CRAB as often is the case, you totally miss a point while you concentrate on scoring points.
O&G pilots fly ARAs to 200 feet using, these days, a CDFA type profile. They are taught to NEVER fly over a red blob unless at 1500 feet. The DR is 0.75 Nm (to cope with separation during a go-around and in recognition that the RADAR is not very good inside 1/2nm.
They will never have Rear Crew, FLIR or NVGs. We need to learn what this crew did and why they did it:
1. Did they really choose to fly over red blobs at 200 feet with the RADALT complaining?
2. Did they see Blackrock on the RADAR and choose to fly over it.?
Or, was the RADAR picture crap due to tuning, setup, malfunctions etc.
Whatever the case SETUP and PROTOCOLS concerning the RADAR almost certainly IS the FINAL HOLE in a pretty porous Swiss cheese that night.
The other holes variously:
1. Recency (as admitted on the CVR)
2. Route Familiarity (as admitted on the CVR)
3. Lack of CDFA procedures (dirty dive too early)
4. ****ty manuals with poor labelling (heights on charts not properly displayed).
5. Poorly designed SOP for the AHCAS setup. (No FLIR selected in cockpit)
6. A really badly designed letdown procedure masquerading as a route ( or vice versa) that, and get this clear, routes the bloody helicopter over terrain when surrounding it is many square miles of open ocean. Absolutely no excuse or reason for this. Since the days of DECCA we can fly to points in space, clear of obstacless waypoints and use the surround terrain on the edges of the radar as validation. Flying over the terrain to validate the waypoint is a joke for a crew and machine designed to find a dinghy in the vastness of the ocean.