Heli ditch North Sea G-REDL: NOT condolences
There are 14 Rollers in the bearing. Turning at twice the RPM than the Rotorshaft. means 2190/min. common denominator between roller position ans Gear Mesh would be 1/15th.
Would be 146/min. Still no match but you get the picture.
You can get resonances from weird combinations...
I wouldn't rule it out completely.
Gearbox Resonances
Henra makes a valid observation.
Anecdotally: The CH-47A production prototypes that we had at the Aviation Test Board in 1963 had developed a problem in the engine nose gearboxes that exhibited itself thru the disturbing propensity of literally exploding in flight, with the resultant debris being ingested into that engine, causing it to fail in a noisy manner. The "Captains and Majors, and Light Colonels too", started shunning the machine and that's how a junior Lt ( me ) got to fly them, tho' I was two weeks out of flight school.
Anyhow, the cause of failure was exactly what Henra referred to, a resonance within the box. Boeing couldn't redesign the box overnight, so the operating Nr was shifted from 204 to 230. Far enough away to keep us off the problem. And doing that, we nor the 11th Air Assault Div ( soon the 1st Air Cav ) CH-47 drivers had any further events due to that cause, as I recall.
In rotary wing machines, its not just the component natural frequencies that can create larger issues.
Thanks,
John Dixson
Anecdotally: The CH-47A production prototypes that we had at the Aviation Test Board in 1963 had developed a problem in the engine nose gearboxes that exhibited itself thru the disturbing propensity of literally exploding in flight, with the resultant debris being ingested into that engine, causing it to fail in a noisy manner. The "Captains and Majors, and Light Colonels too", started shunning the machine and that's how a junior Lt ( me ) got to fly them, tho' I was two weeks out of flight school.
Anyhow, the cause of failure was exactly what Henra referred to, a resonance within the box. Boeing couldn't redesign the box overnight, so the operating Nr was shifted from 204 to 230. Far enough away to keep us off the problem. And doing that, we nor the 11th Air Assault Div ( soon the 1st Air Cav ) CH-47 drivers had any further events due to that cause, as I recall.
In rotary wing machines, its not just the component natural frequencies that can create larger issues.
Thanks,
John Dixson
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SAS
Just for the record the Comet debacle (wing-stall on rotation during take-off) was a problem that had its root in the lack of development via prototype and was covered up not only by the manufacturer but by the UK aviation authority, the accident investigators and the airline (see David Beaty's excellent book The Naked Pilot).
Reading about that incident was for me a life-changing experience for ever since I have never been able to trust anyone in authority to deliver 100% of the truth and have frequently found this approach to be justified. It is a sad indictment of our world. The AAIB was, I believe, formed after the Comet debacle as independent accident investigators and they at least appear to be up to the task. Anyone who believes that everyone in aviation is pure of heart, honest and upstanding needs a reality check.
Does anyone know if EC had a Tech Rep for the 332 in UK/ADN and if so was he consulted? Sometimes a good Tech Rep will be a mine of information that can help hard pushed and shift-working maintenance personnel to react appropriately to the first signs of a major defect.
G.
Reading about that incident was for me a life-changing experience for ever since I have never been able to trust anyone in authority to deliver 100% of the truth and have frequently found this approach to be justified. It is a sad indictment of our world. The AAIB was, I believe, formed after the Comet debacle as independent accident investigators and they at least appear to be up to the task. Anyone who believes that everyone in aviation is pure of heart, honest and upstanding needs a reality check.
Does anyone know if EC had a Tech Rep for the 332 in UK/ADN and if so was he consulted? Sometimes a good Tech Rep will be a mine of information that can help hard pushed and shift-working maintenance personnel to react appropriately to the first signs of a major defect.
G.
Last edited by Geoffersincornwall; 26th Nov 2011 at 22:21.
Geoffers....I was referring to the depressurizations caused by airframe cracks...that resulted in several mid-air breakups fatal to all aboard. That engineering failure led to the Boeing 707 and Douglas DC-8 being the Jets of choice during the early years.
John.....ah yes....Nose Boxes....and how they could liven up a dull day!
Then that takes us to podded engines the British like so much. One dies...pukes up its innards and its next door neighbor gets a terminal dose of FOD. Aircraft like the B-52 and B-47 had that similarity.
I always wondered about the Puma series....except helicopters tend to have very good inlet screeens which cures that problem. Granted two engines being nestled like lovers sets one up for an interesting day if one shucks a turbine wheel and kills the other.
Is there a book somewhere that Design Engineers should refer to when drawing up a new design....to see what ideas from the past did not work out well?
John.....ah yes....Nose Boxes....and how they could liven up a dull day!
Then that takes us to podded engines the British like so much. One dies...pukes up its innards and its next door neighbor gets a terminal dose of FOD. Aircraft like the B-52 and B-47 had that similarity.
I always wondered about the Puma series....except helicopters tend to have very good inlet screeens which cures that problem. Granted two engines being nestled like lovers sets one up for an interesting day if one shucks a turbine wheel and kills the other.
Is there a book somewhere that Design Engineers should refer to when drawing up a new design....to see what ideas from the past did not work out well?
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Geoff
According to the AAIB:
The AMM however was available and required the epicyclic module to be opened and inspected (squib's 'elephant').
According to the AAIB:
a manufacturer’s technical representative is based in Aberdeen to provide direct support to local operators. This representative was not available in Aberdeen on 25 March 2009 due to a pre-planned commitment.
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the cause of failure was exactly what Henra referred to, a resonance within the box
Granted two engines being nestled like lovers sets one up for an interesting day if one shucks a turbine wheel and kills the other.
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After reading the report a couple of times, I would like to throw the following comments up for consideration.
1/ during design, the primary failure mode of the gears was considered to be spalling and all of the maintenance and monitoring tasks were tailored to identify this type of failure, e.g a failure that generates a load of metallic particles.
2/ The AAIB state that the failure of the 2nd stage gear was not consistent with spalling alone, so there may not have been as much metal generated as with a pure spalling failure. In view of this, even had the gearbox been opened there was the possibility that there would not have been enough material to declare the MGB unserviceable. The actual ammount of particles released will never be known as the MGB was not opened.
3/After 25/3 there were no more indications of degradation in the MGB despite the additional monitoring. Failure of a critical component should be preceeded by more than one sign of degradation.
4/ The use of MCD's as the primary method of detecting epicyclic gear deterioration appears to have limited ability to detect a rapid (non-spalling) failure of a gear.
1/ during design, the primary failure mode of the gears was considered to be spalling and all of the maintenance and monitoring tasks were tailored to identify this type of failure, e.g a failure that generates a load of metallic particles.
2/ The AAIB state that the failure of the 2nd stage gear was not consistent with spalling alone, so there may not have been as much metal generated as with a pure spalling failure. In view of this, even had the gearbox been opened there was the possibility that there would not have been enough material to declare the MGB unserviceable. The actual ammount of particles released will never be known as the MGB was not opened.
3/After 25/3 there were no more indications of degradation in the MGB despite the additional monitoring. Failure of a critical component should be preceeded by more than one sign of degradation.
4/ The use of MCD's as the primary method of detecting epicyclic gear deterioration appears to have limited ability to detect a rapid (non-spalling) failure of a gear.
n305 you raise some interesting points, though I would say that you comment in 1/ about "a load of metallic particles" is perhaps a slight exaggeration.
Really we have only two non-invasive technologies for detecting incipient transmission failure - debris monitoring and HUMS (or VHM if you want to be trendy).
Tradionally VHM's strong point has been gear crack detection since a fatigue crack can occur and propagate to near-failure without much or any debris being released. Other types of impending failure such as bearing or spline disintegration are better detected by debris monitoring.
Unfortunately the path of a planet gear's tooth around the sun and ring gears is a little complex and seems to be beyond current VHM implementation's ability to detect cracks. Thus whilst many other elements of the transmission are "protected" by either debris monitoring or VHM, the epicyclic seems to fall between the two of them.
There is a view in the industry that monitoring planet gears is beyond VMH, without rather drastic steps such as fitting sensors onto the rotating planet gear carrier and somehow remotely powering and recovering the signal. I don't really like this idea because adding "stuff" inside the gearbox bolted onto gears seems likely to introduce new hazards when it falls off, disintegrates etc.
Personally I remain to be convinced why current hardware cannot be used to adequately recover gear tooth vibration signal from rotating planet gears. Although each tooth only meshes with a specific location on the ring gear after many rotations, surely the time interval between each occurance is predictable and therefore current techniques of signal averaging could be used to recover an adequate signal for processing in the VMH system. The downside would be that it would take a relatively long time for the acquisition, and one of the goals of VHM system design is to not require too long "on condition" since the aircraft may not be in cruising flight for long (this can be a problem for example on SAR aircraft). However, being selfish about it, oil and gas operations at least in the Northern N Sea tend to spend quite a long time in the cruise and so the time issue is less relevant. Our current VHM systems spend a long time in the cruise doing nothing.
I would like to see more research into this issue, something that unfortunately is not specifically suggested in the report. As I mentioned before, with the exception of AAD, HUMS technology has been resting on its laurels for a long time now, time for some progress! CAA Research Dept, this would be a good one for you!
HC
Edited to say that the report does in a roundabout way recommend further research into VHM for epicyclic, but directs this at EASA who have no track record in VHM research. No doubt putting politics ahead of the optimum. I suppose that in the fullness of the time associated with EASA beaurocracy, the recommendation might wend its way to the UK CAA eventually!
Really we have only two non-invasive technologies for detecting incipient transmission failure - debris monitoring and HUMS (or VHM if you want to be trendy).
Tradionally VHM's strong point has been gear crack detection since a fatigue crack can occur and propagate to near-failure without much or any debris being released. Other types of impending failure such as bearing or spline disintegration are better detected by debris monitoring.
Unfortunately the path of a planet gear's tooth around the sun and ring gears is a little complex and seems to be beyond current VHM implementation's ability to detect cracks. Thus whilst many other elements of the transmission are "protected" by either debris monitoring or VHM, the epicyclic seems to fall between the two of them.
There is a view in the industry that monitoring planet gears is beyond VMH, without rather drastic steps such as fitting sensors onto the rotating planet gear carrier and somehow remotely powering and recovering the signal. I don't really like this idea because adding "stuff" inside the gearbox bolted onto gears seems likely to introduce new hazards when it falls off, disintegrates etc.
Personally I remain to be convinced why current hardware cannot be used to adequately recover gear tooth vibration signal from rotating planet gears. Although each tooth only meshes with a specific location on the ring gear after many rotations, surely the time interval between each occurance is predictable and therefore current techniques of signal averaging could be used to recover an adequate signal for processing in the VMH system. The downside would be that it would take a relatively long time for the acquisition, and one of the goals of VHM system design is to not require too long "on condition" since the aircraft may not be in cruising flight for long (this can be a problem for example on SAR aircraft). However, being selfish about it, oil and gas operations at least in the Northern N Sea tend to spend quite a long time in the cruise and so the time issue is less relevant. Our current VHM systems spend a long time in the cruise doing nothing.
I would like to see more research into this issue, something that unfortunately is not specifically suggested in the report. As I mentioned before, with the exception of AAD, HUMS technology has been resting on its laurels for a long time now, time for some progress! CAA Research Dept, this would be a good one for you!
HC
Edited to say that the report does in a roundabout way recommend further research into VHM for epicyclic, but directs this at EASA who have no track record in VHM research. No doubt putting politics ahead of the optimum. I suppose that in the fullness of the time associated with EASA beaurocracy, the recommendation might wend its way to the UK CAA eventually!
Last edited by HeliComparator; 27th Nov 2011 at 19:37.
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Silver and cadmium are non-magnetic so it seems pretty unlikely to me that they would be stuck to magnetic chip detector
Wrt. the 1,022 Hz anomaly picked up in the acoustical analysis (ref report section 2.5), perhaps this could be a resonant harmonic from a change in the epicyclic module cruise mode signature. Without the missing section of the second stage planet gear it will never be known if this part of the MRGB was the generator of this harmonic. Hopefully the recommendation to further enhance HUMS will look at the addition of acoustical signatures in this specific frequency range.
As with Cougar 491 the key point is that we all learn from these tragedies and improve helo safety for all by negating mis-information and having effective communication protocols.
Safe flying
Max
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Maxwelg2,
WRT your comment
EC will have to capability to produce an acoustic analysis from the known design parameters. It will have been analysed over and over for all known harmonics, especially those which would interfere with all major rotating frequencies (of which there are many in a helicopter).
Whether or not a section of the gearbox is missing or not, a modal/rotor dynamic analysis will produce all possible amplitudes.
Pas.
WRT your comment
Without the missing section of the second stage planet gear it will never be known if this part of the MRGB was the generator of this harmonic
Whether or not a section of the gearbox is missing or not, a modal/rotor dynamic analysis will produce all possible amplitudes.
Pas.
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Hi Pas
Perhaps my syntax wasn't too clear, I was referring more to the point that it would appear that to date nobody has ascertained the root cause of the 1,022 Hz signature and without knowing exactly what the structure of the missing section of gear had and no epicyclic inspection performed post-magnetic plug contamination it is still unclear what the root cause for this harmonic was. Additionally report section 1.11.6 states that this harmonic was not found present in other AS332L2 MRGB acoustic signatures, so it can be assumed that it was specifically related to the condition of the installed G-REDL MRGB.
Safe flying
Max
Perhaps my syntax wasn't too clear, I was referring more to the point that it would appear that to date nobody has ascertained the root cause of the 1,022 Hz signature and without knowing exactly what the structure of the missing section of gear had and no epicyclic inspection performed post-magnetic plug contamination it is still unclear what the root cause for this harmonic was. Additionally report section 1.11.6 states that this harmonic was not found present in other AS332L2 MRGB acoustic signatures, so it can be assumed that it was specifically related to the condition of the installed G-REDL MRGB.
Safe flying
Max
The report does say that the frequency varied with the Nr so it was something connected to the transmission, but there is an awful lot that it could have been - something on an engine Nf shaft, oil cooler fan, accessories such as alternator / hydraulic pump, tail rotor drive or an ac electrical noise (frequency linked to rotational speed of the alternators). I really think it is highly unlikely to be coming from the epicyclic. We would on the one hand be saying that sensitive accelerometers mounted on the transmission are not thought able to pick up anomalous vibration relating to planet gears even after augmentation from say 100 cycles of signal averaging, on the other that it could be heard above the general din in the cockpit, a very long way away from the epicyclic. Sorry but it doesn't add up for me. A red herring.
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Read the facts , not between the lines !
This is an exhaustive report and there are many contributing factors, mis communication being a prime example but in conclusion it was a failure of a component that the systems failed to recognise or identify, not an ommision by an engineer or any other individual,,,,,All recommendations and conclusions are pointed towards failures or short comings either by the manufacturer or by EASA
No need to point fingers and blame the staff or the operator
The conclusions of the report say it all, Eurocopter and EASA need to sort this out , from design failures and manufacturing process to procedures and clear and concise communication methods!
No need to point fingers and blame the staff or the operator
The conclusions of the report say it all, Eurocopter and EASA need to sort this out , from design failures and manufacturing process to procedures and clear and concise communication methods!
No need to point fingers and blame the staff or the operator
That is not finger pointing or laying blame in my view but rather taking an impartial view towards improving the situation we all face on a daily basis.
Humans are not perfect and unfortunately machines are not either.
We have to be willing to examine all the links in the chain....if we have any hope of improving the system from design concept to operation by the end user.
To do anything less is a failure in and of itself.....and is this not all about finding out how the system failed and resulted in the loss of precious human lives?
The one I read was a very detailed and thourough one looking into many aspects that contributed to this tragic accident.
And this also -besides the things you mentioned- included the fact that the epicyclic module was not removed and the magnet ring was not inspected and the misunderstanding with the EC staff on this topic both of which might have broken the chain leading ultimately to the accident.
Safety Recommendation 2011-036
It is recommended that the European Aviation Safety Agency (EASA) re-evaluate the continued airworthiness of the main rotor gearbox fitted to the AS332 L2 and EC225 helicopters to ensure that it satisfies the requirements of Certification Specification (CS) 29.571 and EASA Notice of Proposed Amendment 2010-06.
It is recommended that the European Aviation Safety Agency (EASA) re-evaluate the continued airworthiness of the main rotor gearbox fitted to the AS332 L2 and EC225 helicopters to ensure that it satisfies the requirements of Certification Specification (CS) 29.571 and EASA Notice of Proposed Amendment 2010-06.
It sounds like this situation is not all that different than the Sikorsky S-92 gearbox problems....different symptoms but pretty much a common problem in that the certification standards left users vulnerable to fatal flaws.
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Although there is a need to avoid a blame culture if we are to ensure transparency in operations, it was somewhat surprising to see the following excerpt from the recent statement from "Oil & Gas UK":
It would be interesting to hear other's views of how the underlined statement resonates with the following 'Conclusions, Finding' contained in the AAIB report:
Although all of us welcome the intent of the Oil & Gas UK to restore calm - following a very technical but thorough report, this should not be done by spinning the information.
For the same reason, I find the statement made by 'kennethr' - putting the focus upon EASA and the manufacturer - somewhat misplaced.
Safety depends upon all of us taking responsibility for our actions. Yes, from the outside the system appeared to be complex and lacking in sufficient control and oversight; however, all systems are ultimately dependent upon all of us 'playing our part' and doing what is documented and/or expected. This unfortunate accident emphasizes the fact that 'critical elements' of a system have to have checks and balances.
We will never know whether this chip was shed in isolation; however confirmation of this, by examining the ting of magnets on the oil separator plates, contained in the AMM task 60.00.00.212.001, was not achieved.
As 'Geoffers' has pointed out in a number of posts, the respected HARP report recognised that complexity in the MGB makes eradication of all failures difficult to achieve. For this reason, it is imperative for us to ensure that the tools that we do have are employed effectively. It is the system that has to be made more effective, not the airworthiness code.
Leaving aside the flawed interpretation of FAR 29.927, it was largely the system that was at fault (both manufacturer's and operator's) in the S92 accident; these permitted the somewhat innocuous incident at Broome to turn into the tragic accident at Newfoundland.
While the AAIB report confirms that neither the actions of the crew nor the weather were factors in the accident and that the helicopter maintenance regime satisfactorily complied with existing regulations, it does make 17 recommendations
37. The maintenance recommendations provided by the helicopter manufacturer were based on their belief that small particles had been found on the main module chip detector and that the maintenance actions contained in AMM task 60.00.00.212 had already been completed.
38. The maintenance task to remove the epicyclic module and examine the ring of magnets on the oil separator plates, contained in AMM task 60.00.00.212.001, was not carried out.
39. The standard practices procedure used to identify the origin of metallic particles within the MGB was generic and open to interpretation.
40. The particle discovered on 25 March 2009, from visual examination, was identified as ‘scale’, but the material was misidentified as being silver or cadmium plating.
38. The maintenance task to remove the epicyclic module and examine the ring of magnets on the oil separator plates, contained in AMM task 60.00.00.212.001, was not carried out.
39. The standard practices procedure used to identify the origin of metallic particles within the MGB was generic and open to interpretation.
40. The particle discovered on 25 March 2009, from visual examination, was identified as ‘scale’, but the material was misidentified as being silver or cadmium plating.
For the same reason, I find the statement made by 'kennethr' - putting the focus upon EASA and the manufacturer - somewhat misplaced.
Safety depends upon all of us taking responsibility for our actions. Yes, from the outside the system appeared to be complex and lacking in sufficient control and oversight; however, all systems are ultimately dependent upon all of us 'playing our part' and doing what is documented and/or expected. This unfortunate accident emphasizes the fact that 'critical elements' of a system have to have checks and balances.
We will never know whether this chip was shed in isolation; however confirmation of this, by examining the ting of magnets on the oil separator plates, contained in the AMM task 60.00.00.212.001, was not achieved.
As 'Geoffers' has pointed out in a number of posts, the respected HARP report recognised that complexity in the MGB makes eradication of all failures difficult to achieve. For this reason, it is imperative for us to ensure that the tools that we do have are employed effectively. It is the system that has to be made more effective, not the airworthiness code.
Leaving aside the flawed interpretation of FAR 29.927, it was largely the system that was at fault (both manufacturer's and operator's) in the S92 accident; these permitted the somewhat innocuous incident at Broome to turn into the tragic accident at Newfoundland.
The AAIB report wording is way too polite in some areas....and leaves the interpetation up to the reader when it should be quite specific and point out the magnitude of the action or in-action of various parties.
Having been an Investigator in other fields in the past....I see several "Leads" that are left unanswered and un-explored.
Granted the AAIB is more a technical investigative operation but there are times getting into the "Why" something was done or not-done becomes very important to understanding the overall chain of events.
The important issue to me....due to my background....is "Who" made the decisions, "Why" they decided what they did...."What" they decided...."When" (in the sequence of events) they made the decisions they did...."Where" they made the decision....and "How" they made the decision.
In a Criminal or Civil prosecution...this becomes very important but is just as important in any aircraft accident investigation. Bottomline analysis of any event....it comes down to figuring out "How" something happened once "What" happened is determined.
No one set out to destroy this aircraft and kill the occupants....but that is what happened. What turned the "system" into a killer?
Just as we look back now for indicators that should have warned us about the health of the Gearbox....where are the indicators the system itself was failing?
Perhaps we need to learn from this tragedy and examine our own operations with a critical eye. A proper Safety Program would do so...and do so with a very sharp eye.
As we reflect upon the 92 Gearbox problems....and now the EC gearbox problem...perhaps we can all agree it is a general industry wide problem we confront and that it is not limited to just one builder of aircraft.
Are we not seeing a problem in the design, certification and oversight of maintenance of helicopters within the world-wide Helicopter Industry?
It is not a perfect World we live in....but I firmly believe we can do better....if we don't...how many of us are we willing to write off to that failure to strive for perfection?
Having been an Investigator in other fields in the past....I see several "Leads" that are left unanswered and un-explored.
Granted the AAIB is more a technical investigative operation but there are times getting into the "Why" something was done or not-done becomes very important to understanding the overall chain of events.
The important issue to me....due to my background....is "Who" made the decisions, "Why" they decided what they did...."What" they decided...."When" (in the sequence of events) they made the decisions they did...."Where" they made the decision....and "How" they made the decision.
In a Criminal or Civil prosecution...this becomes very important but is just as important in any aircraft accident investigation. Bottomline analysis of any event....it comes down to figuring out "How" something happened once "What" happened is determined.
No one set out to destroy this aircraft and kill the occupants....but that is what happened. What turned the "system" into a killer?
Just as we look back now for indicators that should have warned us about the health of the Gearbox....where are the indicators the system itself was failing?
Perhaps we need to learn from this tragedy and examine our own operations with a critical eye. A proper Safety Program would do so...and do so with a very sharp eye.
As we reflect upon the 92 Gearbox problems....and now the EC gearbox problem...perhaps we can all agree it is a general industry wide problem we confront and that it is not limited to just one builder of aircraft.
Are we not seeing a problem in the design, certification and oversight of maintenance of helicopters within the world-wide Helicopter Industry?
It is not a perfect World we live in....but I firmly believe we can do better....if we don't...how many of us are we willing to write off to that failure to strive for perfection?
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henra
Spot on.
Mitchaa
I agree with you on counts 2 and 3 and also that this WAS preventable.
On count 1 you are wrong.
One of two accerometers (the one on the lower epicyclic) was moved. The one on the upper (where the failure was occuring) remained.
Mars
I agree totally.
Compliance monitoring of maintenace staffs is what is required.
It was Shell who funded HUMS after the HARP report.
The IHST Maintenance Toolkit give plenty of guidance on using HUMS.
It is sad that Oil and Gas UK made their press release without consulting professional aviation advice, which certain of their members could have given.
One can only assume the AAIB has left the detemination on the maintenance errors to the Scottish Proscurator Fiscle under the UK's Corporate Killing law.
Sasless
While your last post is well written, your appear to be trying to stimulate a particular reaction
for reasons unrelated to this accident and also do not align with your comments on the pilots and their delayed ditching in Canada.
You have also failedto take into account that the AAIB recommendation related to not only assessing the EC products against the latest requirement but also a Notice of Proposed amendment that is not yet a rule!
In comparison, one question about the S-92 relate to wether it actually really complies with the certification standards that were current back when Sikorsky applied for certification.
This is made significant as as an unconventional means of compliance was used when the conventionally done test failed.
The other is wether the action Sikorsky took after Broome was sufficiently prompt for a failure Sikorsky had already said would be extremely remote occurred to simple, non moving componets after about 100000 flight hours.
The AAIB report deals with a type with 6 million flying hours, that had a failure in a complex rotating component, that AAIB still don't understand, and propagated to fatal failure after the operator neglected to follow a key step in the maintenance process.
Spot on.
Mitchaa
I agree with you on counts 2 and 3 and also that this WAS preventable.
On count 1 you are wrong.
One of two accerometers (the one on the lower epicyclic) was moved. The one on the upper (where the failure was occuring) remained.Mars
I agree totally.
Compliance monitoring of maintenace staffs is what is required.
It was Shell who funded HUMS after the HARP report.
The IHST Maintenance Toolkit give plenty of guidance on using HUMS.
It is sad that Oil and Gas UK made their press release without consulting professional aviation advice, which certain of their members could have given.
One can only assume the AAIB has left the detemination on the maintenance errors to the Scottish Proscurator Fiscle under the UK's Corporate Killing law.
Sasless
While your last post is well written, your appear to be trying to stimulate a particular reaction
for reasons unrelated to this accident and also do not align with your comments on the pilots and their delayed ditching in Canada. You have also failed
to take into account that the AAIB recommendation related to not only assessing the EC products against the latest requirement but also a Notice of Proposed amendment that is not yet a rule!In comparison, one question about the S-92 relate to wether it actually really complies with the certification standards that were current back when Sikorsky applied for certification.
This is made significant as as an unconventional means of compliance was used when the conventionally done test failed.
The other is wether the action Sikorsky took after Broome was sufficiently prompt for a failure Sikorsky had already said would be extremely remote occurred to simple, non moving componets after about 100000 flight hours.
The AAIB report deals with a type with 6 million flying hours, that had a failure in a complex rotating component, that AAIB still don't understand, and propagated to fatal failure after the operator neglected to follow a key step in the maintenance process.
Last edited by Shell Management; 30th Nov 2011 at 17:35. Reason: Add HARP detail