Composite aircraft vs aluminum aircraft
AF447 had an unusual amount of composite materials aboard. The portions of the plane that contained the FDR and CVR were very heavily composite.
We know how aluminum, even shredded aluminum, sinks fairly well. Does anybody have any idea how a shredded AF447 might have sunk? How long would it take to reach the bottom if, say, the tail cone came off almost as a single piece? How would that affect the size of the debris field?
Fortunately the engines are likely to be "straight on down" items. So I expect them to be found. Then they have to determine how the debris field is spread out and locate the recorders within that field.
I wonder how difficult that effort will be. I also wonder if it would be a good idea to somehow attach recorders to engines rather than parts of the plane that may have close to zero buoyancy. It might increase their chance of being found in the rare crashes like AF447 over really deep water.
{^_^}