CHC are saying that it was changed in January:

http://uk.reuters.com/article/us-norway-crash-idUKKCN0XQ15K

Any ATC transcript?

electrotor
I stand corrected in my use of loose terminology. Perhaps it would have been more correct to state that the weight of the aircraft is primarily supported by the top bearing in the gearbox casing and as has been previously demonstrated, it is possible for the rotor shaft to pull through the bearing and depart given certain fault conditions.

This accident bears remarkable similarities to the G-REDL incident where the main rotor also departed from the helicopter. I would not be surprised if a similar failure mechanism was found. Height at which the incident occured is almost identical and apparently there was no warning before the main rotor broke away.

I wonder did anyone monitor the last radio transmissions to see if the pilot issued a Mayday alert as was the case for G-REDL in 2009 when metal particles in the gearbox caused it to fail and shear the rotor head.

Helicopters have some graceless failure modes.
Should there be a provision for an emergency parachute, such as offered on some light aircraft, or is that impracticable for this size vehicle?

MR imbalance
 

Blades all look attached, however if a blade failed in the driving region and separated...

That was from flightradar24. There are some anomalies in the way that flightradar24 records flights but looking at the detail there is definitely a record of 3 short flights that are 13 to 16 minutes long and are circuitous around local fjord and nearby islands. The first is 1129h 26th, second 0643h 27th, third 1224h 27th. The first has a routine flight number and so may be a RTB after normal departure. No other flights are shown during that 25 hour period.

Next Theory
 

Jim, with the gearbox change being accomplished in January, it looks like it's time to wait for the sharp eyes to look at what came down with the rotor head and how/where it failed structurally, as well as determining what, if anything, the main blades hit prior to the head separation. Time for the accident investigation pro's and the OEM design/test people to look at the evidence. Still would be of interest to know what the short flights were all about.

HUMS parameters just beyond limits? Couple 'quick fixes' to get it within limits perhaps. Who knows.

It is what it is and it's out there on a public website. What it means is for the professional head scratchers.

For what it is worth.

ETUDIANT - Think about where you would mount the parachute on a light aeroplane ....- away from the rotating parts, so whether the chute is deliberately or inadvertently deployed, it can work without interference.
I cant think where you could mount a safety parachute on a helicopter where it is not going to cause a catastrophic failure if inadvertently deployed, and where it is going to be unimpeded by rotating parts if you want to deliberately deploy it (in all circumstances except complete detachment of the main rotor head, which remains an extremely rare occurrence)
So - chutes are a fairly impractical proposition for helicopters.

How about under a suitable faired structure where the 'chinamans hat" is currently atop the jesus nut?

CC

For F*cks sake! That is the stupidest post I have seen in a long time.

Thanks for your informative input.

CC

Having just watched the video above and I realize I'm asking for speculation, but seeing the video of the rotor head falling and the still pictures would we assume that it failed where the bevel gear is welded to the m/r shaft?

On the EC225 all lift forces are transmitted to the airframe via the bearing housing of the MRH mast not the MGB. 3 suspension bars transmit the lift forces from the mast to the airframe. One of the suspension bars can be clearly seen in the photograph of the detached MRH.

OK, so which actual part would fail that would cause such a clean (relatively) break that would allow the entire rotor head and blades to depart seemingly undamaged.

Again....realizing that it would be speculation, but from someone who has knowledge of how the system is designed ( I'm not an EC/Airbus guy)

The fact that the main rotor has been recovered more or less intact should mean that the cause of the failure gets established pretty quickly. I wouldn't be surprised if we see an AD within the next few days.

Thoughts are with everyone at CHC - sad day for the industry, no matter where you are and what you do. :(

So is this the death knell for the 225 - or will operators continue to operate it even after past issues with it - or in fact is it even feasible to stop using the 225 with the amount operators have invested in it.

And there is no bolt in the end of it or deformation visible as to how it became detached? I would think that the bar would fail long before the bolt sheared unless the bolt is loose then without tension it would snap like a carrot or possibly it was not even there.
The other end is obviously still attached so part of the housing is possibly still attached to the mast. The visible end is the frame end as it is the forked one.

How long would a 225 fly with some of the flight loads through the flared housing?

Looks a little odd. But then again all will be revealed in due course. Just saying.


http://www.eurocopter.com/publicatio...rotorec225.jpg

Really? It took months to fix the 225 and make it ready to go back to pax carrying flights last time.

Just to clarify, the suspension bars are restrained by a pin which is safetied by two 'nappy pins'

One area of interest may be at the bolted joint between the MRH and MGB. The bolts of the MRH mast go into barrel nuts housed in the MGB. These barrel nuts have plastic blanks inserted at the same time to prevent oil leaks. Unfortunately its impossible to tell from the plastic blank if the barrel nut has been inserted upside down. Not sure if could be a factor but it’s been a Murphy for years on this installation.

A truly tragic accident. Horrifying video of the final moments and images that no aviator would ever wish to see. I only hope that this terrible event will provoke some serious, honest discussions about safety but the cynic in me knows otherwise.
How quickly everyone rushes to deflect blame and responsibility.
After the previous accidents involving the type I was sickened to learn that the HUMS had detected signs of impending failure in 2 or 3 flights prior to the accident. Why are operators so reluctant to use the data available to stop accidents like this happening? Why are the authorities so against forcing the operators to monitor and use the HUMS data? Why are the manufacturers trusted beyond logical reason and not forced to produce more useable safety monitoring? I couldn't believe that the authorities accepted returning the puma to service after the last grounding under the terms that they did - allowing aircraft to operate with a known defect in a critical component. What could possibly motivate such a decision, certainly not true safety.
All the corporate proclamations about safety being the primary concern ring very hollow after incidents like this. I fear that costs get in the way of true safety every time.
So will we see a repeat of the process from the other offshore accidents which does very little to prevent further accidents even though the causes are clearly identified? Sad, very sad.

How long would a 225 fly with some of the flight loads through the flared housing?

I think the massive change in cyclic pitch would be the problem.

The suggestion of an RTB followed by a couple of airtests would fit with a gearbox chip light causing the RTB, oil drained and analysed followed by heavy hover and airtest to check for any further chips before sending it commercial again on close monitoring. Again similar to DL, and the way the French like to do things.

RVDT, thanks for the clear explanations.

As you mention it, the fact that the airframe end of the suspension bar looks undamaged questions about the missing bolt. Whatever the securing device for this bolt is - cotter pin, nut, caramel, the question is why is it missing ? Maintenance flaw or metal shear ?

And to be clear for readers, HUMS can not detect missing bolts or nuts

Having flown many thousands of hours in offshore helicopters some decades ago I was truly shocked to see the video evidence of this accident. The whole rotor head with intact blades separated from the gearbox and came down like a sycamore leaf. A structural failure of this magnitude is non survivable in a helicopter.

Also having been involved with the Puma accident in Sarawak in 1980 when the gearbox failed on 9M-SSC I don't recall the main rotor detaching like this. One or two blades detached through the shear deceleration forces and the captains door flying up into a blade when he released the door but otherwise the rotor head was still connected.

This looks like a failure of the rotor head itself (jesus nut?) for the whole rotor system to detach so cleanly.

just to be clear, are you suggesting the end we can see in the picture pointing up is actually the 'bottom' end of the rod that should be attached to the airframe?

But HUMS would pick up the vibration caused by the missing bolt!

To Scuffers : yes,
To redhanded : not sure : if the bolt fits tigh, and has only one axis of motion I am not sure the HUMS could detect the movement of the bolt. More than that, if flight, under high lift, I hardly suspect the bolt from moving.

Years ago, flying Lynx, I encontered unusual vibrations in flight while collective down only. It turns out to be a missing part in the collective control chain, but under lift, there was no vibs.

Agreed, so my point is why is the data not taken seriously enough? The manufacturers should be forced to produce a more user friendly interface for the technicians to be able to interrogate between flights. And the operators should be forced by the authorities to read HUMS between flights. The information is there to make flights safer but we are failing to use it to its full potential. I operate in Norway and am pretty sure the HUMS data is downloaded but couldn't possibly be properly interrogated in the short time between flights. In my opinion HUMS data should be looked at very closely after a MGB caution of any sort. Does it happen now? Doubt it....

Go back to post 23 and the eye witness report of a fire before the separation. Any other evidence of this?

Unrelated question, does CHC have screens over the engine air intakes?

HUMS picks up vibrations and frequencies that could NEVER be felt or heard by humans- that's the beauty of it. The problem is interrogating and deciphering all the data into something meaningful. Cue the authority to take a proactive role for a change.

Older type of helicopters only have fire detection in the engine bays so a fire in the transmission compartment without detection is entirely possible. Planetary gear failure with MRH departure given previous history of transmission problems has got to be a suspect. Condolences to those affected.

To try and avoid a raft of posts along the lines of "I heard that...", the AAIB report on the 2012 225 ditchings details generally how the operators used their HUMS at the time, and then specifically how the HUMS was used on each of the affected aircraft.

https://assets.digital.cabinet-offic...and_G-CHCN.pdf

The relevant sections start on page 45 at 1.11.4.4 G-REDW operator’s internal HUMS procedures.

For the second flight (CHCN), yes. For the first one (REDW) the HUMS was downloaded after the first flight, and according to the report, acted on iaw the AMM.

I just wanted to avoid the usual round of ill-informed posts (that's not directed at anyone) but we went round and round this buoy at the time and it got tedious.

The guidance to operators given in CAP 753 states that the period between the successful download and assessment of any primary VHM indicator, used for monitoring the engine and rotor drive system components, should not exceed 25 hours.

This just isn't good enough. what good is it to read the results of the HUMS analysis which warns of a problem AFTER an accident?!

Tedious??!! Maybe if something was done to take the data and procedures more seriously lives would have been saved.

G-REDW had numerous HUMS alerts warning of a problem in the main gear box in the hours leading up to the accident. It's just not acceptable to say that the proper engineering procedures were followed. The procedures are obviously flawed!