On the subject of the AVAD warning, it must be worthy of note that the cockpit switch was set to the "single pilot" position thus causing the "check height" warning only to be heard when the aircraft descends below the bug height set by the RHS pilot, if the suspend button is not used. The bug on the co-pilot's radalt was set to 500ft (Is this standard CHC policy?), but this was disconnected from the AVAD. We do not know where the commander's bug, which was the one connected to the AVAD, was set.