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Dynamic components after rotor strike

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Dynamic components after rotor strike

Old 6th Jun 2022, 12:53
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Didn't the fatal accident 225 MGB which failed in Norway in 2016 have an episode where it fell off a truck on its way from Perth to Broome in Western Australia?
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Old 6th Jun 2022, 16:47
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Originally Posted by industry insider View Post
Didn't the fatal accident 225 MGB which failed in Norway in 2016 have an episode where it fell off a truck on its way from Perth to Broome in Western Australia?
Yes I heard that too. However I also heard that the transmission was sent to Airbus for overhaul.
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Old 7th Jun 2022, 15:25
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The question that I don't think is answered outside of Airbus is how deep they went in to " repair" the Puma gearbox after it fell of the truck. The mfg. said it was repaired properly and that makes it legal. It might have been good as new or it might have been the initiation for the failure because something was missed on a bearing race. The assumption has to be that they knew exactly what happened and did what needed to be done and that the failure was unrelated because nothing could ever be proved linked to sliding off a truck bed.

As long as there is a population of people certified to perform overhaul and repair by manufacturere and airworthiness authorities, there will be people willing to take chances on components as pointed out above, without being sure of the history. There will always be complicit people who send components out to these shops without adequate description of what the real status of the part is. The question is, is it wrong to perform an overhaul, per the manufacturers specs, on a component that appears de-novo on your doorstep with a request for overhaul, without being able to be absolutely sure about the circumstances that brought it to you? Having been a chief inspector at an MRO and seen parts from a known wreck appear for overhaul, my answer is absolutely not. Safety issues notwithstanding, for no other reason because you cannot know how the legal system will treat you if there is an issue down the road. I'm retired now and feel very fortunate to never have been associated with an aaccident that caused an injury or worse. The manufacture and the airworthiness authorities always tell you the MINIMUM that you MUST do. Hardly ever do they write down what you SHOULD do to look after everyone's best interests. That list is left to the conscience of the MRO. It costs a lot of money to fly around. Too bad, it's just the cost of doing business.
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Old 7th Jun 2022, 17:16
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Originally Posted by roscoe1 View Post
The question that I don't think is answered outside of Airbus is how deep they went in to " repair" the Puma gearbox after it fell of the truck. The mfg. said it was repaired properly and that makes it legal. It might have been good as new or it might have been the initiation for the failure because something was missed on a bearing race. The assumption has to be that they knew exactly what happened and did what needed to be done and that the failure was unrelated because nothing could ever be proved linked to sliding off a truck bed.

As long as there is a population of people certified to perform overhaul and repair by manufacturere and airworthiness authorities, there will be people willing to take chances on components as pointed out above, without being sure of the history. There will always be complicit people who send components out to these shops without adequate description of what the real status of the part is. The question is, is it wrong to perform an overhaul, per the manufacturers specs, on a component that appears de-novo on your doorstep with a request for overhaul, without being able to be absolutely sure about the circumstances that brought it to you? Having been a chief inspector at an MRO and seen parts from a known wreck appear for overhaul, my answer is absolutely not. Safety issues notwithstanding, for no other reason because you cannot know how the legal system will treat you if there is an issue down the road. I'm retired now and feel very fortunate to never have been associated with an aaccident that caused an injury or worse. The manufacture and the airworthiness authorities always tell you the MINIMUM that you MUST do. Hardly ever do they write down what you SHOULD do to look after everyone's best interests. That list is left to the conscience of the MRO. It costs a lot of money to fly around. Too bad, it's just the cost of doing business.
I think that your trying to make an orange an apple. A gearbox or engine that falls off a truck is going to likely sustain some damage. But an engine or gearbox that stops suddenly because of accident is going to sustain a lot of damage some of it visible and some of it won't be know until someone attempts to use it on an airframe. I think that the regulators as a whole need to ban the reusing of any part involved in an accident
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Old 7th Jun 2022, 17:29
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airsail: No idea how many of these types of parts are floating around awaiting recertification.
While there still are those types of parts floating around in the system, their numbers have been decreasing in my experience thanks to technology. Once where the only records were local hardcopies are now part of a digital system that can be accessed on a global scale. Unfortunately, there still are operators who look for the cheapest path to follow which keeps that part of the system viable.



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Old 8th Jun 2022, 04:53
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Originally Posted by Bksmithca View Post
I think that your trying to make an orange an apple. A gearbox or engine that falls off a truck is going to likely sustain some damage. But an engine or gearbox that stops suddenly because of accident is going to sustain a lot of damage some of it visible and some of it won't be know until someone attempts to use it on an airframe. I think that the regulators as a whole need to ban the reusing of any part involved in an accident
Of course it goes without needing to say if the mfg says parts are to be pitched then out they go. In cases where that is not specified there will always be people who see no reason they shouldn't reintrroduce items that pass the prescribed inspection or overhaul back into service. You have no idea how far the gearbox fell, how it landed, if it was properly protected in a can or sitting on rubber tires. I think its fine if regulators were to ban reuse of accident parts or assemblies but they would never do that because there are too many parameters to define. Manufacturers would love it, operators would have some legitimate complaints. Turnng a t/r driveshaft into a twisted broken mess from a tail rotor strike might not be a reason to pitch a gas coupled compressor rotor or at least it's housing, for example. I am not saying it would be a good idea, just that it is more complicated in a world where people weigh money and convenience against what they think is being safe.
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Old 8th Jun 2022, 05:38
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Yes I heard that too. However I also heard that the transmission was sent to Airbus for overhaul.
Yes, albatross, that's correct. My opinion is that any such components should be scrapped to avoid any doubt.
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Old 8th Jun 2022, 06:10
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However I also heard that the transmission was sent to Airbus for overhaul.
And who told Airbus it fell off the back of a truck? I am sure the trucking company didn't adjust the paperwork.

Those in the field who change bits on them will tell you any dynamic components and in particular transmission components are shipped like eggs or better with tell tales and all sorts protection these days on all models.
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Old 8th Jun 2022, 06:11
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Originally Posted by roscoe1 View Post
Of course it goes without needing to say if the mfg says parts are to be pitched then out they go. In cases where that is not specified there will always be people who see no reason they shouldn't reintrroduce items that pass the prescribed inspection or overhaul back into service. You have no idea how far the gearbox fell, how it landed, if it was properly protected in a can or sitting on rubber tires. I think its fine if regulators were to ban reuse of accident parts or assemblies but they would never do that because there are too many parameters to define. Manufacturers would love it, operators would have some legitimate complaints. Turnng a t/r driveshaft into a twisted broken mess from a tail rotor strike might not be a reason to pitch a gas coupled compressor rotor or at least it's housing, for example. I am not saying it would be a good idea, just that it is more complicated in a world where people weigh money and convenience against what they think is being safe.
Yes, the number of parameters to define is what makes the potential recovery method in-adapted and there goes the risk. Especially, rotor strikes can take so many different dimensions. From the heli tipping over with engine off (yes it happened when a drunk driver drove into an EMS heli) all the way to a full-blown shakeout as the movie shown above.

Take the rotor mast for example, it is stainless steel, if it proves to be dimensionally perfect upon inspection with high grade equipement. what are we to think?
  • a pure scientist would say: it proves the metal suffered no plastic deformations and thus as no memory of the event, it is then serviceable.
  • a person with a stake in the safety of the aircraft would say: I don't know…., scrap it!
The aviation industry has been long educated to change parts just because we don’t know any better, but in a world that will become increasingly resource constrained it hold little merit.

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Old 9th Jun 2022, 01:13
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Take the rotor mast for example, it is stainless steel
Really? Quote a model with a stainless steel mast.
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Old 9th Jun 2022, 02:01
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Originally Posted by RVDT View Post
Really? Quote a model with a stainless steel mast.
you are not talking to the expert here, but, I have references that show both the rotor mast of the AS350 astar and the top of the engine deck are stainless steel (I assume it is forged and stress relieved.. but I am drifting)

edit: a bit more research showsFerrium S53 (AMS 5922, MMPDS) is an ICME-designed, corrosion resistant, ultra-high strength steel for structural aerospace and other applications where 300M (BS S155) and 4340 are typically used, but S53 steel provides: much greater resistance to general corrosion and to stress corrosion cracking (SCC); excellent resistance to fatigue and to corrosion fatigue; and high hardenability. Its resistance to general corrosion is similar to that of 440C stainless steel, but it has much greater fracture toughness. S53 steel is double vacuum melted (i.e., vacuum induction melted and then vacuum arc remelted or "VIM/VAR") for high purity, leading to much greater fatigue strength. Because of its high resistance to corrosion and ultra high strength and toughness combination, S53 steel is being used in demanding landing gear and helicopter rotor shaft applications without the use of toxic cadmium coatings.

Last edited by Agile; 9th Jun 2022 at 02:28.
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Old 9th Jun 2022, 03:37
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Airbus provides guidance in SIN 3157-S-63.
Attached Files
File Type: pdf
3157-s-63p3-.pdf (214.4 KB, 12 views)
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