The chain is there to prevent static electricity building-up and causing a spark that could cause an explosion. Any static electricity is led down the chain to earth.
An air tanker is an aircraft used to deliver liquids from the air, such as fuel, fire retardant, or water.
Gross Vehicle Weight 80,000lbs, legal road weight, actual fuel weight varies as vehicle weights vary between 35 and 45 thousand lbs. ie aluminum or steel tank size, engine and trans choices on tractor, aluminum or steel wheels etc etc
Baffle plates separate the inside of the tank into sections, the holes in the plates allow the liquid to pass through and the level in the tank is maintained. The plates prevent a wave from travelling from one end of the tank to the other.