An employee was performing a bail-out training scenario while wearing a harness with a carabiner and a springless belay device. The employee weighted the rope while rolling out of a window to begin his descent down the training tower. He took two or three steps down the side when the belay device failed. The employee grabbed onto the rope with both hands, keeping himself upright while quickly descending approximately 5 stories. He landed feet first on rubber tiles covering the concrete floor and then fell to his left side, resulting in fractures to the thoracic spine and heel of the left foot as well as rope burn abrasions to both hands.