The NY Times wrote:
At a briefing on Monday, investigators said that the remains of the plane were likely to be lying in a relatively limited debris field of a few hundred square yards.
Surely this is mis-quoted or mis-translated. "A few hundred square yards" is perhaps the area of an A330's shadow. Surely this statement was "a few hundred meters square", that is, hundreds of meters on a side.
This might be reasonable for the major debris but I bet there is small stuff spread over a wider area. Judging from the recovered debris, there must have been many small, possibly light pieces. These would drift with the current before landing, while heavier parts, like an engine would fall faster.
The average surface current in the area is seasonal in both direction and magnitude (
The North Equatorial Counter Current). It would appear from that source that the surface current in the target area is dominated, in June, by the southern equatorial current, with a velocity of 0.1-0.3m/sec. This is not likely a constant all the way down (a related article from the same site mentions opposing under currents at 300m farther north), so estimating about 1/3 of the average surface current would be about 0.06m/s. A rough number for sure.
The only decent rate data point I recall is for a manned submersible I used to work on, which is about 8m long, 2.5m wide, and weighted with 200kg; in this configuration it sinks at about 0.5m/s. In a 4000m dive it might thus drift 500m horizontally in a 0.06m/sec current.
An A330 engine is smaller and denser than the sub (
GE - Aviation: CF6). At about half the cross-sectional area and roughly 10 times the in-water weight, it should fall about 6 times faster. (drag = weight at terminal velocity, and drag is proportional to area and to velocity squared). The horizontal drift would thus be on the order of 80m.
Surely there are many small parts, such as pieces of sheet metal or luggage, that would fall more slowly than the sub, say at 0.1-0.2m/s. resulting in horizontal drift of 1200-2500m.
So it seems like the heavy debris would be in area a few hundred meters across, but there is likely a lot of lighter stuff spread farther. Also, any part whose sinking was delayed by slow flooding of an air pocket, would land even farther down-current.