The ATSB is now investigating whether strong winds played a part in the death of three American firefighters whose Lockheed C-130 crashed while they were tackling a bushfire in southern NSW.
The news comes after an interim report, released on Thursday, spoke to multiple witnesses who all reported “very strong winds” on the day of the accident in January this year.
Australian Aviation reported earlier this year that the ATSB weren’t able to recover any audio from that accident that killed Ian McBeth, Paul Hudson and Rick DeMorgan despite investors recovering the voice recorder.
The incident was one of the most high-profile tragedies of Australia’s black summer bushfire season.
“To-date, the ATSB has interviewed other pilots and key personnel from the aircraft operator, NSW Rural Fire Service personnel involved in aviation operations, witnesses, C-130 and other aerial firefighting pilots, and key personnel in overseas aerial firefighting operations,” said ATSB chief commissioner Greg Hood.
“The interim report does not contain findings nor identify safety issues, which will be contained in the final report.
“However, it does detail the extensive evidence gathered to date, which has helped ATSB investigators develop a detailed picture of this tragic accident’s sequence of events.”
The next stage of the investigation will focus on weather and environmental influences, aircraft performance and handling and operating policies and procedures in an attempt to discover the cause of the accident, which still remains a mystery.
So far, the ATSB’s examination of the crash site and wreckage has significantly found no evidence of structural failure or pre-existing damage.
However, investigators have received “multiple witness reports” of the weather conditions at Peak View.
“Witnesses all consistently reported very strong winds from the north-west,” Hood said. “One resident noted that, although the prevailing wind was from the north-west, the direction and strength at ground level were also being influenced by the local terrain.”
“The Bureau of Meteorology considered the conditions on the day were favourable for mountain wave development, and satellite imagery of cloud formations confirmed their presence in the general area of the accident.
“However, from the data available they were unable to determine the severity of mountain wave activity.”
In February, Australian Aviation first reported the details of the traffic flight that occurred as the three men were trying to tackle the Good Good fire.
The Lockheed C-130 flown by the three men was built in 1981 and repurposed for firefighting activities.
It had arrived in Australia in November 2019 but had previously operated in the country during the 2018-19 bushfire season.
The aircraft took off at 12:05pm on 23 January from Richmond RAAF base and approached the Adaminaby Complex bushfire.
However, it was unable to complete its drop and so was diverted to a secondary task to drop retardant on the Good Good fire.
The ATSB reported witnesses seeing the aircraft complete a number of circuits before the crew released 4,500 litres of fire retardant on the blaze, 200 feet above ground level.
Videos taken of the aircraft leading up the accident showed a number of passes were conducted at varying heights prior to the drop.
The C-130 was then observed to bank left before becoming obscured by smoke after about five seconds.
Around 15 seconds later, the aircraft was seen flying at a very low height above the ground in a “left-wing down attitude”.
Shortly after, at 1:16pm, the plane hit the ground and a “post-impact fuel-led fire” ensued. All three crew were killed.
A review of the Airservices Australia audio recording of the air traffic control frequency found no distress calls were made by the crew prior to the impact.
Crucially, no audio was recorded from the in-flight cockpit voice recorder, despite the device being recovered intact. All recovered audio was from a previous flight when the aircraft was operating in the US.
Cockpit voice recorders are usually designed on an “endless loop principle”, meaning the oldest audio is continuously overwritten by the most recent recording. The model on the C-130 had a recording duration of 30 minutes.
The final report into the incident is not expected for many months.