Helicopters can only put out very small fires if the water source is very close by....and the conditions are right. Otherwise at best the fire can be guided a bit.
Where the Helicopter excels is in putting out burning snags and residual fires like stumps and the like.
When a fire grows to be really active and running....there is very little that can be done but get out of its way.
In the USA....one saying re Forest Fires is "Fly Safe, make as much money as you can!".