Originally Posted by
Dave Therhino
You are correct it was not fan blade fragments that broke the window. However, the window was actually struck by a section of the fan cowl door that held the heavy latch structure. When the fan blade released, it happened to hit at a clock position that gave a huge force and displacement to the bottom of the fan case. There is an unusual latch beam support connection to the fan case on this engine due to the flat bottom of the nacelle shape. The support is intended to keep the fan cowl doors tightly up against the engine. When the case in this area was driven outward, it directly transmitted load to the doors and latches and broke the doors open. A piece from the bottom latch end of one of the doors was slung at the fuselage and struck the window area, breaking the one window.
Taken together with
tdracerr post above, the individual details in the subject event are obviously repeatable for a number of reasons not all related to a CFM56 Fan blade failure. Thus the corrective actions as recommended are only minimizations of combinations. Taken in total the end result in this case is very improbable to re-occur. No doubt the manufacturers proposed actions are positive, but in the grand scheme of flight safety are not really news worthy.