Abstract: At 10:00 p.m. on December 12, 2017, an employee was checking control cables and fittings inside of an aircraft's tail using a fixed ladder. The ladder was installed on the aircraft as a walking/working surface. The aircraft was in a weather controlled aircraft hanger. The ladder was approximately 96 inches tall and used for access to cowling. The employee was working with a coworker who was in the cockpit. The employee was completely turned around not facing the ladder. The employee slipped and slid down the ladder and fell on a concrete surface. The employee sustained a fractured vertebrae. Employee #1 was .