Tech. Sgt. Andrew Arnett prepares to swap the #4 engine on a KC-135R Stratotanker aircraft. U.S. Air Force Tech. Sgt. Andrew Arnett, with a maintenance squadron with the 117th Air Refueling Wing, prepares to swap the #4 engine on a KC-135R Stratotanker aircraft in Birmingham, Ala., on July 26, 2011. SHARE: Download: Full Size (0.03 MB) Credit: VIRIN: 936080-E-PRO10-783.jpg Photo Gallery