Firefighting drones in action - GIF

[Frank S]

As a concept it is a neat idea but I have to question the validity of practical use.

The weight of the hose and water will severely limit the effective height. Not to mention the thrust required to counter the reaction forces from the nozzle.

Then you get into the practicality of flight time and manpower. The pilot and hose tender could team up and be on a ladder with a much bigger hose in the same time it takes to set up the drones.

That is providing a ladder truck can even get to the scene of the fire.
Drones can be built as large as is required to lift the hose with a column of water and with enough counter active power to hold against the nozzle force.
Think of a purpose-built vehicle as a drone tender the drone would be carried on top of the vehicle with its pods folded back it could be 8 ft wide and 20 ft long in the stowed position the hose and gun already attached the truck would have its own pump. All that would be required to deploy would be to connect to a hydrant spread the pods and take flight. the vehicle it could be mounted on could be about the size of an ambulance and could arrive on scene before even and engine or pumper truck