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Dynamic components after rotor strike

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Dynamic components after rotor strike

Old 31st May 2022, 07:18
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Dynamic components after rotor strike

Can somebody educate me:
Assume a main rotor gearbox and epicycle (with 300h since New) is involved in a roll over, rotor head and blades are damaged biggly, but gear box looks quite OK.
what hapen to such component:
A: inspection and dynamic testing
B: complete regular 3000h overhaul
C: discarded

if somebody knows how it works please let me know

Thanks
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Old 31st May 2022, 07:25
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Hopefully destroyed before recycling the materials. Id hate to be relying on it
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Old 31st May 2022, 08:19
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You want to buy the parts from the TIMO accident ?
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Old 31st May 2022, 08:22
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Answer - C.
Having seen the internals of a main rotor gearbox that "Looked quite okay" from the outside - the pinions inside it had twisted almost 2 and a half times before snapping.
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Old 31st May 2022, 08:52
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I'd vote for junking all rotating components right the way back to the Tip of the Tail rotor....and start over after making sure the airframe isn't warped or transmission mounts harmed.

A long chat with the Aircraft Manufacturer and getting their input would be wise as well.
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Old 31st May 2022, 08:56
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Originally Posted by GoodGrief View Post
You want to buy the parts from the TIMO accident ?
Well I just put 2 and 2 together: the thread of the TIMO accident and the other thread about EC120 component cost wanting all new components.

that question has been naging my mind:
how much over torque a rotor strike actually is on the MGB?
isn't the inertial shock all from the blades own inertia?
with modern testing method can't we revalidate a part fully?
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Old 31st May 2022, 09:52
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Originally Posted by Agile View Post
Well I just put 2 and 2 together: the thread of the TIMO accident and the other thread about EC120 component cost wanting all new components.

that question has been naging my mind:
how much over torque a rotor strike actually is on the MGB?
isn't the inertial shock all from the blades own inertia?
with modern testing method can't we revalidate a part fully?
Firstly G-TIMO appears to have suffered a sudden stoppage not a blade strike, there is a difference.
Dont forget the engine is still driving as well unless it had been shut down or failed.

We had a 365 that had a tail strike which lead to the fenestron cutting a slot in the duct.
The main gearbox was found to have a hard spot in rotation and was replaced with the other tail drive components..
What was missed was that the engine manufacturer required the engines to be inspected.
Shortly after return to service the aircraft suffered an engine failure.
This incident would have been classed as a strike not a stoppage.

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Old 31st May 2022, 12:02
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Originally Posted by Agile View Post
Well I just put 2 and 2 together: the thread of the TIMO accident and the other thread about EC120 component cost wanting all new components.

that question has been naging my mind:
how much over torque a rotor strike actually is on the MGB?
isn't the inertial shock all from the blades own inertia?
with modern testing method can't we revalidate a part fully?
Its not your choice. AH requires scrapping all dynamic in TIMO case. Overhaul can only save those scenario describe in AMM but will cost you half of new.
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Old 31st May 2022, 12:38
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Look at any video where a main rotor hits a cable, or clashes with another rotor, the whole tail boom is shaken off. Huge forces at work, I wouldn't trust any of those components.
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Old 31st May 2022, 12:56
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Originally Posted by Agile View Post
Can somebody educate me:
Assume a main rotor gearbox and epicycle (with 300h since New) is involved in a roll over, rotor head and blades are damaged biggly, but gear box looks quite OK.
what hapen to such component:
A: inspection and dynamic testing
B: complete regular 3000h overhaul
C: discarded

if somebody knows how it works please let me know

Thanks
Most OEMs have either a published rotor strike special inspection or provide a tailored inspection specific to the incident. Depending on the inspection some are tiered by the level of blade damage or if the blade was powered or not. In your examp!e, I believe those components would require at least an overhaul based on my experience with a proper note on the incident. In addition there will probably be engine related inspections as well due to the strike. The manuals would give more details.
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Old 31st May 2022, 17:22
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It's an open and shut case; the entire power-train, transmission and rotors are unserviceable until a Certificate of Release to Service is issued by an approved maintenance organisation. That is only going to happen if:

1. The type of occurrence is one that's listed in the Special Inspections in the MM, and inspected/repaired accordingly.
or,
2. The circumstances are referred to the Type Certificate Holder, and specific-to-incident approved data is used to inspect/repair.
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Old 31st May 2022, 17:49
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Originally Posted by DuncanDoenitz View Post
It's an open and shut case; the entire power-train, transmission and rotors are unserviceable until a Certificate of Release to Service is issued by an approved maintenance organisation. That is only going to happen if:

1. The type of occurrence is one that's listed in the Special Inspections in the MM, and inspected/repaired accordingly.
or,
2. The circumstances are referred to the Type Certificate Holder, and specific-to-incident approved data is used to inspect/repair.
The wreck becomes the property of the insurance company who sell it for the best price they can get.
This is the point that the dark arts kick in.
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Old 31st May 2022, 18:56
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Originally Posted by ericferret View Post
This is the point that the dark arts kick in.
Well the black art side is finally getting harder depending on your view point. Airbus has seen the light so to speak and now provides a listing of scrapped or destroyed aircraft like other OEMs do. They also provide a means to check serial numbers of items if needed. Have had several checks done but thankfully all was on the up and up with some spare components on the market.
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Old 2nd Jun 2022, 18:50
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Originally Posted by Ascend Charlie View Post
Look at any video where a main rotor hits a cable, or clashes with another rotor, the whole tail boom is shaken off. Huge forces at work, I wouldn't trust any of those components.
remember this one few years ago
at same second the main rotorblade hits the cable the tailboom snaps off
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Old 2nd Jun 2022, 18:56
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Originally Posted by wrench1 View Post
Well the black art side is finally getting harder depending on your view point. Airbus has seen the light so to speak and now provides a listing of scrapped or destroyed aircraft like other OEMs do. They also provide a means to check serial numbers of items if needed. Have had several checks done but thankfully all was on the up and up with some spare components on the market.
True but many aircraft out there have no linkage to the manufacturer.
They can't provide listings that they do not possess.
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Old 2nd Jun 2022, 21:13
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Originally Posted by ericferret View Post
True but many aircraft out there have no linkage to the manufacturer. They can't provide listings that they do not possess.
No "linkage" required. The list is update from 3rd party sources. Last I looked the Airbus destroyed/salvage listing had over 5000 aircraft by model and S/N. While its not perfect it does give a benchmark to research from. For example, the Kiwi Xmas tree B2 above is on the list.

Last edited by wrench1; 3rd Jun 2022 at 15:09. Reason: add example
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Old 4th Jun 2022, 11:03
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Originally Posted by wrench1 View Post
No "linkage" required. The list is update from 3rd party sources. Last I looked the Airbus destroyed/salvage listing had over 5000 aircraft by model and S/N. While its not perfect it does give a benchmark to research from. For example, the Kiwi Xmas tree B2 above is on the list.
actually if you contact local ah rep, they can pull up latest status of any sn within minutes. Even its not official, they can tip you what they know.
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Old 5th Jun 2022, 07:00
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I do not think it is the role of the OEM to police which airframe should be flying and which airframe should not. (especially when it is in their best intrest to "black list" as many serial number as possible to have the least airframe loose on the market)
why do we have an airworrthiness certificate system then? are we saying it cannot be trusted. if something can be repaired, or inspected according to established procedures, it should get an authorized release form, and if it does it should be authorized by the authority FAA - EASA - CASA - CAA ....
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Old 5th Jun 2022, 13:58
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Originally Posted by Agile View Post
I do not think it is the role of the OEM to police which airframe should be flying and which airframe should not. (especially when it is in their best intrest to "black list" as many serial number as possible to have the least airframe loose on the market)
The list is merely advisory by the OEM. They have no legal power to "blacklist" any aircraft. Does the OEM have liability, sure, and that was the reason Bell originally started listing aircraft thought to be destroyed or scrap as they were sued over an aircraft that was not original under its data plate.

why do we have an airworrthiness certificate system then? are we saying it cannot be trusted.
It's not the systems fault as it was not designed to cull out illegal aircraft. Since an AWC is usually issued only once to an aircraft, if one were to remove the AWC, registration, data plate, and logbooks from the original aircraft and use those documents/records with any other aircraft nobody would be the wiser. And given there are people who prefer money over conformity you as a buyer may end up with an aircraft or component with a fraudulent history. There was a previous thread on PPRuNe about this same issue.

if something can be repaired, or inspected according to established procedures, it should get an authorized release form, and if it does it should be authorized by the authority FAA - EASA - CASA - CAA ....
And it still can. I don't know about the other agencies but the FAA has guidance on determining destroyed/scrapped aircraft and the method(s) for which to rebuild that aircraft if one so chooses. Its not the people who want to follow thew rules that caused this, but those individuals who think its okay to break those rules for personal gain.
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Old 5th Jun 2022, 21:35
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I ran a Bell component overhaul shop for a short time. We were often sent components for recertification from third party parts suppliers. We had to be extremely careful with drivetrain components as the Bell sudden stoppage inspection states that if you find any damage as you do the inspection, many components require scrapping, not overhaul.

We had a case where a one 212 fly bar arrived for recertification, the book stated that any damage, both were scrap. I thought it unusual that we asked to only recertify one, not two, this involve a full visual and MPI inspection. We asked were the other bar was, no comment, just send that bar back uncertified.

No idea how many of these types of parts are floating around awaiting recertification.
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