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Old 30th Apr 2016, 06:31   #101 (permalink)
 
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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.
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Old 30th Apr 2016, 06:34   #102 (permalink)
 
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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
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.


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Old 30th Apr 2016, 06:37   #103 (permalink)
 
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I wouldn't be surprised if we see an AD within the next few days.
Really? It took months to fix the 225 and make it ready to go back to pax carrying flights last time.
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Old 30th Apr 2016, 06:55   #104 (permalink)
 
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Just to clarify, the suspension bars are restrained by a pin which is safetied by two 'nappy pins'
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Old 30th Apr 2016, 07:24   #105 (permalink)
 
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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.
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Old 30th Apr 2016, 07:26   #106 (permalink)
 
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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.
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Old 30th Apr 2016, 07:30   #107 (permalink)
 
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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.
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Old 30th Apr 2016, 07:35   #108 (permalink)
 
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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.
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Old 30th Apr 2016, 07:50   #109 (permalink)
 
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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
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Old 30th Apr 2016, 08:08   #110 (permalink)
 
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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.
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Old 30th Apr 2016, 08:08   #111 (permalink)
 
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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?
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Old 30th Apr 2016, 08:10   #112 (permalink)
 
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Quote:
Originally Posted by dipperm0 View Post
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
But HUMS would pick up the vibration caused by the missing bolt!
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Old 30th Apr 2016, 08:47   #113 (permalink)
 
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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.
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Old 30th Apr 2016, 09:11   #114 (permalink)
 
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It's my understanding HUMS picked up on the EC225 bevel failure in advance but due to the once per day download pattern used by the operator at that time, it went out on its afternoon flight and subsequently failed resulting in the ditch. Had the HUMS card been downloaded after its morning flight and before its afternoon flight, the impending failure was clear and would have been caught, the aircraft would never have departed. That's why the industry changed to more frequent after flight HUMS downloads in the aftermath.

If it's a gearbox failure this time around which to be honest, is more probable than probably not, I would expect the HUMS to come under close scrutiny. The difficulty the operators have is deciphering the data and what it actually means to the airworthiness of the helicopter, there are a lot of instrumentation defects for example so these need to be filtered out and it can be difficult to detect genuine mechanical failure modes. HUMS probably catches a lot that we are all unaware of because they get to it in time, it's only when failures happen, HUMS comes under scrutiny.
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....
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Old 30th Apr 2016, 09:21   #115 (permalink)
 
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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?
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Old 30th Apr 2016, 09:37   #116 (permalink)
 
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Originally Posted by dipperm0 View Post
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.
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.
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Old 30th Apr 2016, 10:38   #117 (permalink)
 
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Originally Posted by SLF3 View Post
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?
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.
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Old 30th Apr 2016, 10:42   #118 (permalink)
 
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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 operatorís internal HUMS procedures.
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Old 30th Apr 2016, 11:00   #119 (permalink)
 
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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.
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Old 30th Apr 2016, 11:04   #120 (permalink)
 
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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?!

Quote:
Originally Posted by PlasticCabDriver View Post
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.
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!
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