Actually, WN-3472 (Aug 24th 2016) final report states the engine failure was uncontained (looks like this final report has escaped my attention so far) :
http://data.ntsb.gov/carol-repgen/ap...port/93897/pdf
Quote: "Defining Event: Uncontained engine failure"
This is not being used for WN-1380 (Apr 17th 2018), the NTSB does not state in that final report, whether the engine failure was contained or uncontained at all.
However the investigation's powerplant group spent a whole lot of time and many, many, many pages in their report about those definitions/interpretations in the FAA regulations and advisory circulars:
FAR Section 33.19:
FAR Section 33.19 requires the engine manufacturer (CFM in this case) “…design of the compressor and turbine rotor cases must provide for the containment of damage from rotor blade failure.’’ Although not stated specifically, historically this has been interpreted that engine debris cannot penetrate and pass radially through any of the engine cases, but debris can exit axially out the front or back of the engine. FAR Section 33.19 also addresses engine debris exiting out the front and back of the engine by requiring that “… Energy levels and trajectories of fragments resulting from rotor blade failure that lie outside the compressor and turbine rotor cases must be defined.”
AC 33-5:
According to AC 33-5 ‘contained’ was defined to mean “that no fragments are released through the engine structure, but fragments may be ejected out of the engine air inlet or exhaust” and defined ‘engine structure’ to mean “the engine structure surrounding the main rotors and extending from the forward-most case flange through the rear most flange, as defined by the type design”.
AC 20-128:
For the purposes of airplane evaluations in accordance with this AC, uncontained failure of a turbine engine is any failure which results in the escape of rotor fragments from the engine or APU that could result in a hazard. Rotor failures which are of a concern are those where released fragments have sufficient energy to create a hazard to the airplane.
I am still investigating and engaged in a background research over this discussion to clarify the real definition of contained and uncontained on regulatory level (seeing those three different conflicting interpretations). The question now is: why is the one occurrence rated uncontained, and the other very similair event not categorized in that respect?
Applying the historical definition based on FAR 33.19 the engine failure of WN-1380 needs to be categorized as uncontained just like WN-3472. Applying AC 20-128 or AC 33-5 neither event is uncontained.