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Air France A380 Fan 'separation'

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Looks like 520 people on an Air France A380 are breathing a sigh of relief after the Number 4 engine fan 'separated'. 

The flight diverted to Canada and landed safely, but the photos of the damage show how lucky they all were, and what a sturdy aircraft the A380 is.

 

https://avherald.com/h?article=4af15205

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Seems like the crew handled it well, except the 9 hours passengers were left waiting, military base apparently.

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I can't claim to have yet had a chance to do any kind of detailed look into this, but what I've seen so far seems to suggest a shaft failure that separated the fan from the rest of the engine.  That could have been the result of a fan failure of some kind causing a massive imbalance leading to a very rapid shaft fracture, or alternatively might have been a simple failure of the shaft where the fan in its entirety simply came off.  

 

There are at least a couple of significant differences between this event and the Qantas A380 accident in Singapore.  Most notably, it's a GE/P&W engine, not R-R.  Secondly, the location of the failure is far forward in the engine, not in the hot section as it was in the Qantas/Singapore event.  This is critical because there was much less "collateral damage" in this case.  The Qantas engine shrapnel, originating much further aft in the engine and including massive turbine wheel chunks, did significant damage to systems, structures and components in the wing.  The resulting failures cascaded throughout the aircraft systems and resulted in, among many other things, an aft-moving CG (from fuel loss and the crippling of the fuel transfer system)  that prompted them to land as quickly as possible even though they were still well above the max landing weight for an A380.   The failure site, being far aft in the engine, was in line with much that was critical and as a result, caused massive damage to things other than the affected engine. 

 

The Qantas event damaged the wing spar, fuel tanks and lines, control wiring for the adjacent outboard engine and other very important systems that affected the entire airplane.  In the AF case it appears that the effects were mainly confined to the failed engine itself, making this essentially a single engine failure in cruise to a 4-engine aircraft.  There isn't much in the forward cowl and housing that is critical to anything except that one particular engine - sensors, cowl de-icing ducts and that kind of thing, mainly.

 

The Air France crew deserves all praise for managing this well, but what they were faced with was not in the same ball park with what the Qantas crew had on their plates.  

 

John

 

 

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It now appears clear that the entire low pressure section is gone, including the five LP compressor wheels and blades as well as the associated stationary blading and whatever carries those.  The broken part near the hub is the aft end of a stub-shaft that carries both the fan and the LP compressor stages.  It's a relatively short, hollow thing which doesn't have the look of a shaft at all.  There's a "socket end" that goes over the forward end of the engine shaft and is retained by either a nut or some kind of retainer ring (can't tell which it is) and that socket end and the retainer are there.  It broke off in the larger "hollow part", just forward of the socket end where it fits over the main engine shaft.  There's a pretty good section of the engine missing - more than just the fan.

 

The hollow fan shaft actually carries the forward engine bearing but the point of the break is forward of that and the bearing remains, supporting the forward end of the engine core.  There is no other bearing forward of the break line - the fan and the rotating parts of the LP Compressor section are cantilevered off the front of the engine shaft and on the conical section which is where the break seems to have occurred.

 

There is still not much in this to suggest the initiating cause or the sequence of events, though from the descriptions, it must have been sudden and something must have stopped the rotation of the core or there would have been an overspeed failure of the unloaded turbine with the fan and LP Compressor "uncoupled" from it.  

 

There are a couple of good engine cutaways here...

 

B-1-3_gp7000_cutaway_high.jpg

 

y4m5ktmxE4yyekPoyqW3-G9wgLT4YLXfj0SaBdHy

 

I marked one up to give a rough idea of my take on what's gone and what remains.  

 

y4mSAHvxQA1sT7IpmpcXA78YjaPJSbY_sVftbphD

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Nice work John.:thum: 

 

Even with all the work they do to make sure engines are tested and built to the utmost precision metal will fail. Hopefully they can pin down the failure and so they can lesson the chance of this happening again.

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Wow John, that's some great detective work and very ivery nteresting to read  :thum:

Hey, you weren't a tin-kicker in a previous life were you? 

 

 

 

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I'm a lifetime member of the Society for Prevention of Cruelty to Machinery.  ;)

 

I had my career in a power plant and have an engineering degree.  Steam turbines have much in common with gas turbines, so I've picked up a thing or three along the way.

 

John

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Interesting article, which contains another link to another one, about the 3-engine ferry flight being planned to get the AC back to France.  It sounds a bit more complicated than "Kick the tires and light the fires..."

 

https://www.avweb.com/avwebflash/news/Complex-Three-Engine-Ferry-For-A380-229780-1.html

 

John

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