but a point missed by Sunfish and glossed over by the ATSB is that they were cleared for visual approach. The controllers comments of confirming that the aircraft was low by visual identification confirms that the conditions were visual. Others will correct me if I'm wrong, but I'm pretty sure the command "cleared for visual approach" waives the approach altitude requirements and allows the pilot to descend at his / her discretion to make the landing.
Actually, no. They were cleared for a VOR approach, and subsequently a visual approach once established on the PAPI and inside the circling area (5.28NM final).
At night you cannot commence a visual approach until this point which the controller spelled out to them.
They were on an instrument approach and clearly breached the instrument approach requirements. Using FLCH on an instrument approach at night in rain without the relevant minimum altitude set in the MCP according to the approach plate would be a hanging offence in my airline. The only acceptable modes are V/S or VNAV.