Sergeant (SGT) Ken Wilson of the 21st Civil Engineering Squadron drills holes in a frozen concrete slab as STAFF Sergeant (SSGT) Tim Johnson of the 21st Equipment Maintenance Squadron directs a heating duct to thaw the ground. They are setting up a mobile aerial arresting system (MAAS) on the runway during Exercise COBBLER FREEZE'87, a cold-weather force projection exercise conducted by the Alaskan Air Command