(Source: Wired)

Image Courtesy: Evergreen via Wired

The deadly fires that have blackened more than 105,000 acres around Los Angeles prompted authorities to call in the world’s largest fire extinguisher — a Boeing 747 that can drop 20,000 gallons of retardant over a swath of land three miles long.

The plane made its first-ever drop in the continental United States when fire officials summoned it to the Oak Glen fire east of Los Angeles mid day on Monday. After the successful first drop, the Supertanker was called back into action Monday evening where it made further drops on the massive Station fire north of the city which grew to more than 164 square miles and threatened 10,000 homes. Nearly 2,600 firefighters from as far away as Montana are throwing everything they have at the blaze, and on Monday they called in the biggest tool in their inventory.

Supertanker, a 747-100 modified by Evergreen Aviation of Oregon, can deliver more than 20,000 gallons of fire retardant with considerable accuracy using its unique pressurized delivery system. Although Supertanker can’t snake through canyons like smaller aircraft, nothing can touch its payload or its ability to perform multiple controlled drops during a single flight. The Grumman S-2, a dedicated workhorse of California’s airtanker fleet, carries 1,200 gallons. That’s a thimbleful compared to the Supertanker.

Evergreen spent more than $50 million developing the Supertanker and hopes to sell it around the world as the premier aerial firefighting tool.

Besides being big, the Supertanker is persistent. The pressurized system can make several precision drops per flight. During the flight in Alaska, it dropped 17,000 gallons on its first pass over the fire, then returned to dump the rest of its payload. “If an incident commander says he wants a thousand gallons here, a thousand there and 15 thousand over there, we can do that,” Campfield says. “It’s like an aerosol can. You have much better control with a pressurized system.”

This kind of capability means Supertanker can fight several small fires, after a lightning storm for example, or cover a three-mile swath of property to protect a community. With a top speed in excess of 600 mph, Supertanker can get from its base to the fire line quickly. Currently the 747 is based at McClellan Airfield outside Sacramento. Once it’s over the fire, Supertanker can slow down to around 160 mph while making drops 300 feet above the ground. And unlike many other firefighting aircraft that are flying at or near their maximum weight, the 747 is flying well below its maximum providing an added safety margin for the pilots.

Click here to read the entire article.