150317-N-FB203-285 PACIFIC OCEAN (March 17, 2015) Sailors from the Blackjacks of Helicopter Sea Combat Squadron (HSC) 21 perform maintenance on an MH-60S Sea Hawk helicopter on the flight deck of the Wasp-class amphibious assault ship USS Essex (LHD 2). Essex is underway participating in a composite training unit exercise with the Essex Amphibious Ready Group. (U.S. Navy photo by Mass Communication Specialist 2nd Class Sean P. Gallagher/Released)