Rolls-Royce Corp.’s Indianapolis operations continue to cash in on military contracts, scoring a $26.8 million deal to provide 12 spare engines for the Osprey tilt-rotor aircraft.

The Department of Defense announced the agreement with Naval Air Systems Command on Monday evening. Work is expected to be complete in December 2011.

A year ago, the Indianapolis operation won a $160.6 million contract to make 78 turboshaft engines for the military, and last week the government exercised a $20.3 million option to have Rolls-Royce provide additional maintenance services.

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.