My fracture mechanics training came primarily from Dr. DW Hoeppner who had recently moved from Lockheed where he had been involved in fan disk failures on L1011s equipped with RB211 engines. He started off our first class by showing several airplane and helicopter components that had failed in crashes involving multiple loss of lives. Gets your attention and builds a focus on material selection. At that time, 1974, I remember it being a given that materials were going to fail. The focus was to determine life expectancy to that failure point, material selection matching the requirements, and inspections with the ability to find a crack prior to failure. In the ensuing 40+ years materials may have been developed that will have infinite life. Age and retirement have me out of the loop - note my name reference to an airline of the past. However this failure takes me back to Dr. Hoeppner's lectures and avoiding rush to judgement. One of our lectures was a few days after the DC-10 crash near Senlis, France. He came to class carrying a DC-10 cargo door latch, jumped on the desk and yelled at us how some engineer's mistaken material selection resulted in the death of 346 people. Illustration of rush to judgement. The latch was the failure mode but it was due to poor system design, not material failure.
My rush to judgement on this failure is there is a material inclusion not properly detected initiating a premature fatigue crack that precipitated the front falling off. Having learned from Dr. Hoeppner that this strategic part will have a fault tolerant material, the crack could grow quite large prior to failure. This would result in an AD requiring inspections at intervals where it is felt any crack will be discovered prior to becoming critical size that will result in the front falling off.