Even though similarity of waypoint names, callsigns and such-like are recognized as threats in aviation, I don’t see it as plausible that a crew would physically misidentify the two locations whether seen on a map, radar or terrain-mapping mode.
However, unfamiliarity, mindset and the time of day are ever-present threats, perhaps some of these played a part.
Whether it was the intent or not, the track towards the location of Blackrock was established early in the flight. Then at about the correct distance for an ARA, an offset is followed by a further turn to the right for what looks like a go around.
The trace shows that the aircraft continues for some 3 nm and turns left roughly parallel to the GA track but slowly turning more easterly. At approx. 2nm away it turns towards the landing site at Blackrock but with what intent?
The track as depicted does not suggest to me that this was a westerly let down for an approach to Blacksod. If it was, then perhaps the plan changed when the aircraft made for Blackrock after the turn left onto a southeasterly heading. With no altitude data to assist, the picture is particularly unclear.
During the approach and go around there would be good reason to have had the radar on for the entire time, if not in WXR mode then in GMAP. It would be usual to optimize the WXR display with gain and tilt adjustments. With WXR or GMAP modes selected and even Terrain display, there should have been ample overview available unless marred by some significant malfunction.
Regarding the unattributed call of landing at Blacksod. I understand it was given at around the apex of the turn. Other than to overcome possible challenges with comms at low altitude, wasn’t it a tad early with well over 5 minutes flight time to go to Blacksod or was it a part of a clipped call made under duress with a slip of the tongue regards location?
Only time will tell.