Wreckage Examination
Examination of the wreckage and flight data indicated that the aircraft’s engine was producing power until impact. All major sections of the aircraft were located at the accident site, and there was no evidence of an in-flight break-up or structural failure. The flight data and the presence of all major components at the scene indicate that the aircraft did not experience a pre-impact mechanical or airframe issue that would have contributed to the collision with terrain.
The flap setting of 50% would be used in low and slow manoeuvring such as looking for a landing site under deteriorating weather or manoeuvring through valleys. Flying slower reduces the radius of turns and the use of the flap gives the aircraft a buffer to the stall speed. This setting might be considered a compromise configuration between flying clean and flying full flap, giving these advantages while retaining a greater capability to climb at short notice without the drag of a full flap.
Engine Warnings
When passing Mallacoota Airport, the pilot commenced a descent from about 9,000 ft above mean sea level (AMSL). At that time, the pilot would have seen low cloud ahead and probably descended in order to fly below it or in preparation for an approach and landing at one of the aerodromes along the planned flight route.
Flight data showed fluctuating temperature indications from the number 4 cylinder throughout the latter part of the flight. These temperature fluctuations would have generated warnings displayed to the pilot on the multi-function display, alerting them to a potential engine issue. The first indications of this fluctuation occurred prior to the initial approach to Moruya Airport. The recorded engine data showed that the cylinder head temperature (CHT) rose to the caution range and subsequently progressed to the warning range. There was a reduction in engine power over an approximately 30‑second period, before maintaining reduced power for about a minute further. This was likely to have been initiated by the pilot in response to the high CHT warnings and was consistent with the appropriate response to a genuine warning. The engine was then returned to normal power after the CHT levels dropped back into the normal range.
Shortly thereafter, the CHT again increased, entering the caution range for a second time. After an 8‑minute period with the CHT in the caution range the pilot radioed ATC with their intention to land at Moruya Airport. Given that a landing at Moruya was not planned, it is most likely that the pilot initiated the approach as a result of the warning and/or cloud ahead.
The ATSB assessed that these warnings were very likely spurious, and an attentive pilot with a good understanding of engines could doubt their validity based on the engine instruments. The pilot may have thought the warnings were genuine or spurious, and this understanding could have changed throughout the flight. In any case, the persistence of these warnings throughout the remainder of the flight would have been a continuing source of distraction, potentially increasing workload and reducing their capacity to monitor other operational factors such as navigation, weather conditions, and terrain clearance.
Decision to Continue Flight Past Moruya Airport
After commencing an approach to Moruya Airport, and making a radio broadcast to that effect, the pilot discontinued the approach and continued the flight below the cloud base. Satellite and meteorological data indicated areas of low cloud around the Moruya area, with instrument meteorological conditions (IMC) present as the pilot approached the airport. Additionally, poor weather was observed along the planned route of flight (along the east coast) beyond Moruya. There were no further radio transmissions or position reports from the pilot following the initial call indicating their intention to land at Moruya. Given that poor weather was present ahead of the aircraft and the pilot would have been seeing fluctuating cylinder temperature warnings, it is unclear why the pilot made the apparent decision to continue the flight rather than land at Moruya.
This decision may have been influenced by the perceived presence of a completely clear area in the cloud layer ahead. Analysis of satellite imagery revealed a temporary gap or break in the extensive cloud cover extending from Moruya Airport towards the Great Dividing Range. This gap, evident at the approximate time the aircraft passed to the west of Moruya Airport, would have presented a visually clearer path to the pilot. There was cloud over Moruya Airport and the pilot may have considered that maintaining VMC throughout an approach and landing there might not have been feasible. In any case, the decision to deviate inland from the initial planned track and towards higher terrain was likely influenced by this break in cloud.