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Comment by ajarmst | Hacker News Reader

As well as two demonstrations that the aircraft meets the design specification that even a catastrophic failure in the worst stage of flight is easily recoverable. I'd expect an increased inspection rate, possibly some new mandated ND testing for fractures and discontinuities (the last one was an LP shaft failure, IIRC).

One thing that does bug me, though is that we now have two events where the shroud was lost. Were these uncontained failures (problematic because of potential for wing damage) or contained faiLures followed by aerodynamic shedding of the damaged shroud (system functioning as designed). I'm also somewhat concerned about the fire remaining in the burner stage. Might have just been lubricants, but I'd want to make sure the fire handle had been pulled and investigate whether it worked correctly.

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It looks it’s the “cowling” that was lost, not the protective shroud / containment around the fan (and the rest of the engine) that keeps the fan/compressor/turbine blades from becoming high speed radial projectiles when they break off at full speed.

Agreed. The last one was pretty clearly a failure of a shaft or turbine, and the damage was much more obvious. This might be something completely different.

> As well as two demonstrations that the aircraft meets the design specification that even a catastrophic failure in the worst stage of flight is easily recoverable.

But in that type of failure, you can't control where the pieces go.

https://abc7ny.com/philadelphia-emergency-landing-southwest-...

It resulted in depressurization and partial ejection/death.

That’s a different type of failure. Uncontained vs contained.

Kinda. While the 2018 incident was "contained", it still resulted in damage to the fuselage.

"Two small punctures were found in the right side fuselage just below the window belt with material transfer consistent with impact from pieces of an engine fan blade"

(From the link in parent to this thread https://avherald.com/h?article=4b4e8ca7&opt=0)

Not 'kinda'. Debris exiting the engine housing with sufficient energy and in a direction that leads to damage of other systems is the literal definition of an unconfined engine failure (i.e. it can spit as many parts as it wants to out the exhaust). There is a band of armour around the plane of the fans that should prevent any blades leaving the engine perpendicularly. If there was fuselage or wing damage from debris, that was an unconfined failure and would require investigation as a major fault.

However, loss of the shroud doesn't necessarily imply there was a confinement failure. Damage to the shroud during the event can easily lead to the cowling shedding aerodynamically, which is also part of the design: the last thing you need is more drag on the dead engine side. We can't tell which that was in this case, but it's important that we do---the design criteria specifying that the aircraft can be safely recovered from a catastrophic single engine failure during any stage of flight would assume the failure is confined to the engine.

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