North Sea heli ditching: Oct 2012

[TipCap]

Memory a bit hazy since I haven't flown one for 20 years now but didn't the S61N have an electric emergency MGB oil pump.

TC

[3D CAM]

didn't the S61N have an electric emergency MGB oil pump.


Yes! Your memory is still functioning!
3D

[TipCap]

All is not lost then...........

:ok:

TC

[Rotorhead124]

The H-3 on the other hand, used the Torque Meter Pump as the pressure source for the MGB ELS.

[Peter PanPan]

@albatross: Not sure I am following you on the "The 225 EMLUBE system was, I believe, designed only to deal with a loss of transmission oil not the loss of 2 oil pumps."

The 225 EMLUB system was precisely designed to cope with a complete loss of lubrication, i.e. failure of both Main & Standby pumps.

Proper indication of a functioning EMLUB as you call it would be the absence of any light - Black Panel - And yes according to the Manufacturers ECL "Land as soon as possible - Maximum flight time 30 minutes"

About your edited thought: Again not sure what you mean by "would the crew still have an accurate transmission temperature?" since the Oil temperature switch sits at the bottom of the MGB case, immersed in oil and measuring the oil temperature. Remember the S-92 Cougar crash report, the crew expected an increase in oil temperature associated with a loss of oil, which led the pilots to incorrectly rely on MGB oil temperature as a secondary indication of an impending MGB failure. So regardless of your oil temperature being below 128 degrees following a failure of the EMLUB system, the ECL states explicitly what to do.

[albatross]

Thanks for the info Peter.

When on course the instructor dealt with total loss of oil more than loss of both pumps. At least that was the impression I was left with. As I said I don't have my course notes to hand at the moment. Hence the question.
Of course in either case loss of pressure would lead to activation of the ELUBE system as per ECL.

As for my edited thought: My point (dull that it may be LOL) was that in the event of a total loss of oil there would be no accurate oil temp information but in the event of loss of both pumps there may be.
Just an aside nothing more. The S-92 accident was what brought it to mind.

[industry insider]

A relatively quick and total loss of either engine or MGB oil will, of course, lead to a reduction in indicated temperature as the probe will effectively be measuring internal air temperature. I both cases when I have rapidly lost engine oil, in two different types of aircraft, the indicated temperature went down not up.

[That lights normal!]

My very basic thoughts on Oil Temp indications.

You would have accurate indication of the oil temp (still has oil in this failure mode)
However, the oil is not being pumped past the, now unlubricated, hot parts: so the oil temp is irrelevant, and could be falsely comforting. (Similarities with temp indications when the fluid is below the sensor. The classic case being car radiators: when dry, the indicated temp can drop...)

The elephant in the room, is the pieces of shaft/bevel gear potentially unrestrained in the TXMSN.

No light (on the MLube) is Normal;)

[Colibri49]

"The elephant in the room, is the pieces of shaft/bevel gear potentially unrestrained in the TXMSN."

Having looked up into the bottom of an EC225 MGB with the bottom cover removed, I can assure you that when the shaft driving the bevel gear fractures at the weld and drops into the bottom of the sump, there is no way for shaft or gear pieces to be carried up into the other moving bits inside the gearbox. It is a fully enclosed chamber.

[Pittsextra]

I don't think this will prove to be all that complex in the final analysis. I believe that they will in all likelyhood come back to what was reported here:-

Air Accidents Investigation: S3/2012 - EC225 LP Super Puma G-REDW (http://www.aaib.gov.uk/publications/special_bulletins/s3_2012___ec225_lp_super_puma_g_redw.cfm)

That was back in July 2012.

[Peter PanPan]

Though an issue with the nitrided steel alloy bevel gear vertical shafts has clearly been identified, we have yet to determine why the MGB EMLUB caption illuminated (Further investigative work is planned) despite the emergency lubrication system having worked normally - Glycol sprayed in the main gear box and remaining amount of Hydrosafe 620 in the reservoir -

This special bulletin only details progresses being made through the investigation as clearly stated, no final analysis at this stage, right?

[Pittsextra]

Sure but don't you see that as a secondary issue?

[Colibri49]

Here are links to the subject of carburizing v. nitriding

What is the cost difference between carburizing and nitriding? | Eurotherm Products and Solutions Blog (http://blog.eurotherm.com/what-is-the-cost-difference-between-carburizing-and-nitriding-2/)

Case hardening - Wikipedia, the free encyclopedia (http://en.wikipedia.org/wiki/Case_hardening)

I don't understand much of it, but if all that was changed in the EC225 shaft design was the case hardening process, then what is to prevent EC from producing new shafts using the old process, which gave no trouble for 4.5 million hours?

[HeliHenri]

Some news about Bond 332L2 :

North Sea operator Bond to resume Super Puma flights | Vertical - Helicopter News (http://verticalmag.com/news/articles/22073-north-sea-operator-bond-to-resume-super-puma-flights.html)
.

[Pittsextra]

The problem now becomes one of how to spin the story because of the seemingly repeat failure.

Given the time that has passed they can not just come back and suggest that all they needed to do was change back to their old spec.

As I said before this is going to become a case study and the longer it gets dragged out the bigger the mess becomes.

[SASless]

Does all this beg the question...."What provoked EC to alter what was working just dandy all those years and hours?" That by itself is going to be an interesting story that they probably really do not wish to discuss in polite company.

[Wizzard]

Does all this beg the question...."What provoked EC to alter what was working just dandy all those years and hours?"

Might be something to do with upping the MTOM by 17% from the L2 to the 225 and slapping another blade on the head.

Just saying like...

[Colibri49]

Might be something to do with upping the MTOM by 17% from the L2 to the 225 and slapping another blade on the head.

I don't buy that. How long have we been operating these superb machines on the North Sea? Seven-ish years and many thousands of hours.

If nothing got changed in the gearbox during this period, then to my tiny mind such failures must have occurred long before now.

And another thing upsets me. What on earth possessed CHC Scotia not to do MARMS downloads after every flight since the May ditching? It feels like unforgivable negligence to me. Cavalier or what!

[HeliHenri]

From HeliHub : Eurocopter issues EC225 “Key Messages”
Eurocopter issues EC225 “Key Messages” | Helihub - the Helicopter Industry Data Source (http://helihub.com/2012/11/07/eurocopter-issues-ec225-key-messages/)
.

[Pittsextra]

Interesting isn't it:-

Aircraft equipped with nitrided shafts:


All EC225/725, as the nitrided shaft is the only design certified for this aircraft type.
Some AS332/532 are also equipped with nitrided vertical shafts and as a consequence they are also concerned by the limitation
The first-generation carburized vertical shafts are not concerned.

One assumes they have now moved on from the shaft numbers M330 after the production change and now are focused on material spec. Although it will be interesting to see what changed that view other than simply running down a failure list that was available in the summer.

[cyclic]

And another thing upsets me. What on earth possessed CHC Scotia not to do MARMS downloads after every flight since the May ditching? It feels like unforgivable negligence to me. Cavalier or what!

Shhh! You'll be kicked out of the Brownies :\

[jimf671]

S3/2012 appears to be telling us that the part of the shaft in question was air spec 16NCD13 in the old shaft and air spec 32CDV13 for the new shaft. It is not clear to me what the construction method is for the entire shaft assembly or what the materials are for the other components of the welded assembly.

16NCD13 (old) is an alloy steel presented as a case hardening spec. Tensile strengths of up to 1380 MPa can be achieved. This material has less carbon and less other alloying elements than the newer shaft. Case hardening adds carbon to the surface of the component and typically gives hardnesses of around 700HV/58Rc. Once heat treatment is complete, core and surface properties are different.

32CDV13 (new) is an alloy steel presented as a nitriding spec. Tensile strengths of up to 1350 MPa can be achieved. Nitriding converts certain alloying elements (such as Vanadium) at the surface to nitrides and typically gives similar hardnesses of around 700HV/58Rc. Vanadium is key to the nitriding properties (to spot a nitriding steel, look for V and Ti) but higher levels of chromium and molybdenum also contribute. Once heat treatment is complete, core and surface properties are different.

To most people, 700 Hardness Vickers (about 58 Rockwell C) gives the impression of glassy hard. This surface layer is much harder and stronger than the core. Hardness and tensile strength aren't everything though and a balance needs to be struck between strength and ductility. There is no point in having a very strong component if it cannot absorb the flexing and shock loads of the application. Making things stronger can appear so simple but it is usually a nightmare of conflicting requirements and properties.

How these materials respond to welding is likely to be under intense scrutiny at the moment. Welding different alloys together can be problematic. Different carbon content in each component would be one area of concern. It would be interesting to know the order of processes in the manufacture of these shafts since that might reveal the properties at the time of welding.


JimF

(Automotive background. Spec'd case hardening and nitriding steels for engine components in the past.)

[Pittsextra]

it is interesting Jim although you would like to think that Eurocopter and its parent the €22bn market cap. EADS might have the resources to understand that?

Maybe they had "made in China" stamped on them?

[Geoffersincornwall]

It's not difficult to imagine that those who are responsible for buying helicopter services are going to find it difficult to trust the design/manufacture/certification processes ever again. There will be those who would prefer going back to older designs that are mature and are better understood by those that fly and maintain them.

If new designs are to be accepted by the end users then the certification process needs greater transparency and a more questioning authority. Having made that point it will be difficult for the certification team to get their heads around innovative designs unless they have been exposed, from the earliest possible point in the development process, to the thoughts and computations used by the OEM.

It is quite stunning for this non-technically qualified pilot to hear that the design of both the S92 and the 225 used single pathways for the activation of both main and back-up oil pumps that serve the single most important component in the drive train - the Main Transmission Gearbox. Tell me I have it wrong somebody - please. I cannot believe this is true - I must have misunderstood.

G.

:ok:

[andyhelo]

How many rig workers can tell the difference between the 225 and l/l2? I mean no disrespect to the workforce, I just know I struggled to tell the difference until people showed me what to look for....

[jimf671]

How many rig workers can tell the difference between the 225 and l/l2? I mean no disrespect to the workforce, I just know I struggled to tell the difference until people showed me what to look for....

These guys are doing a decent job of keeping people informed. Not everyone will quite 'get it' and some will sound off regardless of the facts. That's life.


G-CHCN ditching incident - Step Change in Safety (http://www.stepchangeinsafety.net/about/GCHCNditchingincident.cfm)

[bigglesbutler]

It is quite stunning for this non-technically qualified pilot to hear that the design of both the S92 and the 225 used single pathways for the activation of both main and back-up oil pumps that serve the single most important component in the drive train - the Main Transmission Gearbox. Tell me I have it wrong somebody - please. I cannot believe this is true - I must have misunderstood.

I initially thought the same thing, but I saw a picture today of the gearbox minus the housing, so all the gears were exposed and held in place to show how they all mesh. Looking at it the pump drive is simplicity and genius in a sense.

The pumps are driven by the one shaft that never stops when we are airborne, the main rotor shaft.

Each pump has its own gear on that shaft that it is driven by.

The standby pump is lower with a lower intake to draw the oil in reducing the amount of pipework necessary.

The end result is no one looking at that design prior to these two incidents would imagine the shaft(s) shearing and causing this problem. So credit to Aerospatiale when they designed the Superpuma system that the 225 inherited.

Si

[jimf671]

It would also be helpful to understand where the bearings support the shaft(s).

[500e]

biggles
Are you saying the main rotor shaft has an extension welded on under the lower bearing ?

[Colibri49]

Biggles is probably soundly asleep by now, so I'll answer for him with one word, Yes. As I said earlier, I've seen it with my own eyes so I know it is so.

Instead of a weld, I would favour something like a spline joint into the MR shaft. But that would take years to certify.

[riff_raff]

......The end result is no one looking at that design prior to these two incidents would imagine the shaft(s) shearing and causing this problem.......bigglesbutler- You bring up a very good point. It would not seem logical to have both the primary and backup lube pumps driven from the same gear, since this common driving gear creates a single-point-of-failure situation. But you need to understand how the accepted industry approach to system fault tolerance analysis considers such cases. For many flight critical components in the drivetrain that have no functional redundancy (such as certain gears, shafts, hubs, etc.) they are designed, analyzed, manufactured, inspected and maintained under very strict controls. Based on this approach, a catastrophic structural failure is not considered a "credible failure mode" for these components in the fault tolerance analysis. Obviously, while this approach should work well in theory, in this particular case there was a breakdown somewhere in the process.

To make a long story short, from the limited information I have seen, I do not see anything in the design of the EC 225 MRGB that would not be considered currently acceptable design practice. Could the design have been made more reliable? In hindsight, maybe so. But we can also assume that it met all regulatory safety requirements at the time the design was qualified/certified.

Here's a good description of the EC225 lube system function from an AAIB bulletin:
http://www.stepchangeinsafety.net/templates/asset-relay.cfm?frmAssetFileID=1542

[Variable Load]

It is quite stunning for this non-technically qualified pilot to hear that the design of both the S92 and the 225 used single pathways for the activation of both main and back-up oil pumps that serve the single most important component in the drive train - the Main Transmission Gearbox. Tell me I have it wrong somebody - please.

Geoff, the S92 oil pumps are individually driven off the main bevel gear, so there is no single pathway. The two pumps feed the transmission "in parallel", so there isn't a main and back-up as such.

[Lonewolf_50]

Apologies for having used "crash" rather than "controlled ditch and loss of aircraft" in my brief post up there. Not fair to the crew to call a "crash" what was instead an exercise in sound airmanship when faced with a mechanical failure. :O

HeliHenri was quite right to tweak my nose for that (http://www.pprune.org/rotorheads/498649-north-sea-heli-ditching-oct-2012-a-13.html#post7497854). :ok:

[HeliHenri]

Apologies for having used "crash" rather than "controlled ditch and loss of aircraft" in my brief post up there

Hello Lonewolf_50,

Please, don't think I'm a bad man but if you withdraw "loss of aircraft" (it's safe too), it'll be perfect ! ;)

BRGDS Henri
.

[Soave_Pilot]

Bristow signs deal for 10 S-92s to relieve grounding of Super Puma fleet | Vertical - Helicopter News (http://verticalmag.com/news/article.php?aid=22104)

[Lonewolf_50]

Will it fly again? That would be nice! :ok:

Or did the insurance company just "buy" it? I may have misunderstood some of the above discussion.

[Wizzard]

Will it fly again

No probably due to sea water contamination.

She was perfect when she went in the water but she got bent during the night when the tug put a line on her tail to stabilise her, they also broke a couple of windows during the lifting process.

[HeliHenri]

At the present time, even the non salty 225 are'nt flying ... :bored:
.

[HeliComparator]

Rifraf - oil pumps are driven from a single gear but not using the same part of the teeth, so eg if one pump seizes and strips the teeth, the other pump isn't affected.

I am amused by VL's foot shooting where he explains that the S92's pumps are independently driven from the same bevel gear..... Dur ... doesn't that mean that they also have a single failure point - the bevel gear?

It would be nice to have no single point failures in a heli gearbox but That is not really feasible. They all most definitely have a big single point failure item and that is the main rotor mast!

I think one has to distinguish between a single point failure that is catastrophic - eg the main rotor mast, vs something like oil pump drives the failure of which, as has been recently demonstrated twice, is not catastrophic.

[Dry wretched thunder]

What effect is this having on you the pilots, obviously 'we' the bears are very apprehensive and yes most put a face on it but are the the pilots feeling under extra pressure what with offshore aviation being at the highest profile that its been at in 20 years that ive been working offshore id say.

I, like most others have the utmost respect for you guys and am well aware of some of the crap you have to fly in weather wise, but it must be in the back of pilots minds that god forbid another incident related or not to the recent MGB incidents would almost finish helicoper use for rig use.

We are not interested in boats or sea transfers (STV is it seems), we want the quick escape and 45 minutes noddy dog sleep that the choppers offer but there are way to many 'non offshore' flyers who have a lot of clout and swing some heavyweight punches about what we the actual offshore guy does and doesnt want. Peer pressure right now is the last thing that anybody wants ?

[Variable Load]

I am amused by VL's foot shooting where he explains that the S92's pumps are independently driven from the same bevel gear..... Dur ... doesn't that mean that they also have a single failure point - the bevel gear?

They are independently driven from the main bevel gear. If the main bevel gear were to fail then the lack of oil pressure would be the least of your problems - drive from both engines and tail rotor drive would also be lost.... Dur... :ugh:

[terminus mos]

We are hearing that the EC225 will remain grounded for at least another 3 weeks minimum before there is any firm news from EC.

[Mr Whirly]

If the main bevel gear were to fail then the lack of oil pressure would be the least of your problems - drive from both engines and tail rotor drive would also be lost

That's what I've been thinking all along. Am I missing something ... ?

[pohm1]

Vertical (http://verticalmag.com/news/article.php?aid=22104)

BRISTOW SIGNS DEAL FOR 10 S-92S TO RELIEVE GROUNDING OF SUPER PUMA FLEET
Thursday November 8th 2012 - by Vertical Staff
Offshore transportation company Bristow has signed a deal for 10 Sikorsky S-92s as part of the company’s effort to cope with the potential long-term fall-out of two recent ditchings of Eurocopter Super Pumas in the North Sea.

Bristow currently has a fleet of 16 Super Pumas (15 EC225s and one AS332L2) that are grounded following the most recent ditching of a CHC-operated EC225 on Oct. 22. All 17 passengers and two crew escaped the incident without injury, but the follow-up investigation found that a failure of the vertical shaft in the main gearbox was to blame – the same cause for a similar incident back in May.

“We’ve been working very hard with Eurocopter and other industry participants to determine the root cause of the accident and the impact on the long term availability of the Super Puma and the EC225s,” said Bill Chiles, Bristow’s president, CEO & director. “This is a moving situation that’s changing every day."

The purchase of the S-92s was revealed in the company’s recently-released financial results, which said the it was part of the company’s effort to “minimize or eliminate the impact on our clients” of the current grounding.

“We’re supporting very critical operations out there, so we can’t afford to stop the flow of people and material, and that has to continue,” said Chiles. “We’re going to work with each of our clients individually to solve their challenges, because they are different.”

In a conference call following the release of the results, Jonathan Baliff, senior vice president, chief financial officer, said the S-92s would also work to enable fleet replacement. “When we make big purchases, we partner with our OEM suppliers to, in essence, recycle the older technology [in the fleet]. The purchase of these 10 new Sikorsky S-92s has directly led to us being able to exit the old S-76a model completely. That will happen over time.”

Chiles said the company’s focus was currently on safety, as it seeks to relieve the pressure built by the grounding of the Super Puma fleet. “We’re going around and freeing up all available resources around the world, turning over every stone to make sure we’re covered both short term and long term,” he said. “We’re moving new aircraft in, we’re moving AW139s, and S-76s in there and S-92s in there. And that creates a lot of challenges with resources, not only with aircraft, but pilots and engineers. So we’ve got to be very focused in safety.”

Chiles said any specifics on a return to service of the company’s Super Puma fleet was yet to be released. “We’re dealing with the short-term issues and we’re also looking at what we do on the long-term basis if this situation continues,” he said. “It will evolve very quickly. Over the next few weeks, we should be in a better position to talk.”

P1

[HeliComparator]

VL -so you agree that the S92 oil pump drive ultimately has a single path / point if failure, just like the 225 one does.

DWT I can only speak for myself. The industry having had 4 events in the past few years (fortunately none affecting our company) that is pretty unusual compared to the last 10 or so years of calm.

One very nasty event (the L2) stands out as being unsurvivable, with some remaining uncertainty about the cause of the failure. However I am slightly reassured that the event could probably have been prevented had correct maintenance procedures been followed.

The ETAP ditching was a result of inappropriate procedures and a degree of pilot foolishness. Since it would be me at the sharp end, it would be up to me to not repeat that type of accident, but anyway our company's procedures are pretty robust in this area.

The two oil pump drive failures, both detectable by HUMS had it been used rigorously, is what seems to have really upset the apple cart, merely because the cause was believed to be known but then there was a repeat, indicating the cause was not in fact known.

Not that I have any desire to be one of those passengers or pilots finding themselves in the water, but the outcomes were: no injuries except perhaps mental ones. This I think we can put down to wrapping things up in a thick layer of training for both pilots and pax, safety equipment and the availability of SAR. It is this layer of "extras" that turns a potentially disastrous accident into no more than an unpleasant event.

So 1 fatal accident in the last 10 yrs or so, whilst being 1 too many, is not a bad record I think when we in Bristow have completed perhaps 100,000 hrs just out of Abz, with other operators probably matching that.

Put it another way, when you or I die, it will almost certainly not be as a result of a helicopter accident (mind you, I do drive a motorbike!). Drinking and smoking will kill far more of your colleagues than a heli will.

Life is tenuous and precious, but if we become too bogged down with thinking about the remotest possible ways we might die, we would never get anything done and lead a long but valueless life.

Personally I am really looking forward to getting back into the air in an EC225 because it is a fantastic and safe machine, albeit with one component out of thousands suffering from a serious design problem that has to be fixed.

Of course, if my company decides I have to do an S92 conversion in the mean time, that would be a catastrophe!

[Aser]

Of course, if my company decides I have to do an S92 conversion in the mean time...
That would be priceless!!! :D:}

[HeliComparator]

...But at least I would retain my sense of humour - and plenty to laugh about with the S92!

[Colibri49]

Dry Wretched Thunder. Like Helicomparator I would get back into the EC225 right now and fly it knowing that Bristow will be monitoring everything as closely as they have always done, even before the May ditching. Both of the 2012 ditchings almost certainly (some might say certainly) wouldn't have happened if the vibration data had been downloaded after each flight.

Please believe me that I'm a very cautious pilot and have enjoyed a long flying career by striving to fly only when everything indicates that it is safe to do so. My attitude is no different from every North Sea pilot in all the companies. We all want to reach pensionable age without incident.

There is no doubt that Eurocopter will be pulling out all the stops to come up with a very convincing solution, if for no other reason than not wishing to lose even more future sales to their rivals. They know that they can't afford any repeats.

[Pittsextra]

Both of the 2012 ditchings almost certainly (some might say certainly) wouldn't have happened if the vibration data had been downloaded after each flight.


If you read the data from AAIB then that isn't the case

Page 9 of this relates:-

Air Accidents Investigation: S3/2012 EC225 LP Super Puma, G-REDW (http://www.aaib.gov.uk/publications/bulletins/august_2012/s3_2012_ec225_lp_super_puma__g_redw.cfm)

But it says :-


Health and usage monitoring system (HUMS)

A review of the HUMS data showed no indication of any

significant rising vibration trends until approximately six flying hours prior to the start of the accident flight. Prior to this period, the vibration levels on indicators associated with the bevel gear vertical shaft were below the mean level established from data collected from 23 other EC225 LP helicopters.

During the last six flying hours, which covered the two flights prior to the accident flight, the trend for indicator

MOD 45, which monitors the meshing frequency of the bevel gear, and MOD 70 which monitors the meshing frequency of the oil pump wheels, increased. An amber4 alert was generated for MOD 45 following the last flight on 9 May 2012, and for both indicators following the first flight on 10 May 2012. The operator’s engineers followed the fault diagnosis chart in the Aircraft Maintenance Manual (AMM), Chapter 45.11.08.211. The washer on the accelerometer for these parameters was replaced following the first amber alert on 9 May 2012, and the MGB magnetic chip detectors were checked, and found to be free of debris, following the alerts on the 10 May 2012. Thirty six other indicators were checked
and no significant trends were detected. In accordance with the guidance in the AMM, the aircraft was placed on 10 hourly close monitoring and released for flight.

Following the accident, the helicopter manufacturer analyzed the data for indicators MOD 45 and MOD 70 and reduced the vibration level required to generate an amber alert. Red alert thresholds have also been introduced for both these indicators
5.


Footnote

4

An amber alert requires the operator to determine if a maintenance action is required, whereas a red alert requires a maintenance action


Footnote

5
Eurocopter Service Bulletin No 45-001.

[HeliComparator]

Pitts yes I think you are correct in what you say. For the May ditching, the correct manufacturer's procedures were followed, therefore the operator cannot be blamed for failing to follow the rules.

But at the time I was told by our engineers that they would have dropped the sump to have a quick look, rather than presuming it to be a false warning and dispatching it again having re-washered the sensor, and certainly on the second warning. Whether that is a case of hindsight or that is what would genuinely have happened I can't be sure.

But, trying to apportion blame aside, with the hindsight that we now have that accident was technically avoidable even if the manufacturers procedures did not cater for it. Of course they do now and so future such events should be detected before becoming critical... But of course we are not going to put that to the test it seems!

[industry insider]

The longer this goes on the more likely it is that some contracted EC225s will be replaced by S-92s, even though that may not be a perfect solution to some (HC) It is better than flying in 30 year old 332Ls which is happening in some places where they are providing a limited service.

This situation is not good for the helicopter operators. Mixed fleets will be the way of the future and one company one type and another company a different type with mutual cross backup and increased sharing being discussed as the new way forward from now on.

[SASless]

When HC winds up flying 92's.....I will accept there is a God in Heaven!:E

I know I am safe because HC is too old for a Conversion course unless the rules have changed.

[HeliComparator]

II - yes, many years ago we used to have a mixed fleet of S61, SA330, AS332L, B214ST, S76 in Aberdeen. Then it was realised that a single fleet would allow cost reductions because only 1 set of pilots, engineers, 1 pool of spares etc. An accountant's dream.

But now the old lessons have been re-learnt and the single fleet concept is seen as high risk in the event of a grounding such as we have. The future will involve more mixed fleets - that is until the current guard, soon to be old guard, fall off their perches and then the shiny new accountants and business school graduates will make the same mistakes all over again!

SAS - alas no more age discrimination for conversions and I potentially have 9 years left in me so it cannot be ruled out! However it seems we will have some alternatives such as 139, 189, 175 so I may yet be able to stave off the dreaded Shorts 360 bus with bolt on rotors and a dining table on the tailboom!

But hopefully I will be the last of the dying breed of 225 pilots, left to fly single pilot and then turn out the lights at the end...

[Pittsextra]

HC - Yes and actually even in the most recent case the change in trend which leads to alarms are very close to the point of failure (timewise).

What surprises me is that visual inspection of parts physically that yields nothing of interest and then a few hours later its failed.

[Ian Corrigible]

At the present time, even the non salty 225 are'nt flying ...
Henri,

Perhaps you have more up-to-date information, but my understanding from yesterday's customer update was that other EC225s (/EC725s) are still flying, including at least one 'salty' operator in Asia?

I/C

[HeliHenri]

Hello I C,

You're right, I was speaking about flying over water (the main reason of 225's use) but now the Civil Aviation Authority revoked its ban on overwater use, I was late, sorry about that.
.

[Fareastdriver]

including at least one 'salty' operator in Asia?

At this time of year OAT 28 C, sea temp 26 C. People pay money to go paddling in that.

[Ian Corrigible]

People pay money to go paddling in that

I sense a marketer amongst us... :E

I/C

[The Sultan]

Heli,

If you have to fly the S-92 look on the positive side! You will not be able to hear the laughter after a couple of months.

Literally!

The Sultan

[riff_raff]

HC-

Your point is well made. Most folks fail to appreciate that there are numerous flight critical components in a typical rotorcraft drivetrain that have no functional redundancy. The main rotor mast & hub are perfect examples. But as I noted, these flight critical structures are usually subject to a rigorous fracture control plan during design, manufacture and service.

The only other option would be to use functionally independent dual rotors, gearboxes, etc. And obviously that would not be practical.

riff_raff

[Variable Load]

the S92 oil pump drive ultimately has a single path / point if failure, just like the 225 one does.

HC - If you mean that if the S92, EC225 or any other helicopter were to suffer a failure of the main bevel gear then the end result would be the same i.e. catastrophic, then yes I agree. One MGB does provide a single failure path!

However the S92 design is such that it is not susceptible to the kind of failure that led to loss of oil pressure and the subsequent ditching of REDW and CHCN i.e. a welded on addition to the main bevel gear that drives the oil pumps.

But you already knew that :sad:

[Geoffersincornwall]

... but didn't the S92 have a design flaw in the way the two oil pumps were driven? Something about the debonding of a plastic component that had been glued to a metal shaft.

If so then in my book this would count as exposure to extreme risk via single failure in both systems.

Or was this classified as another 'extremely remote' possibility.

Where else could we look for a single design flaw that has serious consequences in the multiple systems of our helicopter fleet.

When you take a well established type of helicopter and make the slightest change to the profile of it's design, manufacture or overhaul you are exposed to the possibility of disaster. Are the certification authorities alive to these possibilities? Are they in the loop?

Examples of what I mean :-

Chinook gearbox - gear wheel design
S61 gearbox - following the outsourcing of overhaul tasks there was a spate of freewheel failures put down to incorrect overhaul procedures.

Perhaps one of our technical guys who subscribe to Prune can add to that list. I'm sure it would be longer than you imagine. Stories abound about the inspector who retired and then his replacement had to pick up the job without the benefit of his years of experience.

One amusing version of the same story was what happened to us at KLM Helis back in the late 90s. Redundancies where being dished out willy nilly as the focus on costs came down to the need for multitasking. We had two storemen who had been there since the year dot but one of them had to go. KLM being what it is - a state run airline - just sent one from Den Helder back to mainline in Amsterdam. Chaos ensued when after a month or so there was a lack of spare hydraulic components. It was then they found out that one guy in stores was in charge of 'parts returned from overhaul' and the second for 'parts to be sent for overhaul'. They made the second guy redundant but turned out he was the only one who knew where each component was supposed to be sent. All outgoing parts ended up in the wrong place and screwed up the turn around times. Sometimes you don't know what you don't know until it bites you in the arse.

G. :sad: :}

[Variable Load]

Geoff, almost right. Each pump is connected to it's individual gearbox drive by a plastic vespel spline (so there are two vespel splines, one for each pump).

There was an issue with the design (now corrected) that led to the vespel spline wearing and then slipping, therefore one of the two pumps lost drive and therefore pressure. There was never a case of both pumps failing as the drive systems are separate (redundant).

[HeliComparator]

... and when 1 pump drive was lost, the pressure dropped such that the flight manual originally said to Land Immediately. That was good design!

But your point about the pumps being driven direct from the main bevel gear raises an interesting design issue. By doing so on the 92, you add some non-flight critical components (oil pump drive) to a flight critical zone (bevel gear). It is not impossible to imagine some failure of the oil pump drive (gear seizing / breaking up and stripping /damaging the bevel gear etc) that could cause a catastrophic failure of the bevel gear. So the design concept trades off reduced probability of non-catastrophic failure (oil pumps) with increased possibility of a catastrophic failure (bevel drive). Of course such a failure is pretty unlikely, but then so is having the lower part of the same equivalent shaft detach in a design that has hitherto successfully flown millions of flight hours.

[terminus mos]

Apparently Lutz Bertling (EC President) has written to CHC saying that the EC225 fleet,will be grounded for another 3 months over hostile terrain while EC does more testing to prove the combined AAIB and EC theory of the failure mode and to continue testing on the Emergency Lube system.

[Fareastdriver]

Looking to the future one must consider a continuous HUMS assessment in flight. Should a HUMS computer be able to download information and analyse the results after a flight then surely it must be within the wit of man for it to be able to do it en-route. The processing capacity to launch an Apollo Lunar Mission is now available in something not much bigger than a smartphone so weight and volume should not be a problem.

How much safer would it be if a HUMS panel would warn you of an unusual occurence within your systems or the reassurance of being able to press a check button on it to ensure that everything is normal.

When HUMS first started all those years ago what we wanted was a light that said. "Do not fly this aircraft."

[[email protected]]

Rolls Royce do that with their Trent engines already - real time monitoring.

[HeliComparator]

Its back to the old problem of the false warning rate. If an engine shows a dodgy HUMS, you just shut it down no big deal. But if a main transmission shows a dodgy HUMS you have to ditch, and would look a bit stupid if it was a false alert. You only have to look at the maintenance actions reported in the May ditching to see that even the manufacturer suspects a false warning as the most likely cause - viz the "replace the sensor mounting washer" action. With current technology having cockpit warnings of main transmission problems would dramtically increase the ditching rate.

I am not saying that improvement in self-monitoring of the HUMS system itself and therefore increase in the system integrity is not possible, but it is an area that has received no investment and so no progress has been made since the early 90s when HUMS was invented.

[industry insider]

At the risk of being flamed by the Comparator a good start would be for Eurocopter to at least have a fleet management operations centre like Sikorsky's FMOC.

Sikorsky takes HUMS from all of its aircraft and compares the readings from the worldwide fleet. Differences in HUMS readouts from the fleet norm are immediately apparent. In fact, some trial aircraft are streamed in real time so it is possible today with helicopters and should be adopted as standard practice.

I would also like to see tail pylon and other cameras fitted to allow the crew to view external parts of the aircraft for oil leaks etc, surely it is also technologically possible to have pictures able to be transmitted back to base.

[HeliComparator]

Yes, the Sik HUMS centre is a good idea, although EC do have continuous access (via VPN) to our M'ARMS server in Aberdeen and other such bases. What degree of comparison with other operators' aircraft goes on I wouldn't know.

It is certainly true that American culture in general, and Sik culture in particular, is very good at presenting a fantastic show of fanfares, glossy websites and brochures, but the reality can sometimes be that it is all for show with no meat (not saying that is the case here necessarily).

EC by contrast just get on with it in some dingy monochrome M'ARMS office in Marignane!

Of course that is the point of the AAD system - to detect the sort of abnormality of one aircraft versus the fleet norm, even without the triggering of a threshold, thus making continuous comparison with other operators unnecessary.

One area in which the Sik system is a bit of a pain in the whatsits is that you need a separate computer for each airframe, whereas all more recent EC aircraft (M'ARMS equipped) can use the same single server at a base, which is surely easier for the operator.

On the cameras, yes why not but I am not sure I could point to an event where it would have made a difference? Once you get an oil leak, everything including the camera would be covered in oil so I doubt you would be able to see where it was coming from, or really get an idea of how bad it was.

[Matari]

HC,
Yes, the Sik HUMS centre is a good idea, although EC do have continuous access (via VPN) to our M'ARMS server in Aberdeen and other such bases. What degree of comparison with other operators' aircraft goes on I wouldn't know.
Are you really saying you don't know if EC compares HUMS data across its fleet?

I am astounded if EC doesn't do this, as I am astounded that you think it might be (but not necessarily) just 'fanfare and glossy websites.'

I would think that this cross-fleet HUMS comparison is essential, and that you would applaud the effort. Instead, you mock it and (strangely) seem more concerned about protecting the honor of a favored manufacturer.

[HeliComparator]

Matari, I am a pilot, not a HUMS engineer so no, I am not familiar with the detail of the processes between our company, other companies and EC with regard to HUMS data.

Perhaps you should re-read my post because I didn't mock it, just put a generic caveat on not necessarily being impressed by the glossy cover of a book.

There is clearly some benefit to fleet wide data awareness, but once the fleet pattern is established that becomes a diminishing return. I can certainly see it being of great benefit to a small operator who has 1 or 2 airframes and doesn't fly that much, but much less so for a high intensity operator of multiple airframes whose own internal data represents a pretty comprehensive fleet sample.

Don't forget that Bristow invented HUMS (and I played my own small part in that development) and it was probably over a decade before the OEMs grasped the ball (longer for Sikorsky) so we are used to doing our own things and in the past, being the world experts in the subject at a time when the OEMs didn't have a clue. I am just saying all that so you realise "where I am coming from"

[Matari]

Large fleet operators like Bristow have the ability to gather large amounts of data and develop specific maintenance programs based on their operating profiles and experience. They do not have the ability to look across the fleet at others.

That's where the OEMs can really help.

If Sikorsky is capturing, analyzing and making recommendations based on that fleet data, then good for them. If EC is not, I have to wonder why they aren't adopting the best practices of others.

Organizations change and evolve. Sikorsky (and EC, and Bell) may have been slow off the mark, but it seems that partnerships with operators do pay off for all.

So bravo for Sikorsky, however flashy may be their style. I just wonder why someone who I believe genuinely strives for safety improvements, hasn't even asked the question about what EC does (or doesn't do) with fleet ops data. Bristow has an opportunity to lead, and force changes at EC if needed. But when loyalty to a certain type or manufacturer trumps basic engineering inquiry, then all operators suffer.

[Geoffersincornwall]

You have to remember that OEMs were not only slow off the mark they were very anti. They faced the prospect of an operator telling them, for example, that a new gearbox was producing vibes detected by HUMS and they wanted it replaced under warranty. They would say "on your bike and a curse on your box of tricks'. As far as they were concerned the scope for serious warranty issues was so great they lobbied against HUMS so Bristow, with I believe some help from Shell Aircraft, put up the cash to develop it.

G.
.

[HeliComparator]

Matari, perhaps you think I am omniscient? We have a HUMS Type Engineer whose job it is to look after this sort of thing. He works with SIK and EC and I am confident that if there was a gap in EC's process that was not in Sik's, he would have done something about it. But I don't need to be breathing down his neck to see if he is doing his job properly. I doubt you would expect other pilots to be intimate with all their company's engineering processes so I don't understand why you think I should be?

I am editing my post to say that I guess the truth of it is that I still suspect that all this global analysis of data lark is just so many words. Exactly what processes do SIK follow with all this data? Easy to put it in a sales brochure but what does it actually mean? Any fleet has refinements made to its HUMS systems in the light of experience, obviously having more data helps this happen quicker, but I wonder if the 92 has had more refinement than other fleets, how often do refinements occur now, with the fleet reaching middle age? Can you give me some actual examples where it has achieved something other OEMs did not? Or is it all just talking up what is a fairly straightforward system?

[Matari]

Geoffers, I agree completely and I think 'slow off the mark' was a bad choice of words.

An analogy might be the industrial gas turbine world, where the OEMs followed the same tack. Early on they simply produced engines to sell to customers, and provided minimal service with new parts. When the competition did something new, they followed. They had no 'P&L' to partner with operators. Some within the OEMs viewed outspoken operators as a nuisance at best.

It took really bright, creative and tough operators like Statoil, GDF Suez, Duke Energy, FP&L, ExxonMobil to force the OEMs to make changes. Things like Remote Monitoring and Diagnostics, hot section component repairs, extended life...all these were forced on the OEMs by operators determined to create value and improve reliability and safety of their equipment.

It is a fundamental difference in what the two cultures are trying to accomplish.

The OEMs want to produce safe, reliable, competitive products. Operators want to get the most out of those products, and make them safer and more cost effective within the constraints of their stakeholders and regulatory authorities. This requires collaboration, give and take, and above all, money. Smart OEMs see this, and change the way they do business.

I am only surprised, and we can leave it at this, that someone who opines on all sorts of engineering subjects seems indifferent to an apparent best engineering practice by an OEM who he constantly berates. Openness to new ideas, even if they come from 'Brand X', should be welcomed.

[flyer43]

If EC are so keen on gathering data to improve the safety of their own aircraft, as well as improving their own understanding of problems that are arising, why don't they offer AAD as a free service instead of charging quite a substantial sum per aircraft?
Some of the smaller operators are not keen to pay this amount, thus everybody is losing out!

[OneManBand]

Forgive me, but I thought this thread was titled "North Sea heli ditching" ..? We seem to have drifted off thread a little.

[HeliComparator]

Matari - you persist in your line and ignore my question about the actual benefits - if any. Therefore, until you prove me wrong I will have to assume that you can't actually quantify the benefits. Perhaps you too are taken in by the glossy spiel?

ps can't help noticing that your profile says "sales manager". Does that tell us something?

Flyer - fair point but unfortunately everyone is in it for the money - the OEMs, the Operators, the Oil companies and even the pilots. Especially the oil companies (just for you!). Why should the OEMs give stuff away for free when the Operators and Oil Cos are making a profit (and the pilots are scraping a meagre living). I don't recall receiving any free petrol recently!

OMB - surely HUMS is a key issue in this ditching and for once, I don't see thread drift.

[SASless]

OMB....and you are trying to take in a completely different path yourself. Folks are quite happy with the discussion which is dealing with topics related to the ditching if you care to check it.

[Matari]

An old boss once had a sign on his wall that said: 'Nothing happens until somebody sells something.' Pretty accurate, if you think about it.

Back to HUMS: You never know what the data will say. The larger the data set, the better. How can that be bad?

I've seen OEM-captured data from a gas turbine on a North Sea platform, used to prevent a failure in a Petrobras gas turbine offshore Brazil. If Petrobras had not had access to OEM captured data, they never would have known about the pending failure.

Two large, capable engineering companies, connected only by the OEM. Everybody benefited. Again, why knock an OEM trying to do the right thing?

[HeliComparator]

Yes, clearly nothing happened in the billions of years before capitalism was invented.

A well timed article here (http://verticalmag.com/news/article.php?aid=22094) . So it's all about cutting costs/increasing profit, and not at all about safety. Our shareholders will like it, not so sure about our passengers and pilots!

[industry insider]

Sikorsky's comparison of all S-92 HUMS data in the "glossy brochure" FMOC shows some very different data between companies who operate their S-92s differently.

The data is now being used to determine the provision of spare parts known to be used more often in some operating regimes. It can also be used, together with historical parts used data to adjust PBH rates to be operator specific.

[The Sultan]

Flyer

What is the cost of GEs AAD?

FYI. Bell's commercial HUMS fleet management system monitors 150+ aircraft at no cost to the customers via an Internet based application. This system allows Bell product support to monitor fleet and individual aircraft health, allows operators to see their ships and the rest of the fleet(with all competitor specifics sanitized so no one knows who is who), and emails alerts to the specific operators.

The Sultan

[Variable Load]

One area in which the Sik system is a bit of a pain in the whatsits is that you need a separate computer for each airframe,

Apologies for dragging this thread back a bit, but my experience with the S92 doesn't agree with HCs. Yes, Sikorsky issue a "toughbook" with each S92 to allow for remote monitoring and maintenance support, however a single computer can be used for HUMS download on numerous airframes. Maybe Bristow haven't realised this yet?

[HeliComparator]

So I am getting the picture now, the centralised fleet monitoring is all about spares / PBH / increasing component lives. Nothing wrong with that of course -it's a good thing - but also nothing to do with safety.

VL that's interesting. We certainly have a networked laptop for each airframe in Scatsta, whether we realise we don't need that, I am not sure. Has it always been the case that a single PC can be used, or was this a development?

[industry insider]

HC, your analysis is one sided and simplistic.

SAFETY was of course the initial priority for the FMOC when the S-92 was introduced as a new type. To impugn Sikorsky is, however, one of your characteristics, and one which belittles your 30+ years in the industry.

However, after 7+ years of operations, including one fatal which did not show on HUMS but we have discussed that one enough, (hopefully) other uses have become apparent. Actually, as much as increase component lives for some and decrease their costs, analysis has even reduced lives for those who thrash their aircraft hard.

[HeliComparator]

Not impugning Sikorsky, merely pointing out that Matari's impugnment(?) of EC for not having the same type of centralised HUMS system ( if indeed that is the case) is correct only on commercial grounds, not on safety grounds.

[Geoffersincornwall]

We have to remember that when HUMS was 'invented' the designers said it would take 10 years to gather enough data to understand what the HUMS is telling the end-user. That would appear to be an underestimate on two counts. The first is the need to extend HUMS usage across the board to expand the spectrum of data accumulated from all types and all applications and the second is to find the tools capable of providing reliable analysis of such a vast quantity of data.

I suspect that the way ahead is to somehow get closer to the problem. Wouldn't it be great if you could implant vibe-sensors into the gear wheels and read the output directly. I wonder if any of the electronics boffins are working on such ideas.

The problems caused by harmonics in a structure with so many rotating components are horrendous and trying to second guess the failure mode is a kind of self defeating process given that identifying a failure mode means that you have put your finger on a weakness. Best answer = remove the weakness. The failure mode is therefore by definition the one that takes you by surprise.

Better sensors could be the way forward.

G. :ok:

[flyer43]

Sultan. The last I heard was around $6K per aircraft - at least that is what one OEM is charging.

HC. Although I agree that everybody is in this for profit. However, on a legal stance - if an accident occurs and it is found that AAD was not being used, although everybody knows that AAD provides enhanced risk management, could the operator and/or OEM be held culpable?

[HeliComparator]

Flyer, perhaps the operator could be found culpable in a civil case, but not the OEM since how the aircraft are operated and the approved maintenance programmes are not within their control. I am sure the OEM would be seen to be squeaky clean if they provided the technology but the operator discounted it on the basis of a reasonable cost.

Geoffers - you are right. It is those un-thought-of problems that catch everyone out. The thought-of ones are usually no problem!

[SASless]

HC....be careful.....you might break your arm patting yourself on the back like that!:=

[HeliComparator]

HC....be careful.....you might break your arm patting yourself on the back like that!

??? I am a simple soul so you will have to explain that if you want me to understand it!

[js0987]

Using HUMS data sounds like a step in the right direction. Afterall, how were component retirement hours figured before? Several thousand hours of test flying, examining the parts and them sitting down in a commitee and more or less compromising on a figure. Then once those components went to their retirement hours, the parts were returned, examined and, after enough were looked at, another committee descision to ask for an extension?

Hopefully HUMS will be another useful tool, as long as it doesn't become the be all and end all in determining a components life.

[Geoffersincornwall]

..... but is it achievable? Probably not. Sad to say that ours is one of the industries that demands the highest standards of manufacturing but it is far from perfect.

One possible step in the right direction is deal with the problems created by the way each OEM works within a silo that generates a terrible mindset that precludes things they have not seen before but have been seen in other types made by other people.

To what extent, I wonder do OEM's study and test the equipment made by their rivals? Are there any formal liaisons between OEMs on safety critical issues? Should there be? What can EASA do about it?

G. :ok:
.

[riff_raff]

It is very worthwhile to work hard at improving drivetrain HUMS technology used by the rotorcraft industry, and there are lots of engineers currently doing just that. But even the best HUMS in use today really only monitor for problems that are already occurring, and they have very little predictive capability.

We should also consider the nature of what occurred in this particular failure. Based on the published statements from Eurocopter, it sounds like there was a manufacturing/QA problem with the weld joint on the shaft:

"....As already indicated in the AAIB Special Bulletin S6/2012, the initial visual examination has identified a 360° circumferential crack on the bevel gear vertical shaft (which drives the two Main Gear Box (MGB) lubrication pumps), in the vicinity of the weld that joins two sections of the shaft....".

Eurocopter's use of welding for highly stressed components is actually very common in the aircraft industry. The process used is friction welding. It is a "solid state" joining process and produces joints of extremely high quality. Friction welding is used to save weight and material cost, primarily in situations where the cross section of the component has large changes, such as the given example of a short large diameter gear disc on the end of a long slender shaft.

However, getting good results from friction welding does require careful control of the process. The other factor that would seem to indicate there was a manufacturing issue is the shaft appears to have failed in a location that would not likely be highly stressed (and that's what makes it a good location for the weld joint).

Just all speculation on my part. But it's certainly an interesting topic of discussion!

[Variable Load]

We certainly have a networked laptop for each airframe in Scatsta, whether we realise we don't need that, I am not sure. Has it always been the case that a single PC can be used, or was this a development?

HC - I can't be totally sure, but I don't think this is a recent development. It certainly has been an option for at least the last 5-6 years. My understanding was that if you didn't want to take the HUMS card to the groundstation (one PC), then you could take each aircraft's toughbook to the aircraft for analysis.

As an aside, the toughbook was also touted as a reference library containing electronic and up to date versions of the MM, IPC, etc that could be used "beside" the aircraft. I'm not sure if they are ever used this way?

[The Sultan]

Flyer,

Thanks, for the info. I assume the 6k is per aircraft per year.

The flip side of the AAD argument is that you are paying for it and something happens then the AAD provider should be held liable. In the recent incidences including the loss of rotor on the Puma the AAIB report indicated that AAD techniques provided no improvement in warning time. Actually if all chip detections had been reported to the crew there would have not been a crash.

The Sultan

[Pittsextra]

HUMS and G-REDL, discuss.

[flyer43]

I meant to add - that's the cost per month per aircraft!

[Pittsextra]

This is what EC concluded:-

Manufacturer’s analysis of G-REDL HUMS

The helicopter manufacturer was provided with a copy of the G-REDL HUMS database and the downloaded HUMS data card from 1 April 2009 operations. Their analysis was performed by two teams; the first being by their customer
technical support team which reviewed all CIs. They concluded that there was ‘nothing abnormal to report’.

[HeliComparator]

Pitts - We have already discussed at great length the problem of using current HUMS technology to establish the health of planet gears in an epicyclic, I suggest you look back for that discussion which was only a month or so ago, rather than trying to re-start it.

[Pittsextra]

HC - no the point I was making is that its irrelevant what data sharing exists or doesn't exist if the data isn't going to make a difference.

In the EC225 cases it alarmed and allowed a controlled ditch but HMES isn't in my view anything more than a "best efforts" and depends hugely on which component fails.

Of greater interest is the mechanical issues which I can't see being resolved anytime soon. Does anyone know what % EC225 sales are as a total of Eurocopter revenues??

[victor papa]

I do not know what to make of this as yes 2 shafts failed and it got the treatment it deserved with all subject to 3hr download of HUMS and yes most grounded in the interest of aviation safety etc. I do find it sad as somebody nowhere involved in this market that the 225 is treated so harshly(correctly again?) and being replaced by models with problems too yet not as defined as a specific shaft failure as on the 225 so flying threw their issues? Are the unions as informed about the MGB cracking and now airframe cracking issues on the 92 or the tailboom issues on the 139 as they are of the obvious and clear issue of the post 2009 shaft with 2 failures on the 225 which has a clear solution? What if the next one is not a 225-and I hope there is no next one?

There is a huge argument between HC and the rest as to HUMS data and the usage there of with speculation on all sides towards what EC does. The facts have been stated about Sikorsy and Bell but has anyone actually established how euroarms work and what EC does or doesnt do with the data? It is a argument with facts from Sikorsky and Bell it seems and a assumption that EC does nothing despite having euroarms I think is the EC specific HUMS version? As said I do not know this market or am involved, just find it astonishing the arguments and sentiment!

Not a good time for EC I presume at all but so the industry goes and it seems that they at least have a clear target to fix and as per the B3e restrictions and issues with the TR bearings after no previous issues on the B3's it seems that maybe our thurst for power has caught up with our technology? People referred in this threat to older more reliable platforms than the 225, 332L2,S-92, AW 139 but then those were the times when we all demanded more power from the engines!?

[HeliComparator]

Victor, I think one thing to bear in mind is that the algorithms, signal processing etc in the HUMS systems of all the OEMs is pretty much the same. The AAD process is a newer devlopment but as far as I am aware, it is not built in to any of the OEM's systems, rather it is a bolt-on provided by GE.

The system on the 225, by the way, is called M'ARMS.

You are of course absolutely right in that the 225 is the demon of the moment, but other types such as 139 and S92 have all had substantial technical problems in the past that grounded or nearly grounded them. I hope and expect that once this shaft issue is resolved, the EC225 will come back into favour, though a lesson has been learnt about not having all your eggs in 1 basket.

[victor papa]

Thanks for the correction HC, I last dealt with a offshore EC many years ago and then the state of the art was the euroarms. It was a L2 and a very old L2. I just wonder if the 2 225 failues had more than 1 possible cause whether it would have been this easy to ground a fleet. It almost is so simple the cause that is so clear and the cure that it is easy to say ground until fixed whiilst most modern helos are flying threw issues but they are not as clearly defined so no clear demand to fix before we fly again etc! I am probably way of base but it seems that the obvious and simple is the problem here?

[Pittsextra]

Given the process - or rather lack of - EC can not be surprised.

In the end, without wishing to sound smart after the event but where in the process have EC taken care of their brand and reputation in this pre-accident?

It all seems very "matey" and customer friendly without a thought that actually if something ends in a million pieces who did we put the trust in the hands of? After all the operator is a commercial entity and personally I don't think it is a great idea having alarms (in this case yellow, red) and then a woolley grey area beyond that.

You look at recent AAIB findings on EC machinary that has HUMS and there is a lack of consistancy with its usage and indeed understanding as to what and how it should be used.

[abzoilworker]

I must say I have found this thread enlightening. I am an amateur pilot who works offshore. We normally fly out on 225's. I must say that a huge majority of the offshore work force has lost all confidence in this aircraft due to the events of late. I am glad to see it is held in such high regard by those who fly it and work on it. Our operator had not had any incidents as I believe they have excellent maintenance procedures.

We have received very little in the way of information as to what the problems actually are with the gearbox issues which only serves to enhance the fear of flying as a passenger in one.

[Lonewolf_50]

HC, I am amazed at your attitude regarding aircraft maintenance. Perhaps what you are saying is not how you actully go about your day to day business.

I doubt you would expect other pilots to be intimate with all their company's engineering processes so I don't understand why you think I should be?
Maybe it was my military training, but I suggest to you that if you don't become personally familiar with what is behind keeping your bird in the air, you are setting yourself up to make some incorrect decisions on taking a bird up, or keeping one flying, or not keeping one flying. (This goes particularly for helicopters, who have more moving parts than fixed wing).

Professional pilot: not only do you need to know your aircraft inside and out, you need to know how it works, and what makes it work.


So I am getting the picture now, the centralised fleet monitoring is all about spares / PBH / increasing component lives. Nothing wrong with that of course -it's a good thing - but also nothing to do with safety.

Nonsense. Chaging or fixing parts before they fail, and hence before they fail In Flight, has a bit to do with Flight Safety. Do you understand?

I mention this in part to me not being the only person who feels this way.

The US Army (operators of the world's largest helicopter fleet) is currently spending millions on a program to improve their Condition Based Maintenance posture. Their intent is to better ensure that parts that are not wearing out (or otherwise showing signs of impending failure) are left on wing and parts that do show those signs are removed in a timely fashion. It has everything to do with a combined set of factors: readiness, cost, and safety. They are all bound together.

Geoffers.
We have to remember that when HUMS was 'invented' the designers said it would take 10 years to gather enough data to understand what the HUMS is telling the end-user. That would appear to be an underestimate on two counts.
Amen, Deacon.
Wouldn't it be great if you could implant vibe-sensors into the gear wheels and read the output directly. I wonder if any of the electronics boffins are working on such ideas.
As I understand it, yes. But one still has to collect data and know what info aides a decision, and what is noise.
The problems caused by harmonics in a structure with so many rotating components are horrendous and trying to second guess the failure mode is a kind of self defeating process given that identifying a failure mode means that you have put your finger on a weakness. Best answer = remove the weakness.
Well put. The fifty pound brains are working on it, but as you point out, it's one of those multi-variable problems that does not lend itself to quick, easy solutions.

Another note on HUMS in real life. (I hope we can all agree that HUMS, in its current form, is NOT a silver bullet by any means).

The US Navy has a number of HUMS-like programs for its helicopter fleet. The operators still run into the problem of identifying and rejecting false positives. It's an ongoing battle no matter who you are, in terms of fleet operation, maintenance, and management.

As Geoffers points out, it's a field with ample opportunity for improvement and development. It is my belief that in due course, HUMS programs and diagnostics will improve and make rotary wing ops both safer and more cost effective.

Tying this post back to the ditching event, the impression being left in some minds, if carelessly presented, might be that HUMS is an ironclad sort of system that allows for no fault or simple go/no go decisions.

That message should be squelched when found.

[HeliComparator]

Nonsense. Chaging or fixing parts before they fail, and hence before they fail In Flight, has a bit to do with Flight Safety. Do you understand?

Of course, however in this case it is being used to increase component lives in order to decrease costs, not to improve safety. In fact reducing safety margins. Do you understand?

abzoilworker, I suppose I can't be surprised about your comments regarding the offshore workforce's confidence in the 225, but suffice it to say that all helicopters have their problem areas and, although the 225 is in the spotlight at the moment, the problem will be resolved. I agree that the lack of clear information leads to crewroom / canteen gossip which usually causes a downward spiral of confidence and the catastrophisation of the situation. That is just human nature, regardless of whether there is sound science behind it.

[Geoffersincornwall]

You wil I'm sure be aware that component lives are given a notional life extension of 10% to allow for the scheduling of maintenance in line with operational requirements. It was envisaged that one would plan to have the component changed as close to the published life as possible and in the UK I believe we were required to base our planning on that strategy.

In other parts of the globe it is common practice to base the DOCs of the component lives plus the 10%. These operators PLANNED to use the life extension as a matter of course.

Now compare that with a military philosophy of keeping the hardware in tip top condition. Why do the military behave this way? Because they know darn well that when the bullets start to fly the maintenance schedule goes out the window and you do what you can when you can and it pays to be ahead of he game when the war starts.

The commercial world is another kind of war but the enemy is Chapter 11. If you can't pay the bills you go down. Those that play the game are those the have been around the longest and have learned the hard way not to cut corners or waste money. They are also aware of the false econmoy associated with cutting corners on maintenance but I doubt that even these guys would be changing a component early because it was looking a bit worn. They might run a surveillance programme on it but if it is going to last the course then they will make it last the course. To be sure to do that you need engineers that know what they are doing - that's another story. Maybe HUMS can be a useful tool in that quality engineer's toolbox but as you say, it's not the be all and end all.

A few years ago I was auditing in the Americas and found a pair of engineers dismembering a C20 (splitting the modules) on a grubby hangar floor. No approvals and no special tools. A Chief engineer had just been disciplined for splitting a pair of u/s 332L1 MGBs and swapping gearwheels in order to make one serviceable unit. Once again no approvals and no special tools. This is what we are up against. Why? Well in my opinion out of sight out of mind. If the person authorising the use of a machine to carry his employees to and fro actually had to fly his wife and kids in them once a week to prove his faith in the choice he has made then maybe things would be different and he would pay the going rate for a PROPER service.

Grrrrrrr.

G. :{

[riff_raff]

.......Of course, however in this case it (CBM) is being used to increase component lives in order to decrease costs, not to improve safety. In fact reducing safety margins.....HeliComparator- You are correct about why CBM was adopted. It allowed components like bearings & gears to remain in service until they gave an indication of the onset of failure, which saves O&M costs. Gears and bearings are designed with very conservative fatigue margins, and in fact current industry practice is to design gears for unlimited fatigue life in tooth bending at 100% torque.

Quite often, due to the statistical nature of fatigue life calculations, gears and bearings may also last 2 or 3 times their predicted fatigue life for surface durability. Gear and bearing surface fatigue failures tend to be fairly benign in nature and are easy to detect with magnetic chip detectors long before they become a serious problem. With regards to false indications, the early types of magnetic chip detectors tended to produce false indications quite often due to nuisance debris in the lubricant. But the new generation of chip detectors have fuzz suppression circuitry and are much more reliable.

[OneManBand]

AbzOilWorker,

Our operator had not had any incidents as I believe they have excellent maintenance procedures.

We have received very little in the way of information as to what the problems actually are with the gearbox issues which only serves to enhance the fear of flying as a passenger in one.

Just to be clear as you're right - information is key:

1) All three operators (at ABZ) have excellent maintenance procedures in accordance with the manufacturers specifications and approved by the CAA.

2) All three operators employ HUMS, analyse the data and refer back to the manufacturer on discovery of any issues.

3) All three operators share an equal risk of having "an incident" - lady luck seems to cast her wand at will. Just because an operator has not had a "recent" incident does not mean they're not going to have one.

4) The ditching of G-REDW in May was caused by a failure in the the MGB module (and subsequent failure of EMLUB) - this is a sealed unit that comes from the manufacturer - NOTHING to do with maintenance procedures. Lady luck deemed that it should be in a red helicopter. HUMS had detected a rising trend - the MANUFACTURER dictated a "close monitor".

4) After the ditching of G-REDW, BOND began a program of communication to customers and workforce - this was well accepted widely.

5) The ditching of G-CHCN in May was caused by a failure in the the MGB module (and subsequent failure of EMLUB) - Lady luck deemed that this time it should be in a red/white/blue helicopter

5) After the ditching of G-CHCN, CHC put out information regarding the incident and what is being done to mitigate risk - I suggest you ask your company reps / OIMs etc to request similar of Bristow if you feel that you're not being given sufficient information.

6) Eurocopter have provided an area of their website for you to track the incidents and what they're doing about it: EC225 (http://www.eurocopter.com/Aberdeen/)

7) None of the three operators would willfully shortcut maintenance procedures - this would be commercial suicide.

8) All three operators cite "satefy is our primary concern" - of course it is - see #7

9) No pilot will take an aircraft if they have concerns over it's integrity - our desire to get home is far greater than your desire to get to work - trust me.


Having worked for 2 out of the 3, I speak from experience and have intentionally avoided praising one / slating another. Please, let us stick to the facts and avoid finger pointing. I would be very careful about "thinking" that one operator is better / worse than another.

The manufacturer is currently working to identify the problem, rectify it and ultimately rebuild confidence in it's product.

Once this is achieved I shall have no qualms about flying the 225 again, although I must confess to wanting some convincing arguments that the problem truly is rectificed rather than a guess at some affected serial / part numbers with a cursory limit on flying hours based upon how long it has taken previous modules to fail.

The problems to be resolved are simply: prevent another MGB shaft failure; and, providing an EMLUB system that is fit for purpose.

Just remember, if the guy up front is happy to take the aircraft, then you should be happy to get on board.

The commercial fixed wing world suffers maintenance / failure issues similarly yet we all take flights to go on holiday, don't have the chance to, or the inclination to question the pilots, maintenance procedures and credibility of the operator.

The North Sea is a unique environment in that respect, and that should give you some comfort.

OMB

[Pittsextra]

The manufacturer is currently working to identify the problem, rectify it and ultimately rebuild confidence in it's product.

Once this is achieved I shall have no qualms about flying the 225 again, although I must confess to wanting some convincing arguments that the problem truly is rectificed rather than a guess at some affected serial / part numbers with a cursory limit on flying hours based upon how long it has taken previous modules to fail.


OMB - and what metric will you use to assess EC's indentification of the problem and its rectification?

There is no way the gearbox in its current state (meaning current design, material spec and production venue) can have been tested properly because in the words of Eurocopter themselves:-

"Eurocopter is able to confirm that the latest analyses have validated various similarities between the two controlled ditchings in the North Sea, which took place in May and October of this year."

i.e. it is beyond coincidence or to use your words "lady luck".

These seems to be a creeping view that HUMS can be used as a safety net for flakey engineering.

[jimf671]

Quote of the Week

... - our desire to get home is far greater than your desire to get to work - trust me.

[OneManBand]

What metric will I use ? Gut feeling - what else can I use ? I am merely a pilot - people with far bigger brains will put the case forward, I will then assess whether I have confidence in the product.

Whether it has been tested properly is not for me to assess. I have to have confidence in the aircraft I fly, and the training I'm given, otherwise I should change career.

I didn't state that the failures were beyond coincidence ... I was merely making the point that it was bad luck for Bond and CHC to have faulty MGBs - it could EASILY have been in a Bristow machine and I wanted AbzOilWorker to understand that it was NOTHING to do with maintenance procedures, and to think that AbzOilWorker is immune from an incident because of the operator that takes them to work would be an incorrect assumption.

I trust your comment regarding "flakey engineering" is directed towards the manufacturer, albeit an unfair comment. I look forward to the day when a product is designed that never has a fault - hindsight is a wonderful tool. Your comment implies that the design process contained an element of "it shouldn't fail, but who cares, we'll try it anyway and not test too thoroughly in case it doesn't pass". What is important is that lessons are learned from these events and the product improved. What more can we expect ?

The offshore workers have a habit of stirring themselves into a flap due to a lack of understanding / information / fear of the unknown. This is certainly not their fault, however, comments that suggest an operators maintenance procedures may be "sub standard" have a detrimental effect on their confidence and (wrongly) sews the seed that an operator may be less than professional.

I, like my peers in the offshore world, eagerly await a satisfactory resolution to the current issues, however a witch hunt helps no one. Lets stay professional and comment from a position of knowledge.

OMB

[Pittsextra]

OMB don’tget me wrong I’m not having a pop at you, the term “lady luck” was merely paraphrase.

I hear you re: gut feel but standalone that risks you becoming an EC test pilot and the pax ballast.

Totallyagree could have happened to anyone (operator wise) and the criticism is squarely aimed at EC. Since May (whichis six months ago btw) tell me how you see the actions that have been taken?

As I callit there has been a punt on part/serial numbers and a (in my view) overreliance on monitoring alarms, which is not and has not been a reliable indicator in predicting failure in Eurocopter products.

In fact itgets worse because now we’ve had a failure in the emergency system such that EASA requires a review of its design.

The comments are not unprofessional nor a witch hunt, but frankly its amateur hour at EC.


Edit: font all gone wrong!!

[HeliComparator]

OMB - as you say, trying to pick on an individual operator as having better or worse maintenance procedures than another is dangerous ground, however overall competancy aside, in the 3 accident reports (interim in the case of the CHC one) there were specific areas where the operator had fallen short of the best practice used by other operators. There is no point in denying that as it makes your credibility seem wanting to observers such as our passengers.

In the case of the L2, the epicyclic was not checked as it should have been following the chip. In the case of the CHC 225, whilst everyone else was reviewing HUMS data prior to despatch (not because it was mandatory, but because it was best practice) CHC didn't and the ditching resulted.

Even in the case of the May ditching, I am told (although this is of course hearsay) that we would have had a look at the oil pump area by dropping the sump prior to despatch.

Therefore whilst overall maintanance standards are generally the same, it only takes one error or sub-optimal practice to allow a preventable accident to occur.

Contributory to these accidents was not "bad luck" but some specific maintenance standard issues, even though in general the companies concerned have good standards.

Edited to say that I would of course agree that the main problem lies with EC's shaft, not the operators. However it is the operators' job to catch EC's mistakes before they become an accident.

[OneManBand]

Pitts - thanks, none taken.

HC - Curious to know how "dropping the sump" would have identified an impending fratcure in a sealed MGB module that had a HUMS trend but was not producing metal ? Do Bristow not "close monitor" but simply change any MGB that has a HUMS issue ? Or maybe the engineers sign out a "hindsight tool" from stores to help identify problems ?

[Camper Van Basten]

Dropping the sump would give internal access to the 'sealed unit' and allow a visual inspection to be carried out on the shaft concerned. I believe Bristow have been doing this, but I'm not sure about other operators. I am sure it would have been done if it had been a requirement, which it wasn't. So HC is correct about that. Maybe Bristow should re-launch their 225 fleet if they and their passengers are so confident in their own ability to detect these defects?

Whether checking Hums before despatch would have prevented the CHC ditching is debatable, it's far more likely the accelerometer would have been checked and the component would have been put on a close monitor, and that certainly wouldn't have prevented the ditching. I am, of course, speculating about that.

The root problem however remains the shaft in question, and why it is suddenly failing on a regular basis after years of trouble free motoring. I have a feeling there is still much more to come out about that.

[DOUBLE BOGEY]

ABZ OIL WORKER - PM me and I may be able to restore at least some confidence that the EC225 is a superb flying machine (albiet with a small problem that will get fixed).

DB

[DOUBLE BOGEY]

OMB - Congratulations on your excellant post to ABZ OIL WORKER. I hope he benefits from the wise words you have written.

DB

[Lonewolf_50]

Geoffers, life limited components in my experience were typically afforded the 10%, depending ... Some parts yes, some no, some with an engineering authorization. (As in actual engineers doing engineering analysis, not "engineers" as "people who repair aircraft" in Brit aviation parlance).

Getting extensions was a bit of an art, depending upon one's aircraft. With the T-700, for example, the Navy started going away from "life" removals and basically "flew to failure" of certain sub components. Brain hazy on details, but I recall the four module/section design being a nice way to make that a practical strategy.

Cheers.

HC:

Of course, however in this case it is being used to increase component lives in order to decrease costs, not to improve safety. In fact reducing safety margins. Do you understand?

I don't think you understand, yet. You are making some assertions and assumptions that I don't think you can support.

As I am not familiar enough with blueprints and particulars of each part on the EC helicopters in question, I'll not defend a particular decision. The criticisms of the maintenance on this particular aircraft loss are of interest to me. My previous point to you was not limited to this mishap. Try not to bait and switch like that, will you?
I tend to agree more with Campen, however.
The root problem however remains the shaft in question, and why it is suddenly failing on a regular basis after years of trouble free motoring. I have a feeling there is still much more to come out about that.

Remember: you can reduce cost without reducing any safety margins if your data tell you that the part remains sound. (Mind you, in service data sometimes give you the opposite result, and life/change cycles shorten, rather than lengthen).

It makes no sense to change a part that is working unless you have a good reason to believe that it will soon not work/perform as needed. The criticism in this case appears to be that there was some reason to believe a given part was in that zone. That doesn't change what HUMS can do, though as I noted above, it is hardly a silver bullet as things stand now.

The belief of the long term benefit of HUMS lives and dies on data, and on detailed anlaysis. Neither data nor analysis come free, nor quickly, nor easily.

Remainder edited, as it was pointless sniping. :oh:

[HeliComparator]

CvB

Bristow is pretty confident that had the CHC aircraft been operated by us, it would not have been despatched. Don't forget that the Maint Manual procs and the general profile of the relevant HUMS parameters had been changed/raised since the May ditching and there is surely no way that any operator who was up to speed with events (which we all are) would simply have put it on close monitoring.

However it is one thing to say that in that particular circumstance the problem would have been identified in time, quite another to say that it would always be. Therefore whilst there remains uncertainty about the exact cause, we will not be operating the aircraft offshore (even if we were allowed to).

[Fareastdriver]

basically "flew to failure" of certain sub components

Fully aware of that practice.

The Sikorsky S76 had its hydraulic pumps lifed as 'on condition'. I had one fail about 60 miles out of Aberdeen. The weather was lousy and I had to go around from an ILS at Aberdeen and proceed IFR to Kinloss on one hydraulic pump knowing that the S76 will not fly without it. It was No 2 so the undercarriage blowdown covered their newly concreted ramp with hydraulic fliud. They were not happy.

The quill shaft had sheared. The other pump I was flying on had 600 hours more than the one that had failed.

[Lonewolf_50]

The quill shaft had sheared. The other pump I was flying on had 600 hours more than the one that had failed.

The qestion this raises to me was "what were the criteria for inspection the pump (and its piece parts)" to determine the "condition" of the pump.
(PS, is the quill shaft that which drives the pump from the transmission, or is it something else? )

(Aren't you glad there were 2? :ok: )

Looks like we are in a bit of thread drift, I'll stop there, even though "shaft failure" looks to be a common theme.

[Oldlae]

Fed.The CAA didn't like both hyd pumps OC, at their request I reviewed all of the Bristow data concerning pump failures and recommended that they had a TBO of 2400 hrs which was taken up. We had a few problems with the ground rigs contaminating the hyd fluid which didn't help.

[Pittsextra]

Bristow is pretty confident that had the CHC aircraft been operated by us, it would not have been despatched. Don't forget that the Maint Manual procs and the general profile of the relevant HUMS parameters had been changed/raised since the May ditching and there is surely no way that any operator who was up to speed with events (which we all are) would simply have put it on close monitoring.

HC - its a big claim and without wishing to get bogged down in the could have, would have, should have... it absolutely highlights the lack of clarity and direction from EC with HUMS. Had you got that there would be no question of any operator handling the situation any differently.

Given what had happened in May it isn't good enough to just direct operators to take a close look at certain part numbers and monitor more closely.

[Colibri49]

Whatever the other operators of EC225s may or may not have done prior to and subsequent to the May 2012 ditching, it remains a fact that Bristow always kept to an "iron" discipline of downloading the HUMS after every flight since the first EC225 in Aberdeen, even when rotors running.

Flight operations are not allowed to continue until our engineers have pronounced their satisfaction with the results of the download. Many's the time that I've been told to shut the aircraft down due to amber warnings of various gearbox and engine aspects, until the engineers have completed a more in-depth inspection.

How much of a difference this might have made to preventing the May and October ditchings, I'm not qualified to say. How good the HUMS is in detecting potential oil pump failures, I'm also not qualified to say.

You can now attack me and tell me that Bristow Helicopters is no better than the rest. I'm not going to get drawn into such nonsensical and pointless altercations. I just happen to enjoy the regime of safety which Bristow imposes and if other pilots from other operators are happy too, so much the better.

[Pittsextra]

Whatever the other operators of EC225s may or may not have done prior to and subsequent to the May 2012 ditching, it remains a fact that Bristow always kept to an "iron" discipline of downloading the HUMS after every flight since the first EC225 in Aberdeen, even when rotors running.

Flight operations are not allowed to continue until our engineers have pronounced their satisfaction with the results of the download. Many's the time that I've been told to shut the aircraft down due to amber warnings of various gearbox and engine aspects, until the engineers have completed a more in-depth inspection.



That sounds all very sensible and one would therefore invite comment as to why 1) EC do not advocate such a process for all and 2) why its not adopted as industry standard

You can now attack me and tell me that Bristow Helicopters is no better than the rest. I'm not going to get drawn into such nonsensical and pointless altercations. I just happen to enjoy the regime of safety which Bristow imposes and if other pilots from other operators are happy too, so much the better.

Why would anyone attack you??? We're not 12 year olds at school....!

[HeliComparator]

That sounds all very sensible and one would therefore invite comment as to why 1) EC do not advocate such a process for all and 2) why its not adopted as industry standard


Good question, but not confined to EC. HUMS is only required at all in EASA-land, and that only due to UK CAA pressure to get their AD for HUMS adopted by EASA against significant resistance (OK it has maybe now been adopoted by others such as CASA, not sure about that). OEMs have historically, and still do to a certain extent, regard HUMS as a bit of a pain since it can result in unscheduled component replacement.

As far as I am aware none of the OEMs require HUMS download on every return to base, and the legislation is a political compromise, requiring HUMS download only every 25 hrs.

Of course many of the turnrounds conducted at base are rotors running. On the L2, rotors running HUMS download is not possible. That was to be carried over to the EC225 and it was only when Bristow, as the launch oil and gas customer, made a big fuss and demanded the ability to rotors run download, and paid for it, did it become available on the EC225.

So in answer to your question, yes the download of HUMS on every return to base should be mandated by the OEM and by industry standard. That it is not is a sad reflection of just how seriously it is taken by the politicians and accountants! Although it has to be said that a conscientious operator should be doing it anyway, regardless of its legal obligations.

[Pittsextra]

HC - I don't doubt any of it... although strange isn't it.

Wonder how many shafts they going to have to save to get back the price of one complete EC225.. and that is CHC. The industry has lost more, Eurocopter much much more, and all for saving a few hours in tech.

Doesn't anyone ever stick their hand up and say, this is stupid? Clearly not.

[detgnome]

I just happen to enjoy the regime of safety which Bristow imposes

So in helicopter deathmatch, which one would win in 'Tiger' Vs 'Hangar Door'?:}

[Aucky]

Any thoughts on what impact this will have on the new EC175? Loss of brand confidence? or perhaps boost in sales as people choose it as an alternative to the 225? On thing for sure is that EC will hopefully be paying special attention to preventing anything similarly embarrassing happening to their new product whether through extra stress testing of MGB's, avoiding manufacturing processes that might be cutting corners now speculated as possible contributors, or a change in the thoroughness of their testing regime (EMLUB). Hopefully some good can be forced out of this B*lls up.

[HeliComparator]

So in helicopter deathmatch, which one would win in 'Tiger' Vs 'Hangar Door'?

There's only one way to find out.... FIGHT!

Or to put it another way, Hangar door defo.

See, if we were not so obsessed with safety we would have just flown it, but as it is, we have had to buy some more rolls of blade tape to patch it up...

[cyclic]

When the remanufactured shaft is brought online, I definitely think it a good idea that safety obsessed Bristow and HC do all the test flying, somewhere between 300 and 2000hrs should be fine - ta.

[Pittsextra]

I wonder if the helicopter safety steering group that meet today have grasped the concept that if you are collecting data to monitor a situation its only of any use if its downloaded and looked at.....

Although according to this:-

http://www.oilc.org/hssg_may_newsletter_-_g-red.pdf

Eurocopter issued specific instructions to analyse data after every return to the hanger, not exceeding 5 flight hours. Yet G-CHCN's data from the first 2 sectors of that day covered 3hours and 50mins of flight and yet it was on a 3rd flight due to cover 226 miles. So how was that ever going have had its data looked at every 5 hours??

[Lonewolf_50]

Pitts, again not being intimately familiar with particulars on this airframe, does the notice establish clear "Go-No Go" criteria?

Can it?

[HeliComparator]

Pitts, I think the chronology was such that the notice you refer to was issued shortly after the ditching, and it was some time later that EC decided that the problem only affected a limited number of shafts, thenceforth the statement about HUMS downloads / durations ceased to apply to non-affected shafts. Of course, as we now know, this was a mistake!

[Dry wretched thunder]

Puma helicopter model involved in ditching 'grounded until February' | Aberdeen & North | News | STV (http://news.stv.tv/north/200742-model-of-helicopter-involved-in-october-ditching-grounded-until-february/)

This is on STVs website today, nothing we dont know but its now been published by them with interview

The model of Super Puma helicopter which was forced to ditch into the North Sea last month is not expected to fly again until February.

A problem in the aircraft's gearbox caused the CHC-owned helicopter to ditch while carrying an oil crew from Aberdeen to a rig 86 miles north-west of Shetland when it ditched at around 3.30pm on October 22.

The 17 passengers and two crew were taken off their liferaft by a rescue craft launched from the Nord Nightingale vessel, which was close to the scene.

A report by the Air Accidents Investigation Branch (AAIB) found that a problem with the main gearbox lubrication system caused the pilots to take action.

Manufacturers Eurocopter said safety is its number one priority and the company apologised for the disruption caused to the oil industry.

The latest ditching, which involved and EC225 Super Puma, was the fourth serious helicopter incident in three years.

In May, all 14 passengers and crew members on a Super Puma helicopter were rescued after it ditched about 30 miles off the coast of Aberdeen. It was on a scheduled flight from Aberdeen Airport to a platform in the North Sea.

On April 1 2009, 16 people died when a Super Puma plunged into the sea off the Aberdeenshire coast. The gearbox of the Bond-operated helicopter failed while returning from the BP Miller platform.

The tragedy happened about six weeks after another Bond Super Puma with 18 people on board ditched in the North Sea as it approached a production platform owned by BP. Everyone survived the incident.

[HeliComparator]

With Lutz turning up to face the flack in Abz, I suppose they must be taking it fairly seriously.

[Pittsextra]

Lone/HC - look at the data.

The helicopter steering newsletter is dated May 2012 in response to G-REDW. You can read it for yourself on the newsletter but it says effectively (and I assume it mirrors advice from the EC service bulletin 45-001??) that EC225 data needs to be downloaded on return to the hanger and in any event not more than 5 hours flight time.

So when G-CHCN shunts on a 200+nm flight having already flown 3hours and 50 minutes how was that ever going to have been done?

[Pittsextra]

Lone :- not being intimately familiar with particulars on this airframe, does the notice establish clear "Go-No Go" criteria?

I believe it does. The newsletter of May 2012 specifically talks of the new thresholds (which would be the RED threshold alarms introduced after G-REDW). It says if these are pinged then you need to contact EC to get clarity to enable the flight.

In the AAIB report of the CHC October crash the data that was available had someone plugged in is very clear that at least a call to EC would have had to have been made.

[PlasticCabDriver]

Pitts, CHC were not doing it because the requirement to download at least every 5 hours was only applicable to those aircraft fitted with the 'suspect' shafts. None of those aircraft remained at Aberdeen, so there was no requirement under AD 2012-0115E to continue such monitoring. Bristow and Bond elected to continue with downloading after every flight, CHC appear to have reverted to the old regime, which still remained in accordance with EC's maintenance regulations. Had CHC continued with downloading after every flight then it is almost certain that the incident would not have happened, but they were not required to do so, as the inital problem that beset G-REDW problem had been fixed......

[Pittsextra]

So aside from a punt at part numbers what analysis had been done to validate that this was the root of the problem that led to AD 2012-0115E?

[PlasticCabDriver]

A very good question. One that EC needs to answer.

[JimL]

Here is an extract from AD 2012-0225-E. It appears to answer the questions from your last and previous posts (I think! Your questions are less than precise).

In May 2012, an EC 225 LP helicopter carried out an emergency ditching in the North Sea after warning indication of MGB loss of oil pressure and subsequent additional red alarm on the MGB emergency lubrication system.

A full circumferential crack of the lower vertical shaft of the MGB bevel gear occurred in the area where the two sections of the shaft are welded together. As a result, the vertical shaft ceased to drive the main and backup oil pumps, leading to warning indications of the loss of the MGB main and standby oil lubrication systems. The crew activated the MGB emergency lubrication system and, following a subsequent warning indicating failure of that system, performed a controlled ditching into the sea.

Results from the investigation of the failed shaft revealed that the crack had initiated from an oxidation pit found in the chamfer of the vertical shaft welding stop hole. This bore hole is fitted with a plastic plug under which the corrosion became trapped into a confined area of the hole chamfer whose shape had been previously modified by a production change in the manufacturing process of the MGB bevel gear. A thorough review of the production files identified the S/Ns of vertical shafts manufactured after the production change as a batch of potentially affected parts.

Although the corroded vertical shaft failed after a low number of accumulated flight hours, the investigation showed that failure could not be precluded at any specific value of accumulated flight hours, therefore the crack could have initiated at low MGB torque levels. This is the reason why AS 332 models might be affected in the same way as EC 225 helicopters.

The investigation also determined that, prior to the flight during which the helicopter ditched, the Vibration Health Monitoring (VHM) system installed on the helicopter had identified a rising trend in certain monitoring parameters associated with the MGB oil pump drive system.

To address the unsafe condition of MGB bevel gear vertical shaft failure, EASA issued Emergency AD 2012-0115-E, which superseded previously issued EASA AD 2012-0107, EASA AD 2012-0104 and EASA Emergency AD 2012-0087-E.

EASA AD 2012-0115-E applied to all AS 332 and EC 225 helicopters equipped with potentially affected shafts, identified by S/N. The AD required for those helicopters, when equipped with a serviceable VHM system and flying over water in either Instrument Meteorological Conditions (IMC) or at night, to download and review some VHM data at different intervals, depending on helicopters models. For helicopters without VHM, or with an unserviceable VHM system, the AD imposed a restriction, to limit flight over water operation to day visual flight rules (Day VFR) only.

Since that AD was issued, a report was received following the ditching in the North Sea of another EC 225 LP helicopter. The helicopter ditched under the same warning circumstances as it occurred for the instance in May 2012, i.e. indication of MGB loss of oil pressure and subsequent red alarm on the MGB emergency lubrication system activated by the crew.

The affected helicopter was equipped with a MGB bevel gear vertical shaft with a S/N outside the identified batch of potentially affected parts and was therefore not subject to the VHM monitoring required by EASA AD 2012-0115-E. While the investigation is still at an early stage, the cause of this new ditching seems to result from the failure of that vertical shaft. Additionally, the analysis of the data recorded by the VHM system of the helicopter, prior to the flight during which it ditched, also showed some VHM rising trends.

For the reasons described above and pending further results from the investigation, this new AD retains the requirements of AD 2012-0115E, which is superseded, extends its Applicability to all vertical shafts, regardless of S/N, reduces the time intervals for downloading and reviewing the VHM data and requires this for any flight over water. Furthermore, for helicopters without a VHM system installed, and helicopters with an unserviceable VHM, this AD prohibits flight over water.

[terminus mos]

The HUMS on G-CHCN gave 4.5 hours of increased vibration signature before the ditching.

[HeliComparator]

It's interesting (depressing!) how thoughtless and parochial these ADs have been. Because the events happened over water, it is over water flight that has been targeted. But would you rather have to ditch on a nice day in N Sea, or be faced with a Land Immedately when flying IMC over mountainous terrain with cloud on the surface? Oh, that seems to be OK according to the AD!

[JimL]

HC,

I find it completely unsurprising that such decisions are made; one only has to examine the structure of EASA to see that there is no Operations Division or Operational Policy unit - as there are in other Authorities.

The decisions made in this AD are analogous to those that were made in the ARRIEL 2 AD - which excluded twin-engine helicopters from the requirement to implement TU166.

Jim

[Pittsextra]

You are right Jim the AD 2012-0115E that was in effect at the time would have excluded G-CHCN.

However what data or analysis was done to to allow the formation of that directive?

If there is a sound body of engineering work then that would be fair enough but if it exists then it isn't in the public domain. Even if it was discussed between the operators it seems extremely odd that 2 (of 3 or the majority) have decided to monitor more closely than the AD. Which suggests the formation of 2012-115E is flakey.

If the logic was flawed then how and what is or should be taken as correct for the future?

[mark one eyeball]

When I was flying the Super Puma in the 80's we didnt have the HUMS gizmo
We relied purely chip detectors.
If the gearbox was suspect it was probably replaced, this happened on a regular basis, on average...pulling a gearbox once a month!

Now this gizmo lets gearboxes go for a much longer time, this is a bit scary because I dont think it is that good at detecting a major fault.
Its not that intelligent, trend analysis or what?
OK for jet engines but not ok for helicopter gearboxes

There seems to me to be a major design flaw.
History will prove this fact.

I know this is not comforting info but I just want to view my feelings about this particular helicopter from my own experience of flying it.

I want to fly with confidence, I never felt confident with this particular helicopter.

Who remembers the first Super Puma to be written off at ABZ G-TIGD yes a flaw that was known in the Puma but forgotten in the Super Puma

Hums is a weak secondary back up, what is needed is a sound design that everyone feels safe with.

[Rigging Pin]

HUMS is a nice tool if you know how to use it.
I don't think all operators train their staff as well as they could do...

In a ideal world items would be strong enough to last but that probably means items will be more expensive and since the safety culture is also based on a risk to money ratio this will never happen:cool:.

RP

[HeliComparator]

M O E

TIGD was of course a tail rotor drive fairing that came open and hit the tail rotor on short finals, there were some injuries but none fatal.

Sorry but you haven't got it right. Chip detection is still just as important as it was in the 80s. Chip detectors are useful for defects when debris is released - eg bearing surfaces degrading etc. But what it was no good at was detecting a crack where no debris was released.

That is the point of HUMS, it can in some cases detect a non-debris-releasing fault before catastrophy. There is certainly no suggestion of continuing to operate a gearbox that is generating debris on the chip detector, just because HUMS says it is OK.

The two techniques are complementary.

There were a lot of debris-releasing faults in the early days of the 332L back in the early 80s, but these were fixed by changes in operational procedure, design and materials, not by the addition of HUMS.

If you are not happy flying this type of helicopter, nobody is forcing you to do it and I suggest you get a different job, or one flying a helicopter that cannot possibly suffer any mechanical problem. Good luck with that!

In truth I'm afraid I read your post as an uninformed gripe against the Super Puma family, trying to "stir it" based on incorrect speculation. You are of course entitled to publicy air your opinion even if incorrect, but it would be better for the industry and the passengers if you desisted.

[Pittsextra]

With respect HC I don't think that is fair.

Just look at the situation that exists around the EC225 right now.

You have EASA airworthiness directives (as recently as August 2012) relating to issues from the accident of G-REDU in Feb 2009.

You have what seems a total mess with the latest issues from REDW and CHCN where you find 3 operators, 2 aviation authorities, a manufacturer, an accident investigation branch and a helicopter safety working group unable to co-ordinate properly which leads to a situation where the CAA and EASA have differing airworthness for the same type.

I mean WTF!?!

[mark one eyeball]

Yes you are right HC
It has a history of design faults and they are still working on how to fix it

[HeliComparator]

It has a history of design faults and they are still working on how to fix it


...as does every other helicopter that ever existed or will exist.

[Fareastdriver]

I want to fly with confidence, I never felt confident with this particular helicopter.

On the other hand I flew 330s and 332 L(1)s from 1971 until 2009 and I never had a moment of concern. I took part in the first trials in 1972 where we intensively flew aircraft so as to prove extensions to the gearbox's life from 800 hrs to 2,400.
The RAF bolted down the inclined shaft hinge pin in 1972. When I joined Bristow I suggested that they do the same thing to their 330Js. I wasn't listeded to because I was a crab but luckily one migrated about six inches out about a week later so they did it. Super Puma comes along, same system. Doogal (RIP) and myself protested. 'This isn't a Puma. this is a Super Puma'. The rest is history.
Neither of the two aircarft that ditched this year ditched because of the geabox mechanical fault. They ditched because the EMLUB warning system failed, otherwise they would have proceeded with their 30 mins clearance and made landfall.

[helicrazi]

made landfall???

really... and on what hard evidence are you going to back that statement? i would love to see where the evidence is that this shaft would have lasted 30 mins having already fractured!!!! :ugh:

[onesquaremetre]

Neither of the two aircarft that ditched this year ditched because of the geabox mechanical fault. They ditched because the EMLUB warning system failed, otherwise they would have proceeded with their 30 mins clearance and made landfall.

The first one had a chip too remember ie multiple indications of something not very nice happening. Why wait for the noise/smoke/vibration?

[I-IIII]

In my small opinion...........those heli has a big insurance at the back......and when the FM say land immediately I will do immediatelyI don't care if is thrue or false and I don't care to wait for see what happen:ugh:

[abzoilworker]

many thanks for your replies to my posts gents. It was not my intention to slate any one of the operators maintenance procedures or finger point. I have absolutely no doubt that they are all of an exceptional standard. After the tragic incident with the bond machine, we were given a tour around their facility and shown how they go about maintenance procedures etc. I was astounded at the attention to detail that goes into aircraft maintenance. It was very reassuring to see this. If only we carried out maintenance like that offshore!

I also take great comfort in the fact that the guys who fly these machines would not be doing so if they believed for one moment that they were unsafe. a point was made about gossip and rumours offshore regarding helicopters, that point couldn't be closer to the truth. the amount of rumours etc and some of the attitudes of members of offshore staff only enhances these rumours.

It would be usefull for us if the operators sent some information as to what was happening as it is found out. although I am sure there are probably legal implications in doing so.

[Colibri49]

Helicrazi.......Made landfall!!!

Absolutely no doubt that the emlube was working in both May and October ditchings and if it hadn't given the pilots a false warning of having failed, they would have been able to continue flight at 80 knots for 30 minutes. Land was within reach in both events, I believe.

How many times does it need to be repeated that the fractured shaft which drives both oil pumps has nothing at all to do with the emlube system which is situated outside the gearbox and has no shaft driving it, ever ? !!!

I have been flying EC225s for over 3000 hours and I'd appreciate that before anyone makes "knee-jerk" comments about this superb helicopter, they should first check their facts.

[Lonewolf_50]

Neither of the two aircarft that ditched this year ditched because of the geabox mechanical fault. They ditched because the EMLUB warning system failed, otherwise they would have proceeded with their 30 mins clearance and made landfall.

FED

Since I am not all that familiar with this aircraft, I ask for understanding:

Am I correct in understanding that the emergency lubrication didn't begin to provide lube (i.e. provide lube to the gearbox when the normal lube failed due to the shaft no longer driving the pumps)
or
that the emergency system (as described by Colibri above) was actually providing the back up lube, but the warning sytem told the pilots a different story.

No, you aren't getting any more lube, emergency or otherwise

hence no choice but to ditch?

My understanding is that "no lube was happening from the emergency lube" but I may be confusing myself or not reading your remarks properly.

[helicrazi]

i dont see how you can conclude that after that fracture the gearbox would withstand another 30 mins, regardless of your 80kts speed, EASA stated it may not be torque related, so flying at 80 kts and low torque seems irrelevant?

i do not doubt that emlube system was working, infract i believe it was working effectively, its the fracture that worries me about the whole integrity

[Bravo73]

Neither of the two aircarft that ditched this year ditched because of the geabox mechanical fault. They ditched because the EMLUB warning system failed, otherwise they would have proceeded with their 30 mins clearance and made landfall.

The aircraft ditched due to a catastrophic failure of a major MGB component, the main shaft.

The indication that the EMLUB system failed was probably their saving grace. Who knows what the outcome would have been if they had continued flight for 30 minutes with the broken part of the shaft thrashing around.

[helicrazi]

Bravo73 :D

Colibri - take note :ugh:

[Colibri49]

No ! You take note. The bevel shaft which drives the two oil pumps is right at the bottom of the main gearbox and it is welded to the bottom of the main shaft.

When it fractured each time at the 360 degree weld, the shaft simply dropped into the sump, so that the bevel gear was no longer engaged with the two pumps.

No other components of the gearbox were, or could have been mechanically affected, except by lack of lubrication. Everything else in the gearbox just carried on working normally and all that was needed was glycol from the external emlube system to keep critical components cool.

This glycol was found in both affected gearboxes after stripping down and no damage was found on any other components. They are isolated from any possible contact with the fractured bevel gear shaft.

[helicrazi]

Ok, you direct me to any publication that states that no other damage was found and i may stand corrected?

otherwise, how do you know that the shaft wasnt tested in its true weight before it was sheared and after it has sheared it is not going to throw all the balances out? personally, i would be ditching as i dont think 'landfall' would ever arrive...

[bigglesbutler]

Am I correct in understanding that the emergency lubrication didn't begin to provide lube (i.e. provide lube to the gearbox when the normal lube failed due to the shaft no longer driving the pumps)
or
that the emergency system (as described by Colibri above) was actually providing the back up lube, but the warning sytem told the pilots a different story.

Your understanding is incorrect, the second comment is correct. The details are in the AAIB bulletin, I shall try and find it, Colibri49 is spot on as that is what I have read also.

That is the cause for the ditching, it is an entirely different discussion of whether if the Emlube didn't give a false indication whether the gearbox would have carried on regardless.
Si

[bigglesbutler]

It's in an EC bulletin (Safety information notice No. 2520-S-00)available to people who fly their products through the TIPI service and the text is:

It has been established that all parts of the emergency lubrication system operated within their specifications.
During examination, glycol was found throughout the gearbox casing and on all the gears and bearings, which
remained in excellent condition.
This evidence indicates that the emergency lubrication system had activated and remained operational for the
duration of the flight. Therefore, the warning of system failure indicated to the flight crew was a false alarm and resulted in the crew making the decision to perform an immediate landing, as required by the Flight Manual.

Regarding the second ditching of an EC225 in October 2012:
An emergency lubrication warning light came on and resulted in the crew making the decision to perform a
controlled ditching, as required by the Flight Manual. The Main Gearbox has arrived at EUROCOPTER‘s
Marignane facility in order to launch a deeper investigation. As already indicated in the AAIB Special Bulletin
S6/2012, the initial visual examination has identified a 360° circumferential crack on the bevel gear vertical
shaft, in the vicinity of the weld that joins two sections of the shaft.
Additionally, the initial examinations performed in EUROCOPTER under the supervision of the AAIB have
shown that glycol was found throughout the gearbox casing and on all the gears and bearings. There appears to
be no visual evidence of heat distress or damage to any of the other components in the MGB, which seems to
indicate that the EMLUB system had operated.

So helicrazi are you standing in a corrected stance?

I'm off to bed, g'night.

Si

[helicrazi]

Yes I am big enough and ugly enough to admit I stand corrected, that report states the rest of the gear box was in excellent condition, however, that was after a few minutes, I'm waiting to see if 30 mins would have the same outcome...

[Colibri49]

I'll leave my good colleague Biggles (Oh! I see that he's replied already) to continue our battle to gain your understanding, but I'll also reiterate something which seems to escape the attention of many.

There are two separate faults to be sorted out by EC, but neither one directly affects the other until the unthinkable and unpredictable events of May and October (perhaps slightly more predictable after May).

The external emlube system works just fine, except that a pressure switch (or switches) is probably set at the wrong value and tells the pilots falsely that the emlube system has failed.

The cracks which allowed the bevel shafts to drop off the bottom of the main shafts in both ditching scenarios have never manifested themselves before in over 4 million flying hours using the same shaft design.

Something got changed relating to factors affecting the shaft in the last 18 months or so and when the shafts failed, this exposed the latent problem in the pressure switches of the external emlube.

Two separate problems ! Both must be sorted out to everyone's satisfaction before the EC225 resumes normal operations.

[helicrazi]

Ok for my understanding, hopefully a simple yes/no answer:

If both oil pumps failed for a different reason, let's say 'sods law' and the shaft is in perfect working order, I am assuming the emlube would have been actived and functioning correctly as before, in this scenario would we have had the 'fail' indication? Or is the fail indiaction purely a symptom of the shaft failure?

[Colibri49]

"If both oil pumps failed for a different reason, let's say 'sods law' and the shaft is in perfect working order, I am assuming the emlube would have been actived and functioning correctly as before, in this scenario would we have had the 'fail' indication? Or is the fail indiaction purely a symptom of the shaft failure?"

My dear Sir. I'm struggling to answer your two questions with one word.

But to your "in this scenario would we have had the 'fail' indication?" my answer is "Yes" because the pressure switches are still faulty.

To your "is the fail indiaction purely a symptom of the shaft failure?" my answer is "No" because the shaft driving the pumps is inside the gearbox and has no connection with the external emlube system.

[AnFI]

these are factors which are not correctly taken into account in the bogus calculations which support the twin engined philosophy .... AND ditching is not dangerous enough to risk the dangers of dodgy gearboxes which can be fatal..

[tonkaplonka]

Helicrazy, the answer is no. As discussed the Emlube is a seperate system. There are 2 sensors on the emlube system. One for glycol pressure and one for p2.4 engine bleed air pressure. It was the p2.4 engine bleed air sensor that threw up the fail emlube caption. This system is in place for total loss of oil, not just loss of pressure due to pump failure. It is an add on and accounts for the mass of extra plumbing around the outside of the MGB. Hope this helps.

[PlasticCabDriver]

Helicrazi, the fail indication is simply that Emlube system has decided that it is not working correctly. It has nothing to do with the shaft, they are completely separate systems. In the event of indications of Total Loss of Oil Pressure, the Emlube is activated by the crew using a switch in the cockpit. If it works correctly, there will be no fail indication until the Glycol starts to run out about 30 minutes later. As far as the Emlube system is concerned, it does not matter what caused the loss of oil pressure, whether this is because ( as in these 2 cases) the shaft failed, or you may have a catastrophic oil leak, or 'Sods law' may have happened as you mentioned below.

However, your point about the balance of the MGB running without the big lump of metal welded to the bottom of the main shaft is, I think, important, and something EC needs to address in their testing.

[Sanus]

I think this may be the first time any Authority (in this case EASA), has predicated the safety of a helicopter based only on HUMS indications. There is no other inspection, visual or otherwise, required.

Does this mean that HUMS has finally come of age?

I know the oil companies and CAA have disregarded the AD but EASA are happy to let the 225 fly if HUMS is closely monitored. This is a big step forward.

[Colibri49]

"However, your point about the balance of the MGB running without the big lump of metal welded to the bottom of the main shaft is, I think, important, and something EC needs to address in their testing."

If you look inside an actual gearbox at the relative size and mass of the main rotor shaft versus the bevel oil pump drive shaft, you will see that the analogy of "elephant vs mouse" would be apposite.

Furthermore, once the bevel shaft has dropped off the main shaft, there is no possibility of an imbalance arising, because the two shafts were centred on the same vertical axis before parting company.

It's about the same relationship in terms of vibrational consequences, as if a hub-cap dropped off your car wheel along the road. You wouldn't even notice it!

[terminus mos]

The shaft failures are just the final symptom. The root cause is more likely something else which changed in the last 18-24 months.

The nitrided steel shaft in question has 250,000 hours of flight time prior to May 2012 with no problems. EC is no longer looking at the shaft itself as being the root cause.

[Pittsextra]

What is the 250k hours stat from? Its certainly not total hours from a fleet leader. In fact the gearbox that failed in October and May were very low hours.

In May the engineering analysis of G-REDW show that the broken components triggered the chip detectors in the sump I believe - which means bits of metal frag was in the oil.. That isn't good but for the fact the pumps aren't working so it goes nowhere unless of course you can suggest fragments travelled before the pumps fail totally (after all they got to the chip detectors).

Beyond that in the case of G-CHCN the HUMS data shows that the Red alarm threshold had been exceeded. So regardless of one pilot suggesting the vibration is insignificant it's significant enough to produce a red alarm.

The 30 min emergency lube is of course a safety net - but not in all circumstances. Given EC225 MGB issues since 2009 you would be almost crazy to continue flying for 30 mins knowing you had a MGB issue when you could have quickly ditched in flat sea alongside a ship. When bits of gearbox fire themselves out of the casing or you loose the main rotor parts being lubricated is irrelevant.

It is also wrong to say it's flown for millions of hours on the same design until 18 months ago. Were that the case you would find the fix to be simple.

This is a big mess - it's been poorly handled with very few on the same page. The worse situation is that there is conflicts between what best practice is and as we speak even EASA and the CAA can't agree how to deal with the EC225.

Seems EC have 'boxes on rigs and a helicopter about to start testing.

[Fareastdriver]

It is also wrong to say it's flown for millions of hours on the same design until 18 months ago. Were that the case you would find the fix to be simple.


I think it is. They have to revert to the old welding system that has proved successful over millions of hours. This means that they have to wait until the welds have aged before being put into service; about three months, plus any certification.
All the bulletens are doing is trying to salvage some essential work out of the aircraft before that happens.

[Colibri49]

What is the 250k hours stat from? Its certainly not total hours from a fleet leader. In fact the gearbox that failed in October and May were very low hours.

Whoever stated that, presumably was taking a guess at the combined total hours of EC225 flying in the last approx 7years.

In May the engineering analysis of G-REDW show that the broken components triggered the chip detectors in the sump I believe - which means bits of metal frag was in the oil.. That isn't good but for the fact the pumps aren't working so it goes nowhere unless of course you can suggest fragments travelled before the pumps fail totally (after all they got to the chip detectors).

It might be possible that in the May ditching, the broken shaft could have fallen against the single chip detector in the sump and damaged it. As regards "bits of metal frag", when a weld breaks there arent any to speak of; perhaps minute particles which couldn't significantly damage other components.

Beyond that in the case of G-CHCN the HUMS data shows that the Red alarm threshold had been exceeded. So regardless of one pilot suggesting the vibration is insignificant it's significant enough to produce a red alarm.

The increased vibration thresholds to produce an amber or a red alarm are also minute, in order to give early warning of failure.

The 30 min emergency lube is of course a safety net - but not in all circumstances. Given EC225 MGB issues since 2009 you would be almost crazy to continue flying for 30 mins knowing you had a MGB issue when you could have quickly ditched in flat sea alongside a ship. When bits of gearbox fire themselves out of the casing or you loose the main rotor parts being lubricated is irrelevant.

Agreed completely. Calm sea and ship in sight which I've spoken to, or land half an hour away? It's a no-brainer.

It is also wrong to say it's flown for millions of hours on the same design until 18 months ago. Were that the case you would find the fix to be simple.

That's not exactly what was meant. There's no suggestion been made that the shaft design was changed 18 or more months ago.

The current lines of investigation by EC include any possible changes affecting the whole gearbox, which could affect the shaft adversely. One thought is that mods to the engine management system in the last 18 months or so, could have changed torque and vibration characteristics detrimentally for the pump drive bevel shaft.

[Pittsextra]

Change of material spec, change of process it is all change of design to some degree - just depends how you use the word.

Any change untested is very silly and I think had I got my feet wet in G-REDW or G-CHC I'd be with my lawyer seeking damages as it's unforgivable to put onto service something untested.

As an aside since when did we start using total fleet hours as a benchmark for fitness for purpose?? 250k hours could just mean 1 million things lasting 15mins as much as 1 thing lasting 250k hours.. To exaggerate the point.

[Sevarg]

As an retired engineer I see 2 problems here, the main one being that the emerg lub system can't be tested on start up. The emerg lub system in the S61 took oil from a low point in the sump of the gear box, this low point was was part of a new sump that was part of the mod, I forget the amount of oil in it that could not be drawn on by the normal pump. The point is that it could be tested before flight. The 225 system can't as it uses glycol. To my mind the best fix (after fixing the shaft) would be to have a lub system that uses the same oil as the MGB so it can be tested.
The secondly the shaft hours might not be the same as the MGB. Some components, in the MGB, have longer ultimate hour than the MGB overhaul life. So the main shaft might be on it's second trip after O/H. I don't have a MM so I don't know the hours the shaft can do and though the MGB hours are said to be low nothing says the shaft is.

[terminus mos]

Pitts

Of course the fleet leader has not got 250k hours.....more like 10k hours! Its 250k fleet hours....

Pitts and Colibri

The 250k hours was quoted by EC in a customer briefing yesterday, their figures not mine. EC is not looking at the shaft or any changes between AS332L and EC225 from Carburised to Nitrided steel as being the primary cause of these failures.....there is something else happening, they think.

[HeliComparator]

Sevarg, people like to hark back to the S61 as if it were wonderful (and in truth it was not bad, in fact very good for its age!). On that old lady, the Emerg lube system as you say was an electric pump using oil from a low point in the sump. It is therefore similar in concept to the standby pump on the Super Puma family, the only difference being the method of pump drive. Of course with hindsight having 2 completely separate types of drive (mechanical and electric) seems a good thing. However neither of these systems meets the need for continued flight following complete loss of oil, the S61 would not be compliant with the current rules in this respect.

This is where the 225 Emerg lube comes in. Since you have to consider the worst location of the leak, it really has to be a total loss system. In order to keep the total fluid required down to a reasonable amount, EC decided to use it sprayed with a lot of air, hence the need for less than 12 litres to last over 30 mins and I suspect ordinary oil wouldn't atomise or do the same cooling trick as the glycol.

Otherwise, I quite agree with you that the system's downfall is the inability to excercise the valves and pump, or test the switches, prior to flight. The only trouble is that the more stuff you add to allow test, eg a means of pressuring the system without putting glycol into the gbx, the more complexity you add and therefore reduce the reliability. On the other hand, we are starting from a place of pretty low reliability!

All that said, the ability to fly 40 miles still air is not the be all and end all, I would rather not have it but have a MGB that didn't suffer from bits breaking off!

[JimL]

Plus the S61 emergency lube only fed the high speed input shaft white metal bearings.

Jim

[HeliComparator]

On the subject of 225 emlube, the problem seemed to be insuffient air pressure to activate the switch even with everything in-spec.

I just wonder if the group who designed the emlube system didn't talk to the MGB designers and so didn't realise that the crew would already have reduced to Vy and so didn't realise the engine would be running slowly hence low P2.4 air pressure.

An expeditious crew, faced with sudden double pump failure, would turn the IAS down to 80kts then the next action is to press the SHOT button to activate the emlube. 225 decel rate is 2kts/sec these days I think, so 150 to 80 is 35 secs plus a bit at each end, so after at the point where EMLUBE failure is being detected the engines are likely to be down around 20% total torque. I wonder if the EMLUBE failure is latched (once its on it stays on regardless) or momentary (would go out if pressure switches activate again.

Maybe the answer is to operate Training Idle switch #2 to get eng 1 working harder. I can just see that going into RFM section 3!

[Pittsextra]

Terminus - they not looking at the shaft material anymore but of course that was the first idea!

What amazes me is the relaxed attitude to spec changes with little idea of the testing regime. You know if we (couple pilots from here say) set up a passenger transport biz with some EC225's and decided we would change drive shafts for our own design/spec or re-mapped the motor - whatever - then lost a couple due to failure we would be destroyed in all ways possible and rightly so.

Here the CEO makes a field trip to spin the PR and charm and puts out completely misleading and meaningless stats (like 250k hours). Lets see what the root of this issue is and how tested it was. I suspect the truth will be alarming.

[victor papa]

Are you sure everything is misleading and just PR? If the CEO didn't go himself you probably would have demanded that he does face the music as EC CEO directly but now that he did it is a farce!? 2 post 2009 shafts cracked inflight and there were 2 ditchings! The material/processes were changed in 2009 but then also there were performance changes on the engines it seems in 2010! Harmonics with so many rotating components is a huge problem(again i am not in this game but just take the FLM on the 350's excl b3 ensuring that no time is spent between 285-315 rpm I think due possible harmonics)! Did they test any 2 of the possibilities so far?-I do not know but neither do you so dont just assume because it is EC they did not!

I am amazed by some of the unknowns in aviation everyday despite the enormous costs and involvement of certification and safety institutions and regulatory institutions! If you were involved on the 350 you would have had a field day with the B3e situation, yet the factory machine has flown a lot of hours without any showing of any possible failure whilst some delivered machines have problems at 20hrs!

Just amazes me as said before that we are refurring to older machines as reliable and should be preferred, but those were the days we complained about engine performance and power! So my question remains: Did we reach a point were engine technology has superseded airframe structure and dynamic ability/technology because we have 3 new generation twin heavy aircraft with excellent performance yet they all 3 have either MGB/structure issues or both and we have a ultra reliable single with TR issues(and dont go off at EC cause we have all been threw the 407 issues a while back so definately not limited to 1 manufacturer).

[cyclic]

The 225 out of Aberdeen at MTOW with no wind and just above average temperatures on a clear area departure has to be treated with respect for fear of much bonging. Watch all three companies as they sink back towards the tarmac on rotation. It feels like an aircraft that is being pushed hard.

The majority of ABZ departures are at MTOW, could this be part of the reason we have seen the failures first on the North Sea?

[HeliComparator]

I think the power to weight ratio of the 225 and 332L are about the same at max wt, of course the difference is that the 225 has a vastly greater disposable load so spends more time lighter.

Despite what you say, unless carrying 19 one is rarely within say 100kg of MTOM and often well below it. I think percentage-wise the 225 flies lighter than the 332L on average (ie % of MTOM). However as you say, it feels heavy at MTOM.

Some people make life difficult by opting for Vtoss = 80. Personally I never go for that because it is a struggle to maintain the prescribed accelerative attitude whilst climbing slightly, within the Tq limit, when approaching 70kts. Better to go for indicated Vtoss + 5 to 10 or so, which never seems to be more than 60.

[rotor-rooter]

Victor Papa, what are the AS350B3e issues you mention?

[terminus mos]

Victor Papa

The material/processes were changed in 2009 but then also there were performance changes on the engines it seems in 2010!

There were some Fadec changes and EC is currently examining the effect of Version 12 Fadec software which was released in response to the 14 Hz vibration to slightly lower the Nr.

[victor papa]

Tks terminus mos, that is very interesting the possible effect of even a small rotor rpm change?

rotor-rooter, the B3e is limited to 100kts VNE due to the Paulstra bearings failing on the TR blade. They are also subject to a 3hr inspection of the 4 laminated(Paulstra) bearings. I believe ECF is starting in Dec to retrofit the load compensator back onto the tail servo and remove the additional flyweights of the TR blade chinese weights. Before we have a EC attack again the factory machine flying all possible conditions apparently has shown no signs of this. Secondly, the load compensator was replaced by the fly weights in order to assist the pilot aerodynamically with RH pedal incase of hydraulic failure I believe whereas the load compensator does it hydraulically trapping fluid over itself and the accumualtor IF YOU LEAVE THE "ACCU/HYD TEST" SWITCH ALONE ON THE CONSOLE. So it seems the purpose was to eliminate human error due using the "test switch" on the console instead of HYD ON/OFF on the collective incase of a hydraulic failure. I thought it was brilliant when I first saw it and received training on it-in hindsight it is not!

Following both incidences on these 2 well known aircraft with interest as all can learn a enormous amount I believe.

[Pittsextra]

Victor P - of course I don't think everything out of EC is PR but it most certainly is when you roll out a CEO who then quoted meaningless marketing type numbers (which the 250k hours stat is). No doubt he continued with lines such as how committed everyone at EC is to safety, how they have full commitment and confidence that all problems will be resolved.. Etc etc blah blah.

It's a CEO what else can he say? It is nothing more than grandstanding so someone can then make a press release saying how serious EC takes this because they sent a lot of men in suits. Kind of patronising really wouldn't you say?

Rather than trot out the 250k hours why not say how many hours they tested these new nitrided shafts or new engine maps or how many hours a fleet leader has done with all the latest updates?

The point which is easy to miss is that the passengers dont care about helicopters or the latest map that someone down loads etc to them an EC225 is like a bus that takes them to work.

My point is that all this fiddling with specs is dangerous because testing will be in simulation and static rigs in the main and sadly it's not good enough. The limitations with new types stem in my belief in manufacturers trying to evolve old designs to increase profit margins - which is fine until it isn't. At some point you can't keep putting patches on things.

The question I'd like to know the answer to is what spec is a 2012 EC225 and in that latest format how many flying hours had the fleet leader prior to the May accident.

[victor papa]

Pittsextra, what does it really matter how many hours the fleet leader has got or the fleet for that matter? Think a figure of 10 000hrs was mentioned for the fleet leader? Should the question you want a answer to not be how many gearboxes has been threw their first or second overhaul instead of airframe hours? What is the TBO on the 225 MGB? Normally it is in the range of 3000hrs and if that is the case the fleet leader at 10 000hrs will be on her 4th gearbox? Is there even a relation between MGB hours and airframe hours as they get overhauled and shipped in most cases to different airframes? How many hours does the leading MGB have should be the question? Where there any signs of failure or possible failure prematurely during the overhauls or repairs if applicable? Where these MGB's brand new or have they been repaired or overhauled? Is their a similiarity in the MGB hours on the 2 that failed even if not between the airframes?

Just asking as a 10 000hr machine can have a incicent on a brand new MGB thus the airframe hours not the benchmark but the MGB hours?

[Sevarg]

V.P. It's might not even be the MGB Hours. In the Maint Manual (MM) is the Component Overhaul Table (COT) which shows the O/H life of each component (which is subject to a life) of the MGB, plus the rest of the aircraft. The main shaft might well have a longer life than the O/H life of the MGB. On some helicopters this is the case but without having the 225 MM to hand I don't know.
So until the life of the main shaft is known the airframe hrs and MGB hrs mean very little.

[victor papa]

Agree with you fully and that was the point I tried to make. On the smaller EC's we have Time Between Overhaul, Operating Time Limit and then Service Life Limit which when reached the component gets replaced regardless(typical example is the starflex). The TBO of a MGB can be 3000hr but the first SLL can be as high as 9000hrs so unless there is a premature failure the MGB will get overhauled twice before the first replacement on the 3rd OH. If most of the critical components have a SLL of say 9000hrs it could mean that a 10000hr MGB has newer components than a 2000hr MGB which has not even reached OH. I also do not have the specific limits for the 225 so do not know what the relationship is which is why I asked Pittsextra what is the real meaning of the airframe hours or fleet hours. Of real interest will be where these MGB's and their components were in their cycles and indeed whether both MGB's had exactly the same part numbers of different components fitted and/or mod status vs other MGB's in the cycle that have not failed?

There are much more to investigate than the shafts that cracked due to the why did they crack if one takes into consideration all the possibilities of hrs, component hrs, component mod status etc

[DOUBLE BOGEY]

PITTSEXTRA - your comments re the EC CEO are way off mark as is your assumption that EC are NOT committed to safety. The fact that the CEO turned up should demonstrate to you just how committed he is to chasing this complex problem down, and it is complex. If it was not it would have been solved by now.

[Pittsextra]

Crikey Double Bogey when I wrote in my last post :-

of course I don't think everything out of EC is PR but it most certainly is when you roll out a CEO who then quoted meaningless marketing type numbers (which the 250k hours stat is). No doubt he continued with lines such as how committed everyone at EC is to safety, how they have full commitment and confidence that all problems will be resolved.. Etc etc blah blah.


You just proved my point.....

I don't care for EC one way or the other, I have no axe to grind but this is what we find.

Helicopter G-REDW ditches 10th May. On the 18th May you get EASA AD 2012-0087E with a suggestion of a manufacturing defect. You then get updates and revised EASA notices such that on 28th June you get AD 2012-0115E which says (to be brief) that crack initiation could occur at lower MGB torque levels than appreciated..... then obviously we get the accident of G-CHCN and suddenly all bets are off regarding a certain batch of shafts and now its looking like the EC225 is out of action until at least Feb 2013 - why because they don't seem to fully understand the issues.

Now forgive me but how does that summary suggest EC have even a good grasp of what they have?

Even 2 of the 3 operators, prior to the October ditching, were running a tighter HUMS download schedule that EC recommended because they were clearly unconfident in the situation at that time. The latest bitter pill is the effective grounding of the craft by the CAA, who have a different take than EASA..

The CEO is lucky to be in his post although maybe after Bristow's move to Sikorsky perhaps that could change and also depending on legal after shocks because there is no doubt the claims will come after this shambles.

Victor - Why do I bang on about a in flight testing and a fleet leader ? because as you can see running things up on a test rig doesn't gain a true picture of the components in normal operation. If it did these drive shafts wouldn't have broken and you wouldn't have this because it would have been sorted from the beginning:-

There were some Fadec changes and EC is currently examining the effect of Version 12 Fadec software which was released in response to the 14 Hz vibration to slightly lower the Nr.

It is cynical but when a CEO starts quoting data like 250K hours its just meaningless, especially since we seem to have new drives shafts and a version 12 (twelve!) Fadec software... I can read this off EC website:-

The EC225 has evolved from the vast experience accumulated by some 100 Super Puma operators; some 900 helicopters have been ordered in 52 countries. The in-service Super Puma fleet has logged more than 4,4-million hours and the fleet leader has flown 39,300 hours.

Oh really 39300 hours? and how many in the spec of the ones that ditched?

[Oldlae]

In the seventies Lycoming had a problem with the T53 turbine nozzle guide vane unit. The original manufacturer had gone out of business so they had someone else make them from the drawings, as I understand it these new ones used to crack and it took some time to sort out.
My point is that why did ECF change the welding technique after so many hours without failure of the shaft. Also, the shaft is said to have failed in the area of the weld, normally any weld is said to be stronger than the original, which indicates, to me, a failure other than the weld failing.

[wobblybob]

Might be a little late for this but here is a photgraph of a sectioned AS332 MGB on a stand - training aid. You can see one of the pumps at the bottom also sectioned.

http://i1308.photobucket.com/albums/s612/Wobblybob57/MGBInternal01.jpg

[Lonewolf_50]

Thank you to Biggles and Colibri for clearing up my misunderstanding.

Also, the last two pages have a lot of good meat. Very glad to have kept following this thread, a great deal of useful analysis and food for thought.

The emergency lube system foibles are an eye opener.

[HeliComparator]

and a version 12 (twelve!) Fadec software...

Don't forget that the very first civilian aircraft were delivered with v7. There was no v8 for some reason. Then v9. V10 was a disaster due to totally inadequate testing (so I agree with your comments on testing!). We spat that one out after a couple of weeks! Then v11 which had known limits pending v12 which required some additional tail temperature probes.

So 7, 9, 11, 12 which doesn't sound so bad!

There have been some good improvements, eg with v7 &9 a double N1 sensor failure would give a FADEC freeze, after v9 a software strategy was developed to deal with that (just as well as we have had a couple of double N1 sensor failures just resulting in a GOV since!)

[Pittsextra]

HC - maybe v.8 was lost as the Chinese would never change from that had it been available!??! :)

On a serious note what is the regulation around testing "upgrades"?

[albatross]

This is meant as humour:
One thing I find amusing is that when I made the mistake of referring to a 225 as a Puma while on course I was informed, in no uncertain terms, that the 225 was NOT a Puma! Incredible new technology ect. ect. :=
Now when some "good" stats about hours safely flown are needed the 225 is suddenly a Puma.:E
I hope we can all go back to work soon!
Time for that second cup of morning coffee.

[Pittsextra]

Offically its a Puma:-

I. General

1. Type/ Variant or Model

1.1 Type AS332

1.2 Variant EC225LP

[jimf671]

Thank you very much for the MGB illustration Wobblybob. Very enlightening.

So, the pump drive is on a short and very substantial shaft (with a high natural frequency presumably). The pumps are driven from independent gears. The general pattern is that ordinary gear sets are helical/spiral except for epicyclic sets AND the pump gears.

What are the relative positions of the two pumps around the central shaft?

Where is the shaft supported (including above the spiral bevel set)?

Is a range of different lubricants specified?

What is the normal range of lubricant operating temperature?

Are the pump gears changed at the same time as the shaft?

Is there only one type of pump on EC225?

Sorry. I'm really nosey when it comes to gears.

[heli-cal]

Offically its a Puma:-

In reality, it's an ornamental Puma!

[HeliComparator]

As we all know the LP is L plus, and within the factory its often know as the Mk II plus. As in Super Puma L2 plus.

[HeliComparator]

What are the relative positions of the two pumps around the central shaft?

They are both on roughly the same side

Where is the shaft supported (including above the spiral bevel set)?

You can just about make out the machined bits where the bearings go, below and above the bevel

Is a range of different lubricants specified?

Yes, a modest range

What is the normal range of lubricant operating temperature?

Mid 80s C at max continuous power

Are the pump gears changed at the same time as the shaft?

Dunno! But shaft is lifed at 20,000 hrs I think

Is there only one type of pump on EC225?

yes, I think so ( if you mean MGB oil pump)

Sorry. I'm really nosey when it comes to gears.

[kannad405]

225 with sump removed. Standby is obviously the lower pump :ok:

http://i1300.photobucket.com/albums/ag81/kannad405/IMG_20121108_204554.jpg

[Fareastdriver]

It's a long time ago but from what I remember the 330 Puma had the single oil pump on the back of the gearbox driven by No1 accessory drive. The shaft was hollow so that with a suitable bottom plate and drag damper oil reservoir a shaft could be extended above the rotor head for optical sighting equipment etc. Your photogragh also shows the No1 engine drive disconnect system where you could run No1 engine with the main rotor stationary but with operational No1 Alt and Hyd1 and drive it around on its own powered tracked undercarriage.

The early (up to the E model) did not have an oil pressure guage so the present problems would not happen. There was just a temperature guage and a MGP(P) on the SWP. A way of checking it was to pull up to about 80 degrees nose up; this would cause all the gearbox oil to flow to the rear of the gearbox, uncover the oil pump inlet followed by the pressure light.

In 1971 the Puma's max was 6,400 Kilos. I last flew them at 9,200.

[Pablo332]

Just to clear up one point when the shaft breaks not only do you lose lubrication pumpsyou also loose the lower roller bearing that was supporting the shaft, now you are left with the ball and roller bearing on the other end. Bit like your hub cap coming of your car and taking a wheel bearing with it.

[Fareastdriver]

Pablo332.

Where did you get that theory from? If you look at the last photo you can see the structure above the oil pump gear ring (where the the cracking is) that supports the lower bearing of the rotor shaft.

[FBav]

Just for others to clerify things please see drawing
there is actualy 3 sets of bearing, one set in the bottom of shaft, one just above where the shaft cracks, and one above the epicyclic gear

http://i1340.photobucket.com/albums/o739/FBav/225-coupeBTP.jpg

[Pablo332]

It’s not a theory , it’s a fact.The shaft cracked above its lower roller bearing. If you look at the cross section it becomes obvious .

[Pablo332]

If you look at the last picture you will see a hole passing through the shaft wall the area where the shaft cracked is above that. The weld area is the next change in colour going up the shaft.

[Colibri49]

"If you look at the last picture you will see a hole passing through the shaft wall the area where the shaft cracked is above that. The weld area is the next change in colour going up the shaft."

The picture is very good, but not that good. Perspective and parallax play their parts and the best I can suggest is that you look up into an actual gearbox. Then it becomes clear that the weld and the adjacent fracture lines are below the bottom of the main rotor shaft bearing.

Here's another thought. Why would a design engineer allow a main rotor shaft to have any kind of weld between its top and bottom support bearings? That shaft in the picture is nowhere near robust enough to take much greater side loads than just the two oil pumps.

I even question why the oil pumps are next to each other, rather than on opposite sides of the driving gear, to mutually counteract sideways reactions to the torque forces driving them. (Excuse my lack of proper engineering terminology.)

[Pablo332]

Looking at wobblybobs sectioned picture you have the oil pump drive gears on the bottom of the shaft, the shaft then tapers in a little to a parallel shiney section this is the location of the lower roller bearing. If you follow the shaft up it becomes obscured by the horizontal torque shaft. Just to the right of the torque indicating gubbins where the shaft reappears is a light coloured band on the main shaft running parallel to the torque shaft, this is where the crack occurred. Shaft length reduced by about half. 1/3 of the bearings now not doing anything.

[Pablo332]

For anyone interested in the published facts on this incident http://www.stepchangeinsafety.net/about/GCHCNditchingincident.cfm (http://www.stepchangeinsafety.net/about/GCHCNditchingincident.cfm) is a goldmine of information. About halfway down the page the link to the EC ditching analysis provides some useful information, page 5 shows the location of the crack.

[kannad405]

Slightly better (?) angle of box

http://i1300.photobucket.com/albums/ag81/kannad405/IMG_20121108_204638.jpg

[Colibri49]

"Looking at wobblybobs sectioned picture you have the oil pump drive gears on the bottom of the shaft, the shaft then tapers in a little to a parallel shiney section this is the location of the lower roller bearing. If you follow the shaft up it becomes obscured by the horizontal torque shaft. Just to the right of the torque indicating gubbins where the shaft reappears is a light coloured band on the main shaft running parallel to the torque shaft, this is where the crack occurred. Shaft length reduced by about half. 1/3 of the bearings now not doing anything."


I understand why you think that the shiny parallel section is where a roller bearing sits, but it isn't so. Why it is shiny is beyond me. If you follow the sectioned picture further up the widening conical shaft, it is just possible to see the right-hand end of the welded join above the horizontal torque shaft.

"Slightly better (?) angle of box"

Unfortunately not for this particular debate, but thanks.

[Pablo332]

Nice pic unfortunately doesn’t show effected area very well.

[Pablo332]

I give up. The information is there for all to see. 3 bearings crack above lower bearing, shaft in half.

[kannad405]

I agree Pablo. Not a good situation to find yourself in if it breaks

[HeliComparator]

It definitely cracked above the bottom bearing, leaving the 2 other bearings to support the main shaft, one being just above the bevel gear (and hence taking most of the bevel gear side loads). I thikn the intention is that the bottom bearing doesn't take much except the pump gear side loads

[Colibri49]

"Just for others to clerify things please see drawing
there is actualy 3 sets of bearing, one set in the bottom of shaft, one just above where the shaft cracks, and one above the epicyclic gear"

Okay, I stand corrected. The shiny part IS for a third bearing which wasn't in place when I looked up into the bottom of a gearbox. But it seems to be there to support against side loads from the reaction to torque driving the pumps, which was bothering me so much.

Even so, when the fractures occurred and the shaft was no longer driving the pumps, there would have been the main rotor shaft bearings still doing their job and the pump drive shaft would have stopped turning.

It might not even have dropped much at all, but there would not have been a noticable imbalance to the pilots and certainly no bearings and metal chunks thrashing around to do further damage.

Well, I live and learn and many thanks to FBav for the diagram on the previous page.

Pass me another slice of humble pie, please.

[Pablo332]

Couldn’t agree more especially as the MOD45 MARMs showed a significant upwards trend at a point I can only assume was post shaft fracture, as it appeared to be towards the end of the flight.

[Pablo332]

Please study the established information. Both remaining bearings are above the bevel gear. One roller one ball. It’s now only supported at one end

[Pablo332]

Trying to make this an exchange of information is very difficult with people going back and editing there contributions. It makes the flow of information very disjointed, and in some cases unfathomable. For information only there are 2 bearings above the gear. Non of them have anything to do with the epicyclic.

[Colibri49]

Referring to FBav's diagram on page 24, and also from a Eurocopter drawing of the 360 fracture, it occurred very close to the horizontal line at the top of the conical shaft, above the hole in the conical section.

I've just removed the second paragraph because of uncertainty as to what I'm looking at, probably mistakenly identifying as bearings.

[dascanio]

Just some clarifications about some of the posts of today:

1. There is a manufacturing reason why the weld is in that place, such kind of bevel gears are finished before welding, because, with an "integral shaft", you physically can't grind the teeth (grinding wheel shall impact with the shaft)

2.If you look at the gear mesh, you see that it is above the weld, no significant torque is transferred to the bottom part of the shaft, below the weld, but "flows" to the top, to the epyciclic stage. What is reacted by the two roller bearings are the side loads of the mesh, i.e., the bending effect on shaft due to axial and radial forces of the bevel gear mesh. I will not speculate on actual stress value or margins of safety, but this is why the bottom shaft looks "thin", there is only bending stress, not bending + torque stress.

3. respect to the Main Rotor Torque, the effect of the pumps should be quite marginal (how many KWs for 2 pumps respect to the MCP...?), besides, they are driven by spur gears, that is, no axial or radial forces are introduced, so no significant side forces.

[Pablo332]

Not sure about the above below weld bit in point 2 for the pumps, probably a typo but the rest is good stuff. Keep it comming.

[Pablo332]

Just reread your post, Your quite right. (in my opinion)


(in my opinion) added as an edit.

[jimf671]

Just some clarifications about some of the posts of today:

1. There is a manufacturing reason why the weld is in that place, such kind of bevel gears are finished before welding, because, with an "integral shaft", you physically can't grind the teeth (grinding wheel shall impact with the shaft)

2.If you look at the gear mesh, you see that it is above the weld, no significant torque is transferred to the bottom part of the shaft, below the weld, but "flows" to the top, to the epyciclic stage. What is reacted by the two roller bearings are the side loads of the mesh, i.e., the bending effect on shaft due to axial and radial forces of the bevel gear mesh. I will not speculate on actual stress value or margins of safety, but this is why the bottom shaft looks "thin", there is only bending stress, not bending + torque stress.

3. respect to the Main Rotor Torque, the effect of the pumps should be quite marginal (how many KWs for 2 pumps respect to the MCP...?), besides, they are driven by spur gears, that is, no axial or radial forces are introduced, so no significant side forces.

Yes.

If we consider a point near to the weld, there is limited torque because that part of the shaft drives only the pumps. This limited torque results in a small shear stress.

The separating force of the spiral bevel (caused by the pressure angle of typically 20 degrees) is that which acts upwards and inwards from the centreline of the pinion towards the centreline of the rotor shaft above the epicyclic. This results in a moment that tries to tip the spiral bevel wheel away from the pinion. The reaction to this moment at the lower roller bearing (near the pumps) is of a similar scale to the gear separation force. However, at the weld, because it is significantly closer to the centre of the moment, the forces are higher. This results in bending stress at the point we are considering.

As the spiral bevel wheel turns, the bending stress oscillates from positive to negative. This oscillating stress component is far higher than the shear stress, or any stress due to the weight of the shaft or the reaction of the pump gears, and is the dominating stress in the area of the weld.

The splines for the epicyclic input gear are a small distance above the spiral bevel wheel. Since the spiral bevel wheel is a very substantial component and the input gear is a thin-walled component, it seems unlikely that there is any force from the driving of the epicyclic influencing the weld area.

Thin-walled shaft with holes in it subjected to oscillating bending stress. Interesting.

[riff_raff]

1. There is a manufacturing reason why the weld is in that place, such kind of bevel gears are finished before welding, because, with an "integral shaft", you physically can't grind the teeth (grinding wheel shall impact with the shaft)dascanio- I agree with your comment regarding the location of the weld. The bevel gear shaft is made in two pieces to allow milling & finish grinding of the gear teeth. In a previous post (before I saw the nice cross section drawing), I speculated that the joint was a friction weld. But since the weld appears to have been made after finishing of the bevel gear teeth, it most likely is a laser or EB weld.

Another interesting feature shown in the cross section drawing is that the oil pump drive gear is separate from the shaft. It appears to be attached with some sort of internal threaded faster and possibly a narrow curvic face coupling(?). The joint seems to be just below the lower roller bearing. There is also a separate inner bearing race clamped in place by the pump gear.

Thanks to FBav for the nice drawing. Very interesting discussion.

[bigglesbutler]

New bulletin from EC, I need someone more versed in EC documents to explain i and confirm my understanding.

Si

[Pittsextra]

Given the comments here:- EC225 (http://www.eurocopter.com/Aberdeen/20121120.html)

I'm not really sure what value add any new bulletin will give??

[Pablo332]

It would appear from the latest revision to Emergency Alert Service Bulletin 04A008 that EC share my concerns about the viability of half a shaft and a reduction in supporting bearings.


Text size edited.

[Pittsextra]

Is there any practical advice or they just communicating further concerns......

[Colibri49]

"EC share my concerns about the viability of half a shaft and a reduction in supporting bearings."

Looking at the diagram and considering that it is very unlikely that the high torque and load bearing section of a MR shaft would be designed with a welded join, I must agree with the quote from Helicomparator.


"It definitely cracked above the bottom bearing, leaving the 2 other bearings to support the main shaft, one being just above the bevel gear (and hence taking most of the bevel gear side loads). I thikn the intention is that the bottom bearing doesn't take much except the pump gear side loads"

[dascanio]

Colibrì, the power required to drive the two pumps is minimal, respect to, say, MCP,( less than 10 HP, I imagine), their contribution to the Bearings reaction is truly minor, the side force of the two spur gears being very small, respect to the balance of the bevel gear. The bottom roller bearing is there to support the Shaft, its main loading IS due to the bevel gear mesh, and the bearing is smaller than the top roller one because (like in a lever...) its load is inferior since its distance from the gear mesh is bigger.

[Pablo332]

From Emergency Alert Service Bulletin 04A009 Rev 2


In case of bevel gear failure, the top part of the bevel gear continues transmitting the power to the main
rotor, but all the meshing loads are transferred to the upper bearing.
Following the investigations conducted on the 2 bevel gears, it was found that this bearing and the meshing
part of the bevel gear were in good condition after having operated during
almost 10 minutes after failure. Supported by the calculations performed, EUROCOPTER is therefore
confident that in similar cases, the 30 flying minutes permitted by the Flight Manual after activation of the
emergency lubrication can be performed without worsening of the scenario.
Nevertheless, EUROCOPTER will launch tests to demonstrate the latter. Pending the results of these tests,
a new procedure requiring immediate landing is defined for this specific case.

The whole SB is worth a good read. Bottom line at the moment EC thinks the shaft can last 30 mins in this condition, but untill they can prove it an immediate landing is require.

[Pablo332]

I hope by now the queries on how the main gearbox is constructed with regard to the shaft and the purpose of the various bearings has been established to everybody’s satisfaction.
I would now like to move on to another aspect of the current situation.
6,4.5,X what is X
X being the time in hours between a MOD45 MARMs acquisition showing the start of a crack and the next shaft failing.
EC predict this figure to be 4.5hrs that’s why you are allowed to fly for 3 hours after a successful in limits MOD45 acquisition, this allows a 50% safety margin.
Up until yesterday the measures in place were flawed. The measures at that time allowed an aircraft that had just completed a 3hr flight with a single MOD45 acquisition at the beginning of the flight to depart on another 3 hr flight. With the times between detection and failure being 6hrs and 4.5hrs for the first 2 incidences it was possible to lose another shaft, despite MARMs monitoring.
Today we have to consider the available time for a flight is dependent on when the last MOD45 acquisition took place.
All of this is dependent on accurately predicting X.
EC predict X to be 4.5. On the 25 July after the first incident EC issued a statement saying The probability for another component to be equally affected is extremely low. We all know how that prediction went.
I hope x is 4.5

[Pittsextra]

So if Iunderstand your post Pablo you are saying that the clock starts at data downloadtime and not from the actual time of the alarm?? I take that from your comment:-



“The measuresat that time allowed an aircraft that had just completed a 3hr flight with asingle MOD45 acquisition at the beginning of the flight to depart on another 3hr flight.”



Is thatbecause there is no way to look at the whole of the data in detail - forinstance like this:-



http://us1.webpublications.com.au/static/images/articles/i1082/108255_4lo.jpg (http://us1.webpublications.com.au/static/images/articles/i1082/108255_4lo.jpg)



This is asimple example of some race car data which in this case looks like a MagnetiMarelli system. The X axis being time, theY axis displaying the range of a variety of inputs. So here you can see clearly if a thresholdwas breeched you could see exactly when that might be.



Otherwiseyou are left with a system that says during this period the threshold wasbreeched and if that is the case the safe option would be to assume it happenedat the start rather than at the end!!



Beinteresting to here how it works.

In any event the message the current bulletin gives is terrible and reliesentirely on the emergency lubrication system and a punt that the hunches arecorrect from a bunch of people who have been proved to have not that good at predictingthe future.

[Pablo332]

Pittsextra
The MARMs information is displayed on download as separate acquisitions. For an acquisitions to be made in the first place the aircraft needs to be in a stable state. If the aircraft is not within certain parameters no acquisition is taken. If you are flying to rigs with a lot of straight and level you would probably get a couple of acquisitions per hour. If you are logging or constantly training you may never get an acquisition.
You can tell from the download at what point in the flight time wise the acquisition was made.
Previous to yesterday the requirement was to check the download at the end of the flight and if the MOD45 acquisition was below the limits and no significant upward trend was noted the aircraft could go for another 3 hrs. This was reasonably fine for people who do a lot of straight and level with lots of acquisitions. However it didn’t cater for the people with a low number of acquisitions, the change is to tighten up on the foreseeable possibilities of operation.