What happened
Following an initial RNAV GNSS approach to runway 30 at Lockhart River and a subsequent missed approach, the pilot of a Cessna 404, registration VH-OZO, immediately began a second approach to the same runway. During this second attempt, the aircraft maintained a descent gradient that was significantly lower than the recommended profile, sitting approximately 1,000 ft below the prescribed path.
As the aircraft continued its descent, it dropped below the minimum descent altitude and the segment minimum safe altitude. The aircraft eventually collided with terrain approximately 6.4 km before the runway threshold. At the time of the accident, the area was experiencing intermittent rain and cloud, with visibility levels that had deteriorated to 80 and 800 m during certain periods, potentially placing the aircraft in significantly reduced visibility.
The investigation
The ATSB examined the flight data, weather records, and the aircraft's equipment. The investigation found that the aircraft was in controlled flight until the moment of impact and showed no signs of mechanical failure or pilot incapacitation. However, the extent of the damage prevented a definitive conclusion regarding the aircraft's serviceability.
Investigators noted that while the aircraft was equipped with GPS units capable of visual terrain alerts, it lacked a Terrain Avoidance and Warning System (TAWS) that provides both visual and aural alerts. Furthermore, the aircraft lacked a system providing vertical guidance, which could have alerted the pilot to the fact that the aircraft was flying well below the recommended descent profile. The investigation also highlighted that the pilot's lateral tracking was significantly off-course, exceeding full-scale deflection on the course deviation indicator for an extended period.
Findings
- The accident was likely a result of controlled flight into terrain (CFIT).
- The pilot's workload was likely elevated due to the immediate second approach, the need to correct lateral deviations, and flying in instrument meteorological conditions.
- The pilot failed to execute a missed approach despite exceeding the operator's stabilized approach criteria regarding lateral deviation.
- The aircraft was not equipped with a TAWS, which would have provided critical terrain alerts.
- There were gaps in regulatory guidance regarding stabilized approach criteria and TAWS requirements for certain piston-engine aircraft in Australia.
Safety message
Operators conducting flights in instrument meteorological conditions or degraded visibility must implement robust risk controls to mitigate CFIT risks. This includes ensuring effective monitoring of altitude and descent rates, adhering to stabilized approach procedures, and utilizing all available terrain awareness functions.