Date & Time:
Feb 6, 2023 at 1614 LT
Type of aircraft:
Boeing 737-300
Operator:
Registration:
N619SW
Flight Phase:
Flight
Flight Type:
Fire fighting
Survivors:
Yes
Site:
Plain, Valley
Schedule:
Busselton - Busselton
MSN:
28035/2762
YOM:
1995
Flight number:
Bomber 139
Country:
Australia
Region:
Oceania
Crew on board:
2
Crew fatalities:
0
Pax on board:
0
Pax fatalities:
0
Other fatalities:
0
Total fatalities:
0
Captain / Total hours on type:
1399
Copilot / Total hours on type:
128
Aircraft flight hours:
69187
Circumstances:
The air tanker, callsign Bomber 139, departed from Busselton Airport, Western Australia (WA) on a firefighting task to Fitzgerald River National Park, WA. There were 2 pilots on board, the aircraft captain in the left seat as the pilot flying and a copilot in the right seat as the pilot monitoring. At about 1614, during the go-around from a second partial retardant drop, the aircraft impacted a ridgeline at an elevation of about 222 ft and subsequently crashed, bursting into flames. The pilots suffered minor injuries and the aircraft was destroyed by a post crash fire.
Probable cause:
The ATSB found that the accident drop was conducted at a low height and airspeed downhill, which required the use of idle thrust and a high descent rate. 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. 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 also found that the operator and tasking agency had not published a minimum drop height, which resulted in the copilot, who did not believe there was a minimum drop height, not making any announcements about the low energy state prior to the collision. The ATSB found the operator’s pilot monitoring duties were reactive to the development of a low energy state and did
not include call-outs either before or at the minimum target parameters to reduce the risk of a low energy state developing.
The ATSB benchmarked the WA, New South Wales and National Aerial Firefighting Centre standards against the United States Forest Service and United States National Wildfire Coordinating Group standards and found inconsistencies between the Australian agencies’ standards but not among the United States agencies’ standards. This was likely a result of each Australian state participating in the LAT program independently producing their own standards.
The ATSB also found that the operator and tasking agency had not published a minimum drop height, which resulted in the copilot, who did not believe there was a minimum drop height, not making any announcements about the low energy state prior to the collision. The ATSB found the operator’s pilot monitoring duties were reactive to the development of a low energy state and did
not include call-outs either before or at the minimum target parameters to reduce the risk of a low energy state developing.
The ATSB benchmarked the WA, New South Wales and National Aerial Firefighting Centre standards against the United States Forest Service and United States National Wildfire Coordinating Group standards and found inconsistencies between the Australian agencies’ standards but not among the United States agencies’ standards. This was likely a result of each Australian state participating in the LAT program independently producing their own standards.
Final Report:
N619SW.pdf5.56 MB
