Firefighting specialist Coulson Aviation has implemented a minimum drop height of 200ft following the non-fatal crash of a Boeing 737-300 firefighting aircraft in Australia in 2023.
In addition, Australia’s state of Western Australia is implementing an air tanker drop height of 200ft for large tankers, according to a final report into the 6 February 2023 crash from the Australia Transport Safety Bureau.
Australian national air tanker standard operation procedures are also being developed.
The changes stem from the crash that saw the aircraft (N1619SW) hit a ridgeline while attempting a go-around from a second partial retardant drop.
The report reveals that during the second drop the aircraft was at a height of just 57ft travelling at 110kt with the engines at high idle. The aircraft recovered to 81ft and 107kt at the end of the drop, and the pilot advanced the thrust levels as the descent rate peaked at 1,800ft/min.
The pilot started to pitch the nose up, but the engines did not respond quickly enough.
“The delay in the engines reaching go-around thrust at the end of the drop resulted in the aircraft’s height and airspeed (energy state) decaying as it approached rising terrain, which was not expected or detected by the pilot flying,” says the ATSB.
“Consequently, the aircraft’s airspeed and thrust were insufficient to climb above a ridgeline in the exit path, which resulted in a controlled flight into terrain. The operator’s practice of recalculating, and lowering, their target drop speed after a partial load drop also contributed to the low energy state of the aircraft leading up to the collision with terrain.”
The ATSB observes that the co-pilot, in the belief that there was no minimum drop height, made no announcements about the aircraft’s low energy state before the crash.
At 16:14 local time, the aircraft impacted a ridgeline at an elevation of 222ft.
The two crew, who suffered only minor injuries, escaped through the left cockpit window. Fire largely destroyed the aircraft.
The ATSB adds that the nature of aerial firefighting lends itself to a greater tolerance of risk.
“The lessons from this accident indicate that standard operating procedures and crew resource management should be implemented with the intent to prevent an unsafe situation from developing,” says the ATSB.
“While they should also include recovery actions, there may be insufficient safety margin available for a successful recovery and therefore the safety standards should not be solely dependent on the performance of the pilot flying and recovery call-outs.”
