Last December firefighters from New South Wales began using their DC-10 Large Airtanker in a fashion that, while not necessarily an innovation, has not been commonly practiced elsewhere.
Historically airtankers began with the capacity to carry enough retardant to hit a spot, or small section of line, before returning for another load. As the size of airtankers increased, so did the size of the loads they carried, creating the ability to split loads into multiple drops. Todays Next Generation Airtankers carry between 3000 and 11,600 US gallons, but curiously the number of splits on the average mission has remained relatively static. In fact it is safe to say that the majority of airtanker runs made today are either single drop or two drop loads. To be sure it is not uncommon to see a load split into three drops, but anything more is relatively rare.
Now enter a week-long period in late 2015 when 18 DC-10 loads of retardant were dropped on fires in NSW, and those 18 loads were split into more than 60 separate drops. While that average is only 3.3 drops per load, the reality is that many of those loads were split into six, or even seven, drops. Since then, reports indicate the practice continued as the NSW season progressed.
So why the difference, and what does it matter?
The difference, I believe, is both cultural and tactical. Culturally, firefighters in Australia have developed tactics that work well with repeated Sky Crane drops of 2000 gallons, and obviously six drops from a DC-10 fits into those tactics quite well. Tactically, Australian firefighters “build” less indirect line with retardant, and rely instead on tactical application of the suppressant directly on, or close to, the fire line. This tactic usually means shorter runs to follow an uneven line.
The reason this matters comes back to the basic questions of cost efficiency and operational effectiveness. The DC-10, and the amount of retardant it carries, has become regarded as a good example of the benefits of economy of scale. The more suppressant you can carry to the fire line in a single load, the cheaper it becomes. What NSW is showing us is that effective tactical application and economy of scale are not mutually exclusive principles.
Images courtesy of 10 Tanker Air Carrier
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