Australia's Bushfire Co-operative Centre has concluded that, based on the evidence collected during a three-month trial of a McDonnell Douglas DC-10-30 air tanker in Victoria earlier this year, such an aircraft is not suitable for effectively suppressing fires under most Australian wildfire conditions. The drops from the DC-10-30 were found to have "limited effectiveness" during the trial, the report says.
Following the Black Saturday bushfires in Victoria in February 2009, in which 170 people died, the Victorian state government leased the DC-10-30 from US company 10 Tanker Air Carrier for a 10-week operational trial during the 2009-10 fire season from January. The trial was the first of its kind in Australia of a very large air tanker.
The DC-10-30 has three tanks with a total capacity of 45,400l (12,000 USgal) and can be used to deliver retardant and suppressant mixes to fires at a range of coverage levels.
© 10 Tanker Air Carrier
The intention of the trial was to deploy the aircraft to active wildfires in the state, plus additional non-fire missions, in order to evaluate its operation in Australian fuel and weather conditions, says the report. However, the mild fire season meant that the aircraft was only deployed to one actual wildfire where it dropped one load. "While the drop was on target, the fire behaviour did not seriously challenge the drop owing to moderate weather and discontinuous fuels, leaving the question of its effectiveness in wildfire conditions unanswered," says the Bushfire CRC.
Five subsequent missions were conducted to address the firefighting capabilities of the aircraft, but none of these were conducted under conditions typically found in a severe wildfire, it adds.
The report says most of these drops resulted in a pattern of alternating thick and thin sections of coverage, with the light coverage sections allowing fire to pass across them with minimal slowing effects. This was due to a combination of the fast drop speed and the design of the delivery system, says the report. Two drops delivered in open eucalyptus forests penetrated the canopy and provided a good coverage of surface fuels, says the report. One of these drops, however, caused severe damage to the vegetation. "This drop could have potentially injured people or damaged buildings and highlights the need to ensure that people are not in the drop zone. Clearly, the significant potential for damage from a drop precludes a role in an urban interface situation while safe drop heights cannot be guaranteed," says the report.
"The results from these evaluation missions indicate that there are often problems with the consistency of many drops from the DC-10 air tanker," says the Bushfire CRC.
It notes, however, that the evaluation was severely limited by the lack of tracking data from the DC-10, which had been requested from the operator. Tracking data would have allowed flight characteristics to be determined and allowed better comparisons between drops, it says.