During the approach to Bangkok the weather conditions deteriorated significantly, from 8 km visibility half an hour before landing to 750 m at the time of landing.:1 The flight crew observed a storm cloud over the airport and ground reports were that it was raining heavily. However these conditions were common at Bangkok. Seven minutes prior to landing a Thai Airways Airbus A330 landed normally, but three minutes before landing another Qantas aircraft (QF15, a Sydney-Rome via Bangkok service), a Boeing 747, conducted a “go around” due to poor visibility during final approach.:3 The crew of Qantas Flight 1, however, were unaware of this.
The first officer was flying the plane during final approach. The aircraft’s altitude and airspeed were high, but were within company limits. The rain was now heavy enough that the runway lights were visible only intermittently after each windscreen wiper stroke. Just before touchdown the captain, concerned about the long touchdown point (over a kilometre past the runway threshold) and unable to see the end of the runway, ordered the first officer to perform a “go-around” and the first officer advanced the throttles to TO/GA power. Seeing that visibility had increased markedly and the landing gear contacted the runway, the captain then decided to cancel the go-around by retarding the thrust levers even though he was not flying the plane. This caused confusion as he did not announce his actions to the first officer who was still flying the plane. When overriding the first officer’s actions, the captain inadvertently left one engine at TO/GA power and as a result canceled the preselected auto-brake settings.
The landing continued, but manual braking did not commence until the aircraft was over 1600 metres down the runway. Company SOP mandated that idle reverse thrust should be used for landings and that flaps should be set at 25 degrees,:17 not the maximum of 30 degrees. The combination of flaps 25, no auto-braking, idle reverse thrust, a high and fast approach, a late touch down, poor Cockpit Resource Management and the standing water on the runway surface led to an inevitable runway overshoot.
The aircraft in fact accelerated for a few seconds after touchdown. Then it proceeded to hydroplane and skid its way down the runway, departing substantially from runway centreline. It gradually decelerated, but far too slowly to save the aircraft, which proceeded past the runway end, over a stretch of boggy grassland, colliding with a ground radio antenna as it did so, and came to rest with its nose resting on the perimeter road. Source: Wikipedia.