Preliminary information from the investigation into the TransAsia Airways ATR 72 crash in Magong shows that the crew opted for a non-precision approach after initially intending an ILS approach to the airport.
The crew of the aircraft, operating flight GE222 from Kaohsiung, had been cleared to cruise at 7,000ft for the 23 July service.
Weather conditions at Magong were poor with visibility down to 800m. Although the flight was typically 35min, the crew was still waiting for ILS clearance to runway 02 an hour after departure.
Rather than staying with the ILS approach to runway 02 – for which the meteorological data was indicating tailwinds gusting to 11kt – the crew changed to a VOR approach to the opposite-direction runway 20.
This decision followed approval for a Uni Air ATR to land on runway 20.
The TransAsia flight was cleared to land shortly before 19:04, says Taiwan’s Aviation Safety Council, and informed of wind from 250° at 19kt.
Around 2min later the crew disengaged the autopilot but, some 14s afterwards, the ATR began deviating to the left and losing height.
The crew called for a go-around but, almost immediately afterwards, the cockpit-voice recorder picked up an “unknown sound”, says the inquiry, adding that another was heard about 5s later, just before the recorders ceased to function.
Only 10 of the 58 occupants of the turboprop survived after it crashed into a residential area of the Huxi township, just east of the runway 20 threshold.
Aviation Safety Council investigators have not given a reason for the deviation from the approach path nor indicated a source for the unknown sounds heard. The inquiry expects to produce a draft report within a year and a final report in 18 months.