AN-124 Uncontained Engine Failure
Join Date: Jul 2013
Location: Everett, WA
Age: 65
Posts: 3,064
Typically uncontained failure issues with existing engines are addressed with a combination of increased inspections and hard time life limits (cycles and/or hours) - usually enforced by AD.
Sometimes there are changes that can be reworked into existing parts (during a shop visit) such as machining an increased radius into a high stress area to improve the crack resistance.
The trick is finding the correct inspection intervals and life limits to prevent future failures. I know this was on ongoing issue with the CF6-50 turbine discs installed on older 747 Freighters. The Feds kept changing (reducing) the inspection intervals and hard time life limits, but they kept failing at the rate of one or two a year right up to the time I retired. Fortunately they never did enough damage to serious threaten continued safe flight and landing, but I suspect if the event aircraft had been carrying hundreds of passengers instead of tons of freight, it would have gotten a lot more attention.
Sometimes there are changes that can be reworked into existing parts (during a shop visit) such as machining an increased radius into a high stress area to improve the crack resistance.
The trick is finding the correct inspection intervals and life limits to prevent future failures. I know this was on ongoing issue with the CF6-50 turbine discs installed on older 747 Freighters. The Feds kept changing (reducing) the inspection intervals and hard time life limits, but they kept failing at the rate of one or two a year right up to the time I retired. Fortunately they never did enough damage to serious threaten continued safe flight and landing, but I suspect if the event aircraft had been carrying hundreds of passengers instead of tons of freight, it would have gotten a lot more attention.
Join Date: Mar 2002
Location: Florida
Posts: 5,415
Titanium fan disks separation tend to have material property problems rather than wear out modes. This often can be parsed down by a group within a manufacturing date making it easier on forced inspection to only a few engines in the suspect batch.
Gross material defects tend to fail at half life design cycles and are more often small batch related. Failures at very low cycle counts are extremely rare and unlikely to be manufacturing related.
No idea what this one is, but there are some hints in the photos in post #3 matched with some of the earlier posts in this thread. and you don't need all the disk pieces to confirm where the fracture initiation came from
Gross material defects tend to fail at half life design cycles and are more often small batch related. Failures at very low cycle counts are extremely rare and unlikely to be manufacturing related.
No idea what this one is, but there are some hints in the photos in post #3 matched with some of the earlier posts in this thread. and you don't need all the disk pieces to confirm where the fracture initiation came from
Join Date: Jun 2002
Location: Geneva, Switzerland
Age: 55
Posts: 1,666
tdracer
Thanks. But in this case there is the extra complexity of the D-18T not being produced anymore, not to mention the less than cordial Russia vs Ukraine relations as of late. I know their resourcefulness and I'm sure parts can be sourced but I fear they can not extend the useful life of the current engines indefinitely. I really hope this was a "one off" but somehow doubt it.
Thanks. But in this case there is the extra complexity of the D-18T not being produced anymore, not to mention the less than cordial Russia vs Ukraine relations as of late. I know their resourcefulness and I'm sure parts can be sourced but I fear they can not extend the useful life of the current engines indefinitely. I really hope this was a "one off" but somehow doubt it.
Join Date: Mar 2002
Location: Florida
Posts: 5,415
Well somebody has to own the airworthiness certificate else the plane can't fly so either an inspection or retrofit is required or the fleet grounded in all countries whether it's a one-off or not
I supposed a more cordial response might be an easy inspection interval since it doesn't carry many passengers
I supposed a more cordial response might be an easy inspection interval since it doesn't carry many passengers
Join Date: Jun 2002
Location: Geneva, Switzerland
Age: 55
Posts: 1,666
I'm certainly not the ultimate specialist but I think you will find that things are a bit muddy when it comes to the AN124 & airworthiness certificates...
Last edited by atakacs; 1st Dec 2020 at 07:53.
Join Date: Jun 2002
Location: Geneva, Switzerland
Age: 55
Posts: 1,666
Join Date: Jun 2002
Location: Geneva, Switzerland
Age: 55
Posts: 1,666
You are correct. Maybe the Antonov one are "better" maintained (access to parts ?). It is pretty clear that the Ukrainian are trying to make things difficult for VDA (not taking sides here, just stating facts).
Join Date: Sep 2008
Location: Where it is comfortable...
Age: 56
Posts: 780
It is a paradox situation, because while the design type certificate is held by the (Ukrainian) Antonov Design Bureau, the manufacturing (and heavy maintenance) license is held by the Ulyanovsk Aviation Plant (now Aviastar, Russia), where not surprisingly Volga-Dnepr is based. In the former USSR aircraft design and manufacture was done by distinct entities, the design bureaus had no manufacturing facilities, while factories were only for production, they had no R&D functions. When dealing with operational issues, the customer airlines liased with the manufacturing plant, not the design bureau. It was also the manufacturing plant who issued any Service Bulletins. I'm not privy to what certification regimes apply to the UR and RA registered Antonovs, but I would expect given the 'cordial' relations between the two countries, that completely separate ones.
