Probability/Statistics are fraught with peril!

As noted....167 hours and 4,000 hours on something that was supposed to be safe to some astronomically figure to the 10 to the umpteenth power as I recall.

Add in the fact it happened to exactly one Operator and that really begs the imagination!

The view must be great out there where you lurk.....bit wobbly when the wind blows though I bet!

??? Why??? because prior to the MOD45 alarm you'd be oblivious anyway?

But that isn't the case now is it? Now you have the same data as you had before but available real time (effectively) so is the process for dealing with MOD45 alarm the same?

What was the protocol when you had MOD45 alarm before??

HC -

hence why I said in the post before -

and this sounds like press-on-it is

This circular Q&A is making me dizzy. Ridiculous.

Pitts, do you realize how many a/c, certified and happily flying pax every day, are out there with AD's and additional inspections to components just as critical as the 225 MGB? For instance blades (main and tailrotor), grips, shafts......

This is how it works! Every a/c ever certified and every a/c that will be certified will encounter a situation where real life differs from the computer model and things must be tweaked. We don't go back to a clean sheet design every time this happens.

It is NOT press-on-it is to follow what is written. Some crews will choose to be more cautious and that is their prerogative just as it is situational. If a corporation chooses to be additionally cautious because they work for risk averse customers, that too is their prerogative.

Land as soon as POSSIBLE, not IMMEDIATELY. Or perhaps to be interpreted as POSSIBLE with an escalation to IMMEDIATE is a better interpretation. The professionals are accustomed to dealing with these kind of decisions, THAT is why they make the big bucks, not for pushing buttons when things are going well.

Personally, I would have no qualms about riding in the back of 225 offshore today. And yes I understand the consequences as I have already rode one [helicopter] in!

I don't know why people get stressed. I've not said the 225 is going to go down in a huge fireball and sea monsters be 'ere!

Like you say / like I said recently EC have thrown the sink at this, etc, etc but my point is this. If a MOD45 alarm can be for other things beyond this issue and the previous actions for an alarm were not fly up to 2 hours then....

BBC News - Heathrow emergency: Nine passengers sue

P&A, as I mentioned earlier its actually "limit duration of flight" which is the same as "land as soon as practicable". It is not "land as soon as possible"

Pitts, as usual I don't think you quite understand what you are talking about. Let's put the shoe on the other foot and ask you what you think should happen?

SAS, no it happened to exactly two operators. And yes, the breeze is pleasant out here during such hot weather!

I stand corrected....got the Fatal One mixed up.

Well that didn't take long to get the "you're a git, know nothing, etc,etc"..

When someone asks a question I don't know how it suggest to you they know anything! I just asked what the previous action was if you got a MOD45 alarm. I hope the EC PR machine is a little more able to put the message across to people.

You know you hammer people for reading the material that actually EC themselves have put out there and then say don't ask questions and there is more information out there etc.. So what can you do!?

What would I do?

Firstly it depends which hat I had on.

If I was Eurocopter I'd wait the year until I had a proper fix in place. I'm not sure who is pushing to fly the 225 as it seems operators have coped for the last 9 months and as I said it would seem Bristow won't fly anyway until near the end of the year.

Whilst the chances are slim to none the risk is massive and if I have changed the treatment of MOD45 alarm in order to fly again then frankly it would be the end.

If I was the operator I'd wait. Take Bristow and their zero accident policy, how would they explain that to their stock holders, management, employees and customers were anything to happen.

If I was the customer I'd wait for the same reason as the operator.

If I was a passenger I'll do what my boss tells me, but I'd be asking questions like "have you changed the treatment of the MOD45 alarm..."

Whilst its a thorn and easy to call people names in the last year the company you are asking everyone to trust "this time" has had two accidents, the second after the first solution wasn't correct. You've had a problem with wiring and EMLUB was it / wasn't it working. Now the EMLUB doesn't fully work. You've had a shaft re-design that goodness knows who signed off on it as it failed after 160ish hours and yet the problems were the same for that as the prior shaft that ran almost 4000hrs. You have a HUMS system that if you look at the data in the existing AAIB reports has had threshold changes yet this is the same system that we all should believe is cock on this time and you have this constant suggestion that the Super Puma has never had an oil loss in its gearbox - despite a specific report on this type of subject written for EASA with Super Puma G-REDL inside.

What part of that is scare mongering and what part of that is fact?

Pitts, in fact you are quite right. The best thing to do, from a flight safety point of view, is to leave the aircraft in the hangar and never fly them again. That way you can be certain that a shaft will never break again, there will be no unknown MOD45 alarms and everyone is a winner!

HC .....in that case would the Company just mail me my pay check and not insist upon all those check rides and such?:ok:

MR PITTS
 

I do not think anybody called you a "Git", but it is comforting that you have at last inferred correctly!!

DB

PS as you are a PPLH maybe you can enlighten us as to which types you fly then we can see what ADs are in place for those that you routinely live with.

I think we need Pitts to come over our way and explain to our crowd why he would want to ground all 27 A380s we have - despite the known wing issues. I would not even have to guess at the response from the owners/lessors/passengers. Which ever way you slice the business, 19 from ABZ to NS or 540 from DXB to JFK, it is ALL about risk management - balancing safety against productivity. EC have made that assessment in the full glare of an EASA oversight program, risk is still present - yes, but to an acceptable level to all the stakeholder decision makers. HC, I can see why you shrug your shoulders!;)

All I asked was what did you do when you had a MOD45 alarm before... I guess its pretty complex as no one is able to answer.

When you had a MOD 45 alarm before, you were standing in the line office so you went for a cup of tea whilst the engineers went through the relevant work cards.

Thridle, a great posting. Common sense at last.

Pitts. We have never had a MOD 45 exceedance before the first shaft rupture. That was one ofthe most confusing aspects of the entire issue.

At the risk of being branded like Pitt......if no exceedence in the past....are we guaranteed a Warning this time? The AD talks plenty about what happens "after" and excellence.

SAS - it just means that there has never been degradation of the bevel gears resulting in an M'ARMS alert, which is quite reassuring since they are fairly important! The system obviously does work because the M'ARMS data viewed post the ditchings showed a rising trend and threshold exceedance some time before the shaft rupture.

The information to prevent the ditchings was available but as we know from the reports, unfortunately the data wasn't looked at and/or the thresholds weren't optimal, hence the ditchings.

DB yeah I'm sure and you know I'm sure its a very fine piece of kit with clever people involved at every step. Its very clear that there is a motivation to get the 225 flying with the interim solution and good luck to all concerned but this is an interesting situation.

You say no MOD45 exceedance but just look where the limit is now to where it was! Read it for yourself in S7/2012 AAIB and I quote:-

At the time of the first accident in May 2012, the MOD-45 and MOD-70 indicators only included amber thresholds; these were ‘learned’ thresholds each with a maximum value of 0.6

After the accident to G-REDW, Eurocopter published EC225 Service Bulletin No 45-001, in July 2012 that included the introduction of a red threshold and lowered the fleet-wide maximum threshold values for both indicators. For MOD-45 the amber alert was reduced to 0.3 and a red alert of 0.4 was introduced.

After the accident to G-CHCN, Eurocopter published an Emergency Alert Service Bulletin (ASB), on 21 November 2012, which removed the maximum amber alert threshold for MOD 45 and lowered the red alert threshold to 0.2.

I guess you guys know where it is now but crikey that's some difference!

Another interesting aspect of the in-cockpit MOD45 warning is that it is a shift in thinking for EC because after G-REDL they resisted AAIB recommendation for an in cockpit chip warning system I believe, suggesting that existing checks were sufficient.

Pitts, are you sure you aren't a Daily Mail reporter in disguise?

Firstly, you say "...its very clear that there there is motivation to get the 225 flying..." - as if that is surprising or unreasonable. Surely the point of having a helicopter is to fly it. So try not to make it sound like a bad thing!

Secondly, on the subject of the MOD45 threshold, you are correct it has been significantly reduced. However, this relates to the point in a degradation process where the alert is triggered, not whether it is triggered or not. Once degradation starts, it is a continuous and worsening situation so it won't be the case that a MOD45 warning would be received by the new threshold and not by the old one, it will just happen sooner in the process.

If you are concerned that there may be spurious MOD45 warnings, that is a more reasonable position because I think that is certainly a possibility. EC have reprocessed a lot of HUMS data and we are assured that virtually no data would have exceeded the new thresholds. Virtually none, so in fact some would! However if you look at the consequences, the pilot has to reduce power a bit and land within 2 hours, not exactly a major crisis. An operational inconvenience, not a safety hazard.

Finally on the L2, had the HUMS data been properly regarded with the proper maintenance actions occuring, the accident would have been prevented. Adding a cockpit light would have been a "belt and braces" boost to flight safety by reducing the probability of a maintenance error leading to an accident, but its requrement is not really up to EC. Had EASA thought was merited, they would have mandated it but they did not. The L2 had of course managed to operate for the best part of 20 years without it anyway.

Yes I take your point basically once it starts to trend upwards its not coming back and I guess the lower limit is more relevant when its being downloaded back at base as it needs to fly a long sector without further checks.

Timely
 

Never say never....


Heathrow: Plane Catches Fire On Runway

HC, what's the next layer below 'Daily Mail'?

Sorry PE, you are now officially on my ignore list, I have not occasioned someone more prone to exceedances of nonsense. I might concede a point if the ET 787 had the same point of failure - i.e. the Li Battery, but since the scorch mark is safely above the rear galley on the pressurised side of the rear dome I am pretty confident that the failures do not have a common source expect perhaps some escaped electrons in the wrong place. The battery is in the pointy thing at the back next to what is called the 'APU'. To provide a link which says "Plane Catches Fire On Runway" from Sky News, when the aircraft was on a remote stand only amplifies your shaky grasp of the factual. On the same scale maybe you want to prolong the 225s loitering on the ground because the TR gearbox may leak it's lubricant and seize - it's all part of the same transmission - tell you what, lets make EC redesign the entire transmission prior to RTF.

TOD you are the one drawing conclusions about whatever caused the 787 fire, my post was pretty minimal on the subject.

Whatever the cause of the fire as you can see making assumptions that you now have some Titanic of the air bites sooner or later.

If you do want to make a parallel to a fire on a 787 by another means then perhaps it might be that a MOD45 alarm is always related to the known vertical shaft issue......

TOD, surely there is nothing worse than the Daily Mail! With his penultimate post I felt there was hope, but then it was dashed! On my DNFTT list too!

As a spectator and reading the reports -

The primary common denominator in the issue seems to be corrosion.

The crack propagated from the PTFE plug.

Fatigue life is not a factor so much when you look at the disparity between the fatigue cycles. 167 hours?

MOD 45 and MOD 70 trend happened within ~ 6 hours!

It would seem to me that the corrosion issue needs to be addressed first.

The change in material, higher power, 5 blades and subsequent change in cycle fatigue etc etc are the differences from a Super Puma which doesnt have a problem.

For me there is still a way to go to a conclusion to place the thing back in service.

But surely that has been done by the internal cleaning and inspections? Only the two affected aircraft seemed to have visible corrosion, the rest of the fleet doesn't. So whilst you are right, corrosion seems to be the primary factor, there is now a process in place to ensure it doesn't develop in other aircraft.

I find the hole and the plug to be the oddest aspects of this.

If it's OK to have a hole; and I am not sure that it is; then why plug it when this can result in crevice corrosion and the plug material is a quarter of the weight and therefore brings no benefit in rotational balance.

Then there is the question of "Hot spots". Are these related to the presence of the hole? One might expect them to be.

If there is moisture that can promote corrosion, and there is a hole, then surely the hole is a potential escape route for moisture (hone and polish?). The question that then arises is where would the moisture go after that. Is that the reason for the plug?

Not simple, whatever way you look at it.

As we know, the hole is there to stress relief the end of the circumferential weld. As to the plug, good question but I think its just there to avoid excess oil escaping. The important point is to avoid containing any moisture. The inside of the shaft is ventilated elsewhere (oil for spline lubrication runs out at the bottom) and if the plug is a good fit, there is no cavity to trap moisture. That just leaves the moisture trapped in the sludge, which recurrent cleaning will eliminate.

Holes are normally used to stop the propagation of cracking. But in the Bond case, it was where the crack initiated, apparently caused by trapped moisture between the plug and the shamfer surface around the edge of the hole.

My problem is believing that the moisture had enough time to cause corrosion in the Bond gearbox after only 167 hours. Since the root causes seem to be twofold, corrosion AND residual stress, one wonders what proportion each root cause played in each shaft failure.

If EC explanations are to be believed, both failures have the same root cause(s) but originating in two separate areas of the shaft culminating in almost the same failure mode.

II - don't forget that it was 167 hrs flight time. We don't know how long it was sat on a shelf or in a heli under construction before that. Probably thousands of static hours. So lots of time for the corrosion to develop, just not very long for the consequential crack to develop!

Yes, two separate areas of the shaft and two different crack locations, but very close to each other so the net result was the same.

Good point HC. However, with crevice corrosion, I am not sure if I really have much of a problem with 167 hours. It depends on the alloy and I don't have a history with that one.

It would appear they are doing pretty much that....one component at a time!

Type of cracking
 

Guys

I am only just looking at this thread, and I note the comments on cracks and corrosion. Be aware that there are essentially two types of cracks associated with corrosion. 1: fatigue initiated by the stress concentrations caused by corrosion pitting, and 2: stress corrosion cracking (SCC) caused by the combination of a corrosive environment, a residual stress and an alloy which is susceptible to stress-corrosion.

167 hours seems far too short for fatigue, even if corrosion was extant prior to service. I would be very suspicious of SCC and this is an alloy selection issue.

Regards

Blakmax

It's the disparate flight hours (Bond = 167 CHC = 3800) and the fact that the Bond corrosion started from a hole and the CHC corrosion started from moisture trapped by sludge but both led to the same result that leaves me wondering. From day 1, these two failures have been treated as the same under the same investigation. I can't convince myself that approach was not conveniently expeditious.

On day one, they were, hence the time wasted looking for resonance issues etc. however it was eventually realised that the two events were not from the same cause, although from 2 very similar causes. The only thing I find surprising is how long it took to identify the corrosion from the wear sludge. You'd think you would extract the failed bits, wipe them clean and notice the corrosion, then check some other aircraft and find much less sludge and no corrosion, and voila!

We can all speculate all day (all year) on our pet theories (including conspiracy ones) but really we are all talking from positions of ignorance and personally I think its unlikely that AAIB, EASA and CAA would be acting as they are if the evidence wasn't convincing, and even EC must surely realise that they are in last chance saloon!

It took a while to figure out what was doing in Comets as I recall....and the 707 became the mainstay of jet passenger liners and the Comet became Nimrods or something like that.

Is that what is going on before our eyes today with the 225 and the 92?

Comet
 

No, I don't think so. The Comet killed lots, the 225 none. The comet had a fundamental airframe design issue, the 225 has a potential issue with 1 component ( I say "potential" because it only is an issue when a number of factors come together). Both the 92 and 225 had or have issues which make the passengers nervous. Ultimately when the dust has settled, the oil companies will remember they like the better range-payload of the 225 and even the passengers will like the "never bumped" aspect of the 225. Of course, the passengers will never like either the 92 or the 225 because by are both inherently uncomfortable and frightening, and take them out for 2 weeks of purgatory!

HC,
Thanks for your knowledgeable and enlightening posts :ok:. However, on those occasions when I've been SLF, I've loved the room and air conditioning, but hated the noise and air-stair door vibrations in the S92, and hated the claustrophobic cabin and lack of air conditioning in the EC225. I'm almost convinced that you're right, the EC225 is a better pilots' machine with an inherently safer and more modern design than the S92, but from a passenger perspective, the S92 wins (for now). I hope that eventually both will go on to be safe and successful, like the S61 and Super Puma eventually did in their day. The only real difference nowadays is instant opinions of others on the internet influencing the (mostly unreasoned) opinions and thinking of the herd :uhoh: