Chris Scott
Can I assume that you also think the engines would have gone pretty-well straight to the bottom, having separated in the first second of this low-speed impact, therefore giving some indication of aircraft heading at sea-level impact?
Hi Chris, yes I do. The engines were likely separated from the aircraft within the first 1/100th of a second post impact. Water is such a dense medium that I would expect it to rapidly remove all residual velocity vectors resulting from the crash. The only velocity vector then remaining would be the velocity vector being generated by gravity as modified by any hydrodynamic forces that might result. Even with an engine generating hydrodynamic forces from its travel through water, it likely that the forces would not be completely symmetric and would thus create some rotational velocity along some axis as the engine falls to the ocean floor. This rotating force would create dispersion from the ideal. Of course the engines would move with the slow moving current, but their time of fall (due to their massive nature) would be short and total displacement minimal with both engines displaced almost identically (Assuming the final configuration of both engines was indeed comparable.)
The fact that the engines are about twice the distance apart on the ocean floor than they were on the aircraft might result from the total mass of the aircraft displacing and entraining a local segment of the ocean that absorbed its energy, and the mass of downward moving water and wreckage would fan out radially from the initial point of impact for a brief time until the impact energy was fully dissipated. This should displace wreckage away from higher velocity cores, but since this energy would be rapidly dissipated, the effect would be short lived but not entirely negligible.
For a mental picture, imagine dumping a bucket of dirty water into a clear lake. The initial interface between the two would look something like an inverted mushroom.