The Forest Service then stopped contracting all PB4-Y and C-130A planes, a total of 11 planes out of a fleet of 46.
While Evergreen has been flying the Supertanker with its retardant tanks during tests, it hasn't made a drop from the tanks yet.
Evergreen is based in Oregon and maintains locations in 36 U.S. and 12 international cities, but it is testing the Supertanker at the Pinal Air Park at Marana, which it has leased from Pinal County for more than three decades.
Until further testing, Evergreen officials are being somewhat tight-lipped about the Supertanker, although the company has produced a brochure about it with the following details.
The modifications to the Boeing 747 are fairly minor.
While the company developed the Supertanker for wildland firefighting, it also envisions using the Supertanker for everything from oil spill containment to biohazard response.
Evergreen has decades of experience in aerial firefighting and is an owner/operator of 10 Boeing 747 aircraft.
Evergreen's team of more than 50 engineers and scientists is spending more than 20,000 hours on the Supertanker.
Boeing has worked with Evergreen to support preliminary engineering studies and the certification of the Supertanker's components.
The Supertanker will be able to perform segmented drops so that it can fight multiple fires on a single mission.
Even with 24,000 gallons of retardant, the Supertanker still is 150,000 pounds less than its maximum takeoff weight capacity and less than its maximum landing weight.
While current air tankers have to fly down to 200 feet because they use a gravity drop system, the Supertanker's new type of pressurized system allows it to fight fires from higher altitudes.
It can disperse retardant under high pressure for an "overwhelming" response, or drop it equivalent to the speed of falling rain.
The retardant drop speed is approximately 140 knots, providing a 30 percent cushion over its stall speed.
Evergreen studied seven catastrophic wildfires that destroyed 1.5 million acres in 2002, and calculates that it could have saved the government $108 million in suppression and rehabilitation costs related to those fires alone.
Savings to the timber industry likely would have exceeded $418 million, the company estimates.
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