Originally Posted by
Stumpy Grinder
LOL
"considered to have" infinite energy and I retracted the explosion hypothesis, do keep up.
I apologise to BluSdUp if English is not your first language.
Lots of miss-information on this thread, and Stumpy you're not helping. I also hate repeating myself, but here goes:
1) Released/broken blades are not considered 'infinite energy' - engines are certified to contain
blade failures - fan blades by the fan case containment ring (used to always be steel - many newer engines use Kevlar). Compressor and turbine blades are contained by the engine case (nearly always steel). Fan blades can and do initially move
forward when released - remember they are basically pulling the aircraft forward so there is a significant forward force vector on the blade. The fan case containment ring extends well ahead of the fan to account for that but it's certainly not uncommon for fan debris to damage the inlet forward of the fan case.
2) Burst engine
discs are considered 'infinite energy' and are allowed to be uncontained since sufficient shielding would be impractical (they are also not supposed to ever happen). The Iowa City DC-10 was a burst fan disc, the Qantas A380 was a burst turbine disc.
This event does not appear to be a burst disc.
3)The fan inlet cowl is
not intended to contain engine parts - the fan case does that. It's purpose is purely aerodynamic (to provide 'clean' airflow to the fan face and a smooth aerodynamic surface around the engine) along with acoustic treatment to suppress fan noise. However it's not supposed to fail due to the forces of a fan blade out - and they are designed to contend with the forces associated with a fan blade out event. I'm sure the NTSB, FAA, and Boeing are all concerned that there have been recent fan blade out events where the inlet departed the aircraft.
4) The preliminary report on the 2016 Southwest fan blade out event attributed the release to metal fatigue, and the fan blade inspection requirements were supposed to updated to address that failure.