| Occurrence Briefs are concise reports that detail the facts surrounding a transport safety occurrence, as received in the initial notification and any follow-up enquiries. They provide an opportunity to share safety messages in the absence of an investigation. |
What happened
On 13 November 2019, a Bell 214B helicopter was water bombing during fire control operations near Pechey, Queensland. At 1344 Eastern Standard Time, the helicopter approached the bushfire downwind and downhill from the north-west at about 60 knots, and made a descending right-hand turn back into wind over the fire.
The descent was continued towards the drop zone. The airspeed was further slowed and the height was reduced to about 150 feet above ground level (50 feet above treetop level). The pilot then released the load of water before departing the drop area into rising terrain. The pilot heard the low rotor RPM warning and had insufficient altitude and clearance from obstacles to recover the rotor RPM and continue flying. He was concerned that further actions required to recover the rotor RPM would result in the helicopter possibly striking trees or ending up in the actively burning fire.
In maintaining the climb to avoid rising ground, trees and fire, the rotor RPM appeared to decay further. As the helicopter cleared the trees, it began to descend, yawed to the right and the left-hand skid collided with the ground. The helicopter rolled onto its left side resulting in substantial damage. The pilot was able to turn off the fuel to stop the engine and exited the helicopter via the overhead window with minor injuries. Neither the g-force activated ELT beacon or flight tracking alarm were triggered.
The distance from the last water drop to the impact point was less than 100 metres and the recovered aircraft showed little evidence of damage from forward moment.
Figure 1: Aircraft prior to recovery – looking at reciprocal direction of approach. The final water drop occurred beyond the fuselage where the smoke is rising.
Source: Operator
Figure 2: Aircraft wreckage
Source: Operator
Operator’s investigation and comments
Based on the pilot’s account of the accident and assessment of the recovered aircraft, mechanical malfunctions were ruled out as a contributing factor. The operator determined that the accident was most likely the result of a loss of rotor RPM that the pilot was unable to recover, due to a downwind descending turn, low altitude for the water drop, and a departure into rising terrain. The pilot had to make a decision between putting the helicopter into tall trees and active bushfire or climbing over the trees to clear ground. In choosing the latter, the rotor RPM decayed further, and the helicopter contacted the ground.
The operator stated that the helicopter type is renowned for its ‘hot and high’ performance making it a very effective firefighting platform. Firefighting combines a number of factors which result in flying that is close to the performance limits of the aircraft – high gross weights, low airspeeds, low altitude, close quarters manoeuvring, high work rate environment and adverse weather conditions. In this case the combination of factors immediately leading up to the accident resulted in the helicopter operating outside its performance envelope without having enough space and height to recover.
Safety action
As a result of this occurrence, the aircraft operator has advised the ATSB that they are taking the following safety actions:
The operator has provided a briefing to all of their pilots on the circumstances and the outcome of this accident. The pilot involved in this accident will be involved in future training and checking to enable the recognition and avoidance of the circumstances that saw the limitations and flight envelope exceeded. This training will become part of the operator’s annual training for all pilots conducting fire control operations.
Safety message
Fire control flying operations can involve challenges and complexities that require crews to maintain a heightened awareness of their aircraft’s operating limits and the environmental conditions. Flying within operating limits can ensure pilots have a performance margin to react to unforeseen circumstances.
About this report
Decisions regarding whether to conduct an investigation, and the scope of an investigation, are based on many factors, including the level of safety benefit likely to be obtained from an investigation. For this occurrence, no investigation has been conducted and the ATSB did not verify the accuracy of the information. A brief description has been written using information supplied in the notification and any follow-up information in order to produce a short summary report, and allow for greater industry awareness of potential safety issues and possible safety actions.