A CH-47 Chinook helicopter prepares to unload two 500-gallon fuel blivets during a sling-load training exercise, Bagram Airfield, Afghanistan, July 30, 2013. A CH-47 Chinook helicopter prepares to unload two 500-gallon fuel blivets during a sling-load training exercise, Bagram Airfield, Afghanistan, July 30, 2013. SHARE: Download: Full Size (2.71 MB) Tags: photo essays Credit: VIRIN: 591302-N-VNF30-698.jpg Photo Gallery