Accident Summary
On the morning of 28 October 2023, a SOCATA-Groupe Aerospatiale TB-20, registered VH-JTY, departed Montpelier aircraft landing area, Queensland, for a visual flight rules (VFR) private flight to Palmyra aircraft landing area, Queensland. The flight was expected to last just over one hour, and both the pilot and passenger were familiar with the route.
During the flight, the pilot contacted a friend at the destination to obtain an appreciation of the weather. After the friend advised of the prevailing conditions, including cloud, the pilot replied that they would need to pass through some cloud before arriving.
Approximately 30 nautical miles from the destination, shortly after commencing descent for the intended landing, the aircraft began a steep descending turn to the left toward mountainous terrain. During this descent, the aircraft exceeded the airframe’s designed maximum airspeed before pitching up and passing over the top of Bull Mountain. The aircraft then entered a second steep descending turn, this time to the right, after which the recorded flight path data ceased.
The wreckage was located in dense forest on the north-east face of Bull Mountain. The accident site indicated that the aircraft had collided with terrain at a steep angle and with significant forward velocity. The aircraft was destroyed, and both occupants received fatal injuries.
Investigation Findings
The Australian Transport Safety Bureau (ATSB) investigated the accident. The investigation found that after encountering cloud en route, the pilot elected to continue along the intended flight path through the cloud instead of diverting around it or remaining on top. Shortly after, it is very likely the pilot entered weather conditions not suitable for visual navigation, leading to spatial disorientation and a descent into mountainous terrain.
Evidence from the OzRunways electronic flight bag application showed that shortly after commencing descent from 5,500 feet, the aircraft made a series of turns with excessive sink and climb rates before colliding with terrain. This maneuvering indicated that the autopilot was not being used during this part of the flight. Site and wreckage examination indicated that the aircraft was complete, had significant forward velocity, a high angle of entry, and the engine was producing power. These findings suggested that the aircraft was most likely in an uncontrolled state when it hit the ground.
The ATSB considered possible explanations for the departure from controlled flight, including pilot incapacitation, technical failure or malfunction, decision making, and spatial disorientation. Pilot incapacitation was considered unlikely given the short timeframe between the phone conversation and the loss of control, and the pilot’s pre-existing condition was being appropriately managed. The passenger was also a pilot, though not current, and could have taken control. Technical malfunction was excluded because structural failure was not evident, and the engine was producing power at impact. The autopilot had been repaired nearly a year prior, and no radio call was made that would indicate an emergency. Decision making and spatial disorientation were identified as the most likely factors.
Probable Cause
The ATSB found that the pilot encountered cloud en route and elected to continue through cloud instead of diverting or remaining on top, and it is very likely the pilot entered weather conditions not suitable for visual navigation, leading to spatial disorientation and a descent into mountainous terrain.