Flight and Weather Encounter
VH-HWY departed Darwin Airport at 1307 on 23 October. The area forecast indicated thunderstorms and reduced visibility. However, weather conditions developed rapidly, making accurate prediction difficult before departure. Fourteen minutes after departure, the left-seat pilot requested a diversion left or right of track to avoid weather. Air traffic control (ATC) prompted subsequent diversions of 10 and 20 nautical miles, transmitting 'advise if you need further right of track' to the aircraft. While a left diversion was possible, adverse weather also existed in that area.
The aircraft's recorded track, overlaid on weather radar and satellite cloud images, showed it tracking close to a precipitating cell and a rapidly developing towering cumulus cloud. The last recorded position at 1332 was within the developing cell, an area likely containing strong convective activity including updrafts and downdrafts. Altitude changes in the final minutes indicate the aircraft likely experienced severe convective turbulence. Reduced visibility may have occurred, increasing the risk of spatial disorientation and potential loss of control.
Wing Separation
The aircraft's track data and witness reports indicate a very high rate of descent from about 10,000 feet until impact. The wings were found in close proximity, likely tethered together until low altitude or tree impact. Deformation of the fractured wing spars was upward and rearward. This evidence indicates the wings separated in-flight due to excessive wing loading beyond design limits. Based on calculations of calibrated airspeed and recorded ground speed (without localized wind data), the effects of turbulence and any control inputs would have increased wing loading. A combination of airspeed, turbulence, and control inputs probably led to excessive loading, causing the wings to separate from the fuselage before the aircraft collided with terrain.
Pilot Experience Considerations
After diverting right of track, pilots may have perceived an opportunity to return to the planned track but then re-diverted south to avoid further hazards, inadvertently positioning the aircraft in adverse weather that led to wing separation. The ATSB considered whether motivational factors—such as concern about a late departure, a perceived need to deliver a coffin to Elcho Island in a timely manner, or implicit pressures as new crew members—influenced in-flight weather-related decision making. These factors could lead to plan continuation bias, but it was not possible to determine if they actually affected decisions. A likely influence, supported by research, was the pilots' level of operational experience in the wet season. The 'build-up' period to the wet season in Darwin is known for hazardous weather, and pilots with limited experience in such conditions may not accurately assess the risks.