Staff Sgt. Eric Smith, 28th Maintenance Squadron repair and reclamation technician, greases a wing sweep drive shaft during an isochronal inspection at Ellsworth Air Force Base, S.D., April 10, 2012. The wing sweep drive shaft allows the wings on a B-1 to sweep back during high subsonic and supersonic flight. (U.S. Air Force photo by Airman 1st Class Alystria Maurer/Released)