Excluding any loose ends that will be found from the wreckage, the interim report contains most that is required to understand what happened. It is likely that a combination of company organizational issues and SAR culture were the key elements. It resulted in a bad plan that was executed accurately.
Helicomparator makes an interesting point that the culture of SAR in the civil era needs a review; it would benefit from a process similar to that used in CAP 1145.
It is likely that APBSS was a VFR procedure that had been in place for some time. Blackrock is an island that, in VFR, can be seen from a distance; it allows an accurate placing of the aircraft for a series of visual manoeuvres leading to a VFR approach to Blacksod. It is unlikely that it was ever risk assessed for use in weather below VFR limits (cloud base - day 600ft, night 1,200ft; visibility – day 1,500m (800m for short periods), night 5km).
Descent from IMC to VMC/VFR in Class G airspace over the water is permitted in accordance with procedures Approved by the Authority; such a procedure would be permitted only with a serviceable RADAR and to an altitude/height where a continuation of the flight under VFR would be possible. (It is likely that SAR has a derogation from the VFR minima under operational conditions.)
The SOPs of SAR (and additional equipment on board) permit a let-down, and a continuation of flight, over water below normal VFR limits – this would have been standard for the SAR crew. It is likely that this alleviation would extend to the approach and landing at Blacksod (which appears to be the refuelling site of choice).
The linking of the en-route descent (to SAR limits) and the APBSS approach (under SAR limits) from Blackrock to Blacksod does not appear to have been risk assessed when the APBSS procedure was incorporated into the SAR Operations Manual. If it had then there should have been bold warnings on the plate and/or a limitation on height and visibility on the route.
The lack of an instrument approach to Blacksod under conditions where it was a principal SAR refuelling site appears to be an organizational issue.
The lack of adequate notation on the APBSS plate appears to be an organizational issue.
The combination of SAR culture and standard VFR routing to Blackrock/Blacksod increased the probability of an accident. It would appear that, the Captain was unaware of the height of the terrain/obstructions on Blackrock (from the CVR “Eh just a small little island… that’s B L M O itself”). The choice of APBSS routing and SAR limits probably resulted from a misunderstanding that Blackrock posed no threat and was intended to be overflown - from there confirmatory bias was in play.
It was unfortunate that Blackrock was missing from the EGPWS data-base - an issue that now has to be addressed in the provision of the eTOD for EGPWS and synthetic vision systems. The lack of knowledge on the thread about the functioning of EGPWS is a little sad; however, in mitigation, this is a device that does not require anything from the pilot but reaction to the ‘callout’ (questioning the EGPWS would be counterproductive). Had Blackrock been in the data-base, it is likely that it would have been 'called out' in the lookahead function.
This was an unfortunate accident that, hopefully, will result in an examination of civil SAR and leading to a process of improvement.