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Originally Posted by TenTon
(Post 9361797)
Anyone who thinks HUMS data could be interpreted in real time has never seen the Data before. Please stop thinking HUMs is a magic tool to determine maintenance requirements. HUMs has always been and still is a maintenance TOOL. Not a determining factor nor reliable enough to make a decision such as ditching a Helicopter as some seem to think or those in suits want everyone to believe. Some HUMS indications are so vague it can take a LONG time to determine if the HUMs system or aircraft is faulty. Much longer than your typical out and back trip offshore helicopters take making real time impossible. Whatever failed on this Helicopter happened incredibly fast. Faster than even the Pilots onboard to realize something was wrong. HUMs=USELESS in that situation. If the data is still intact on the card then it may help investigators determine what failed easier.
In 6 months time reading an accident report stating that HUMS data indicated a trend 3 days before the accident. |
OK, looking at the pictures etc.
If the vertical 'lift' loads are taken by the 3 rods, how does the gearbox failing cause the rotor head to break away? What exactly is on the airframe end of the rods? |
Are these 2 strut rods maybe the same component ?
http://i86.servimg.com/u/f86/11/94/64/62/hub7b10.jpg http://i86.servimg.com/u/f86/11/94/64/62/hub910.jpg |
The separation point must be below the green bolts since we can se the suspension bar on the picture.
One strut rod by the red arrow(suspension bar),and one pitch link(with black tape) i think. |
So if we can see the swashplate, the likely separation point is at the row of green bolts underneath. (where the struts attach)
Not very likely , not a lot going on here unless you install barrel nuts upside down. Next MGB joint is to the ring gear of the epicyclic reduction gear, lots going on here. After looking at the end of the suspension bar we can see with the pictures available Pin/washer and securing pins could be intact. The MRB leading edge protective covering shows buckling approx. 1/3 from root which may have been caused by excessive bending of the spar due to excessive pitch. |
just hope I'm not sitting In 6 months time reading an accident report stating that HUMS data indicated a trend 3 days before the accident. |
Pablo, so you think the separation point is the row of bolts at the bottom of the diagram? (grey casing)
The ring gear has a bit of previous on this type of helicopter. At the moment all is speculation. |
Some similarities to G-AWAP
Take a look at the AAIB report for G-AWAP lost in 1983 off Norfolk coast.
The report concludes that the accident was caused by the disengagement of the main rotor head retention bolt, with consequential detachment of the rotor, due to corrosion of the engaging threads between it and the mast. Not to say this was the case but as an inspection engineer that regularly flew in G-AWAP and took an interest in her fate, I was struck by the recent video and the eyewitness reports of G-AWAP, a loud crack and a detached rotor landing away from the main wreck. https://assets.digital.cabinet-office.gov.uk/media/5422ed76e5274a1317000199/3-1985_G-AWAP.pdf |
Am I right in saying that the material failure of the planet gear G –REDL is still unexplained by the manufacturer?
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https://assets.digital.cabinet-offic...REDL_08-09.pdf
The initial examination of the wreckage, in conjunction with radar, HUMS, CVFDR and witness data, determined that a failure within the epicyclic reduction gearbox module of the MRG resulted in the rupture of the gearbox case. This allowed the main rotor head, together with the upper section of the MRG, to separate from the helicopter. |
Does anyone have an illustration showing the lower attachment points of the strut rods?
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Just a slight impostor here but reading this and other accidents the MGB sudden seizure tears the whole assembly out of the top?
If so is there any way of making a shear ring that would fail but leave the blades attached ? I know it's a wild stab in the dark but there appears to be no redundancy if it fails. Like the old safe life on fixed wing structures . |
What to do pilots?/Help us!
Offshore workers feel let down-what is happening with this aircraft? For many people its stick or bust time.
Transit to and from offshore is becoming a gamble and in a professional environment it should not be thus. |
Originally Posted by Hangarshuffle
(Post 9362015)
Offshore workers feel let down-what is happening with this aircraft? For many people its stick or bust time.
Transit to and from offshore is becoming a gamble and in a professional environment it should not be thus. |
VG.NO (Norwegian Newspaper) is now reporting that LN-OJF made a RTB on Tuesday, 16 minutes into a flight, due to a Warning Light (not specified). On Wednesday an engine part was changed and a short local test flight was made. The same Warning Light appeared once again (still not specified), and yet another engine part was changed. Another test flight was then performed. This time everything appeared to be OK. LN-OJF then performed six commercial flights on Thursday without remarks.
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Originally Posted by Hangarshuffle
(Post 9362015)
Offshore workers feel let down-what is happening with this aircraft? For many people its stick or bust time.
Transit to and from offshore is becoming a gamble and in a professional environment it should not be thus. The alternative is transfer by boat and lifting men on and off the rigs by crane. Would that be safer than helicopters? I doubt it. |
Originally Posted by TenTon
(Post 9361864)
Its not impossible at this point. I don't work in Norway so I don't know what the environment it like there or the events leading to this situation. If it turns out the indications were there but missed I hope the CAAs involved investigate how poorly the helicopter industry trains engineers on HUMs at least as they all should get F grades on this subject. Not just CHC. Power point training on a computer or MAYBE actually getting a hums course but 10 years ago is not sufficient to keep anyone proficient. Maybe the signs were there but no one recognized them since the training was either non existent or sub par. As for checking the HUMs Data it is CHC wide to do this after every flight and signed for as a maintenance release before the next flight.
In fact after this was put into the Statoil contract (several years ago) CHC check all HUMS data between flights. |
Condolences to the families of the crew and passengers - so many people hurt & directly affected
Frightening footage! The forum with discussions and theories of the cause is interesting and some of you obviously have a high level of technical knowledge however regardless of what is determined as the cause and any potential flaws with the IHUMS or the procedure of downloading and interpreting the information, the damage is done and the confidence, whether warranted or not, seems to be lost in the EC25. Any shortfalls in procedures should of course be addressed appropriately but especially in today's environment it wouldn't want to cost too much. Affordable safety in world of greed. Sorry a cynical view I know but some of you may share my view. |
There was an initial report of fire before the separation. Now statements that engine parts were changed in the days before the crash. Is there an escalation path from an engine 'issue' to separation of the rotor head?
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I think if the MGB was undergoing the process of self destruction, with all that heat and oil, as soon as the case cracked it is quite feasible that oil ignition would be likely.
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