What happened
Shortly after departing Cottage Point, New South Wales, the DHC-2 aircraft, registered VH-NOO, performed a 270-degree right turn over Cowan Water before entering Jerusalem Bay. Witnesses observed the aircraft fail to maintain its climb, instead flying at a level or descending altitude through the confined waterway. While navigating the bay, the aircraft entered an extremely steep right turn with a bank angle estimated between 80 and 90 degrees. During this maneuver, the nose dropped, leading to an aerodynamic stall at an altitude too low to allow for recovery. The aircraft subsequently struck the water, resulting in six fatalities and the destruction of the aircraft.
The investigation
The ATSB examined the wreckage and analyzed passenger photographs to reconstruct the flight path. The investigation focused on the pilot's physiological state and the mechanical condition of the engine. Toxicology reports confirmed elevated levels of carboxyhaemoglobin in the pilot and several passengers, indicating significant exposure to carbon monoxide. Investigators also identified structural issues in the engine compartment, specifically cracks in the exhaust collector ring and missing bolts in the main firewall, which allowed exhaust gases to leak into the cabin.
Findings
- The pilot's ability to safely operate the aircraft was likely impaired by carbon monoxide exposure caused by exhaust leaks.
- The aircraft entered a known confined area at an altitude below the surrounding terrain without operational necessity.
- The aircraft underwent an aerodynamic stall during a high-angle turn that exceeded standard operating procedures.
- The effectiveness of the onboard chemical CO detector may have been compromised by sun bleaching.
- Maintenance discrepancies, including the use of non-specific bolts on the firewall, contributed to the gas leak.
- The lack of mandatory flight recorders for aircraft under 5,700 kg hindered the ability to fully analyze the flight data.