This is the machine you must fight in order to find Katara. Dodge the fire bending. 
Try running left to right, then right to left. Continue this until you see a flashing 
light near it. This is your chance to attack. Hit it with Aang. 
You may use a Chi attack but just a plain attack should work just as well, however it 
takes time. You will have Saka (Katara's brother) fighting with you to do double damage. 
After about a quarter way down on HP, the machine will start throwing fire around. Keep 
a safe distance from this attack. It causes no real threat to your or your partner as 
long as you stay as far away as possible.