Rolls-Royce Corp. won a $20.3 million contract extension to provide maintenance services for the helicopter engines it makes for the U.S. military, the Department of Defense said Monday.

About 30 percent of the work will be performed at the manufacturer’s facility in Indianapolis by November 2013; the remainder will occur in Oakland, Calif.

The contract calls for Rolls-Royce to provide a range of services including low-power repairs, program management and site support for the turboshaft engines that power Osprey tilt-rotor aircraft for the Air Force, Navy and Special Operations Command.

Last year, the Indianapolis operation won a $160.6 million contract to make the engines.

Rolls-Royce’s Indianapolis manufacturing facility employs about 4,300, making the British aerospace firm the city’s second-largest manufacturer behind Eli Lilly and Co.