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-   -   North Sea heli ditching: Oct 2012 (https://www.pprune.org/rotorheads/498649-north-sea-heli-ditching-oct-2012-a.html)

Cuddles 1st Nov 2012 18:43

Oddly enough I was having just this conversation with a crew on their way into Norwich last night, and, co-incidentally, they'd also just finished said discussion when I butted in and interrupted their consumption of snack - a - jacks.

Helinut 1st Nov 2012 22:56

Could/are BIH's S61s being used to fill gaps??

902Jon 2nd Nov 2012 08:26


Some crashes have more profound after effects than others, and I suspect this is one of those.

Which crash are you talking about ?
The Chinook crash (BAH) had a huge effect on the North Sea. Following this accident, the Shell offshore workers refused to fly in the type, and so it became useless in Aberdeen. The airframes were eventually sold, and the type has never flown on the North Sea since.

In contrast, the S76A+ that crashed out of Norwich 10 years ago was seen as an exceptional accident, due to having had a lightning strike on the blade in the past. Engineering inspections were carried out and procedures changed, and the aircraft returned to service. S76's are still flying on the North Sea (including now 2 in Aberdeen covering from this latest incident).


Whoever decided to sell off all the Bristow 61's is probably wishing he had remembered the Old Man's practice of shoving surplus machines over into the corner just in case of a rainy day or a golden opportunity presenting itself.
Unfortunately that mentality has long gone. Each "business unit" has to "lease" the aircraft from the parent company. So if an aircraft is not on contract and earning money, it is seen as a huge drain on that unit. This also has the knock-on effect that that business units' manager is not achieving budget targets, and their personal bonuses are affected.

SASless 2nd Nov 2012 10:40

Ah yes.....the "Manager's Bonus" and Quarterly Report....which now drives all thinking. When we use a 90 day window for planning....and pay manager's bonuses for squeezing every last penny from an Operation we foster some very short sightedness don't we! Almost like some Nigerian Grocery Stores I remember!

Pittsextra 2nd Nov 2012 12:52

I see Flight international journo's are on the pulse. In future maybe they could cut costs at the magazine and just publish press releases from various parties.

js0987 2nd Nov 2012 12:58

My guess is the old man stuffed them over in the corner because there were no available buyers not because some unforseen incident 5 years hence might require them.

There is the matter of cost. A certain amount of hull insurance may be neccessary. Do you pull them out peridically and exercise them or just let them sit? If you exercise them - another expense. How about crew training? Do you keep crews current or just try and get them up to speed when the aircraft are pulled out of mothballs?

Remember in business you spend a dollar (or euro or pound) and hope to earn say $1.10-1.25 in return. You save a dollar and you just earned a dollar.

albatross 2nd Nov 2012 14:54

Failure Modes on the test stand.
 
The 225 EMLUBE system was, I believe, designed only to deal with a loss of transmission oil not the loss of 2 oil pumps.
In these 2 cases there was not a loss of fluid but an internal failure of the shaft.

So my question is this:
Would proper indication of functioning of the EMLUBE system in this scenario have allowed the safe continuation of flight for the "sacred" 30 minutes (29 minutes 59 seconds as one friend defines it) or would there have been a catastrophic failure of the transmission shaft beforehand?

There would be no way for the crew to differentiate between the two failure modes - except perhaps increasing vibration levels in the event of further shaft failure. With no oil flow through the system there would be no chip detection to advise of things going pear shaped.

I am also told that with dual pump failure and no oil loss from the transmission that the EMLUBE system injecting glycol into an already "full" transmission would cause overflow of a mixture of glycol and oil from the transmission vent which would flow around the transmission area and perhaps even down into the passenger compartment. Would this venting cause a fire hazard?

It would be interesting to see if EC is going to test the transmission and EMLUBE system with this failure model and a fully set up system (alternators producing power ect.) on the test stand.

Edited to add a thought: Since the transmission is still full of oil or an oil/glycol mix would the crew still have an accurate transmission temperature? Don't have my 225 manuals close to hand unfortunately.

kannad405 2nd Nov 2012 16:11

I see what you are getting at with regards to the mix of oil and glycol, however, the glycol isn't pumped in as such and is actually mixed with the P2.4 air from #1 engine and sprayed onto the hottest parts of the box. I think I'm correct in saying it sprays periodically rather than dump it all in one shot. Also, the actual volume of glycol isn't that much (can't recall exact volume) and as such, I don't think venting out the box would be too much of an issue especially when 1. I'd hope the crew would be landing sooner rather than later and 2. The box vents to the aft of the mgb area and would run along outside of sliding cowl

Fareastdriver 2nd Nov 2012 16:41

One must wonder how much lubrication there is with a tranmission case full of oil and inoperative pumps. The input pinion and bevel gear would be totally immersed going around at a cosiderable rate. Gears have rough edges so it would be like a big high speed food processor inside the gearbox. How much would this activity lubricate the reduction gears and more importantly, how much oil mist for the top bearing? Obviously in a fairly short time the oil would start to overheat but how long is a fairly short time?

The Newfoundland S92 ran out of oil. The Puma Mk2 had a component failure internally, the first for 4 million hours. Both the 225s ditched with no apparant complaint from the gearbox apart from warning lights. All the trials so far have assumed the gearbox to be dry. Have they tried to run one without oil pressure to see what its running time is? It could be a nice surprise, there are enough gearboxs in this world that do not have the luxury of an oil pump.

The biggest problem is working out whether you have lost your oil or your oil pump, that is for somebody else to sort out.

Cuddles 2nd Nov 2012 17:22

They run electric fuel and hydraulic pumps, why not an electric GB oil pump?

TipCap 2nd Nov 2012 18:27

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 3rd Nov 2012 16:06


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

Yes! Your memory is still functioning!
3D

TipCap 3rd Nov 2012 19:00

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

:ok:

TC

Rotorhead124 4th Nov 2012 12:18

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

Peter PanPan 4th Nov 2012 20:18

EMLUB
 
@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 4th Nov 2012 20:35

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 4th Nov 2012 22:05

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! 4th Nov 2012 22:11

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 6th Nov 2012 12:26

"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 6th Nov 2012 13:04

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

That was back in July 2012.

Peter PanPan 6th Nov 2012 15:16

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 6th Nov 2012 16:14

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

Colibri49 6th Nov 2012 16:23

Here are links to the subject of carburizing v. nitriding

What is the cost difference between carburizing and nitriding? | Eurotherm Products and Solutions Blog

Case hardening - Wikipedia, the free encyclopedia

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 6th Nov 2012 16:30

Some news about Bond 332L2 :

North Sea operator Bond to resume Super Puma flights | Vertical - Helicopter News
.

Pittsextra 6th Nov 2012 16:33

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 6th Nov 2012 18:59

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 6th Nov 2012 19:28


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 6th Nov 2012 21:29

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 7th Nov 2012 07:47

From HeliHub : Eurocopter issues EC225 “Key Messages”
Eurocopter issues EC225 “Key Messages” | Helihub - the Helicopter Industry Data Source
.

Pittsextra 7th Nov 2012 09:06

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 7th Nov 2012 09:30


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 7th Nov 2012 13:41

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 7th Nov 2012 13:59

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 7th Nov 2012 17:18

The future?
 
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 7th Nov 2012 17:25

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 7th Nov 2012 19:19


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

bigglesbutler 7th Nov 2012 20:45


Originally Posted by Geoffersincornwall
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 7th Nov 2012 21:11

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

500e 7th Nov 2012 21:28

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

Colibri49 7th Nov 2012 22:33

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.


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