BOAC,
Could someone explain the point of all this 'terrain modelling' stuff?
Because there appears to be good reason to "speculate" that the crew may have been using rad alt as their primary means of vertical navigation.
Only a fool would use a rad alt on an NPA unless it was a dire emergency
I think the legality or otherwise of using rad alt during a NPA has already been established and agreed upon by most posters.
You have already posted your speculated analysis. Many here appear to think there is merit in considering the rad alt theory....that is why the discussion is centred on this "terrain modelling stuff."