Except that the 332l has been flying with a welded shaft for over thirty years.

Of course. However in the 332L and L2, it was subjected to lower torque and consequent bending/flexing/vibrations?/whatever other manifestations of stress might exist.

The EC225 seems to have reached the limiting threshold for welding in this application.

(Edited to add this genius idea.) How about thickening and extending vertically the wall of the lower shaft, at the top where it meets the upper shaft, cutting a screw thread into both shaft sections with suitable radii to minimise stress risers and screwing the shaft sections together?

I think I'll apply to be a consultant for Eurocopter. All I'll ask is Euro 250k per annum and little perks, like a comfortable pension.

Long bolting could be worth a look but screw threads on the component mess up alignment and are not useful with gearing.

However, it is funny how the welded shaft was fine for the first 120 or so EC225 aircraft and 75,000 hrs just in the Bristow fleet.

HC,

I think you are a brave man to make such assertions. Maybe, just maybe all the Super Puma MGB issues are the symptoms of a more fundamental sickness. If so the regulatory/investigative diagnosis must be absolutely thorough. Otherwise EC will be reaching for the first aid kit when only major surgery will cure this malady. I desperately hope your feelings are based on hard fact not blind faith.

Colibri,

The day they let a pilot design a helicopter gear box is the day I stop sitting in one. Screw threads are for bottle tops, not holding shafts together.

Yes thats a puzzle... apart from the change in the countersinking of the hole -maybe they changed supplier ?

Screw threads
 

Droopystop, quote " Screw threads are for bottle tops, not holding shafts together".

Or rotor heads?

FERetd,

How many heads are screwed directly onto the shaft, ie the axis of the screw thread coincides with the drive shaft axis and the torque is transmitted throught the threads?

Droopystop, maybe they are all a symptom of fundamental sickness. Maybe the gearbox internals are made of cheese, just like the moon? Maybe a mouse got inside to eat the cheese?

On the other hand, perhaps you are just over-reacting to a very successful transmission design that has had 2 problems. One catastrophic (L2) the lack of an exact explanation for which does make me uncomfortable until I remember the 3 million flight hours that the identical design has flown without a problem, and that it probably wouldn't have happened if correct maintenance procedures had been followed. And recently, the other problem rearing its head which is non-catastrophic but we suspect the result of a design change. Hardly an indication of fundamental sickness unless you are determined to exaggerate the problem.

The S92 churning events were of similar severity to the shaft breakages, requiring an immediate landing. Ditto the vespel drive failures which required an immediate landing according to the RFM of the time. The difference is they didn't happen in UK waters and you have forgotten about them!
Clearly the gearbox is not perfect, but it is no more imperfect than any other helicopter.

Sorry HC, but you are wrong. The S92 RFM has always had a Land Immediately requirement when the MGP Oil Px is below 5 psi. A single vespel spline failure/oil pump failure did not produce an Oil Px indication below 5 psi.

Also the first churning event produced a number of (startling) indications that resulted in the crew electing to carry out a forced landing, however it was not an RFM instruction but an airmanship decision.

Correct insofar as the decision at the time was airmanship based, but actually with the smoke in the cabin the RFM did say "Land Immediately." You may recall that SAC wanted to remove that line subsequently!

Anyway, back to the 225.......

so what is being used now in place of the 225s, have the old tigers had a call up, sorry if this has been answered

Well irony of ironies you know that Italian machine that had a tail boom that kept falling off? Well guess what? It is now doing a sterling job in certain parts of the North Sea flying up to 10 hours per day taking up the slack.

Bottle tops?
 

Droopy, now you are just nitpicking.

The reason that your rotor head stays where it should is because of the friction provided between the threads of the "Jesus" nut and the main shaft. The torque is transmitted by the splines - but you knew that.

If, quote:- " screw threads are for bottle tops", try flying your helicopter without the "Jesus" nut.

Good luck!

P.S. The B747 trailing edge flap drives are of "bottle top" design - works well.

FER - listening to too many urban myths! Jesus nuts are fitted to ancient teetering-head helicopters, not to modern articulated head ones.

HC,

I genuinely hope you are right and I am over reacting. If these three incidents are the only gearbox malfunctions ever experienced by the Puma family then I certainly am and stand corrected. All I hope is that EC catch all their mice so we can sit back and know the MGB is going to work every time, all the time. And that goes for every helicopter manufacturer.

FERetd,

As you point out the thread on the Jesus nut (although big helicopters have a lot more than one) doesn't transmit torque. Colibris solution appears to have a thread that transmits torque, just like a bottle top.

VL, perhaps it was before you did your 92 course, but in 2005 before the Norsk vessel spline incident, this is what the S92 RFM said verbatim:

start quote:

MAIN GEAR BOX OIL SYSTEM FAILURE

Symptom:

MGB OIL PRES or MGB OIL HOT or MGB CHIP or ACC 1 CHIP or ACC 2 CHIP

CAUTION
The main AC generators are cooled by main gearbox oil. Loss of cooling oil may result in mechanical failure of the generators and loss of main electrical power.

Confirming:

Main gearbox oil pressure is less than 35 psi, or*
Main gearbox oil temperature is greater than 130 degrees.

Action:

1. Descend to minimum safe altitude.
2. APU - ON
3. APU GEN - ON
4. Land as soon as possible.

If the MGB OIL PRESS warning indicator also illuminates:

1. MGB OIL BYPASS switch - BYPASS

WARNING
BYPASS must be selected within 5 seconds after the warning indicator has illuminated to ensure an adequate quantity of oil remains in the gearbox. DO NOT activate BYPASS if the warning indicator is not illuminated.*

2. Land as soon as possible.

If MGB oil pressure continues to decrease or there are loud/unusual noises, unusual vibrations or progressively increasing power required to maintain flight:

3. Land immediately.

end quote

So, pressure falls below 35 psi, button is pushed, pressure continues to decrease down to a little over 5psi ("continues to decrease" being the operative words) then it is land Immediately. The mention of 5 psi was only added after this event.

HC.....could we avoid going back through another rehash of bashing the 92 and just stick to the issue at hand. The 225 MGB problems has effectively grounded the aircraft, destroyed faith amongst its passengers, and caused a hell of a disaster for the Operators and Customers.

The cause of the problem, the cure for the problem, and whether the reputation of the 225 can be salvaged....are what needs to be discussed.

We are not here to compare the 92, 225, and 139 to each other.

We are here seeking answers to the problems extant for the 225, EC, and the Operators.

I know it must be annoying to see the 92 prevail over the 225 as you certainly had a lot of "stock" in the 225 and spent a great deal of time talking down the 92 while extolling the many virtues of the 225 as you saw them then.

So....when can we expect to see some resolution of this problem with the 225 MGB? What effect has this had on the Operator's profitability? Are the Operators going to file suit against EC? What is EC's Liability here? How bad has the damage to the 225's reputation has occurred? Tell us your thoughts on those issues and leave off harping on the 92 please.

SAS, yes I agree it seems to be going off topic, but my point is that although the spotlight is on the 225/L2 at the moment, it has also been on other modern types such as the 92 in the past for events of the same severity. In part the spotlight was less bright because these events didn't happen in CAA-land.

Yes I am saddened to see the 225 taking a beating because I know just what a good aircraft it is, always accepting that all helis have their issues including this one! But those specific issues aside, it is overall a really good pilot's machine with better range/payload than the competition.

It's interesting to review the S92 EOP and see just how clunky it is compared to the Super Puma family.

Anyway, regarding your specific points yes it is bound to affect profitability in the short term. I suspect that EC's liability in law goes no further than the purchase cost, since consequential losses are always excluded in sales contracts. You wouldn't buy a new car and then sue the manufacturer if it broke down on the way to work and you lost a day's pay.

Yes it's reputation has obviously suffered but hopefully this is only a short term issue and in 5 years time it will all be forgotten, just as its competitors' major events have been.

As to resolution timeframe, I know no more than you do which is that the current thinking is February.

HC Just like the Chinook after Sumburgh?

How is the EC725's affected? Are they also grounded/limited/etc? Have they had any incidences? Just wondering as it could be interesting if they are still flying?

Original RFM Procedure
 

HC,

The procedure you quoted "verbatim" is missing three items in my copy of the original RFM approved by the FAA 9/11/04:

There were two explanatory notes following the Warning in para 1.

There were two Land Immediately paragraphs, number 3 and 4.

Perhaps there was a revision between the original and the one you quoted?

Thanks,
John

John, possibly. When I cut that out in 2005 I didn't cut anything from within the quoted area, so perhaps your bits are outside the quoted area? But if within, I would say there must have been a revision in the mean time

Sevarg, no hopefully not like the Chinooks. They died because of the fundamental design issue ie intermeshing rotors, plus a lot of deaths. The 225 has yet to kill anyone and if you are a passenger, I suspect that is the major consideration.

Odd.....the old girls are still flogging the skies around the World with fleet hours in the Millions....and a safety record as good as any other helicopter. The North Sea machines that got flogged off are still out there earning a living hauling massive loads all day long for Columbia.

You suppose if the Brits had listened to those who had operated the things for decades before the first one arrived in Blighty....things might have gone a bit differently? I should think the continuing success of the Chinook in other parts of the World and the RAF.....should confirm the validity of the design.

Some folks just have a narrow minded view of things.

SAS, OK happy to change that to "fundamental design issue ... in the eyes of pax and oil companies".

Well if the two 225 ditchings had happened in different sea states without S+R close at hand they may well have killed a lot of good folks.
I put that down to good piloting skills, adherence to check lists, and more than a little bit of luck.
I don't think that the passengers are comforted to any great extent just because of the good outcome of events in the two cases.

"In part the spotlight was less bright because these events didn't happen in CAA-land." Come on HC that's a little bit over the top don't you think! Not all of us work in CAA land and the CAA is not the be all and end all of helicopter safety.

albatross, yes the sea states were good but they have to be pretty bad before fatalities become probable rather than possible. There are certainly such days but the vast majority of days are not like that. And as I said, exactly the same applies to other type's non-catastrophic events resulting in "Land Immediately"

92 RFM
 

No, HC, they were in that section of para. 7.1 that begins with: " If the MGB OIL PRESS warning light illuminates...

The second Land immediately action, sub para 4 within the section you quoted, is the last entry in the general para. 7.1.

Thanks,
John

A quick google search on "helicopter ditching statistics":

http://ftp.rta.nato.int/public//PubF...HFM-152-05.pdf

Interesting read amongst many others.

Of course we know that are "Lies, damned lies and statistics" LOL

Interesting thread - I think we may be headed for a record number of pages.

Cheers
Albatross

albatross, as far as I can tell that doc doesn't really distinguish between intentional controlled ditching, and accidentally flying into the water. At first glance, that devalues the research in my eyes.

Albatross, I have seen this document quoted a number of times and as HC highlights, it does not limit itself to controlled ditchings in reaching the supposed survival rates. I would go so far as to say the document is dangerous, as it does not present pilots with the true risks associated with a controlled landing on water.

I have always wondered if the Captain of the Cougar aircraft, who ignored the Land Immediately situation the aircraft was in, had seen this document and these statistics were part of his decision making process?

A quick aside - HC, the S92 RFM I was referencing for my earlier response was dated November 2005, obviously an amendment after the incident you are referring to.

Good point guys.

I wonder also if those stats influenced the crew off of NFLD.

The weather/ sea state and temperature at the time was far from ideal.

I found another site in my quick search that posted some truly horrific stats which I will not quote here as they seem more scare mongering than anything else.

Like anything else on the internet the application of a little bit of salt is required.

Cheers
Albatross

Seems the 225 is doing that salt thing really well!:E

The stats do force us to consider the effect Sea State, Water Temp, Amount of natural light (Day-Night), Visibility, and response time of SAR in their effect upon Air Crew Decision making.

Ditching in the Bahamas is not the same as ditching north of Deadhorse or in the North Sea or off Newfoundland.

HC

But sadly the passengers never did like it much and now don't want to go near it. My company is being pressured to replace them with 92s, memories are short it seems. But, the 92 has been doing better recently.

terminus, there are also plenty of stories of passengers routinely using the 92 not liking it either. Let's face it, the offshore community just don't like any helicopters, and why should they when we scare them sh**less by showing them scary videos before each flight!

I suspect it is "grass is greener" but no less unfortunate for the future of the 225 at least in the short term.

Colibri49-

While EC apparently seems comfortable with EB/laser welding finished gear shafts, I know that other transmission OEMs prefer not to use this approach. The problem is that since the weld is performed after heat treatment of the gear, the metallurgical properties in the weld HAZ (heat affected zone) will remain in the as-welded condition, which is not optimum. The weld HAZ cannot be improved even with a thermal stress relief and normalization cycle.

If the reports of weld failures are true, even if EC retains the welded shaft design (with any necessary design changes) then there will still be a lengthy re-qualification process. Since the gear shaft is a flight critical component, the weld process itself and any post weld QA procedures (such as NDI, etc.) must also be re-qualified.

I appreciate why EC chose to use a welded bevel gear shaft design. And that is because it is definitely lighter than the conventional 2-piece mechanically fastened design approach, as well as being less expensive. However, there is a very good reason many OEMs still use the 2-piece design, and that is because it is very difficult in a production environment to ensure the extremely high quality levels needed in the welds.

Here is a link to a drawing of an older MGB design (I believe it's a Huey MGB) that has a similar layout to the EC225, with a spiral bevel input gear stage. You can see how the spiral bevel gear is mechanically fastened to the shaft. While it may seem counter-intuitive, from an overall fault-tolerance standpoint this design is actually better than the EB/laser welded design. Since it is an easier QA task to verify the correct installation of fasteners than it is to verify the integrity of an EB/laser weld joint.

Very interesting discussion! I've even learned a few new things.

riff raff

As before, your explanations make perfect sense and strengthen my first gut reaction in the days after the May 2012 ditching when I was astonished to learn that welding gets used in such an application. To put it simply "It just don't seem right".

This part of the EC225 gearbox is probably approaching the limit of horsepower/torque/vibration stresses that this latest version of the Super Puma family can tolerate. Something changed in recent times, perhaps caused by V12 software, to push things just beyond that limit, I guess.

But I very much wish to see the EC225 back in business soon. So if my whacky idea of threading and screwing the shaft sections together is a non-starter, what about the suggestion from jimf671 "Long bolting could be worth a look" ?

Not only would this clamp the lower shaft section safely in place, but it seems to me that it would create two redundant load paths; the weld and the long bolt. I like "belts and braces" as a principle.

ALBATROSS - your comment about luck alluding to the forced landings in calm sea states is not an accurate reflection of the Puma design's inherent ability to float. Throughout this issue I have come across a couple of good images of Pumas floating quite happily in fairly unpleasant sea states. One in the Norwegian sector and Bristows Tiger after the lightening strike. (I think the Tiger rolled over only after the salvage boat stabbed the floats).

It floats low in the water but it does seem to float well so I do not think your point is valid.

DB

Attempt to sort out IB db update failure
 

Well years ago I had the engine of a Bell 206L self destruct in a most unexpected and spectacular manner.
I had just spent 40 minutes inserting crews into 3 confined areas in the bush and had just departed camp to return to the area with the second crew over unbroken forest and small lakes.
When Mr. Turbine resigned I just happened to be nearly overhead an abandoned sandpit into which I was able to do a successful 270 auto thanks to the 206L doing that so well.
In my case I call that luck - 206 auto rotational capabilities and the good training I had received notwithstanding.
When I refer to luck in this case I call the good sea state and proximity of rescue vessels the same thing.
I in no way try to take away from the professional conduct of the crews or the seaworthiness of the 225 when ditched.
I just think that it could just as easily have happened to another aircraft, elsewhere, in a worse environment. Hence luck, fate whatever you want to call it playing a roll.

Yet....does not the UK CAA encourage "Side Mounted" flotation to ensure the helicopter stays at least mostly upright? The majority of drownings post-ditching/crashes comes from the aircraft rolling over and filling with very cold water.

I know they did lots of expensive testing to confirm that notion.