The deaths of five people in a light plane crash in bad weather in far north Queensland could have been avoided if the aircraft had a terrain avoidance and warning system, investigators say.
The Cessna 404 was making its second attempt to land at Lockhart River on Cape York in heavy rain and cloud when it hit sand dunes, killing the pilot and four passengers, on March 11, 2020.
An Australian Transport Safety Bureau probe found the aircraft was being flown about 1000ft below the recommended height before it crashed.
However, the pilot had been in control until the point of impact and there was no evidence of mechanical problems in the lead-up to the accident, the bureau's report released on Thursday found.
ATSB Chief Commissioner Angus Mitchell says the plane didn't have a black box, which wasn't required, so it's impossible to work out a conclusive cause.
However, investigators have decided that the pilot had probably failed to check the Cessna's height and tried to land it solo in very poor visibility.
"Overall, misreading the altimeter by 1000ft appears to be the most likely scenario, although there was insufficient evidence to provide a definitive conclusion," Mr Mitchell said in a statement.
"Regardless, 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, and that they were probably experiencing a very high workload."
The pilot had five years of experience flying into remote airports and had landed at Lockhart River Airport eight times previously.
However, he was "probably experiencing a very high workload" due to the bad weather, poor visibility, having to take a different approach to the airstrip and keep checking that approach, and coming in at a faster speed than normal.
The ATSB said its probe highlighted the importance of terrain avoidance and warning systems (TAWS) in helping pilots to avoid flying into the ground, particularly when visibility is poor.
The Cessna did not have a TAWS at the time as they were only mandated in December 2021, but Mr Mitchell said the system could have prevented the accident.
"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 added.
In light of those findings, the ATSB said air transport operators should install a TAWS in aircraft, or if that's not viable they should ensure they understand the limitations of terrain warnings in GPS or navigation systems.
"The ATSB urges all operators conducting air transport operations to evaluate the risk of CFIT (controlled flight into terrain) in your operations and to actively seek to install TAWS in your aircraft to maximise the safety of your operations," Mr Mitchell said.
