The Evergreen Supertanker is a Boeing 747-200, modified by Evergreen International Aviation into a 24,000 US gallon (94,850 litre) capacity aerial firefighting aircraft. This is double the capacity of the next largest air tanker in operation, the Tanker 910. The Evergreen Supertanker will be available to fight fires from summer 2008.
The 2002 fire season saw the fatal crashes of two airtankers in the USA. The accidents, involving a Lockheed C-130A Hercules and a Consolidated PB4Y-2, prompted the U.S. Department of Interior to issue an official Request for Information on next-generation airtankers.
The response from Evergreen was a proposal to develop up to four of its Boeing 747-200 Freighters into massive 'Supertankers'. The first converted Boeing 747 (N470EV) first flew on February 19, 2004. By June 2006, Evergreen had spent $40 million on the project and were hopeful of both FAA certification, and an evaluation contract from the US Forest Service
A stop work order issued by Evergreen Aviation in 2007 seemed to have cancelled the project, but the latest information from the Evergreen Aviation website suggests that the aircraft will be operational in summer 2008.
Unique technology is used on the Evergreen Supertanker in order to allow an aircraft as large as a 747 to carry out aerial fire fighting.
Current fire fighting aircraft use a gravity drop system. Doors in the underside of the aircraft open, allowing the contents of the tanks to discharge. This type of system requires an aircraft to fly very low, typically 200ft above ground level. The Evergreen Supertanker has a pressurised system. This can disperse retardant under high pressure, for an overwhelming response, or drop retardant equivalent to the speed of falling rain. This system allows the aircraft to operate within its design criteria.
Using the pressurised system, the aircraft can deliver retardant to the scene of a fire whilst flying at a height of 400 to 800ft, at approximately 140kts (160mph) (260kph), configured as if it were on approach for landing.
The Evergreen Supertanker’s tank system can be configured for segmented drops, allowing the contents of the tank to be released at multiple intervals while in flight.
The Supertanker can operate from any aerodrome with an 8,000ft long runway and suitable facilities. Evergreen have identified several airports across the US and claim that 80% of US airports meet or exceed the criteria.
Evergreen Aviation is studying other applications for the Supertanker. Oil spill containment, chemical decontamination and weather modification are being considered. Also, regulations allow for five individuals that are not crewmembers to be carried in the upper deck. This area could be used for command and control, mapping, incident monitoring and video/communications operations.
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