serious achilles heel which unfortunately ruined the type, but in every other respect it was fantastic.


Bristow engineering did what they had to do and more. I don't know what the culture at the other operators was but from where we stood, it did sometimes seem as though they only did what the had to do. HUMS downloads being an obvious example.

[SASless]

HC,

Reducing Cruise Torque did alleviate the problem in the gearbox though did it not?

That is what I was told seemed to make the major difference in the frequency of MGB replacements....or was I told wrong?

During acquisition of the 225....did the issue of increased loading of the MGB become a topic of discussion?

[Mee3]

It does beg the question.....and remembering the two crashes were not Bristow machines. Were they doing something the other operators were not?

Perhaps you are not familiar with the history of discussions about the various merits of the 225 and 92 that went on here for years.

Thus, you might not t have the background to make the comment you just did.
Not really interested in that fanboy fight. But I know BHL well enough to pick out your BS.

[SASless]

Not really interested in that fanboy fight. But I know BHL well enough to pick out your BS.

Please feel free! We would all like to hear what you have to say.

[HughMartin]

HC,

Reducing Cruise Torque did alleviate the problem in the gearbox though did it not?

That is what I was told seemed to make the major difference in the frequency of MGB replacements....or was I told wrong?

During acquisition of the 225....did the issue of increased loading of the MGB become a topic of discussion?


If you are referring to the early days of the AS332 on the North Sea, there were excess wear issues with the gearbox when operating it at “fast cruise” pitch setting of 16° pitch which Bristow did for some time in order for the Bristow “Tiger” not to be outpaced by the Bell 214ST which was being operated by British Caledonian Helicopters (BCal). Bristow had a very high rate of in-service gearbox rejections during this period but I must emphasise that normal maintenance routines did not allow this to become a safety issue, it was purely a financial and maintenance burden. At or about the time Bristow bought BCal, Bristow reduced their normal cruise setting to 15.5° in line with the other operators.

North Scottish/Bond Helicopters always flew the AS332 at 15.5° pitch which was the recommended normal cruise pitch setting and never had any issue with gearbox rejection rates. It also made for a much more comfortable ride.

There is no point comparing the AS332 historical experience with that of the EC225 as it is a different gearbox. The EC225 is always best cruised at just below max continuous power. It keeps the vibration level down and there is absolutely no evidence that normal cruise power settings (used by all operators) cause any reliability issues.

[industry insider]

If you are referring to the early days of the AS332 on the North Sea, there were excess wear issues with the gearbox when operating it at “fast cruise” pitch setting of 16° pitch

BHL used 16.5 degrees pitch when 332 operations started then reduced to 16 degrees

[HughMartin]

BHL used 16.5 degrees pitch when 332 operations started then reduced to 16 degrees

16.5° could only be used below a certain mass, the exact value I cannot remember but it equated to about 3/4hr of flying if take-off was at MAUM. Vibration level was not good at max pitch and specific fuel consumption worked against you unless flying into a strong headwind.

15.5° was the recommended cruise pitch by AS which is what BHL reduced to after management came to their senses.

[industry insider]

Recommendations maybe but in BHL marketed the 332L at 145 KTAS. Take off from ABZ in April 1982 was at 18410 lbs Planned fuel burn 1140lbs and planned TAS 145 at 16.5 degrees from TOC.

[henra]

But the 225 was the greatest thing since sliced bread according to some at Bristow....far better machine than the very inferior 92 as some told us at great length.


So what's exactly your point?
(Apart from showing again that you are a dyed in the wool Sikorsky admirer?)

Any new findings?
Any sign that the early Gearbox changes of the original 4 - blade Puma family had any failure path similarities with the problem in the 225?
Wear and internal cracking are totally different beasts. The 225 didn't (literally) lose its head due to simple wear.
Reducing torque wouldn't have necessarily prevented the cracking. The level of vibration isn't a linear function of torque. It is a complex function of multiple variables and there will often be vibration spikes at lower torque levels.

[HeliComparator]

HC,

Reducing Cruise Torque did alleviate the problem in the gearbox though did it not?

That is what I was told seemed to make the major difference in the frequency of MGB replacements....or was I told wrong?

During acquisition of the 225....did the issue of increased loading of the MGB become a topic of discussion?



In the case of the 332L, yes definitely. But that was a different beast. It was rough as old boots at 16.5 CP. But presumably the reduction in CP was as much about sustained gearbox torque as it was about reduction in airframe vibration. I don't know.


In the case of the 225 it was much smoother at MCP than it was at reduced power. Also it was designed to be flown coupled in 4 axis but once you decided to reduce power, that was a bad idea (lots of collective adjustments being automatically made to hold a set speed). Or of course you could fly it in 3 axis but that had its own safety implications (look at the Sumburgh L2 accident) and the 225 had a big variation in torque with turbulence and roll. Although in both modes (3 and 4 axis) the 225 "protected" against overtorque by lowering the lever, in 3 axis this only happened after MCP was exceeded, in 4 axis it maintained torque a % or two below MCP.


And one has to be careful not to create new problems with a knee jerk change of policy. So if we had reduced cruise power, and lived with the increased aiframe vibration and slight safety reduction, who knows what damage that might have accumulated over 100s of 1000s of hours. Maybe the gearbox would have lasted longer but maybe something else would have failed sooner. Bear in mind this gearbox issue only manifested itself once in the hundreds of thousands of hours - albeit in a pretty catastrophic way. What other failures could increased airframe vibration due to cruising slower have created in those 100s of thousands of hours?


On your point about topics of discussion, yes having gone from the L to the L2, I felt that the L2 might have been a step too far in terms of the engines and transmission. And then along came the 225 with MUCH more power, same phyisical size engines, MUCH higher MTOM, a cruise power similar to both engines a OEI max contingency power on an L. Impossible!


But the reality was that it seemed less stressed than an L2, and in the context of Bristow did 100,000 hrs or so without major issue. Once people flew it, their doubts vanished.