The ATSB has found that an IFR Cessna 404 that crashed at Lockhart River, QLD, in 2020 was 1000 feet below the approach profile as the pilot made a second attempt to land.
C404 VH-OZO crashed into the sand dunes in marginal weather after a charter flight from Cairns on 11 March. The pilot and all three passengers on board were killed in the crash.
"There was no evidence of any conditions or circumstances likely to induce a medical problem or incapacitation for the pilot and the aircraft appeared to be in controlled flight up until the time of the impact," the ATSB concluded.
"There was also no evidence of any aircraft system or mechanical anomalies that would have influenced the accident. Therefore, based on the available evidence, the accident was very likely the result of controlled flight into terrain (CFIT).
"The most likely scenario to explain the descent 1000 ft below the recommended descent profile on the second approach could not be determined.
"Regardless of the exact scenario, it is evident from the continued descent that the pilot did not effectively monitor the aircraft’s altitude and descent rate for an extended period."
Images taken from the aircraft and posted to social media by one of the passenger show low cloud and reduced visibility, which would have created a very high workload for the pilot.
“The aircraft appeared to have been in controlled flight up until the time of the impact, and there was no evidence of any medical problems or incapacitation for the pilot, nor pre-existing mechanical problems with the aircraft or its systems,” said ATSB Chief Commissioner Angus Mitchell.
“In addition to the normal high workload associated with a single-pilot hand flying an instrument approach in poor visibility, the pilot’s workload was elevated due to conducting an immediate entry into the second approach, conducting the approach in a different manner to their normal method, the need to correct lateral tracking deviations throughout the approach, and higher than appropriate speeds in the final approach segment.”
Mitchell said the ATSB’s investigation highlighted the importance of a terrain avoidance and warning system (TAWS) in preventing controlled flight into terrain (CFIT) accidents, and urged operators of smaller aircraft conducting passenger operations to consider fitting TAWS even when not required by regulation.
“Given the aircraft’s descent profile on the second approach, a TAWS would have provided the pilot with both visual and aural alerts of the approaching terrain for an extended period," he said.
As part of the long-planned introduction of CASR Parts 121 and 135 on 2 December 2021, CASA mandated TAWS for piston-engined aeroplanes used for air transport with a passenger seating capacity of 10 or more.
However, there was at the time of the accident no requirement to fit TAWS to VH-OZO.
The full accident investigation report is on the ATSB website.