North Sea Helicopter ditching 10th May 2012
Cyclic.....I will grant 24 hours grace before reminding some folks of past statements perhaps....as this latest event is certainly going to cause (or should at any rate) some serious reconsideration of the relative merits proclaimed so loudly and at length in the past.
I wonder if other operators are having similar problems with Main Gear Boxes?
Bond appears to have grounded their fleet.....why would they do that and other Operators not do the same.....what do the other Operators know that Bond doesn't? Are the Bond Aircraft unique? Are the other Operators carrying out special inspections and/or reviews of HUMs data (or both)? Has there been any AD action by Eurocopter or any of the Administrators? Any industry wide notifications yet?
Bond easily could be the tragic victim of Fate but one does have to wonder if there is some organic cause similar in nature to the Norwegian S-61 Spindle failures many years back. That had to do with an operational technique that was unique to them. Is there something similar going on here?
Not suggesting there is but merely raising one of many questions that begs asking. i would think the AAIB will take that as one of the many lines of questioning they will apply to this and other events re the 225/L2 MGB design.
Helicopters suspended as gearbox fault blamed for SuperPuma ditching | News | Aberdeen | STV
I wonder if other operators are having similar problems with Main Gear Boxes?
Bond appears to have grounded their fleet.....why would they do that and other Operators not do the same.....what do the other Operators know that Bond doesn't? Are the Bond Aircraft unique? Are the other Operators carrying out special inspections and/or reviews of HUMs data (or both)? Has there been any AD action by Eurocopter or any of the Administrators? Any industry wide notifications yet?
Bond easily could be the tragic victim of Fate but one does have to wonder if there is some organic cause similar in nature to the Norwegian S-61 Spindle failures many years back. That had to do with an operational technique that was unique to them. Is there something similar going on here?
Not suggesting there is but merely raising one of many questions that begs asking. i would think the AAIB will take that as one of the many lines of questioning they will apply to this and other events re the 225/L2 MGB design.
Helicopters suspended as gearbox fault blamed for SuperPuma ditching | News | Aberdeen | STV
Last edited by SASless; 13th May 2012 at 12:53.
Seems almost certainly a manufacturing defect of the shaft (AAIB says crack in the vicinity of a weld joining 2 halves of the shaft). I see EC now has a bulletin on TIPI indicating that there is a batch of suspect shafts - I believe a recent batch. Fortunately we don't have any of that batch on our fleet so we are not affected.
PCD - yes I noticed the wording as well, and of course they said some glycol was found in the MGB. There are 2 pressure switches, one for the bleed air and 1 for the glycol. After pressing the SHOT button, the system waits 20 secs and then expects both pressure switches to be showing pressure. If not, MGB EMLUBE illuminates and it is Land Immediately.
Trouble is those pressure switches are only activated with a real emergency or during maintenance, the rest of the time they do nothing except sit there and degrade. When we first got our fleet, the maintenance interval was 750 hrs and we routinely found 1 or other switches inop. We reduced the check to 375 hrs and I think we change them at 375 hrs(?). I am not sure whether this is our company procedure, or whether it is now manufacturer's procedure. In any case, chances are that the EMLUBE was working but they had indications of failure. In that respect it is a poorly designed system.
We just fleet checked the pressure switches and all ours were found to be working correctly.
This would explain oil leakage - with the engine bleed air pressurising the gearbox, oil is forced out of every orifice and low pressure seal making a right mess. (it has happened, though fortunately only on the ground!)
HC
PCD - yes I noticed the wording as well, and of course they said some glycol was found in the MGB. There are 2 pressure switches, one for the bleed air and 1 for the glycol. After pressing the SHOT button, the system waits 20 secs and then expects both pressure switches to be showing pressure. If not, MGB EMLUBE illuminates and it is Land Immediately.
Trouble is those pressure switches are only activated with a real emergency or during maintenance, the rest of the time they do nothing except sit there and degrade. When we first got our fleet, the maintenance interval was 750 hrs and we routinely found 1 or other switches inop. We reduced the check to 375 hrs and I think we change them at 375 hrs(?). I am not sure whether this is our company procedure, or whether it is now manufacturer's procedure. In any case, chances are that the EMLUBE was working but they had indications of failure. In that respect it is a poorly designed system.
We just fleet checked the pressure switches and all ours were found to be working correctly.
This would explain oil leakage - with the engine bleed air pressurising the gearbox, oil is forced out of every orifice and low pressure seal making a right mess. (it has happened, though fortunately only on the ground!)
HC
Last edited by HeliComparator; 13th May 2012 at 13:52.
Coatimundi
HUMS is a fantastic safety tool but not perfect. One problem is that there is so much data, that a "top level" reporting system is needed to interface between all the data and the engineers. This reporting system uses various thresholds and triggers - anything below the trigger / threshold is not presented "in the face" of the engineer, but can be viewed by delving into the raw data.
The thresholds have to be set somehow, and in the early days of HUMS it was mostly guesswork. Various events and experience with false alarms etc have allowed the thresholds to be refined over the years. But since there has not been a previous failure of this shaft, there was no information to allow refinement of the appropriate thresholds. Now there is, so hopefully another small improvement to HUMS will result.
For the time being, the operators now know to keep a close eye on this parameter pending refinement of the thresholds.
HC
HUMS is a fantastic safety tool but not perfect. One problem is that there is so much data, that a "top level" reporting system is needed to interface between all the data and the engineers. This reporting system uses various thresholds and triggers - anything below the trigger / threshold is not presented "in the face" of the engineer, but can be viewed by delving into the raw data.
The thresholds have to be set somehow, and in the early days of HUMS it was mostly guesswork. Various events and experience with false alarms etc have allowed the thresholds to be refined over the years. But since there has not been a previous failure of this shaft, there was no information to allow refinement of the appropriate thresholds. Now there is, so hopefully another small improvement to HUMS will result.
For the time being, the operators now know to keep a close eye on this parameter pending refinement of the thresholds.
HC
HC -my thanks for the clarification on those points. As a former pilot I have been asked to speak with my colleagues on my offshore installation this evening, and your input is much appreciated.
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(There’s a gearbox diagram on the G‑REDL accident thread here.)
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I would be surprised if it comes back into service. I think the damage and cost of repair would make it a write off.
I also noticed that the BBC tv news today mentioned the controlled ditching (they may have said landing) however the newsreader felt the need to offer his own comment and call it "a crash landing to the rest of us". Irritating buffoon.
I also noticed that the BBC tv news today mentioned the controlled ditching (they may have said landing) however the newsreader felt the need to offer his own comment and call it "a crash landing to the rest of us". Irritating buffoon.
We were told offshore some time ago that HUMS was a wonderful addition to helicopter safety. With this in mind, would someone care to comment on these words from the Interim Report:
These sensors had recorded increasing vibration
levels during the previous few flying hours prior to the
accident flight and were being monitored, in accordance
with the manufacturer’s maintenance manual.
It has raised questions out here on Safety Meeting Sunday - it would be good to give the troops some more feedback.
These sensors had recorded increasing vibration
levels during the previous few flying hours prior to the
accident flight and were being monitored, in accordance
with the manufacturer’s maintenance manual.
It has raised questions out here on Safety Meeting Sunday - it would be good to give the troops some more feedback.
On 21 February the RMS parameter threshold was breached, - this is also shown in Figure 4. This is the Root Mean Square of the signal and is a measure of the total energy, the value of which will tend to increase in the event of damage to the component. The EuroARMS Training Manual notes that defect detection using this parameter occurs "at a fairly late stage" in the damage process. Following a review of the thresholds, it was decided to continue monitoring both the RMS and the RMSR parameters. The MGB chip warning and oil cooler drive shaft failure occurred on the following day, some 21 flight hours after the initial alert on 21 February. The final EuroARMS data was sampled only 2 minutes prior to the chip warning.
jimf
I think it would be mistake to read into these texts that operators are not bothering too much about HUMS alerts. The nature of the HUMS beast is that it is uses external accelerometers to monitor and extract vibration signatures for individual shafts, gears and bearings within the tranmission (ie it is non-invasive) all in a pretty nasty environment of heat, dirt, salt, oil and grime not to mention overall flight vibration (not to be confused with transmisison vibration).
The net result is a relatively high false alarm rate, or at least a need to be circumspect in not jumping in with both feet when the HUMS squeaks, without thinking carefully about it.
The false alarm rate is much lower these days - as I mentioned earlier, HUMS is an evolving science (or maybe an art!). It is not perfect, but I get nervous when it is implied that "it don't work so it ain't worth having" because whilst far from perfect, it is still a quantum step forward in flight safety.
In our company we have a couple of very experienced engineers whose sole job is to keep tabs on the HUMS systems, even though these are supposed to be "user friendly" to line engineers, and we do take any such trends very seriously, but at the end of the day a qualitative judgement has to be made as to whether it is a significant issue or not. 99% of the time we get this right, and it doesn't make the papers. Just occasionally it goes wrong and then does make the papers!
I think it would be mistake to read into these texts that operators are not bothering too much about HUMS alerts. The nature of the HUMS beast is that it is uses external accelerometers to monitor and extract vibration signatures for individual shafts, gears and bearings within the tranmission (ie it is non-invasive) all in a pretty nasty environment of heat, dirt, salt, oil and grime not to mention overall flight vibration (not to be confused with transmisison vibration).
The net result is a relatively high false alarm rate, or at least a need to be circumspect in not jumping in with both feet when the HUMS squeaks, without thinking carefully about it.
The false alarm rate is much lower these days - as I mentioned earlier, HUMS is an evolving science (or maybe an art!). It is not perfect, but I get nervous when it is implied that "it don't work so it ain't worth having" because whilst far from perfect, it is still a quantum step forward in flight safety.
In our company we have a couple of very experienced engineers whose sole job is to keep tabs on the HUMS systems, even though these are supposed to be "user friendly" to line engineers, and we do take any such trends very seriously, but at the end of the day a qualitative judgement has to be made as to whether it is a significant issue or not. 99% of the time we get this right, and it doesn't make the papers. Just occasionally it goes wrong and then does make the papers!
Just as a postscript to the HUMS issue, apparently the user can adjust the thresholds at which alerts are generated and we have now significantly reduced the thresholds for the oil pump drive parameters as of this morning.
In our company, we have always downloaded and analysed the HUMS when we return to base, even when it is a rotors-running turnround (as it often is). On the 332L2 this is not possible since there is no method of forcing a termination of the HUMS session onto the card whilst rotors running. The ability to rotors-run download is something we insisted on before taking delivery of the first 225 (and I recall we had to pay EC extra to develop it!). However the manufacturer's procedures do not require HUMS to be dowloaded like this - their view is that once every 25hrs is adequate. I am not sure whether other operators routinely download on every arrival at base - it would be interesting to hear if they do?
In my view the manufacturer should be more proactive in encouraging operators to make the most of HUMS. For the time being, they regard HUMS as an "optional extra" (although of course it is a regulatory requirement for N Sea) and I think it is time this view changed!
In our company, we have always downloaded and analysed the HUMS when we return to base, even when it is a rotors-running turnround (as it often is). On the 332L2 this is not possible since there is no method of forcing a termination of the HUMS session onto the card whilst rotors running. The ability to rotors-run download is something we insisted on before taking delivery of the first 225 (and I recall we had to pay EC extra to develop it!). However the manufacturer's procedures do not require HUMS to be dowloaded like this - their view is that once every 25hrs is adequate. I am not sure whether other operators routinely download on every arrival at base - it would be interesting to hear if they do?
In my view the manufacturer should be more proactive in encouraging operators to make the most of HUMS. For the time being, they regard HUMS as an "optional extra" (although of course it is a regulatory requirement for N Sea) and I think it is time this view changed!
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With the small amount of information regarding a 360Deg crack near to or in the vacinity of a production weld joining two parts together , could indicate a production problem related to inncorrect stress relief/ normalising after heat induction caused by welding, unless carried out almost like a scientific test normalising will cause either embrittlement or loss of tensile strength.
But for so many Helis to have the same fault would need all of them to have been fitted with the same sort of faulty shaft/bevel gear from the same possibly faulty batch of shafts, which almost seems to be impossible..!
Does anyone know if this affects the Military Pumas?
Peter R-B
Lancashire
But for so many Helis to have the same fault would need all of them to have been fitted with the same sort of faulty shaft/bevel gear from the same possibly faulty batch of shafts, which almost seems to be impossible..!
Does anyone know if this affects the Military Pumas?
Peter R-B
Lancashire
Originally Posted by Peter-RB
But for so many Helis to have the same fault would need all of them to have been fitted with the same sort of faulty shaft/bevel gear from the same possibly faulty batch of shafts, which almost seems to be impossible..!
Last edited by diginagain; 14th May 2012 at 08:52. Reason: Clearer English
Certainly none of Bristow nor CHC aircraft in Abz have these suspect batch of shafts, not sure if Bond do but there are only 9 affected shafts in existence worldwide (and not all those necessarily installed in an aircraft). The shaft design is a different part number than installed on the 332 and 330, though I believe retrofit is possible at least on the 332. All the shafts are visually very similar, the ones fitted on the 225 have modified treatments as the primary difference.
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HC- I have been out of the HUMS arena for a few years now (Formerly Systems Engineer on IHUMS) back then (Early part of the Noughties) we had pretty good control and interpretation of the systems data output, however even in mature airframes, we had the odd failure which was on something we hadn't actually been monitoring directly.. anyway, my question..
The CAA funded a study (carried out by Smiths) to develop a "neural networked" HUMS system which would be smart enough to evolve its own thresholds levels. What was the outcome? I was recently at an HM Gov Tech Strat Board competition launch where they invited bids for funding to develop HUMS systems, although after I questioned the TSB staff it turns out that they felt it was a good subject matter, although they had no idea that in fact it was already a mature system as they had not carried out any research..
Nor had they had any contact with CAA SRG on the subject 
So are you guys still plodding on with the systems we had ten years ago, or has there been significant technology advances in terms of data collection, processing and interpretation? Is SMART HUMS any nearer reality? I mean real advances here.. not just a sexy new name or a swish new display format on the PC's. I look at advances in data processing and application engineering in areas such as communications and entertainment and can't help but think HUMS should have evolved at the same rate by virtue of the same architecture?
Interested in yours and others opinion on the matter..
The CAA funded a study (carried out by Smiths) to develop a "neural networked" HUMS system which would be smart enough to evolve its own thresholds levels. What was the outcome? I was recently at an HM Gov Tech Strat Board competition launch where they invited bids for funding to develop HUMS systems, although after I questioned the TSB staff it turns out that they felt it was a good subject matter, although they had no idea that in fact it was already a mature system as they had not carried out any research..
Nor had they had any contact with CAA SRG on the subject So are you guys still plodding on with the systems we had ten years ago, or has there been significant technology advances in terms of data collection, processing and interpretation? Is SMART HUMS any nearer reality? I mean real advances here.. not just a sexy new name or a swish new display format on the PC's. I look at advances in data processing and application engineering in areas such as communications and entertainment and can't help but think HUMS should have evolved at the same rate by virtue of the same architecture?
Interested in yours and others opinion on the matter..
We will do our best to keep our customers happy and pick up some slack, but there is certainly not sufficient spare capacity to replace all Bond's flights so I am afraid some disruption to you guys is inevitable.