North Sea heli ditching: Oct 2012
BigglesB - Of course I take you point although there is always a danger that one can make the mistake [in thinking] that their perspective is the only one but its limiting.
Last edited by Pittsextra; 23rd Nov 2012 at 12:21.
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TERMINUS MO - Are you speaking from personal flight experience of the EC225 or just an opinion in general??
Technically speaking, the part of the shaft that is failing is not subject to any more torque than it was in the AS330, AS332, AS332L1 or AS332L2 as all it does is drive the MGB oil pumps. I am not sure torque is the root cause but this is a very ill-informed opinion as I am a Pilot and not a design engineer.
DB
Technically speaking, the part of the shaft that is failing is not subject to any more torque than it was in the AS330, AS332, AS332L1 or AS332L2 as all it does is drive the MGB oil pumps. I am not sure torque is the root cause but this is a very ill-informed opinion as I am a Pilot and not a design engineer.
DB
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DB
Flown many hours as PIC on the L and L1 and a few on the 225. Now I pay the bills. Our people didn't like the 225 much before these recent episodes, the Puma family generally was not liked after April 2009, especially so hard on the heels of Cougar, all helicopters were feared.
I spent many hours after REDL explaining the 225's outstanding features and the differences from the L2, trying to assure them of the integrity of the 225 MGB without trashing the L2's reputation. Now I am struggling to maintain any trust with passengers.
Whether I turn to AW (tail) Sikorsky (MGB) or EC (MGB) I find myself unable to offer reassurance. Now, passengers are over all things Puma and want the S-92, it's performance over the last 3 years has earned it some tentative trust.
Flown many hours as PIC on the L and L1 and a few on the 225. Now I pay the bills. Our people didn't like the 225 much before these recent episodes, the Puma family generally was not liked after April 2009, especially so hard on the heels of Cougar, all helicopters were feared.
I spent many hours after REDL explaining the 225's outstanding features and the differences from the L2, trying to assure them of the integrity of the 225 MGB without trashing the L2's reputation. Now I am struggling to maintain any trust with passengers.
Whether I turn to AW (tail) Sikorsky (MGB) or EC (MGB) I find myself unable to offer reassurance. Now, passengers are over all things Puma and want the S-92, it's performance over the last 3 years has earned it some tentative trust.
Hello terminus mos,
You're quite right, nobody is able to offer reassurance. This AD is only few months olds :
One More AD for the Sikorsky S-92's Gearbox | Aviation International News
.
Whether I turn to AW (tail) Sikorsky (MGB) or EC (MGB) I find myself unable to offer reassurance. Now, passengers are over all things Puma and want the S-92, it's performance over the last 3 years has earned it some tentative trust.
One More AD for the Sikorsky S-92's Gearbox | Aviation International News
.
Last edited by HeliHenri; 23rd Nov 2012 at 13:10.
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Double Bogey
Its probably not torque thats breaking the shafts. The shaft is subject to cyclic loads generated by the meshing of the pinion gear. These forces are greater then the previouse versions due to the 17% ish hike in power.
Edit due to spelling
Its probably not torque thats breaking the shafts. The shaft is subject to cyclic loads generated by the meshing of the pinion gear. These forces are greater then the previouse versions due to the 17% ish hike in power.
Edit due to spelling
Last edited by Pablo332; 23rd Nov 2012 at 13:19.
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TERMINUS MO - Ok I hear you and I do not want to bore you with the stats on the massive number of offshore flights compared to the incidents as just one is always too many.
In respect of the EC225, I feel we should make distinction between Operational Capability and Technical Serviceability. Of course they are two different things.
The EC225 has been designed with offshore safety in mind. As you have L, L2 and 225 experience you will know well the step changes in capability and safety enhancements that the L2 and 225 represent when compared to the L/L1, with each step being a significant move forward from the last variant.
In respect of the EC225, I feel we should make distinction between Operational Capability and Technical Serviceability. Of course they are two different things.
The EC225 has been designed with offshore safety in mind. As you have L, L2 and 225 experience you will know well the step changes in capability and safety enhancements that the L2 and 225 represent when compared to the L/L1, with each step being a significant move forward from the last variant.
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PABLOS 332 - How do you know that? Are you a design engineer? Are you testing it? Have you got a strain gauge on it?? Come on lets at least deal in facts when it comes to the technical bits!!
To be fair we do know:-
Before next flight, install a placard “MAXIMUM CONTINUOUS TORQUE LIMITED TO 70% DURING LEVEL FLIGHTS AT IAS ≥ 60KTS
” in full view of the pilots, in accordance with instructions of
Eurocopter EC225 ASB No.04A009 revision 2.
Because:-
Eurocopter have shown that crack propagation is slower with reduced Maximum Continuous Power (MCP).
Before next flight, install a placard “MAXIMUM CONTINUOUS TORQUE LIMITED TO 70% DURING LEVEL FLIGHTS AT IAS ≥ 60KTS
” in full view of the pilots, in accordance with instructions of
Eurocopter EC225 ASB No.04A009 revision 2.
Because:-
Eurocopter have shown that crack propagation is slower with reduced Maximum Continuous Power (MCP).
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PABLO 332 - You are not causing offence but:
For example, you imply that there is more load on the shaft due to the higher torques through the box as a likely cause to the failure but this is not consistant with 8 years of trouble free operation!!
Like I said, how do you know the shaft suffers greater lateral loads??? My understanding, and I am far from a design engineer, is that this type of pinion/crown arrangement is self engaging and expressly designed to reduce the effect you describe...but like I said I am not an engineer.
Facts only are needed now.
DB
For example, you imply that there is more load on the shaft due to the higher torques through the box as a likely cause to the failure but this is not consistant with 8 years of trouble free operation!!
Like I said, how do you know the shaft suffers greater lateral loads??? My understanding, and I am far from a design engineer, is that this type of pinion/crown arrangement is self engaging and expressly designed to reduce the effect you describe...but like I said I am not an engineer.
Facts only are needed now.
DB
As I understand it, the proposed reduction in torque is to reduce the propagation rate of a crack once it has formed, rather than to reduce the probability of the crack forming in the first place.
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Double Bogey
It would appear that its sentence one and two that you take exception to.
The shaft is subject to cyclic loads generated by the meshing of the pinion gear.
This information was presented as a matter of fact to illustrate this section of the shaft is just not there to drive the oil pumps.
These forces are greater than the previous versions due to the 17% ish hike in power.
I’m not suggesting this is the cause of the current problems, but any load taken by the 2 roller bearings will be increased with an increase of power over the 332 instalation.
It would appear that its sentence one and two that you take exception to.
The shaft is subject to cyclic loads generated by the meshing of the pinion gear.
This information was presented as a matter of fact to illustrate this section of the shaft is just not there to drive the oil pumps.
These forces are greater than the previous versions due to the 17% ish hike in power.
I’m not suggesting this is the cause of the current problems, but any load taken by the 2 roller bearings will be increased with an increase of power over the 332 instalation.
As I understand it, the proposed reduction in torque is to reduce the propagation rate of a crack once it has formed, rather than to reduce the probability of the crack forming in the first place.
So suggesting you fly on with known crack but at less torque?? From the latest AD.
EASA EAD 2012-025-E
If, during the MOD-45 reviews as required byparagraph (2.3) of this AD, the last MOD-45 record occurred more than 3 FHbefore the actual accumulated FH, before next flight, inspect the installed MGB bevel gear vertical shaft, for absenceof cracks in the area of the weld, byHFEC in accordance with instructions of Eurocopter EC225 ASB No.04A009 revision 2, and if any crack isfound, before next flight, replace the vertical shaft with a serviceable part
No, to increase the safety margin if a crack forms in flight after the last M'ARMS download, as part of the justification for allowing 3 hrs flight between downloads.
Last edited by HeliComparator; 23rd Nov 2012 at 17:12.
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Technically speaking, the part of the shaft that is failing is not subject to any more torque than it was in the AS330, AS332, AS332L1 or AS332L2 as all it does is drive the MGB oil pumps. I am not sure torque is the root cause but this is a very ill-informed opinion as I am a Pilot and not a design engineer.
While I understand the point you are trying to make about the modest amount of pump driving torque transmitted thru the lower portion of that shaft, in reality the torque transmitted thru the bevel gear mesh is what creates forces and moments on the shaft, housing and bearings.
I'd bet than when this issue if finally resolved, the one-piece welded shaft will be replaced by a two-piece shaft design with no welding. As always, just my humble opinion.
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Henri
Your point on the S-92 AD is well taken, but our offshore workforce in the majority don't see the ADs and inner workings of the airworthiness systems.
The Union guys who do take an interest say that while the S-92 has and may still have a few issues, Sikorsky generally understands the problems and works on a fix while EC doesn't seem to fully understand the 225 (or L2) MGB problems.
The passenger perspective is that the expensive ($) new technology helicopters from an airworthiness point of view are less safe than some of the older generation aircraft and I find this a difficult argument to counter. Notwithstanding the "working but not indicating" EMLub, the concept of a safer gearbox to the workforce does not exist.
Your point on the S-92 AD is well taken, but our offshore workforce in the majority don't see the ADs and inner workings of the airworthiness systems.
The Union guys who do take an interest say that while the S-92 has and may still have a few issues, Sikorsky generally understands the problems and works on a fix while EC doesn't seem to fully understand the 225 (or L2) MGB problems.
The passenger perspective is that the expensive ($) new technology helicopters from an airworthiness point of view are less safe than some of the older generation aircraft and I find this a difficult argument to counter. Notwithstanding the "working but not indicating" EMLub, the concept of a safer gearbox to the workforce does not exist.
TM, with the L2 and now these 2 ditchings, I suppose the workforces's feeling that you mention are not surprising. However I don't think the 225 is an intrinsically unsafe (or less safe) heli and if I did, I would be the first to not want to fly it. The trouble is that a generally well designed heli is only as good as its weakest bit, so if 99.99% is really good, there can still be a rogue bit that can cause a big problem.
I do agree that a brand new type may be less safe from an airworthiness point of view, than a well established type. However the current N Sea "new generation" aircraft are now 7 or so years old, so hardly spring chickens.
It is perhaps more relevant to consider what will be the next fatal accident. Yes, we all hope that there won't be one, but with 30yrs + of N Sea life left, that is quite a hope.
The sophisticated autopilots of the new types, coupled with good operating procedures and a proliferation of simulator training does make a "pilot error" type accident much less likely these days. That puts the focus onto airworthiness accidents, even if they are no more likely, and hopefully less likely, than before, they may again become the predominant factor in the accident statistics.
However, if I was a gambling man I would put money on the next accident NOT being related to a Super Puma family gearbox issue. By the time we resume flying it will surely have had more scrutiny than just about anything else! Something unrelated will come out of the woodwork on that or another type.
I am not sure if that is reassuring, but it is realistic! But for those of your colleagues unfortunate enough to suffer an untimely death, it will almost certainly not be due to a helicopter accident. Heli flying is really very safe.
I do agree that a brand new type may be less safe from an airworthiness point of view, than a well established type. However the current N Sea "new generation" aircraft are now 7 or so years old, so hardly spring chickens.
It is perhaps more relevant to consider what will be the next fatal accident. Yes, we all hope that there won't be one, but with 30yrs + of N Sea life left, that is quite a hope.
The sophisticated autopilots of the new types, coupled with good operating procedures and a proliferation of simulator training does make a "pilot error" type accident much less likely these days. That puts the focus onto airworthiness accidents, even if they are no more likely, and hopefully less likely, than before, they may again become the predominant factor in the accident statistics.
However, if I was a gambling man I would put money on the next accident NOT being related to a Super Puma family gearbox issue. By the time we resume flying it will surely have had more scrutiny than just about anything else! Something unrelated will come out of the woodwork on that or another type.
I am not sure if that is reassuring, but it is realistic! But for those of your colleagues unfortunate enough to suffer an untimely death, it will almost certainly not be due to a helicopter accident. Heli flying is really very safe.
Last edited by HeliComparator; 23rd Nov 2012 at 22:42.
riff raff (you aren't by any chance ex-RRAF, Royal Rhodesian Air Force? Riff-Raff was their sobriquet.) Anyway..............
"While I understand the point you are trying to make about the modest amount of pump driving torque transmitted thru the lower portion of that shaft, in reality the torque transmitted thru the bevel gear mesh is what creates forces and moments on the shaft, housing and bearings.
I'd bet than when this issue if finally resolved, the one-piece welded shaft will be replaced by a two-piece shaft design with no welding. As always, just my humble opinion."
Thanks for perfectly encapsulating the shaft issues for me. I would even venture, now that I slightly better understand things, that if there were no bottom bearing resisting the side loads, then there would be less stress on the weld as a consequence of the flexing/bending happening above the bevel gear between the other two bearings.
Yes. Right on! I vote for a new shaft without any weld, except that it would take years to certify.
"While I understand the point you are trying to make about the modest amount of pump driving torque transmitted thru the lower portion of that shaft, in reality the torque transmitted thru the bevel gear mesh is what creates forces and moments on the shaft, housing and bearings.
I'd bet than when this issue if finally resolved, the one-piece welded shaft will be replaced by a two-piece shaft design with no welding. As always, just my humble opinion."
Thanks for perfectly encapsulating the shaft issues for me. I would even venture, now that I slightly better understand things, that if there were no bottom bearing resisting the side loads, then there would be less stress on the weld as a consequence of the flexing/bending happening above the bevel gear between the other two bearings.
Yes. Right on! I vote for a new shaft without any weld, except that it would take years to certify.