Firefighting helicopter accident due to Bambi bucket lines entangled in skids, says ATSB

During the water rise, control of a Bell 204 helicopter was lost because the cables attaching its fire bucket became caught over the left rear skid, causing a shift in the center of gravity.

The helicopter was used for firefighting operations on the afternoon of September 20, 2023, as it approached the dam on a property in Tarome, southeast Queensland, according to the final report of the ATSB investigation into the details of the accident.

“The cables attaching the Bambi bucket to the helicopter became caught over the left rear skid as the helicopter approached the dam and delivered water into the bucket,” ATSB Director of Transportation Safety Kerri Hughes said.

“As the pilot began to lift the bucket from the dam, the helicopter’s center of gravity shifted rearward and to the left due to the weight attached to the left rear skid. This created asymmetrical lift loads, which caused the helicopter to lose control.”

The helicopter hit the water and the pilot reported that it turned over almost immediately, filled with water and began to descend to the bottom of the dam.

The pilot initially tried to escape the sinking helicopter via the front left door. Unable to open it, they swam to the back of the cabin, where the helicopter was almost completely submerged. After attempting to open the right rear door and throwing out the windows, they escaped by using considerable force to open the left rear door.

“The pilot had completed HUET (helicopter underwater escape training) approximately 2.5 years before the accident, which increased his chances of survival when the helicopter went down in the dam,” Ms Hughes said.

“Helicopters tend to be top-heavy, with the engine, gearbox and main rotor system located above the cabin, and therefore can tip over quickly when they hit water. Therefore, this accident highlights the importance of conducting HUET to increase the chances of survival of helicopter occupants in the event of a water impact.”

The accident also highlights the complexity of conducting external load operations over water, where research has shown that the risk of an accident involving a firefighting helicopter is twice as high as operations involving private helicopters.

“There can be a lack of visual references, visual illusions over water, limited visibility and vertical reference of the hook and external load through mirrors and bubble windows, all of which increase the complexity of operating helicopters with external loads over water,” Ms. said Hughes.

“Contamination of external load carrying cables on the airframe can result in rapid changes in weight distribution, asymmetrical lift and loss of control.

“As Australia faces another fire season, this accident investigation highlights the importance of correct cable positioning to the safety of external elevator operations.”