I had missed the fact that the small search area was due to signals picked uo by HMS Echo.
Regarding this larger area that Inmarsat have calculated, can someone confirm my understand below is correct.
A) Some time back there was a diagram showing three segments of the southern arc based on the finalpartialping , if i recall they were called something like the northern section, the middle section and the southern section, and calculations favoured the northern section, which was when they moved from the south of Perth way up north.
B) This section then has to be extended south eastward (approx flight path) to account for the final glide and that is the area they will be searching first. It is also the last area they searched for debris (presumably shifted somewhat to allow for ocean currents/time lapse).
Is that correct.