EC225 crash near Bergen, Norway April 2016
Join Date: Jan 2007
Location: Melbourne
Posts: 32
Likes: 0
Received 0 Likes
on
0 Posts
Mitchaa,
The only thing I would say about your reasoning is that you are assuming that if the head was installed on 27th March, it hadn't been disturbed since. We don't know the full maintenance history for the aircraft. It surely is possible and plausible that the system had been disturbed between 27th March and the fateful day.
The ASB issued by Airbus covered only the suspension bar attachment and fittings:
Check for correct installation of the suspension bar assembly:
- correct fitting of the lower and upper pins
- presence and correct position and condition of the locking pins
- check the tightening torque of each of the attachment bolts of the MGB bar fittings as per MMA 53-26-00-212 and correct any discrepancy according to the task. Measure the values in accordance with Figure 2.
It was the EASA AD that introduced MGB filter chip and HUMS checks.
Once again, I'm not suggesting that suspension bar failure or error is the cause, but it's possible. Just because it hasn't happened before...........
The only thing I would say about your reasoning is that you are assuming that if the head was installed on 27th March, it hadn't been disturbed since. We don't know the full maintenance history for the aircraft. It surely is possible and plausible that the system had been disturbed between 27th March and the fateful day.
The ASB issued by Airbus covered only the suspension bar attachment and fittings:
Check for correct installation of the suspension bar assembly:
- correct fitting of the lower and upper pins
- presence and correct position and condition of the locking pins
- check the tightening torque of each of the attachment bolts of the MGB bar fittings as per MMA 53-26-00-212 and correct any discrepancy according to the task. Measure the values in accordance with Figure 2.
It was the EASA AD that introduced MGB filter chip and HUMS checks.
Once again, I'm not suggesting that suspension bar failure or error is the cause, but it's possible. Just because it hasn't happened before...........
Join Date: Aug 2013
Location: Perth Western Australia
Posts: 2
Likes: 0
Received 0 Likes
on
0 Posts
A three leg chair & suspension rods, 100% speculation but willing to be educated.
I’m not sure the EC225 suspension rods are best represented by the three leg chair / Jesus nut theory. Several points to think about:
I assume they are normally subject to a stretch force but it you look at the diagram in post 42, at an angle of around 45 degrees they should also provide a degree of longitudinal support, via the rotor bearing / casing (although I can’t find what type of bearing this is). I’d guess the rods can act to stretch and compression forces as that is what they look to be designed for (it is a rod).
Now the Rotor shaft, this seems to be supported against gyroscopic / asymmetrical lift forces by the main rotor shaft, gearbox bearings, & rotor bearing. The three leg chair does not fit this situation. I can imagine the loss of one support rod would place an additional load on the bearings that may lead to eventual failure, but not an instantaneous failure.
I’m not sure the EC225 suspension rods are best represented by the three leg chair / Jesus nut theory. Several points to think about:
I assume they are normally subject to a stretch force but it you look at the diagram in post 42, at an angle of around 45 degrees they should also provide a degree of longitudinal support, via the rotor bearing / casing (although I can’t find what type of bearing this is). I’d guess the rods can act to stretch and compression forces as that is what they look to be designed for (it is a rod).
Now the Rotor shaft, this seems to be supported against gyroscopic / asymmetrical lift forces by the main rotor shaft, gearbox bearings, & rotor bearing. The three leg chair does not fit this situation. I can imagine the loss of one support rod would place an additional load on the bearings that may lead to eventual failure, but not an instantaneous failure.
Join Date: May 2016
Location: Norway
Posts: 1
Likes: 0
Received 0 Likes
on
0 Posts
B
In post 493 (picture) you can see the rh coupling flenge is bendt upward. This is a steel tube that work as a rear engine mount with the high speed shaft innside. I belive that if the forward suspension bar breaks this tube will be bendt downward since the MGB will tilt backward.
I don't want to open another can of worms but, if, for any reason, the mast and head moves with respect to the rest of the airframe the control systems WILL cause the blades to fly in un-commanded ways. Either the swashplate follows the mast and the rods that position it will cause unwanted control inputs or the swashplate stays aligned with the airframe and the links to the blades will move them in unwanted ways. I suspect that a small amount of mast relative movement could put enough control input to the blades/head to cause it to be ripped out of the airframe. This might explain the rocking motion seen by the observer before the head departed.
The same might happen if the control system gave a sudden un-commanded input if, say, something else let go that impacted or disrupted it.
The same might happen if the control system gave a sudden un-commanded input if, say, something else let go that impacted or disrupted it.
Join Date: Apr 2009
Location: France
Age: 66
Posts: 45
Likes: 0
Received 0 Likes
on
0 Posts
Popular proverb : There Are None So Blind As Those Who Will Not See
G.REDL fuselage end of suspension bar : bented, twisted
LN.OJF fuselage end of suspension bar : looks undamaged
G.REDL fuselage end of suspension bar : bented, twisted
LN.OJF fuselage end of suspension bar : looks undamaged
I am amazed no one has latched onto the barbecue plate. You are all so preoccupied with support rods you are not considering 101 other causes.
Let's face it, none of us have a clue what happened and are just wasting time speculating. Let's just leave it up to the experts who have (nearly) all the evidence in front of them and will produce some answers as soon as they can.
Let's face it, none of us have a clue what happened and are just wasting time speculating. Let's just leave it up to the experts who have (nearly) all the evidence in front of them and will produce some answers as soon as they can.
Join Date: May 2016
Location: UK
Posts: 6
Likes: 0
Received 0 Likes
on
0 Posts
There seems to be some confusion about the loads taken by the suspension bars and by the main gearbox attachment to the airframe structure.
The suspension bars carry the vertical loads. The lift force is transmitted through them to the structure and so they are under tension. In the hangar the weight of the head and gearbox is transmitted through the struts and so they are under compression.
The gearbox is attached to the structure via the barbeque plate which is designed to take up the horizontal forces and not the vertical loads. It picks up the main rotor reaction torque and the longitudinal and transverse loads while damping the vibrations. The fact that it is not designed to transmit vertical forces is obvious from its design. For an example of a main gearbox attachment that is designed to transmit the lift forces look at Sikorsky.
During flight the aircraft is actually hanging from the suspension bars.
The suspension bars carry the vertical loads. The lift force is transmitted through them to the structure and so they are under tension. In the hangar the weight of the head and gearbox is transmitted through the struts and so they are under compression.
The gearbox is attached to the structure via the barbeque plate which is designed to take up the horizontal forces and not the vertical loads. It picks up the main rotor reaction torque and the longitudinal and transverse loads while damping the vibrations. The fact that it is not designed to transmit vertical forces is obvious from its design. For an example of a main gearbox attachment that is designed to transmit the lift forces look at Sikorsky.
During flight the aircraft is actually hanging from the suspension bars.
Join Date: Sep 2007
Location: Birmingham
Posts: 244
Likes: 0
Received 0 Likes
on
0 Posts
Nobody is listening anymore
Despite more than 4 million hours of safe flight and that a rational explanation of the cause is in progress it would seem that the passengers and the E&P companies have already decided that this is one catastrophic mechanical failure too many. CHC is in poor financial help, Airbus has a PR and sales nightmare.
The outcome of the investigation is necessary for the victims families to understand what happened, for manufacturers and operators to learn lessons but whatever the conclusion the Superpuma's days as the North Sea workhorse are surely over.
If companies wont rent it and passengers wont ride in it it is a legacy helicopter
The outcome of the investigation is necessary for the victims families to understand what happened, for manufacturers and operators to learn lessons but whatever the conclusion the Superpuma's days as the North Sea workhorse are surely over.
If companies wont rent it and passengers wont ride in it it is a legacy helicopter
Join Date: May 2012
Location: Aer
Posts: 431
Likes: 0
Received 0 Likes
on
0 Posts
Birmingham
You are welcome to your opinion but if this is down to a failure mode which is simple to fix like the strut mounting bolts being checked by the latest EASB, the 225 could fly again. As for CHC having financial problems, Chapter 11 could be just what CHC needs to stop bleeding cash to the leasing companies who won't negotiate. As for Airbus, well they can spin their way out of most things.
As an oil and gas company advisor, I have spent many hours this week in front of my CEO and Directors. Not one member of our board has a closed mind to re habilitating the 225. We have all flown in the 225 and as a company, we have many safe hours of 225 flight.
If and when appropriate, we will design and follow a process with our stakeholders and passengers, regardless of the time and complexity of such a process. We are not at all desperate, we run a mixed fleet and activity levels are such that we can make do with the other aircraft we have contracted for a while.
it would seem that the passengers and the E&P companies have already decided that this is one catastrophic mechanical failure too many. CHC is in poor financial help, Airbus has a PR and sales nightmare.
As an oil and gas company advisor, I have spent many hours this week in front of my CEO and Directors. Not one member of our board has a closed mind to re habilitating the 225. We have all flown in the 225 and as a company, we have many safe hours of 225 flight.
If and when appropriate, we will design and follow a process with our stakeholders and passengers, regardless of the time and complexity of such a process. We are not at all desperate, we run a mixed fleet and activity levels are such that we can make do with the other aircraft we have contracted for a while.
Join Date: Aug 2008
Location: Canada
Posts: 15
Likes: 0
Received 0 Likes
on
0 Posts
john6016
Would this be possible:
1. Holding pin of suspension bar pops out in flight (possibly due to improper install)
2. This allows transmission to move a little in the vertical axis
3. This causes engine input shaft bearings to experience massive side loads, leads to failure of bearings.
4. Engine input shaft start to wobble causing inter-meshing of gears
5. Transmission produces metal causing failure of epicyclic
6. The rest same as L2 (REDL)
I can imagine the loss of one support rod would place an additional load on the bearings that may lead to eventual failure, but not an instantaneous failure.
1. Holding pin of suspension bar pops out in flight (possibly due to improper install)
2. This allows transmission to move a little in the vertical axis
3. This causes engine input shaft bearings to experience massive side loads, leads to failure of bearings.
4. Engine input shaft start to wobble causing inter-meshing of gears
5. Transmission produces metal causing failure of epicyclic
6. The rest same as L2 (REDL)
Join Date: May 2016
Location: Home
Posts: 72
Likes: 0
Received 0 Likes
on
0 Posts
Birmingham - never say never! Let's just replace 60% of the helicopters in the North Sea. What do you suggest we replace them with? Guess it would be great if we could replace it with something that is guaranteed not to fail. Even with the guarantee, the cost and down time implementation of this would be astronomically. The retraining(hopefully) of everyone from drivers, maintenance, ramp staff to passenger and management would be astonishing. Now minus the guarantee of a perfect aircraft, because that does not exist, I think the safety factor would drastically decrease with drivers that have limited experience of type, engineers that are fixing aircraft they are as familiar with and even ramp staff doing daily operations around aircraft they are not use to. The downtime and limit aircraft support while waiting for aircraft to be manufactured and staff ramped up would have oil companies crippled for passenger movements. The spin off to this would have massive consequences, from cost, fatigue, moral, etc.
Letmein,
You beat me to it!
I just want to add the the shaft will probably also be subjected to tilting moments.
And the pin failure might be caused by missing or failing nappy pins?
Did we see a complete fork on the suspension bar or might there be one side missing?
SLB
You beat me to it!
I just want to add the the shaft will probably also be subjected to tilting moments.
And the pin failure might be caused by missing or failing nappy pins?
Did we see a complete fork on the suspension bar or might there be one side missing?
SLB
john6016
Would this be possible:
1. Holding pin of suspension bar pops out in flight (possibly due to improper install)
2. This allows transmission to move a little in the vertical axis
3. This causes engine input shaft bearings to experience massive side loads, leads to failure of bearings.
4. Engine input shaft start to wobble causing inter-meshing of gears
5. Transmission produces metal causing failure of epicyclic
6. The rest same as L2 (REDL)
Would this be possible:
1. Holding pin of suspension bar pops out in flight (possibly due to improper install)
2. This allows transmission to move a little in the vertical axis
3. This causes engine input shaft bearings to experience massive side loads, leads to failure of bearings.
4. Engine input shaft start to wobble causing inter-meshing of gears
5. Transmission produces metal causing failure of epicyclic
6. The rest same as L2 (REDL)
I took this very simplistic example to show that two out of three remaining suspension points do not simply equate 2/3 of the strength.
I can imagine the loss of one support rod would place an additional load on the bearings that may lead to eventual failure, but not an instantaneous failure.
That would happen if the remaining structure would be sufficient to keep everything in its place.
However, the suspension rods in the 225 are there to take the vertical load. I can't imagine the relatively fragile conical housing and joiners will be able to take the load from a missing front suspension. They are not designed for that. And in that case it would rip off the epicyclic module and/or conical housing and the whole Main Rotor would tilt rearwards with whatever remains of the structure underneath.
Join Date: Sep 2007
Location: Birmingham
Posts: 244
Likes: 0
Received 0 Likes
on
0 Posts
Birmingham
You are welcome to your opinion but if this is down to a failure mode which is simple to fix like the strut mounting bolts being checked by the latest EASB, the 225 could fly again. As for CHC having financial problems, Chapter 11 could be just what CHC needs to stop bleeding cash to the leasing companies who won't negotiate. As for Airbus, well they can spin their way out of most things.
As an oil and gas company advisor, I have spent many hours this week in front of my CEO and Directors. Not one member of our board has a closed mind to re habilitating the 225. We have all flown in the 225 and as a company, we have many safe hours of 225 flight.
If and when appropriate, we will design and follow a process with our stakeholders and passengers, regardless of the time and complexity of such a process. We are not at all desperate, we run a mixed fleet and activity levels are such that we can make do with the other aircraft we have contracted for a while.
You are welcome to your opinion but if this is down to a failure mode which is simple to fix like the strut mounting bolts being checked by the latest EASB, the 225 could fly again. As for CHC having financial problems, Chapter 11 could be just what CHC needs to stop bleeding cash to the leasing companies who won't negotiate. As for Airbus, well they can spin their way out of most things.
As an oil and gas company advisor, I have spent many hours this week in front of my CEO and Directors. Not one member of our board has a closed mind to re habilitating the 225. We have all flown in the 225 and as a company, we have many safe hours of 225 flight.
If and when appropriate, we will design and follow a process with our stakeholders and passengers, regardless of the time and complexity of such a process. We are not at all desperate, we run a mixed fleet and activity levels are such that we can make do with the other aircraft we have contracted for a while.
Join Date: Jun 2007
Location: foot of a mountain
Posts: 293
Likes: 0
Received 0 Likes
on
0 Posts
The mgb stay lower attachment have nothing to do with MRH removal/installation. In fact unless you remove the mgb stays for a scheduled inspection they are often not even desturbed for mgb removal except for the upper pins.
The pins are a close tolerance fit safetyied by the nappy pins so that if they move they cant move beyond the safety pins. So no they wont just fall out especially seeing they carry vertical loads after 1 or 2 flights. However over time and the inevitable torque reaction off the strut it will work loose eventually. How long this will take is anybodies guess but it will be more than a few flights.
I can not remember the maintenance manual instructions on the 332 but on the 350, 120 you can fit the upper attachment bolts in their case anyway round but the lower must be in the direction indicated in the manual which funnily enough is in the torque opposing direction so if they come loose somehow they will work themselves towards the stay not away.
For those continuing to compare to REDL pls read the report and the full report on that tragic accident and do not miss the parts referring to chip warnings, HUMS thresholds adjusted, etc. It did not happen out of the blue! Is someone to blame? No but loads of human factors and system failures were identified and it did lead to increased awareness to follow OEM instructions and improve comms in writing with OEM's to prevent a reoccurance.
If we all could take the time to actually read the full reports on all 332/225 accidents and/or incidents and make sure we know where what is on the aircraft then maybe we could have more intelligent debates without emotion from all speculating and argueing for and against on here but please go read the actual reports and not the newspapers first.
The pins are a close tolerance fit safetyied by the nappy pins so that if they move they cant move beyond the safety pins. So no they wont just fall out especially seeing they carry vertical loads after 1 or 2 flights. However over time and the inevitable torque reaction off the strut it will work loose eventually. How long this will take is anybodies guess but it will be more than a few flights.
I can not remember the maintenance manual instructions on the 332 but on the 350, 120 you can fit the upper attachment bolts in their case anyway round but the lower must be in the direction indicated in the manual which funnily enough is in the torque opposing direction so if they come loose somehow they will work themselves towards the stay not away.
For those continuing to compare to REDL pls read the report and the full report on that tragic accident and do not miss the parts referring to chip warnings, HUMS thresholds adjusted, etc. It did not happen out of the blue! Is someone to blame? No but loads of human factors and system failures were identified and it did lead to increased awareness to follow OEM instructions and improve comms in writing with OEM's to prevent a reoccurance.
If we all could take the time to actually read the full reports on all 332/225 accidents and/or incidents and make sure we know where what is on the aircraft then maybe we could have more intelligent debates without emotion from all speculating and argueing for and against on here but please go read the actual reports and not the newspapers first.
Please forgive my not being familiar with 225 slang/jargon, but what's the barbecue plate?
Transmission picture
Install Bevel Gear Video
Rotor/transmission/struts figure
In these various pictures and the video of putting the bevel gear into the transmission, where do I find the barbecue plate? (Please don't tell me "in the lunch room, of course!" )
Transmission picture
Install Bevel Gear Video
Rotor/transmission/struts figure
In these various pictures and the video of putting the bevel gear into the transmission, where do I find the barbecue plate? (Please don't tell me "in the lunch room, of course!" )
Last edited by Lonewolf_50; 5th May 2016 at 16:05.
