There is clearly a great deal of S92 SAR expertise following this thread. The co-pilot, who was monitoring the radar, called a "small target at 6 miles at 11 o'clock" when they were 1 mile west of Blackrock. Do others agree this could have been Duvillaun More island? Followed by "Large out to the right there, ehm" - pretty vague. Achill Island maybe, assuming the lack of distance and bearing meant it was not too relevant? Hard to believe such a casual comment would be so vague if it was Blackrock a mile away - and anyway, that would have been ahead, not to the right.
What do the radar experts think about the notion that Duvillaun and Achill were seen, but not, apparently Blackrock? Are there radar modes and settings that could explain that?
Given that the captain was targeting 200ft before turning back east for BLKMO, assuming say a 70kt GS and the APP1 500ft/min descent, I make that passing Blackrock eastbound at about 1000ft. And again, it seems this wasn't seen on radar either, though perhaps to be more expected as still 700ft below.
It appears it was the FLIR operator that picked up Blackrock. The time from the rear crew observation to the impact was about 13 secs, so that would mean it was seen at 550m range, assuming 90kts GS. Again do our S92 experts agree with that, and what might that tell us about visibility and IMC/VMC? What range does FLIR have in clear air and cloud?
Apologies if some of this has been answered before - a lot of ground has been covered!