Preparing retardant: part 2

I came across this link -- thank-you, TL Stein, to a web camera at the Ramona CDF Air Attack Base. The web cam takes pictures every two minutes 24/7. Look at the above image that I downloaded from the Ramona webcam, you will see a white tank and a red trailer. The red trailer is known as a mobile mixing unit. The white storage tank is the retardant holding tank. The retardant powder is mixed with water based on the manufacturers recommendations. Most of the time, the ground crews at the air attack bases do the mixing.

The simple explanation is that a trailer is filled with retardant powder. A water supply line is attached to the trailer. The retardant is mixed with water in a piece of equipment attached to the trailer called an eductor. After the retardant powder has been mixed with water it is pumped into the white storage tank.

For a more technical explanation of retardant mixing as applies to the type of equipment referenced in the above discussion, see this pdf document (requires a pdf viewer). According to TL Stein, the water tanks referenced in this document are no longer used and have been removed or altered into tool storage areas." 

Loading the air tanker comes next. The air tanker taxis into a loading pit, one of the ground crew releases vent plugs on the air tanker, a filler hose is connected, a valve on the filler hose is opened, and the retardant is loaded into the tank(s) on the tanker. There are a series of vent holes (with vent plugs) in the plane’s storage tanks. When the retardant reaches the desired level in the tanks, the retardant starts to spill from the vent holes. The valve in the hose is closed and the plugs are inserted to reseal the vent holes (see the attached photo)  And the plane, loaded with retardant is ready to go.

In closing, I should say that the simple scenario of mixing and then loading retardant is based on facilities, equipment, and aircraft at the CDF Ramona Air Attack Base using a Phos-Chek powdered retardant. The specifics of mixing and loading retardant onto the aircraft will vary depending on the brand of retardant, the type (liquid concentrate or powdered), equipment and facilities, and type of aircraft (SEATs, multi-engine air tankers, or helicopters). For example, to see a brief discussion of retardant mixing for SEATs go here.