Final Report is out.
https://www.bea.aero/uploads/tx_elyd...17-0568.en.pdf
Fan Hub affected by a crack and fracture in a blade slot. Crack initiation was subsurface.
Also interesting, crew could not maintain calculated drift down altitude, had to go below that by 7000ft. That's more than a small inacurracy, isnt it.
From BEA Final Report page 47:
Left slot 10 was the initiate of the fracture
Detail View of slot 10
Quote from report:
The metallurgical examinations of this fragment found that the fracture was due to a cold dwell fatigue phenomenon. It originated in a macro-zone where the orientation of the grains is unfavourable with respect to the (hoop) maximum stress direction, in the middle of slot No 10. The crack progressed around 19.7 mm (0.775 inches) before becoming unstable. No material quality (chemical composition, microstructure) or manufacturing related anomaly was found which could be associated with the area in which the fracture originated. No evidence of damage arising from a maintenance activity was found on the front face of the hub in the vicinity of slots No 10 and No 18. The various metallurgical and mechanical checks carried out during the investigation found that the material was consistent with properly processed Ti-6Al-4V alloy vs. existing P&W requirements for rotor-grade material.