Does the reduction in MCP "reduce" or "stop" the propagation of the cracking?

In about a half dozen posts....we have directly contradictory comments.

Am I the only one here that sees this 225 MGB problem being far more dangerous than EC is letting on?

Are we seeing Operators and EC conspiring to put the 225's back into Service without FIRST determining exactly what is causing the Failures....and THEN re-designing the MGB to ELIMINATE the problem and doing the necessary TESTING to CONFIRM/CERTIFY the CURE.....BEFORE putting the aircraft back into service?

SASless, if a crack is detected, it sounds like one needs to overhaul the box, which isn't a cheap evolution.

I'd be surprised if the operators are too keen on that as the condition for return to overwater flights.

"We'll slow the crack propogation down" may also mean the bird is left on the rig for a few days while they sort out an overhaul/shaft replacement on the rig.

So, let me get this right. 'Supposedly', Eurocopter is saying that the shaft can still crack. But if/when it does, there will be a warning in the cockpit so that the pilots can slow down a bit and then land as soon as possible.

Really?

You really think that the CAA are going to go for this? That they are going to release to service an aircraft with a know fault of a major critical component?

And even if the CAA do go for it, do you think that the various unions are going to let their members get on an aircraft with this known fault?

And what about the pilots? Do they want to fly an aircraft with a gearbox with a shaft that is prone to shearing? I know that I don't.

North Sea heli ditching: Oct 2012
 

So there is a procedure for the shaft, might it be wrong or right, who knows. What is done about the emergency lubrication system that failed as well, or at least indicated that it failed? Are there changes in the design of that system?

From AAIB Special Bulletin S2/2013 p6:

They (EC) reckon that they have fixed the problem with the EmLub system.

But it's still bit of a red herring. The EmLub is designed to work when there has been a total loss of oil (ie the case cracks). It's not going to help much when a) the gearbox is still full of oil and b) the main shaft has sheared in half and is thrashing around inside the casing, ie the situation with both REDW and CHCN.

Bravo 73 even though the MGB is still full of oil, with a shaft failure it doesn't lube the bits which need to be lubed so therefore using the Emlube will at least provide cooling of those critical items in the box so it should be of some help.

And as far as I am aware even though the shaft broke and therefore dropped down a little... it didn't trash the inside of the gearbox...
I stand to be corrected on that one though cause I haven't seen any of the gearboxes myself:E

RP

Not when the EmLub system pressurises the gearbox, hence forcing out most of the remaining oil and glycol (onto the head of the passengers sitting underneath). :{


Are you aware of the principle of how a fluid coupling works? Then imagine what would happen to the unsupported broken shaft after 30 mins of flight (the limit for the EmLub system). :eek:

I am not, I guess. What do you have in mind?

Bravo73- Your point is mostly valid. The changes to the emergency lube system do not address the bevel shaft fracture issue. However, due to the location of the weld joint and the bevel gear shaft's bearing configuration (ie. two cylindrical roller bearings and one 4-point ball bearing) it is also unlikely that any shaft "flailing" would occur from a weld joint fracture. The driven end of the bevel gear shaft would be sufficiently constrained by a single cylindrical roller bearing and the 4-point ball bearing to prevent flailing. But it would not be sufficiently constrained to prevent gross misalignment of the bevel gear/pinion mesh, which would quickly result in catastrophic structural failure of the bevel gear teeth.

There is also the fundamental issue of what caused the fracture failures in the bevel shaft weld joint. Was it a design issue? Was it a material issue? Or was it a manufacturing process control issue?

While I have not seen detailed engineering documentation of the bevel shaft components or weldment, I have seen a cross section drawing of what appeared to be the EC225 MGB. The first thing I noted was that the bevel shaft EB weld joint appeared to be a simple butt joint. In this instance, a simple butt joint shaft weld would not have any fault tolerance in the event of a weld joint fracture. I would suggest that a more fault tolerant weld joint design would be a butt weld backed-up by a lap joint. Thus, even in the event of a complete fracture in the butt weld joint, the back-up lap joint would maintain alignment of the two halves of the shaft, and would allow the bevel gear mesh to continue functioning in some capacity.

So why does this exist?


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Quote:

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shows the mark of TM that in the spirt of open debate he has deleted all of his posts. No doubt makes the PR easier if the grunts are left in the dark?

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Pitts, based on the interchange between TM and 212 man that I read yesterday, I am guessing that he may have re-assessed his posts here as "talking out of school." I think he made a decision (based on potential traceability) to return to a position of professional discretion.

People have jobs.

If they jeopardize them via a bit too much sharing on public forums, it can be costly.

I for one would not want to have goaded someone into professional "own goal" by demanding adherence to some the "spirit of open debate."

If you doubt me, you may wish to look up any number of folks in the last year or so who have run into trouble with their bosses over what they post on facebouk.

Pitts. see above and grow up!

TM indicated that he was about to withdraw from this thread for the reasons already discussed.

I thought EC said they wanted to be transparent about all of this? Isn't that what the helicopter safety group is all about, or the YouTube clips, or the new PR guy.

But sure getting someone fired etc isn't cool so take my comment as an easy cheap shot.

In the meantime...how about a view on corrosion and MCP?

Problem with emlube system solved?

Incorrect specification caused EC225 emergency lube fault

skadi

212 - FL100 near Malta in summer (ie hot) just hitting the engine limit so torque down by a couple of % ie MCP around 80% Q (though AP limiting it to around 78%) so it's hard to imagine flight conditions where you would get near to 70% Q - maybe equatorial at FL100?

Pitts, regarding the torque limits, I know its complex but do try to keep up! 70% Q now, because one needs to have a reasonable flight duration between HUMS downloads. Once the MOD 45 airborne alert is in place, no point in limiting torque until after a crack is detected. Hopefully not that often, after all we did manage nearly 100,000 hrs in the company and no cracks at all, so its not as if its going to be cracking every other flight! One needs to keep a sense of scale!

Lonewolf and Wizzard. thank you. I do not work fior EC. I do work with a company that is very affected by the EC225 issue. I would love to be able to share all I know but I probably can't.

Hmmm, any idea what happened to my post from about the 12th/13th March? It seems to have been disappeared... :suspect:

You made 4 posts on two other threads: they are still there. Nothing shows as being deleted on this thread; the last post of yours that was deleted was by you on the 8th February 2013 on another thread.

A bit early for dementia at your age ;)

Oops. You're right. My 'disappeared post' about the 225 (directed to terminal mouse) was actually in the 'Eurocopter CEO deserts the sinking ship' thread.


Doh. My bad. :O






PS How do you know how old I am? :confused: