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EC225 crash near Bergen, Norway April 2016

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EC225 crash near Bergen, Norway April 2016

Old 6th Jun 2016, 08:16
  #1221 (permalink)  
 
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Originally Posted by turboshafts View Post
Hi,

the systems for an aircraft has to be fool-proof

the same is valid for the manintenance
There are some pretty creative fools out there
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Old 6th Jun 2016, 10:30
  #1222 (permalink)  
 
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Lonewolf_50 I have no idea who did this particular installation sorry
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Old 6th Jun 2016, 15:00
  #1223 (permalink)  
 
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If oil system volume is decreasing you should see an increase in temperature as the available oil is spending less time cooling down before it's heated up again.
???? Just the same as it spends less time heating up again? Common misconception and wives tale.

Low volume where the oil reservoir is integral i.e. a gearbox will actually run cooler as the oil visits the cooler more in a given time period.

Bell 206 overfilled due to people misunderstanding the correct level in the MGB is a classic example.
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Old 6th Jun 2016, 17:22
  #1224 (permalink)  
 
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Originally Posted by turboshafts View Post
With respect to the LN-OPG accident, I have read the report again to understand a bit more further the strategy of the ongoing investigation. It is written explicitly in the report, that gearboxes are interchanged between helicopters in the fleet. The same is said for the engines. After overhaul they could be mounted on any aircraft of the type (per my understanding).
The ability to replace major components (like gear boxes and engines) is a desirable design feature for a variety of customers. Modularity does not, by itself, lead to gear boxes or engines failing. (I am not sure what point you are trying to make with that observation). Your reference to that accident led me to the very thorough report AIBN did for that accident: it was interesting from a lot of angles. (Thank you!) Your question on "what if" regarding TBO differences (higher or lower) probably can't be answered definitively without being able to account for the health of the fleet overall, and how frequently this family of main gear boxes have to be removed before the TBO due to various removal criteria.
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Old 7th Jun 2016, 00:51
  #1225 (permalink)  
 
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@RVDT: What I said at #1217 is what is taught in flight training based on manufacturer supplied training material. Not common misconception and wives tale. If you're losing oil volume the oil temperature should rise slightly. We are not ones to teach something other than what the manufacturer espouses.
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Old 7th Jun 2016, 06:44
  #1226 (permalink)  
 
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Gearbox maintenance quality control

Birmingham wrote in #1213
Diversification; There is no way that a company of HS/CHC's standing operating a contract for Statoil would knowingly use old parts (unless part of a fully approved refurbishment program with full traceability). There is an outside chance it would happen without their knowledge but so many systems and checks are there it is next to impossible. There have been a number of statements made about maintenance and we haven't yet had the report. But the standards these guys work to are the highest in the world. We should certainly give them more than the benefit of the doubt until some evidence is produced. I don't know any more than anybody else but I would be very surprised if they weren't entirely exonerated.

After reading of the AIBN report about LN-OPG dated 2001 it is clear to me that at that time (2001) the procedures applied for quality control of some parts made by Eurocopter and their suppliers in France as well as by HS in their own refurbishing of gear boxes. One can only hope that the findings in that report from AIBN had a major impact and was followed up later.
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Old 7th Jun 2016, 10:30
  #1227 (permalink)  
 
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Originally Posted by GR4 View Post
Except it wasn't increased to 4400hrs it was reduced to 2000hrs.
If that is the case, it´s good.

But it is truly stated in an interview with the CEO Arne Roland after CHC last week press conference that they follow a maintenance program where the gearbox at 4400 hours is sent to overhaul

here is the article
CHC-sjefen: - Vi har ikke tilgang til girkassen - Bergens Tidende

However, in the interview with NRK, BT or TU
he refuse to tell how many flying hours the gearbox had before the accident.

The main point he made several times is that CHC does not have access to the gearbox and is sent to an external supplier for overhaul.
He refuse to say where and who is doing the overhaul.

In the topic here it was mentioned that the overhaul is done by Heli-One
and is 100% owned by CHC.

Both Heli-One and CHC Headquarters are at Sola Airport in Norway.
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Old 7th Jun 2016, 18:38
  #1228 (permalink)  
 
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CHC-sjefen: - Vi har ikke tilgang til girkassen - Bergens Tidende

Ny girkasse i januar

- Vi følger et vedlikeholdsprogram som tilsier at girboksen etter 4400 flytimer sendes til en leverandør som utfører vedlikehold, sier Roland videre.

Girboksen på ulykkeshelikopteret ble installert i januar. Under vedlikehold blir enkelte deler utbedret, mens andre blir skiftet helt ut.

Roland vil ikke svare på om planetgiret, som ifølge Havarikommisjonen er utsatt for tretthetsbrudd, ble skiftet ut i januar.

- Jeg kan ikke gå inn på spesifikke opplysninger om de ulike delene.

Directly translated to English by me:

New gearbox in January

- We follow a maintenance program that says that the gearbox
after 4400 flying hours is shipped to a supplier that perform maintenance, says Roland further.

The gearbox on the accident helicopter was installed in January.
During maintenance some parts are refurbished, some are completely replaced.

Roland does not want to answer, if the planetary gear, that according to the Accidentboard is subject to fatigue cracks, was replaced in January.

- I can not go into specific information about the different parts.
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Old 7th Jun 2016, 22:53
  #1229 (permalink)  
 
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Some news from the investigation, not previously mentioned in this thread:

Spricka funnen i kraschade helikopterns rotorväxel | Ny Teknik

Utredarna i den norska haverikommissionen som granskar vad som gick snett i den norska helikopterolyckan den 29 april har upptäckt en utmattningspricka i ett av kugghjulen som ingår i huvudrotorns växel. Det uppger myndigheten i en första rapport om händelsen. Det finns också andra tecken på metallurgiska utmattningsproblem.
My translation:

The investigators in AIBN, who studies what went wrong in the Norwegian helicopter accident the 29th of April, have discovered a fatigue crack in one of the wheels in the main rotor gear box. AIBN states this in the first report about the accident. There are also other indications of problems of metal fatigue.
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Old 8th Jun 2016, 01:06
  #1230 (permalink)  
 
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Originally Posted by MrSnuggles View Post
The investigators in AIBN, who studies what went wrong in the Norwegian helicopter accident the 29th of April, have discovered a fatigue crack in one of the wheels in the main rotor gear box. AIBN states this in the first report about the accident. There are also other indications of problems of metal fatigue.
This is already known, is described in the latest preliminary report, and has been discussed here extensively.
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Old 8th Jun 2016, 10:50
  #1231 (permalink)  
 
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I haven't looked at this topic for a few weeks, so hopefully I'm not about to repeat something which might already have been raised by others. As someone with thousands of hours flying the EC225, I know that there is a chip detector spring-loaded toggle switch above the pilots' heads. Moving it one way tests all chip detectors, both for the engines and gearbox. While holding the switch against its spring you see in sequence "Chip1" for engine 1, "Chip2" for engine 2 and "Chip" for the gearbox, all showing on the VMS display panel. This test gets done before every flight. Moving it the other way in flight would put a high voltage electric pulse through the very smallest (hair fine) metal particles on the detectors and burn them off.


Two such "fuzz burns" are allowed in flight, after which if it's a gearbox "Chip" warning a landing must be made as soon as possible e.g. on the nearest available helideck offshore. I've only ever had a "Chip 1" in flight and I brought engine 1 back to idle in the cruise, to minimise further possible damage. The particle was found to be negligible and the engine was returned to service.


With the removal of the magnets from the gearbox after the REDL disaster, I would hope that the slightest particles from wear or spalling in the epicyclic gears at the top of the gearbox would be detected long before any risk could arise. But this doesn't seem to have been the case in Norway. Yet photographic evidence and some opinions suggest that there was wear. In which case why weren't particles being detected during several hours of flight before the rotor head came off? As for missing roller bearings in one of the planet gears, is the metal of the gear-wheels elastic enough to allow rollers to escape during violent deformation of all components?


I still feel on balance that the cause was detachment of one of the gearbox suspension rods, for as yet unknown reasons. Sudden shattering of gearbox internal components without any prior signs of wear seems beyond belief.

Last edited by Colibri49; 8th Jun 2016 at 11:18.
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Old 8th Jun 2016, 11:51
  #1232 (permalink)  
 
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That does not sound good for the 225

Super Pumas Finished in North Sea - Oil and Gas News
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Old 8th Jun 2016, 12:25
  #1233 (permalink)  
 
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Originally Posted by Colibri49 View Post
I haven't looked at this topic for a few weeks, so hopefully I'm not about to repeat something which might already have been raised by others. As someone with thousands of hours flying the EC225, I know that there is a chip detector spring-loaded toggle switch above the pilots' heads. Moving it one way tests all chip detectors, both for the engines and gearbox. While holding the switch against its spring you see in sequence "Chip1" for engine 1, "Chip2" for engine 2 and "Chip" for the gearbox, all showing on the VMS display panel. This test gets done before every flight. Moving it the other way in flight would put a high voltage electric pulse through the very smallest (hair fine) metal particles on the detectors and burn them off.


Two such "fuzz burns" are allowed in flight, after which if it's a gearbox "Chip" warning a landing must be made as soon as possible e.g. on the nearest available helideck offshore. I've only ever had a "Chip 1" in flight and I brought engine 1 back to idle in the cruise, to minimise further possible damage. The particle was found to be negligible and the engine was returned to service.


With the removal of the magnets from the gearbox after the REDL disaster, I would hope that the slightest particles from wear or spalling in the epicyclic gears at the top of the gearbox would be detected long before any risk could arise. But this doesn't seem to have been the case in Norway. Yet photographic evidence and some opinions suggest that there was wear. In which case why weren't particles being detected during several hours of flight before the rotor head came off? As for missing roller bearings in one of the planet gears, is the metal of the gear-wheels elastic enough to allow rollers to escape during violent deformation of all components?


I still feel on balance that the cause was detachment of one of the gearbox suspension rods, for as yet unknown reasons. Sudden shattering of gearbox internal components without any prior signs of wear seems beyond belief.
what we do know is this:
TURØY - Helikopteret avbrøt flygning tre dager før ulykken

There where some "indication lamp" that was providing several messages
in the days before the accident causing the flight to be canceled and the
helicopter to return to base immediately.
After that it was also occuring during test flights, after which
a "component" was changed

if this is coupled to detecting metal particles is too early to say
and purely speculation without having the first hand info.

In which case why weren't particles being detected during several hours of flight before the rotor head came off?

It could be days before, hours or it could be minutes.

Until we know the facts it is impossible to answer that question.

Still to me the last conclusion in your post is a bit too soon.

My personal opinion is that 3 rollers missing from the planetary gear isnt
enough to kill the gearbox even if the roller would get stuck between the carrier and the sun gear.

but it would probably cause surface deterioration that would significantly accelerate the wear on all components in the gearbox.

some signs of wear can be seen on the components. some other components look to be damaged upon impact. The rollers are inserted by squeezing
the outer ring on normal bearings.
if you squeeze a ring gear it will break, so probably there are other methods
of installing the rollers without squeezing the outer ring, and thus
it must also be possible that the rollers can escape.
but honestly i find that as well not very probable.

I guess a part of the analysis is to predict/simulate if there was shearing of the gearbox during rotation. There are many methods to do this
could be a reason that AIBN was doing extensive search for parts in the area
after the accident.

I guess as well there are pilot voice recorder readings to say
how eventual indications lamps or error messages was interpreted during the flight before the accident
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Old 8th Jun 2016, 12:27
  #1234 (permalink)  
 
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Would it be more accurate to say "...without any signs of wear being detected by the Aircraft systems or Engineering surveillance procedures..."?



Originally Posted by Colibri49 View Post
I haven't looked at this topic for a few weeks, so hopefully I'm not about to repeat something which might already have been raised by others. As someone with thousands of hours flying the EC225, I know that there is a chip detector spring-loaded toggle switch above the pilots' heads. Moving it one way tests all chip detectors, both for the engines and gearbox. While holding the switch against its spring you see in sequence "Chip1" for engine 1, "Chip2" for engine 2 and "Chip" for the gearbox, all showing on the VMS display panel. This test gets done before every flight. Moving it the other way in flight would put a high voltage electric pulse through the very smallest (hair fine) metal particles on the detectors and burn them off.


Two such "fuzz burns" are allowed in flight, after which if it's a gearbox "Chip" warning a landing must be made as soon as possible e.g. on the nearest available helideck offshore. I've only ever had a "Chip 1" in flight and I brought engine 1 back to idle in the cruise, to minimise further possible damage. The particle was found to be negligible and the engine was returned to service.


With the removal of the magnets from the gearbox after the REDL disaster, I would hope that the slightest particles from wear or spalling in the epicyclic gears at the top of the gearbox would be detected long before any risk could arise. But this doesn't seem to have been the case in Norway. Yet photographic evidence and some opinions suggest that there was wear. In which case why weren't particles being detected during several hours of flight before the rotor head came off? As for missing roller bearings in one of the planet gears, is the metal of the gear-wheels elastic enough to allow rollers to escape during violent deformation of all components?


I still feel on balance that the cause was detachment of one of the gearbox suspension rods, for as yet unknown reasons. Sudden shattering of gearbox internal components without any prior signs of wear seems beyond belief.
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Old 8th Jun 2016, 16:58
  #1235 (permalink)  
 
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Originally Posted by Colibri49 View Post
I know that there is a chip detector spring-loaded toggle switch above the pilots' heads. Moving it one way tests all chip detectors, both for the engines and gearbox. While holding the switch against its spring you see in sequence "Chip1" for engine 1, "Chip2" for engine 2 and "Chip" for the gearbox, all showing on the VMS display panel. This test gets done before every flight. Moving it the other way in flight would put a high voltage electric pulse through the very smallest (hair fine) metal particles on the detectors and burn them off.

With the removal of the magnets from the gearbox after the REDL disaster, I would hope that the slightest particles from wear or spalling in the epicyclic gears at the top of the gearbox would be detected long before any risk could arise. But this doesn't seem to have been the case in Norway. Yet photographic evidence and some opinions suggest that there was wear. In which case why weren't particles being detected during several hours of flight before the rotor head came off? As for missing roller bearings in one of the planet gears, is the metal of the gear-wheels elastic enough to allow rollers to escape during violent deformation of all components?
.

Well just to be picky, not "high voltage pulse" since the "chip" will be making a short circuit, across which it is very difficult to generate a "high voltage". In fact is a measured dose of charge (set current for a set time) such that a small chip will be vapourised, a larger chip won't be.


I presume that the body of the chip detector has a high-ish value resistor across it and the test procedure checks that this resistance is in circuit. Open circuit (wires disconnected) would therefore not give a good test, and of course a short circuit (chip present) would leave the light permanently on. A bit like the fire detection system in reverse!
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Old 8th Jun 2016, 16:59
  #1236 (permalink)  
 
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Originally Posted by turboshafts View Post

There where some "indication lamp" that was providing several messages
in the days before the accident causing the flight to be canceled and the
helicopter to return to base immediately.
After that it was also occuring during test flights, after which
a "component" was changed

This was said to be an engine gov warning light -according to rumour anyway.
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Old 8th Jun 2016, 21:35
  #1237 (permalink)  
 
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I'm not sure that the missing rollers are significant, it's very hard to imagine those falling out prior to the accident without being noticed in some way. I'm not sure they can escape while in one piece. To me it's by far most likely that they disappeared during the break up or ground impact.

When it comes to how the bearings are put together, I'd guess that they shrink the inner roller surface by cooling it down.
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Old 8th Jun 2016, 23:38
  #1238 (permalink)  
 
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So here we are, 5 weeks or so after the crash. Suggestions coming out of AAIBN about metal fatigue in a planet gear even though the proper metallurgical examination has not been carried out yet. All clever and tricky stuff.

And yet on some of the basics such as the maintenance history, component hours, history of HUMS data, in fact anything that could reflect on things Norwegian, they are strangely silent even though this info must surely be readily available just a day or two after the accident. Why the secrecy? Is there a rat to be smelled out?
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Old 9th Jun 2016, 00:02
  #1239 (permalink)  
 
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The rollers can exit easily when gears have left the carrier wheel
(I.e. after the epicyclic has been torn apart)
when cage and core rotate 30 degrees out of plane with race the first rollers can leave the cage.
see how they are put together.
https://youtu.be/ZvZfgVP-nvA

SLB
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Old 9th Jun 2016, 00:38
  #1240 (permalink)  
 
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Originally Posted by HeliComparator View Post
Well just to be picky, not "high voltage pulse" since the "chip" will be making a short circuit, across which it is very difficult to generate a "high voltage". In fact is a measured dose of charge (set current for a set time) such that a small chip will be vapourised, a larger chip won't be.


I presume that the body of the chip detector has a high-ish value resistor across it and the test procedure checks that this resistance is in circuit. Open circuit (wires disconnected) would therefore not give a good test, and of course a short circuit (chip present) would leave the light permanently on. A bit like the fire detection system in reverse!
Some Aircraft like the S76 also use a set of contacts on the Chip Detector relay to latch and hold the Chip light on. Not sure if this aircraft is a latch hold circuit or not.
Fire Detectors use an Integrity Resistor to prevent False Fire Warnings. Chip detectors do NOT have any Integrity resistors.
Test resistors are used on Fire Bottle, Winch Cut, ETC type Squibs to limit the current during integrity test.
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