What happened
While descending from 5,500 ft, the VH-JTY, a single-engine aircraft, entered a series of turns characterized by extreme climb and sink rates before striking the ground. Data from the OzRunways electronic flight bag indicated that the aircraft was not utilizing autopilot during this phase of the flight. Examination of the wreckage showed the aircraft was intact and traveling at a high forward velocity with the engine producing power at the moment of impact, suggesting the aircraft was in an uncontrolled state prior to the collision.
The investigation
Investigators examined several potential causes for the departure from controlled flight, including pilot incapacitation, technical failure, and decision-making. A medical event was ruled out as the timeframe between the pilot's last phone call and the accident was too short, and the passenger was also a qualified pilot capable of taking control.
Regarding technical issues, the presence of the propeller, wing tips, and stabilator at the site ruled out an in-flight structural breakup. Furthermore, the engine and propeller damage confirmed the engine was functioning correctly. While the autopilot was considered, there was no evidence of a malfunction that would have induced uncommanded inputs, and the pilot's familiarity with the system made a sudden, uncorrected failure unlikely.
Findings
- The pilot chose to descend through cloud layers rather than divert around the weather or remain in visual conditions above the clouds.
- The pilot likely entered weather conditions that were unsuitable for visual navigation.
- Spatial disorientation is the most probable factor leading to the loss of control and subsequent terrain impact.