Turbine disk failure is one thing that can down a plane, and you can only reduce the probability so much.
Fan blades and turbine blades can be contained by containment cases if they break off, but turbine disks can't. When a disk breaks, it's an uncontained engine failure. A 20 kg disk fragment flying at Mach 1 goes through everything.
Airframes are have a 30-degree fragment spread cone around every disk stage. Airframes are designed so that no single fragment can destroy all redundant systems at once in this zone (flight controls, fuel lines, and hydraulic systems). Jet fuel cannot be stored in the wings in this zone.
I admit that I glossed over the section on the machining of the oil pipe, but the facility appears to bear most of the blame.
These were pulled and scrapped from the whole A380 fleet.
"Investigators also criticized the culture within the Hucknall facility that manufactured the HP/IP bearing hubs, identifying signs of complacency and widespread procedural non-compliance. A paperwork review showed that the required signatures were missing from 131 out of 138 retrospective concessions issued between 2009 and 2011, and a large number of minor non-conformances had not been properly handled through the normal chain of command."
That's an oversight failure as much as a failure of that plant.
The oversight was at the plant.
Yes, but there are levels of oversight and this kind of thing should not be possible to hide. Someone on the official side of this messed up as well.
But it seems to me that the whole failure could have been prevented with a bunch of temperature sensors spread throughout the engine, and a good anomaly detection system.
Don't know why you're getting faded out, because having worked on exactly this engine, software mitigations were put in place. That's exactly your `anomaly detection system`
It was a belt-and-braces fix, because the primary fix was of course to manufacture the engines correctly in the first place.
The "lots of temperature sensors" thing is actually easier said than done; jet engines already have lots of temperature sensors, and they will turn the engine off if a huge overtemperature is detected, but it's not a free win to add more of them. It increases the risk of a faulty sensor shutting down a perfectly good engine in flight, which from a safety-critical perspective is a borderline disaster condition all by itself.
(technically you usually cross-correlate temperature sensor readings with pressure sensor readings to prevent sensor faults turning engines off, but still, extra sensors isn't always a free win.)
It is worse than even that:
> Within the space of four seconds, the energy from the annulus gas flow accelerated the IP turbine past its critical speed, until centrifugal forces exceeded the ultimate strength of the nickel alloy disk. The red-hot, wildly spinning disk instantly fractured into several sections, which rocketed outward in multiple directions at incomprehensible speed.
“It goes without saying that if any of the turbine fragments had entered the passenger cabin, there would have been injuries, if not fatalities, even if the plane later landed safely.”
They got lucky.
The fact that it's assumed to have infinite energy when planning for this is crazy. Engineers saying yeah there is no material in the world that can stop it.
> Jet fuel cannot be stored in the wings in this zone.
TFA describes a fuel leak resulting from a piece of the turbine disk passing through a fuel tank located within the wing:
"When the fragments of the IP turbine disk passed through the wing and belly of the A380, they caused considerable secondary damage along the way, not only to the №2 engine but also to the left wing fuel tank, which sprang a leak"
It also includes a photo of the inside of the damaged wing tank.
Was the requirement you describe added after this incident?
Seems close to impossible for existing designs. The wings are commonly almost entirely full of fuel at max fuel, and I doubt that taking the capacity hit is an option even in newly designed planes.
What's a turbine disc?
It’s explained in the article