Aerodynamic and Hydrodynamic etc
@A0283:
With respect, nothing that I have seen so far leads me to believe that the main body of the aircraft was separated from the aft section prior to impact with the surface of the ocean. If it had separated then one would expect to see a more intact empennage; no burst bulkhead and more of the aft floor section still attached, or some remnants of floor frame. During a water impact, the hydrodynamic scour that occurs forces the floor section upwards, and in the process causes it to become detached from the side frames – exactly what we see in this instance. Ok, the floor frame complex could have pulled out in one if aerodynamic separation was the cause, but that still does not explain the burst bulkhead. The most likely reason for the distance in separation is probably down to the fact that since this part of the intact aircraft probably made first contact with the water ( ie: the aircraft is in a pitched up attitude), the break that occurred between it and the main section was well developed by the time the lower skin of the the main fuselage failed, thus allowing hydraulic surge (impulse) to flow through the cabin in fractions of a second, particularly to the now open ended rear – scouring everything in its way. Given that the APU and other heavy bits appear to have detached, plus maybe some level of buoyancy remaining (inflated rear exit slide ) in the aft section and a 5k current, it is not difficult to imagine the aft section drifting apart from the heavier main body. The rear end of the fuselage, as seen in latest photo, appears to show floor frames – presumably pulled out from the missing aft section once the connections to the side frames failed. There is also the evidence of one of the data recorders being found under the wing. If the aft had detached in the air, then is it probable that the recorder be found under the wing?
Chronus: The terms used in the literature (NASA Langley Research Center – vertical drop tests) for an airframe impact with water are often referred to as Hydrodynamic impact loading. In the past I have also come across the terms Hydrodynamic Ram effect or Hydraulic surge.