at, #274, (as I assume you know) accidents or near misses are rarely a simple issue.
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The crew expected visual conditions, they elected to fly a RNAV NPA. Unknown to them, and as explained in the report, the wx vis reduced below minimums (new, but unannounced ATIS).
The assumptions (and hazards) in NPAs are that the final approach will be completed visually, requiring contact with the airport environment, that the content of a visual scene is sufficient to determine position, and manoeuvre vertically and laterally towards the runway.
The crew appeared to have contact with the ‘ground’ - sea, the local coastline and hotel, but not necessarily the runway. Did the featureless seascape provide sufficient cues to establish pitch reference, altitude, and manoeuvre; were the costal features sufficient for navigation.
As the actual visibility in the rain shower was less than required we might assume that the cues were insufficient; the vis was below minima, but how would the crew know (old ATIS), how do you judge viability in rain over the sea. Would a crew fair any better in other circumstances e.g. night if allowed, snow covered terrain.
Does the regulator assume a reference glide path based on RNAV, but RNAV may not be approved below MDA, particularly if dependent on altitude-range.
If the above applies, or even if not, then what might we learn; what forethought might a regulator or operator apply in order to avoid a similar situation.
Do all operators duck under; we have records of what happens in incidents, but few (none) in normal operation. Why should we judge a single ‘non standard’ event when we have no ‘norm’ base line for comparison. No norm for approach path, for communication, wx / ATIS, navigation standard, crew and system procedures, etc?
What might we learn, as much we choose to?