GROVELAND, Calif. — Firefighters battling the giant wildfire burning in the Sierra Nevada added a California National Guard Predator drone to their arsenal Wednesday to give them almost immediate views of any portion of the flames chewing through rugged forests in and around Yosemite National Park.
The MQ-1 unmanned aircraft being remotely piloted hundreds of miles away quickly alerted fire bosses to a new flare-up they otherwise would not have seen immediately.
‘‘They’re piping what they’re seeing directly to the incident commander, and he’s seeing it in real time over a computer network,’’ said National Guard Lieutenant Colonel Tom Keegan.
Previously, ground commanders relied on helicopters that needed to refuel every two hours.
The 12-day-old Rim Fire continued to grow, expanding to 292 square miles, and containment remained at 23 percent.
But increasingly confident fire officials said they expect to fully surround it in three weeks, although it will burn for much longer than that.
‘‘It’s looking better every day,’’ said incident spokesman Glen Stratton.
While unmanned aircraft have mapped past fires, use of the Predator will be the longest sustained mission by a drone in California to broadcast information to firefighters in real time.
The plane, which is the size of a small Cessna aircraft, will remain over the burn zone for up to 22 hours at a time, allowing fire commanders to monitor fire activity, determine the fire’s direction of movement, the extent of containment, and confirm new fires ignited by lightning or flying embers.
The drone is being flown by the 163d Wing of the California National Guard at March Air Reserve Base in Riverside and is operating from Victorville Airport, both in Southern California.
It generally flew over unpopulated areas on its 300-mile flight to the Rim Fire.
Outside the fire area it will be escorted by a manned aircraft.
Officials were careful to point out the images are being used only to aid in the effort to contain the fire.