Radio Communication Breakdown
The pilots of both aircraft did not hear some important radio broadcasts made by the other regarding their location and intention. Direct communications between them were not established until after UJS was airborne. The pilot of UJS likely did not have his radio on at the time the flight crew of VQG made their inbound radio broadcasts, thus missing the opportunity to understand that VQG intended to land on runway 18. About 97 seconds elapsed between UJS's taxi and take-off broadcasts, reducing the time available for determining VQG's location and intention. Additionally, the flight crew of VQG did not hear UJS's rolling broadcast because it occurred simultaneously with Brisbane Centre contacting VQG on the Centre frequency.
Wind Information Discrepancy
The flight crew of VQG recorded the aerodrome wind direction as 230° magnetic during approach planning. However, the local aerodrome wind direction was reported as 329° magnetic. It is unknown whether the crew misheard the airport weather information recording or if the recording itself was incorrect, as a copy of the recording could not be obtained. This incorrect wind information led the crew to plan their approach on the least favorable runway for the actual wind conditions, putting them in conflict with other aircraft operating at the airport.
Conflict Development
The pilot of UJS believed that VQG would land on runway 36, as it was the most suitable for the wind conditions at the time and other aircraft had been using that runway. This belief led the pilot to rely on unalerted see and avoid to de-conflict with the inbound VQG, which occurred after UJS became airborne and the reciprocal trajectory of VQG was observed.