Key Safety Issue(s)

The key safety issues identified as a result of this accident are:

  1. The destructive "interactive" fan blade and fan case vibration mode within the engine operating envelope.
  2. The number 3 engine failure resulted in a large number of complete fan blades (nearly every blade) being released from the fan disk at high speed coincident with the fan containment case separating from the engine. This reduced its effectiveness in containing the engine debris and minimizing the hazard to the aircraft. High energy uncontained engine debris caused damage to the aircraft.
  3. Not all passenger masks were presented at the same time, some taking as long as three minutes to deploy after the decompression. In addition, three oxygen canisters were improperly mounted. As a result, the canisters fell in the passenger seat cushions, burning the fingers of a crew member when she tried to remove them and severely scorching the seat upholstery.
  4. Portable oxygen bottle storage and availability was inadequate and resulted in two two flight attendants losing consciousness.
  5. Separate pressure losses of different magnitudes occurred throughout the airplane and the aneroid device - which detects unacceptable cabin pressure altitude and deploys the oxygen masks - was only located in the forward passenger cabin. This prevented supplemental oxygen from being available to the occupants in the lower galley.

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