Amazing Video: Aerial Assault Team Battles California Fire

This photograph shows the Rim Fire burning in California at night on August 21, 2013. (Image credit: InciWeb)

The U.S. National Guard has released a series of stunning cockpit videos from the aerial assault team battling the Rim Fire, which is tearing toward San Francisco's water supply and protected giant-sequoia groves.

"The landing-gear warning is heard by the pilots in the C-130J only," according to a note posted with the video. "Because the 'J' is such a high-technology aircraft, disabling the audible warning has proven difficult. Lockheed, the [Air National Guard] and [U.S. Air Force] have determined a software solution and, with luck, will be integrating the fix before next fire season." [Video: Rim Fire Seen Through Airborne Firefighters Eyes]

California's Rim Fire has burned nearly 180,000 acres (72,843 hectares) since it started Aug. 17 in the foothills of the Sierra Nevada. Burning east and south into Yosemite National Park, the growing fire threatens the Hetch Hetchy Reservoir, the source of drinking water and hydroelectric power for San Francisco. The city and county of San Francisco are under a state of emergency because of the potential threat to the electrical and water supplies. The fire also threatens two of Yosemite's three groves of giant-sequoia trees.

The blaze was 20 percent contained as of Tuesday morning (Aug. 27). More than 3,600 personnel are battling the fire as it approaches Yosemite. Labor Day weekend is one of the park's most popular tourist weekends of the year, and one of its main western entrance routes, Highway 120, is closed due to the Rim Fire. The National Park Service's website has current fire information and closures.

The Rim Fire is one of six wildfires in California, Idaho and Nevada being fought by planes equipped with the Modular Airborne Firefighting System (MAFF), according to a statement from the National Guard. The fleet included aircraft from the Wyoming National Guard's 153rd Air Wing and the Colorado Springs Air Force Reserve Command's 302nd Air Wing.

The last three years have required above-average use of MAFF resources, the statement said. Since 1973, the heavy air tankers have averaged 210 air drops per year. But in 2012,Air National Guard crews flew 884 air drops and dropped more than 2.3 million gallons (8.7 million liters) of water or retardant, the National Guard said. In 2011, crews flew 443 missions and dropped 1.2 million gallons (4.5 million liters).

This year, crews had been called in for 378 air drops by Aug. 26, the National Guard said.

The specially modified planes release a burst of water or retardant over an area approximately 1,320 feet long by 100 feet wide (400 by 30 meters), which can provide critical fire breaks, the National Guard said.

Email Becky Oskin or follow her @beckyoskin. Follow us @livescience, Facebook & Google+. Original article on LiveScience.

Becky Oskin covers Earth science, climate change and space, as well as general science topics. Becky was a science reporter at Live Science and The Pasadena Star-News; she has freelanced for New Scientist and the American Institute of Physics. She earned a master's degree in geology from Caltech, a bachelor's degree from Washington State University, and a graduate certificate in science writing from the University of California, Santa Cruz.