EC225 crash near Bergen, Norway April 2016
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Re: Concentric
" Thirdly, Figure 7 and Figure 9 show how the epicyclicexternal ring gear burst open across both 1st and 2ndstages around the 4 o’clock position directly adjacent to an M/R servo location.What would be the effect of a planet gear or fragment bursting out and breakingthe right hand rear servo ? "
Could damage to a servo theoretically cause a cyclic change so abrupt that it could over stress the front suspension strut and cause it to fail ? That might explain the fast horizontal fuselage deceleration you described. I know the answer is not within our grasp but it is one possible sequence of events that would explain why/if the strut failed after the event started.
Seems there is possibly evidence (failure under extreme tensile load) that the strut was intact when the event started, which would make it more unlikely that the strut failed first and that caused the event.
Interesting post.
" Thirdly, Figure 7 and Figure 9 show how the epicyclicexternal ring gear burst open across both 1st and 2ndstages around the 4 o’clock position directly adjacent to an M/R servo location.What would be the effect of a planet gear or fragment bursting out and breakingthe right hand rear servo ? "
Could damage to a servo theoretically cause a cyclic change so abrupt that it could over stress the front suspension strut and cause it to fail ? That might explain the fast horizontal fuselage deceleration you described. I know the answer is not within our grasp but it is one possible sequence of events that would explain why/if the strut failed after the event started.
Seems there is possibly evidence (failure under extreme tensile load) that the strut was intact when the event started, which would make it more unlikely that the strut failed first and that caused the event.
Interesting post.
I'm pretty sure any servo damage caused from an exploding gearbox would be easily identified, due nature of the damage, especially when compared to the other 2 Servo's
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I suggest that you are making most of that up because you don't actually know. Not out of malice, of course. What you say is as it should be, however you fail to address the issue that some quite complex pieces of information, pictures, titbits etc have been released whilst some very basic facts, easily available without any need for interpretation, have not been released. Until that can be explained I'll remain a bit suspicious.
Re your comments, fortunately what I said was based on experience of being directly involved in a significant accident investigation, it wasn't made up. The investigation releases information for two reasons, to provide the general public and media with information on the progress of the investigation and secondly to publisise issues of immediate airworthiness concern. Obviously the AIBN will not publish everything they have analysed and "closed off" it would be a waste of investigation resources which are better directed at the significant issues of the investigation.
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HC,
I guess I can see your point and I must admit I would like for the aibn to come out with some of the above details but at the same time, they must not feel it is pertinant information for the general public at this point.
Here's my take for what it's worth.
The epicyclic TBO hours will be somewhere less then the TBO, and that's all that really matters. As far as I know, we do not know the MGB or MRH hours at this point either. I believe it is turboshaft that has been pushing the MGB TBO. Seeing how it came from AH overhaul and was installed in January, who cares, it is no where near TBO. If the TBO was 1000 hours, let alone 2000 or 4400, it would not be at TBO.
The HUMS must not be telling to much or the AIBN would not be able to say that current means the detect failure are not adequate. If there was an obvious vibration trend or chips detected in the days/weeks on HUMS prior to the accident then I think they could state that it was detectable and avoidable.
We all know there was a substantial amount of suspension bar maintenance prior to the accident. Both the MGB and MRH were replaced in the months prior. This is in no means abnormal maintenance, they have to be disconnected to remove these major components. I do believe it was stated early on that there were no "human misinterpretions", so one should assume this maintenance was performed correctly.
As far as what was still connected to where, you seen the pics of the wreckage correct?? It's not only if the fitting was still attached to the deck or not. If not, was it the cause, was it ripped off as a result of the cause or was it detached when the aircraft hit the the ground at 13000 +feet/min. All this I'm sure they have highly trained individuals working very hard to figure out. Can only imagine the amount of speculation on here if they just said all 4 bolts were sheared off!
Just my thoughts
I guess I can see your point and I must admit I would like for the aibn to come out with some of the above details but at the same time, they must not feel it is pertinant information for the general public at this point.
Here's my take for what it's worth.
The epicyclic TBO hours will be somewhere less then the TBO, and that's all that really matters. As far as I know, we do not know the MGB or MRH hours at this point either. I believe it is turboshaft that has been pushing the MGB TBO. Seeing how it came from AH overhaul and was installed in January, who cares, it is no where near TBO. If the TBO was 1000 hours, let alone 2000 or 4400, it would not be at TBO.
The HUMS must not be telling to much or the AIBN would not be able to say that current means the detect failure are not adequate. If there was an obvious vibration trend or chips detected in the days/weeks on HUMS prior to the accident then I think they could state that it was detectable and avoidable.
We all know there was a substantial amount of suspension bar maintenance prior to the accident. Both the MGB and MRH were replaced in the months prior. This is in no means abnormal maintenance, they have to be disconnected to remove these major components. I do believe it was stated early on that there were no "human misinterpretions", so one should assume this maintenance was performed correctly.
As far as what was still connected to where, you seen the pics of the wreckage correct?? It's not only if the fitting was still attached to the deck or not. If not, was it the cause, was it ripped off as a result of the cause or was it detached when the aircraft hit the the ground at 13000 +feet/min. All this I'm sure they have highly trained individuals working very hard to figure out. Can only imagine the amount of speculation on here if they just said all 4 bolts were sheared off!
Just my thoughts
In both the EC225 gearbox removals the forward Sus Bar was never removed from the Aircraft. Only the upper attachment on the forward Bar was disconnected. This is due to the nature of the firewall from memory and it differs from the AS332 gearbox installation, in a lot of ways, this is just one example.
The Engines of these Aircraft come out very easily and quickly. You are looking at around 200 man hours to change the Gearbox, so those quick release Pit Pins sure save heaps of time....I really think the Frogs don't get it sometimes.
HC
Re your comments, fortunately what I said was based on experience of being directly involved in a significant accident investigation, it wasn't made up. The investigation releases information for two reasons, to provide the general public and media with information on the progress of the investigation and secondly to publisise issues of immediate airworthiness concern. Obviously the AIBN will not publish everything they have analysed and "closed off" it would be a waste of investigation resources which are better directed at the significant issues of the investigation.
Re your comments, fortunately what I said was based on experience of being directly involved in a significant accident investigation, it wasn't made up. The investigation releases information for two reasons, to provide the general public and media with information on the progress of the investigation and secondly to publisise issues of immediate airworthiness concern. Obviously the AIBN will not publish everything they have analysed and "closed off" it would be a waste of investigation resources which are better directed at the significant issues of the investigation.
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Concentric,
I had not noticed the distortion on the suspension bar fitting eye, I would concur that it was overloaded at time of failure. It is of course possible that a fatigue started there prior to final overload, but we probably would have heard about that already from AIBN.
I had not noticed the distortion on the suspension bar fitting eye, I would concur that it was overloaded at time of failure. It is of course possible that a fatigue started there prior to final overload, but we probably would have heard about that already from AIBN.
Last edited by Concentric; 11th Jun 2016 at 10:58. Reason: terminology
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Concentric:
Yes really good to see some engineering insight into this. I don't fly the EC225/332and never have but it is always interesting to read Pprune posts from those knowledgeable in the industry. Thank you.
Yes really good to see some engineering insight into this. I don't fly the EC225/332and never have but it is always interesting to read Pprune posts from those knowledgeable in the industry. Thank you.
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Buzz66,
You are right ... Lol. Been a while since working on the puma but how could I forget those clamps. Usually not too bad going on but could be a pain at times to get the self locking bit to release coming off. I said gen/alt because many on here I'm sure have only been around the Sikorsky products and only refer to an alternator when talking about cars. Well now that you have corrected me, let me say maybe then it could be as simple as damage to the alternator mounting flange (where the clamp goes) 
Where I could from, this is still considered maintenance to the suspension bar. Hence why I stated disconnecting suspension bars, not removing. I too have been involved in several AS332 gearbox changes, but will admit, never a 225.
Just for your info, the Alternators are NOT mounted to the gearbox by studs. It's held in Place with a Clamp...It does have a locating Pin thou, and provision for oil cooling, but I get your point.
forward Sus Bar was never removed from the Aircraft. Only the upper attachment on the forward Bar was disconnected.
Are the planetaries replaced at overhaul, do they have a fatigue life, or are they on-condition?
Last edited by JohnDixson; 11th Jun 2016 at 14:00. Reason: Typing
Nice to see some engineering insight to this. Very well thought out, and presented.
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If Engineers had wanted to work with their hands instead of their Brains.... they would have been Pilots instead of Engineers.
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I'll take that as a compliment, thank you Sir! This particular engineer has never been afraid to get his hands dirty when necessary but has never had the delicate touch to be a (successful) pilot. I have the greatest respect for you guys in the front seats.
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Your post seems a bit of a non-sequitur. What you are saying is what should happen, which is not necessarily the same as what is happening. In the accident investigation I was involved in (not AAIBN) no information was released for public consumption until the report was produced. However AAIBN seem to be releasing information selectively, the question is what is behind the selection process.
You and I obviously have had different experiences of accident investigation, all of the ones I've been directly involved with, or on the sidelines of have followed the process I've described regarding the release of info. You have obviously had a different experience. Lets leave it at that.
Last edited by n305fa; 11th Jun 2016 at 17:50.
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The MGB had a total flight time of 2300 hours before OH according to the PR agency Zync reports to media. (Incl 4 extensions of TBO, recorded in OEP)
Zync has also reported TBO is 2000 hours.
17. of January this was changed to a new unit. According to reports in the media.
At time of accident this unit had 1300 flying hours .
CHC Helikopterserice CEO claims during press conference they follow a maintenance program which says the gearbox is sent to a supplier for maintenance at 4400 hours. It could be wrongly cited, we are here talking about something else.
What is not clear is that Zync claims the AC had a new approval after 17 th of January for the MGB change. There is still no documentation stored in OEP about this. (until the accident it should at least be protocolled)
Firstly, with reference to the AIBN Preliminary Report dated 27/5/16, Figure 4 shows the broken upper end of the front suspension bar which has clearly fractured in a ductile manner from a gross tensile overload, evidenced by the elongation of the male eye. Any suggestion that it was not properly pinned at either end or that the lower connecting lug bolts were incorrectly torqued contradicts the evidence. The bar must in fact have been very well restrained and under a tensile force much greater than its design load before it failed in this manner, assuming it was made of the correct material. For anything not designed to, other than the pins and bolts, to have transmitted this force is, frankly, far-fetched. For the front bar at least, it would also appear that the direction of loading was close to its normal arrangement as the pin is not bent and failure was across minimum tensile section.
(on picture in prel report it looks like this).
Then it could be the remaining front susp bar could already be in such torsion
that the upper mount have recieved all of the bending torque, of the rotor on its way loose.
Secondly, the ATC radar plot (Figure 1) gives a timeline and some indication of groundspeed of LN-OJF. The radar returns are at approximately 4 second intervals and the (straight line) distance covered between 09:54:44 and 09:54:48 is only about 50% of that covered in the preceding 4 seconds. If I have scaled off the map correctly, the initial groundspeed appears to be approximately 148 knots but the average groundspeed for the 4 seconds after 09:54:48 appears to be approximately 74 knots (it could be higher if the aircraft followed an S-turn). The CVFDR is reported to have shown everything ‘normal until a sudden catastrophic failure developed in 1-2seconds’.
The (average) groundspeed after 09:54:48 scales as approximately 52 knots, by which time, taking the wind direction (190 – 200degrees) and final position of the MRH into account, the MRH had probably separated from the aircraft. Thereafter the fuselage would be a ballistic projectile with only air resistance having any effect on its groundspeed. Within the 4 seconds after 09:54:44 the aircraft had decelerated from 148 knots to slightly over 52 knots regardless of flight path. It is even possible it could have been during just the last 2 seconds of that interval.
This would appear to be a very high rate of horizontal deceleration (up to 2.5g) in addition to normal ‘g’ and any additional vertical acceleration and/or rotational acceleration. I will leave it to the professionals to suggest whether this is within normal airframe loading limits and how a helicopter can be made to decelerate this rapidly. Presumably it requires a very severe flare and the rotor to be attached? On top of mast axial loading such a rotation must impart a moment to the top of the gearbox, increasing load on the front suspension bar.
The (average) groundspeed after 09:54:48 scales as approximately 52 knots, by which time, taking the wind direction (190 – 200degrees) and final position of the MRH into account, the MRH had probably separated from the aircraft. Thereafter the fuselage would be a ballistic projectile with only air resistance having any effect on its groundspeed. Within the 4 seconds after 09:54:44 the aircraft had decelerated from 148 knots to slightly over 52 knots regardless of flight path. It is even possible it could have been during just the last 2 seconds of that interval.
This would appear to be a very high rate of horizontal deceleration (up to 2.5g) in addition to normal ‘g’ and any additional vertical acceleration and/or rotational acceleration. I will leave it to the professionals to suggest whether this is within normal airframe loading limits and how a helicopter can be made to decelerate this rapidly. Presumably it requires a very severe flare and the rotor to be attached? On top of mast axial loading such a rotation must impart a moment to the top of the gearbox, increasing load on the front suspension bar.
the rate of deceleration before the incident. (Which could indicate a free fall)
I wouldnt put too much certainty in the recorded speed on the radar readings.
It could well be that the resolution is not small enough to include the exact speed
upon impact. The radar plots I have looked at (flightradar24) you see the
last recording is about 52 knots. It could well be the last recording upon ground impact. (That occured before the last recorded point on the radar)
In the very first reports of the accident in the a newspaper.
there where also an amateur video of the incident. You can see the aircraft coming
in at altitude, huge mechanical noise, the rotor shear of (not in focus on the film)
and there is a black cloud upon impact. The video then focus on the separated rotor flying its own way. (the same film after this moment is still public)
I refer to this only to avoid speculation of this part. I would say it came
in at normal altitude (400-600 m on the film) before it dropped
After seeing this I was in total shock.
Last edited by turboshafts; 11th Jun 2016 at 20:15.
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1300 hours in about 3.5 months is about 12 flying hours per day seven days per week.
With the current economic climate are NS shuttles really averaging this? it seems very high to me. I don't fly the NS but a couple of years back S92s world wide average less than 1000 hours per year each. I know the NS schedules are v demanding but are they as high as that? With all the associated maintenance is that even possible?
With the current economic climate are NS shuttles really averaging this? it seems very high to me. I don't fly the NS but a couple of years back S92s world wide average less than 1000 hours per year each. I know the NS schedules are v demanding but are they as high as that? With all the associated maintenance is that even possible?
Last edited by birmingham; 11th Jun 2016 at 19:16.
1300 would be about the top end for a years flying on the North Sea.
If you look on G-INFO you can calculate the average hours for a UK aircraft. I doubt the Norwegians are any different.
GINFO Search Results Summary
Further to this it seems to me that there is a lack of understanding about the terminology.
As an example from above
"17. of January this was changed to a new unit. According to reports in the media.
At time of accident this unit had 1300 flying hours ".
1300 since new, since overhaul or since repair? Without knowing which, the figure means nothing.
The way components are tracked on aircraft can mean that a component that has 5000 hours consists of the data plate and the log book with every other item being replaced and therefore having lower hours. Without sight of the log cards you cant tell a thing.
If you look on G-INFO you can calculate the average hours for a UK aircraft. I doubt the Norwegians are any different.
GINFO Search Results Summary
Further to this it seems to me that there is a lack of understanding about the terminology.
As an example from above
"17. of January this was changed to a new unit. According to reports in the media.
At time of accident this unit had 1300 flying hours ".
1300 since new, since overhaul or since repair? Without knowing which, the figure means nothing.
The way components are tracked on aircraft can mean that a component that has 5000 hours consists of the data plate and the log book with every other item being replaced and therefore having lower hours. Without sight of the log cards you cant tell a thing.
Last edited by ericferret; 11th Jun 2016 at 21:38.
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Luftfartstilsynet: Ulykkeshelikopteret skiftet girkasse og rotor i år - Helikopterstyrten i Hordaland - VG
"I løpet av perioden fra 17. januar og frem til ulykken hadde helikopteret rundt 1300 flytimer, opplyser CHC Helikopter Service til VG gjennom kommunikasjonsbyrået Zync."
My transl:
"During the period from 17th of January until the accident the helicopter had around 1300 flying hours, informs CHC Helicopter Service to VG, through the PR-agency Zync."
So according to the article it is 1300 flying hours since January 17th when the gearbox was changed.
"I løpet av perioden fra 17. januar og frem til ulykken hadde helikopteret rundt 1300 flytimer, opplyser CHC Helikopter Service til VG gjennom kommunikasjonsbyrået Zync."
My transl:
"During the period from 17th of January until the accident the helicopter had around 1300 flying hours, informs CHC Helicopter Service to VG, through the PR-agency Zync."
So according to the article it is 1300 flying hours since January 17th when the gearbox was changed.
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So according to the article it is 1300 flying hours since January 17th when the gearbox was changed.
I can tell you without a doubt turboshaft, either the PR staff have it wrong or the news have reported it wrong. Don't think anyone on here can verify a helicopter in any type of operation that would be on track for 4000 + hours per year. As others have said, 1300 hours would be a decent year ... I have seen aircraft doing upwards of 2000 but they were super busy aircraft.