EC225 crash near Bergen, Norway April 2016
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JCCMJ1
I agree.
Gimbal bearings would feel extreme lateral load and fail. The inside of the transmission would be sprayed with chucks of metal as the gears start to inter-mesh. Epicyclic would jam-up not long after that.
If the front suspension bar becomes loose, the engines will hold the bottom of the mgb from the front. Since it's not really designed to work that way, it will eventually separate.
Gimbal bearings would feel extreme lateral load and fail. The inside of the transmission would be sprayed with chucks of metal as the gears start to inter-mesh. Epicyclic would jam-up not long after that.
SMW72, yes it does help, thank you and that makes much better sense! (just north of you at Banff...)
Still of interest is the accounting for all pins and 'nappy' pins - will standby further.
cheers,
PJ2
Still of interest is the accounting for all pins and 'nappy' pins - will standby further.
cheers,
PJ2
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CAAs grounding of the L2 certainly points in a little different direction then the suspension bars or maintenance error. Just my opinion! If they were determined it was an issue with suspension bars or airframe fittings then they may have included the L/L1 (not sure how many are still flying in the NS), however, maintenance error would not warrant the grounding of another type.
Again I may eat my words but have not believed the suspension bar idea from the beginning.
Again I may eat my words but have not believed the suspension bar idea from the beginning.
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But, "single person" independent inspection may be carried out, but only if critical safety tasks MUST be carried out at a remote base. (Example).
It is clearly stated in the company MOE / CAME for how to do that.
Norwegian choppers are often grounded due to lack of independent inspectors.
(Often holidays etc). Other AC is then used.
This is to ensure proper and safe maintenance.
I dont know if some "small airlines" are abusing this rule, and signing of critical tasks on a regular basis without having an independent person to do the re-inspection, but I can tell you all for sure that this does not happen in CHC and Bristow.
Loose bolts or missing parts does not make any sence in this case.
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the whole concept is wrong
this is what happens when legislators try and design helicopters
EDML: “A helicopter does not have a lot of redudancy at all. There are hundreds potentially fatal single points of failure.“
quite right, and easy to make these parts reliable as long as the payload isn't wasted on bogus redundancy instead
riff raff: "...rotorcraft systems/structures are designed to provide a specific level of fault tolerance (zero, single, or dual fault tolerance) based on a criticality designation...."
but when you have 3 of something performing one function that all have to work then what do you call that?
You need a new category Triple Fault Intollerant perhaps?
this is what happens when legislators try and design helicopters
EDML: “A helicopter does not have a lot of redudancy at all. There are hundreds potentially fatal single points of failure.“
quite right, and easy to make these parts reliable as long as the payload isn't wasted on bogus redundancy instead
riff raff: "...rotorcraft systems/structures are designed to provide a specific level of fault tolerance (zero, single, or dual fault tolerance) based on a criticality designation...."
but when you have 3 of something performing one function that all have to work then what do you call that?
You need a new category Triple Fault Intollerant perhaps?
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but when you have 3 of something performing one function
OK, what about the rotor blades then? You have 5 pcs but any single failure will surely bring that thing down.
Same for the wings of a fixed wing A/C
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I would like to ask what i hope is not a too obvious question regarding the supposed suspension bar issue, bearing in mind we have already seen the unpleasant video of a mostly intact rotor disk descending on its own.
If the forward suspension bar failed for whatever reason, would this not cause the rotor disk to tilt backwards relative to the body of the helicopter quite possibly at a large angle which would lead almost instantaneously to a loud and brief argument between blades and tail boom which would certainly not leave an intact disk.
Even assuming the mgb took the strain briefly i suspect initially there would be some tilt back then when the epicyclic or whatever failed, the two remaining rear suspension bars would again instantly pull the disk back with the same result.
I dont post often but wondered if this could be clear enough evidence that at least the front suspension rod may not be the cause.
I feel the need to point out that i am not a pilot but a regular slf on these unpleasant machines with a good technical background and strong interest in aviation.
If the forward suspension bar failed for whatever reason, would this not cause the rotor disk to tilt backwards relative to the body of the helicopter quite possibly at a large angle which would lead almost instantaneously to a loud and brief argument between blades and tail boom which would certainly not leave an intact disk.
Even assuming the mgb took the strain briefly i suspect initially there would be some tilt back then when the epicyclic or whatever failed, the two remaining rear suspension bars would again instantly pull the disk back with the same result.
I dont post often but wondered if this could be clear enough evidence that at least the front suspension rod may not be the cause.
I feel the need to point out that i am not a pilot but a regular slf on these unpleasant machines with a good technical background and strong interest in aviation.
Dakarman,
(slf= self loading flier??). The problem with speculating to the extent you outline is not that it has no value (all possibilities deserve discussion). It is because there are so many parameters in an accident like this that you have to be willing to accept that although your postulate does make sense, it doesn't take into account the pilot or failure induced reaction of flight controls, gust loading or aircraft attitude at the time of failure or a myriad of other factors that might affect the departure of a massive chunk. There were undoubtedly pieces of MRB missing during the hub's descent and who knows how much or what caused that. Unless someone here knows what the investigators know, I think any of the theories proposed might have pieces of reality. I have seen one tail rotor blade destroyed by a blade strike and the other blade untouched. Anything is possible until you have ruled it out based on all the evidence. ‘Eliminate all other factors, and the one which remains must be the truth.’- S. Holmes, who also said ‘There is nothing more deceptive than an obvious fact.’ and last but not least ‘Having gathered these facts, Watson, I smoked several pipes over them, trying to separate those which were crucial from others which were merely incidental.’ Concentrate on what you have evidence for, not what didn't happen-Me.
(slf= self loading flier??). The problem with speculating to the extent you outline is not that it has no value (all possibilities deserve discussion). It is because there are so many parameters in an accident like this that you have to be willing to accept that although your postulate does make sense, it doesn't take into account the pilot or failure induced reaction of flight controls, gust loading or aircraft attitude at the time of failure or a myriad of other factors that might affect the departure of a massive chunk. There were undoubtedly pieces of MRB missing during the hub's descent and who knows how much or what caused that. Unless someone here knows what the investigators know, I think any of the theories proposed might have pieces of reality. I have seen one tail rotor blade destroyed by a blade strike and the other blade untouched. Anything is possible until you have ruled it out based on all the evidence. ‘Eliminate all other factors, and the one which remains must be the truth.’- S. Holmes, who also said ‘There is nothing more deceptive than an obvious fact.’ and last but not least ‘Having gathered these facts, Watson, I smoked several pipes over them, trying to separate those which were crucial from others which were merely incidental.’ Concentrate on what you have evidence for, not what didn't happen-Me.
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@roscoe1:
SLF is generally accepted as: 'Self Loading Freight' ie it walks on by itself.
Not to be confused with 'Self Loading Rifle' a fine infantry weapon beloved by former 'cold warriors' which will stop anything human in its tracks but isn't much good against Daleks or Cybermen if Dr Who is to be believed ;o)
EG
SLF is generally accepted as: 'Self Loading Freight' ie it walks on by itself.
Not to be confused with 'Self Loading Rifle' a fine infantry weapon beloved by former 'cold warriors' which will stop anything human in its tracks but isn't much good against Daleks or Cybermen if Dr Who is to be believed ;o)
EG
I hope they find the cause of the accident.
RW
From Australian ABC
Offshore workers delayed returning to WA's Pilbara after helicopters grounded - ABC News (Australian Broadcasting Corporation)
Oil and gas workers have been left stranded on a rig off Western Australia's north west coast after a fleet of helicopters was grounded in the wake of last month's Norway crash.
Commercial flights of the EC225LP Super Puma helicopter were suspended worldwide by Airbus after the accident near the Norwegian city of Bergen killed 13 people on April 29.
Two of the helicopters, also known as the H225, are normally used to transfer workers from the Ocean Monarch drilling rig back to the mainland in the Pilbara.
The company which transports the offshore workers, CHC Helicopters, said it was using smaller aircraft to try to clear the backlog.
However a spokeswoman said the new aircraft could only take between three and five people at a time, resulting in minor delays getting workers home.
The ABC understands some employees have been waiting up to five days for alternative transport.
It is also believed some stranded workers may have been transferred to the mainland by boat - a trip which takes about 13 hours.
The National Offshore Petroleum Safety and Environmental Management Authority said it was aware of the matter and was currently making inquiries with the operator of the Ocean Monarch.
The crash off Norway came after two EC225LP Super Puma helicopters ditched in the North Sea off Scotland in 2012, with all passengers and crew rescued.
Both accidents were blamed on gearbox problems.
The helicopters were grounded in the UK before being given the go-ahead to resume flying in August 2013.
Four people died later that month when a different model of Super Puma, the AS332 L2, crashed off Shetland.
RW
From Australian ABC
Offshore workers delayed returning to WA's Pilbara after helicopters grounded - ABC News (Australian Broadcasting Corporation)
Oil and gas workers have been left stranded on a rig off Western Australia's north west coast after a fleet of helicopters was grounded in the wake of last month's Norway crash.
Commercial flights of the EC225LP Super Puma helicopter were suspended worldwide by Airbus after the accident near the Norwegian city of Bergen killed 13 people on April 29.
Two of the helicopters, also known as the H225, are normally used to transfer workers from the Ocean Monarch drilling rig back to the mainland in the Pilbara.
The company which transports the offshore workers, CHC Helicopters, said it was using smaller aircraft to try to clear the backlog.
However a spokeswoman said the new aircraft could only take between three and five people at a time, resulting in minor delays getting workers home.
The ABC understands some employees have been waiting up to five days for alternative transport.
It is also believed some stranded workers may have been transferred to the mainland by boat - a trip which takes about 13 hours.
The National Offshore Petroleum Safety and Environmental Management Authority said it was aware of the matter and was currently making inquiries with the operator of the Ocean Monarch.
The crash off Norway came after two EC225LP Super Puma helicopters ditched in the North Sea off Scotland in 2012, with all passengers and crew rescued.
Both accidents were blamed on gearbox problems.
The helicopters were grounded in the UK before being given the go-ahead to resume flying in August 2013.
Four people died later that month when a different model of Super Puma, the AS332 L2, crashed off Shetland.
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So, are they linking the a possibility of the same failure occurring in the L2 as may have occurred on the 225 or are they linking this 225 with the previous L2 epicyclic failure?
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@Vibetribe: Simple, logical arguments and procedures which should be acknowledged by every EASA-Member-State.
Last edited by AW009; 12th May 2016 at 17:26.
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"....but when you have 3 of something performing one function that all have to work then what do you call that? You need a new category Triple Fault Intollerant perhaps?"
AnFI- in terms of FMEA the 3 tension struts are not performing the same function. Each one is performing a separate function, but they are part of a common system. Since an individual tension strut will experience total loss of function due to a single (structural) failure event, the tension strut itself has zero fault tolerance for this failure mode. And since the MRGB attachment system will lose the capability to perform its function due to the failure of a single tension strut, the MRGB attachment system also has zero fault tolerance for the failure mode. If the tension strut and MRGB attachment system perform a critical function required for safe flight and have no fault tolerance for this failure mode, it must be shown by analysis that the failure mode is an "extremely improbable" event.
Here's a relevant section from FAR 23.1309:
"(c) The airplane systems and associated components considered separately and in relation to other systems, must be designed and installed so that:(1) Each catastrophic failure condition is extremely improbable and does not result from a single failure;
(2) Each hazardous failure condition is extremely remote; and
(3) Each major failure condition is remote."
If you have an interest in learning more on the subject I recommend reading FAA AC23-1309-1E. It's not specific to rotorcraft, but the basic principles still apply.
AnFI- in terms of FMEA the 3 tension struts are not performing the same function. Each one is performing a separate function, but they are part of a common system. Since an individual tension strut will experience total loss of function due to a single (structural) failure event, the tension strut itself has zero fault tolerance for this failure mode. And since the MRGB attachment system will lose the capability to perform its function due to the failure of a single tension strut, the MRGB attachment system also has zero fault tolerance for the failure mode. If the tension strut and MRGB attachment system perform a critical function required for safe flight and have no fault tolerance for this failure mode, it must be shown by analysis that the failure mode is an "extremely improbable" event.
Here's a relevant section from FAR 23.1309:
"(c) The airplane systems and associated components considered separately and in relation to other systems, must be designed and installed so that:(1) Each catastrophic failure condition is extremely improbable and does not result from a single failure;
(2) Each hazardous failure condition is extremely remote; and
(3) Each major failure condition is remote."
If you have an interest in learning more on the subject I recommend reading FAA AC23-1309-1E. It's not specific to rotorcraft, but the basic principles still apply.
Or, of course, you can read the rotorcraft specific document - AC29
http://www.faa.gov/documentlibrary/m...r/ac_29-2c.pdf
http://www.faa.gov/documentlibrary/m...r/ac_29-2c.pdf
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Thanks for the link to AC29-2C.
Of course, the section AC 29.1309(b)(3)(i)(E) regarding catastrophic failure of flight critical systems is similar:"(E) Catastrophic Failure Conditions must be Extremely Improbable."
It's also worth noting that the full FAA AC29-2C document from 2014 is 1258 pages. This is probably many times the number of pages in the FAR 29 regulations at the time the EC225 was FAA certified.
Of course, the section AC 29.1309(b)(3)(i)(E) regarding catastrophic failure of flight critical systems is similar:"(E) Catastrophic Failure Conditions must be Extremely Improbable."
It's also worth noting that the full FAA AC29-2C document from 2014 is 1258 pages. This is probably many times the number of pages in the FAR 29 regulations at the time the EC225 was FAA certified.