A preliminary report into the crash of a Boeing 737-300 firefighting aircraft in Western Australia shows a last moment attempt to pull up before the aircraft impacted a ridgeline.
During a low-level drop of fire retardant onto a downward slope in Fitzgerald National Park, the captain of the Coulson Aviation aircraft (N619SW) advanced the throttles – the engines were at high idle – before the jet’s rate of descent peaked at 1,800ft/min, and started to pitch the nose up.
“The nose-up pitch preceded the acceleration of the engines, resulting in a reversal of the rate of descent, but also a decay of the airspeed,” says the report from the Australian Transport Safety Bureau (ATSB).
The captain announced “fly airplane”, which was followed by stick shaker activation. Then the crew experienced “an abrupt vertical acceleration” as the aircraft impacted a 222ft ridgeline at an airspeed of 104kt (192km/h).
The jet then cleared a line of foliage before impacting the ground a second time and sliding to a halt.
Underlining the aircraft’s low altitude immediately before the initial impact, the report illustrates two “jet blast corridors” produced by the aircraft’s CFM International CFM56 engines.
The crew, who suffered only minor injuries, were able to escape through the left cockpit window. They moved clear of the fire, which largely destroyed the aircraft, and were rescued by a helicopter.
The report offers no analysis but details the specifics of the crash. Both the cockpit-voice and flight-data recorders were recovered. Although the aircraft was destroyed, ATSB personnel were able to assess the positions of flight-control surfaces.
“Despite extensive fire damage, ATSB recorders specialists in our Canberra technical facilities were able to download files from both the flight-data recorder and cockpit-voice recorder,” says ATSB commissioner Angus Mitchell.
“As well as information from those recorders, interviews with the flightcrews, a 3D map of the accident site created using a drone, and other recorded flight information will be instrumental to the ongoing investigation.”
Cirium fleets data indicates that the aircraft’s career as a tanker was short. Delivered new to Southwest Airlines in 1995, it carried passengers until 2017, when it was purchased by Coulson.
Coulson converted it to a tanker in 2021, and it commenced firefighting duties in July 2022. The 737 is fitted with a patented aerial delivery system capable of dropping up to 4,000USgal of retardant.