Aircraft can be an impressive sight on a fire ground as they drop their loads of water, foam, gel or retardant. But it is important to realise that aircraft don't put out fires, they are simply a tool to assist firefighters on the ground. As with any job, it is important to select the right tool for the task at hand.
Factors that influence aircraft selection
South Australia believes in the philosophy of hitting a fire 'hard and fast'. CFS volunteers and aerial firefighting aircraft are responded within minutes of a bushfire being reported and as many resources as possible are deployed to keep the fire small and reduce the chance of it getting out of control. It is not widely known that South Australia has a world class initial attack strategy of aerial firefighting. The value of a rapid aerial firefighting approach has been supported by Bushfire Cooperative Research Centre research. In their 2009 report titled 'The cost-effectiveness of aerial fire fighting in Australia, the Research Centre wrote the following in their summary
The results of the analysis show that the use of ground resources with initial aerial support is the most economically efficient approach to fire suppression. Aircraft are economically efficient where they are able to reach and knock down a fire well before the ground crew arrives. This buys time for the ground forces to arrive and complete the containment. Rapid deployment of aerial suppression resources is important. This advantage is much greater in remote or otherwise inaccessible terrain. Where other suppression resources are unable to reach the fire event within a reasonable time period, sole use of aircraft is economically justified.
To facilitate the rapid deployment recommended by the research, CFS select aircraft that can be airborne quickly. Aircraft such as the Air Tractor, can achieve this due to their single engine and simplicity of operating systems. They can be on their way to a fire within 3 minutes. This compares to about 20 minutes for many twin engine aircraft and helicopters which take longer to warm up and have more complicated systems and procedures for engine start up.
To further enhance the speed of response, CFS prepositions aircraft across our vast State thus reducing transit time.
South Australia features a mix of landscapes ranging from large expanses of flat cropping land found on the Eyre and Yorke Peninsulas to steep hilly terrain of the Mt Lofty and Flinders Ranges. Each terrain type presents its own aerial firefighting challenges. For example a grass land fire can benefit from the application of a fixed wing bombing aircraft that can lay a long line of fire suppressant. A fire in a hilly landscape with thick bush coverage, can be better served by a rotary wing bomber that can follow the contours of the terrain. In this situation, helicopters have the added benefit of slower dropping speeds which enables better penetration of the tree canopy.
Access to water
Aerial firefighting aircraft are only as good as their ability to access water quickly. While helicopters will take longer to reach a fire because of their longer start up time and their slower flying speed, they can be extremely effective if there is a water source close by. Helicopters can hover fill from a static water source such as a dam and if this water is near to the fire, then turn around times can be extremely quick.
The dry nature of South Australia, particularly in mid summer, means however, that in many cases there are often no suitable locations for hover filling. This is when fixed wing aircraft come into their own. Particularly air tankers such as the Air Tractor 802, which is capable of taking off and landing from small country airstrips.
The air tanker will use an airstrip close to the fire and is refilled with water from either a rainwater tank located at the strip or from a mobile water tanker. Being able to use a short country airfield is a great benefit as this negates the need to travel back to larger airports and thereby reduces turn around times. (This is one of the major disadvantages with large air tankers)
Access to fuel
Firebombing aircraft use Jet A1 fuel. In order to sustain fire bombing activities, this fuel must be readily available and the larger the aircraft, the more fuel it needs. Aircraft such as the Air Tractor 802 uses 280 litres per hour while the Erickson Aircrane uses significantly more at 2,080 litres per hour. If a fire occurs in a remote area, where no or limited fuel supplies are available, a mobile fuel tanker will be dispatched with the aircraft. Going by road takes a lot longer than by air which means a bombing aircraft must have a reasonable level of endurance such that it can continue to operate until the fuel truck arrives. Given the rate of fuel burn for helicopters, particularly large types, there is little value in dispatching them to remote locations because they will run out of fuel long before their reserve supply arrives by road.
Selecting aircraft is the same as selecting any other tool for a task. The tool must do the job you want while being within the budget you can afford and a large expensive tool doesn't always mean it will do the job better than a smaller cheaper version. This is particularly the case with fire bombing aircraft. Throughout the world there are a number of firebombing aircraft to select from, including some extremely large planes such as the Ilyushin-76, the DC-10 tanker and the Canadair scooping aircraft. While these are all capable aircraft, they come at significantly greater operating costs.
The sheer expense of operating a very large air tanker would mean the CFS would have to reduce its existing fleet significantly if it wished to invest in one. From an operational perspective however, it is preferable to invest in a larger fleet of smaller aircraft that have more versatile capabilities than fund just one large aircraft. CFS achieves its current success in aerial firefighting through an integrated approach which sees fit for purpose aircraft working with ground-based firefighers.
From experience, CFS has learned that a fleet of smaller more versatile aircraft provide the best value for money for the South Australian tax payer while not compromising on the firefighting capabilities they provide. Having more aircraft available, means the CFS can preposition air tankers in key rural population centres such as Mt Gambier and Port Lincoln to enable a fast response. Not only are smaller aircraft cheaper to operate, they are better at tackling fires in hilly terrain such as that found in the Adelaide Hills. They can also be far more effective in their accuracy at pin pointing their drops.