Evergreen Supertanker: the world's largest firefighting aircraft
By Loz Blain
June 30, 2008
July 1, 2008 As global temperatures slowly increase, a number of nations, including the USA, are finding themselves battling widespread droughts and huge, devastating wildfires that threaten properties, lives, infrastructure and ecosystems alike. Whatever the causes, new tools are clearly required to help subdue the massive bushfires that have destroyed an area the size of Oregon over the last 18 years. Aerial fire suppressant drops are sometimes the only way to effectively fight huge firefronts, and Evergreen's new Boeing 747-based Supertanker promises to be the daddy of them all, carrying seven times more drop capacity than most dedicated firefighting aircraft. Evergreen expect the Supertanker to be a quicker, cheaper, safer and more effective aerial firefighting tool than anything else on the market - and its 747 base platform gives it the ability to operate throughout the USA and around the world wherever it's needed.
Aerial attack is often the quickest and most effective response to a large wildfire front - fixed-wing planes or helicopters can dump water or fire retardant chemicals directly onto the advancing fire front in large volumes that dwarf the comparatively puny streams put out by a firetruck. But there's never been an aerial firefighter as big as Evergreen's Supertanker before.
Where the smaller planes and helicopters have carried around 1000 gallons, and the largest firefighting aircraft have carried as much as 12,000 gallons, the Evergreen has tank space for up to 24,000 gallons. The capacity is so large that Evergreen have devised a special system that allows multiple dumps on the one flight, where most firefighting planes simply drop all their fire suppressant at once.
Previous aircraft have tended to be WW2-era planes that have been modified to carry large volumes of liquid - and this approach has had its issues; many of the planes come right up to their maximum possible takeoff weight capacity when filled with water, making them difficult to handle and removing a degree of safety margin. Additionally, many of these older planes can't land with full water tanks, meaning that if they don't discharge their water at a fire zone they have to empty their tanks elsewhere before landing, wasting thousands of gallons of precious water in the process.
The Supertanker, on the other hand, will still be well inside both its takeoff AND landing carrying capacities even at full load.
This kind of jumbo aerial firefighting system has been very difficult to achieve in the past because of the low altitudes required for an effective drop when water is simply released from a plane. Jumbo jets like the 747 can't safely pass at these altitudes, usually around 200 feet, and it's a fairly dangerous exercise even in the older, smaller aircraft.
Evergreen addressed this problem with a high pressure delivery system that allows a wide range of drop speeds, from all-out maximum speed where an overwhelming attack is needed, right down to a lower setting that's roughly the equivalent of heavy rain. The pressure system allows the Supertanker to make effective liquid deliveries from an altitude of between 400 and 800 feet.
The drop speed is around 140 knots, and the plane approaches the drop zone in exactly the same way as it would approach a landing zone, meaning that the drop stays comfortably within the 747's speed and flight parameters.
The 747 platform, apart from delivering enormous carrying capacity, also gives the Supertanker an extraordinarily long range. This means that a single unit based in North America could service the entire country from its home base, provided refilling options and landing zones are available. It also means that in the US winter, the Supertanker could feasibly be deployed around the world - a possibility that Evergreen is definately investigating.
The international range of the Supertanker could also make it a viable platform for helping to contain oceanic oil spills or drop biochemical decontaminants on areas affected by chemical weapons or other hazards.
The supertanker is still currently in the development stage, and no costing is currently available, but Evergreen claim that the Supertanker's massive carrying capacity coupled with the proven reliability of the 747 platform should help save millions of dollars, both in fire suppression costs and damage rehabilitation after major fires.
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