Мартин Марс был первоначально разработан как  бомбардировщик , но переделан   для транспортировки   тяжелых транспортных средств. 
 Продан ВМС США  как самолет-заправщик, который использует их в качестве пожарного самолета.

The Martin Mars was originally designed as a long range bomber, but redesigned and classified for long-range general transport because of its heavy-lift capability. 
They established airlift and endurance records which still stand today and logged more than 87,000 accident-free hours before being retired by the US Navy and sold to Flying Tankers which uses them as waterbombers.

Water is picked up with the aircraft 'on the step' at about 70 knots. 
With the scoops down, the ram pressure injects water into the tanks at in excess of a ton per second. 
Throttles are gradually advanced to account for the added weight, maintaining a skimming speed of 60-70 knots to keep the aircraft on the step. 
Pickup time is, on average, 25 seconds.
Foam concentrate is then injected into the water load where it remains inert until the load is dropped. 
Once dropped, the tumbling action causes expansion which converts the water load into a foam load.

Nice pictures FL and the video too, PB.

About three years ago, my son, who was in Victoria BC, drove out to a fire near the edge of the city to see the Mars at work. Knowing of my interest, he phoned me on his mobile and said "Dad, listen to this!." And I heard the unmistakeable sound of a Mars flying over.

He also commented "It's really, really big!." And so it is; a wingspan of 200', bigger than a 747 Classic (196').

His wife was working for the BC Forest Protection Service at the time and she sent me some photos of a trip to Sproat Lake: