G'day all.
As this is my first post, perhaps I should introduce myself. By profession I'm a farmer - and I should make it clear that I'm neither a pilot, nor a pilot-wannabe. However I'm also a volunteer firefight and Air Attack Supervisor (Trained with DSE, work with NSWRFS) This doesn't mean that I'm the Great Guru on all things to do with fighting fires from the air, but I might be able to offer a certain amount of information and perspective.
Firstly - and I must emphasise that i don't speak for any service - IMHO there is always going to be a certain amount of politics involved in the letting of such contracts. The media likes large, camera-worthy items, and booking a big bomber has a certain cachet. Not saying that this makes it wrong, just that you need to be wary.
Secondly, there are three issues relating to waterbombing that are more important than the capacity of a single aircraft. One is the capacity of your system over time. The second is placement. The third is flexibility.
The capacity of your system is measured in litres per hour on target, rather than litres per tanker. If your 50,000litre tanker has a turnaround time of 90 minutes (not unreasonable given that it can't land on every bush strip) then 4 AT802s on 20 minutes turnaround will give you a higher capacity system.
Some of you will be far more familiar with the capabilities of the larger aircraft than I am, but I suspect that they will have difficulty operating at 50-100' above tree-tops in the terrain that often confronts us when fighting fires. Consider the impact of wind upon foam or retardant, and how this increases with drop height. The bad fires do not occur upon days that give perfect drop conditions.
A number of smaller tankers give greater flexibility in that they give a more constant delivery. In rapidly-developing fires this can be a considerable advantage as we respond to changing conditions and new threats. Not that a larger aircraft cannot split loads, but once empty, we must wait for its return.
The advantage of the larger aircraft - if it can drop accurately - is its ability to create a more effective retardant line due to length of drop. This is particularly useful during first response situations in seeking to prevent the fire from developing in the absence of a full compliment of ground crew. It was on this basis that the 1986 CSIRO study into the cost-effectiveness of Aerial fire-fighting recommended a single DC6 and a combination of smaller aircraft as the optimum configuration for fire suppression in Victoria
Under the costs then applicable, the Trackers, Neptunes and C-130/MAFFS were all not cost-effective in a normal year.
Please bear in mind that we prefer to not kill our pilots. The conditions prevailing during the worst of Black-Sat were not conducive to safe flying at low levels over rough terrain and with reduced visibility. Add in the fire intensities and fires spotting ahead of the main front at an average distance that is measured in kilometres, and you can understand how aircraft effectiveness is reduced on such days.
Another point that should be made is that no government has an unlimited budget. In comparison, poor roads kill more people in a year than Black-Sat, and an inadequately-funded health system kills more people per year than bushfires have in the past two centuries. We have no right to demand funding if we cannot demonstrate a return on investment.
All that said, we CAN do some very good and cost-effective work with aircraft. Particularly in a first-response mode, or in backing up ground crews in rough terrain. We just need to be smart about it.
Regards..... Pete