Accuracy
Speaking to a couple of mates in the RFS over the Christmas break - one a Brigade Captain & the other an Air Attack Supervisor - both think that the 747 and other large a/c cannot get close enough to our fires, due to terrain issues, to get the kind of accuracy needed for effective fire fighting. Smaller a/c get much closer in the tight/difficult terrain.
Hope all had good Christmas and have a safe & prosperous year.
ABX