Evergreen 747 Supertanker

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747 Supertanker
Evergreen Supertanker 947 N470EV take-off from Ben Gurion 20071116.jpg
The Evergreen Supertanker
Type Boeing 747-100
Registration N479EV (previously N470EV)
Owners and operators Evergreen International Aviation
In service 2009 - 2013
Status Stored at Marana Pinal Airpark

The Evergreen Supertanker was a Boeing 747-100 widebody aircraft that was modified into an aerial firefighting aircraft by Evergreen International Aviation. The aircraft was originally manufactured by Boeing in 1971 for Delta Air Lines.[1] With a capacity of 20,500 US gallons (77,600 liters), it was the largest aerial firefighting aircraft in the world.[2] The next largest firefighting tanker aircraft is the Ilyushin Il-76P. The Supertanker entered service for the first time in 2009, fighting a fire in Cuenca, Spain.[3] The tanker made its first American operation on 31 August 2009 at the Oak Glen Fire.[4][5] The current tanker is N479EV, tanker/tail number 979. (The previous plane was: N470EV, tanker/tail number 947.)

Development[edit]

Development started after the 2002 fire season, which saw the fatal crashes of two air tankers 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.[6]

Evergreen proposed to convert up to four of its Boeing 747-200 Freighters into massive 'Supertankers'. The first converted Boeing 747 (N470EV) made its maiden flight on February 19, 2004.[6] The current Supertanker is N479EV, a 747-100.

By June 2006, Evergreen had spent $40 million on the project and was hopeful of both FAA certification and an evaluation contract from the US Forest Service.[7] In October 2006 the FAA issued Evergreen a supplementary type certificate for the installation and removal of internal tanks, associated systems and the support structure for the aerial dispersal of liquids.[8]

An issue that impacted usage by the Forest Service was the USFS requirement for using fire retardant rather than water. When Evergreen attempted to convert the system from water- to retardant-dispensing, they encountered objections from the FAA. The FAA was concerned about the much greater density of fire retardant and the corresponding increased stress on the airframe. The FAA determined that the Supertanker's service life would be diminished and also raised concerns about the dangers of additional stress on the airframe during firefighting operations and heavy weight maneuvering.

Design[edit]

The 747 Supertanker during the 2010 Carmel forest fires in Israel

The Evergreen Supertanker is equipped with a pressurized liquid drop system, which can disperse retardant under high pressure or drop retardant at the speed of falling rain. This system allows the aircraft to operate within its design criteria.[2] Using the pressurized system, the aircraft can deliver retardant to the scene of a fire while flying at a height of 400 to 800 feet (120–240 m), at approximately 140 kn (260 km/h, 160 mph), 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.[2] According to the company, the aircraft is capable of laying down a swath of fire retardant three miles (5 km) long and as wide as an American football field.[9]

Because the tanker is based on an airliner, it can fly at speeds of around 600 mph (970 km/h; 520 kn) during cruise.

Operation[edit]

The Supertanker can operate from any airport with an 8,000-foot (2,400 m) long runway and suitable facilities. Evergreen identified several airports across the US that met or exceeded the criteria.[2] In late 2009, the aircraft was under a call-when-needed (CWN) contract with Cal Fire and was stationed at McClellan Field outside of Sacramento, California.[9]

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.[10]

On 5 December 2010, the Supertanker was deployed to Israel to fight the Mount Carmel forest fire. This was carried out along with crew and utilities donated by other international fire agencies.[11] On 9 June 2011 the Supertanker was also deployed to fight the Wallow Fire in Arizona, which was at 607 square miles (1,570 km2) burned and 0% contained at the time.[12]

As of 21 May 2013 the Supertanker is stored in the boneyard at Pinal Airpark outside Marana, Arizona, with plans to be scrapped.[13]

On 1 January 2014, parent company Evergreen International filed for Chapter 7 bankruptcy and is no longer in business.

References[edit]

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