Abstract: At approximately 9:20 a.m. on September 5, 2012, Employee #1, a 49-year-old male aircraft mechanic with United Air Lines, was using a three-foot step-ladder to inspect a fuel tank area which was located under the left wing of an aircraft. The stepladder was an Alco-Lite serial number 501186 and was an extra heavy-duty aluminum ladder. The ladder was built with a wide top surface (approximately twenty-one inch by twenty-inch platform) which allows for a person up to 300 pounds to stand on it. Employee #1 stated that normally before he stands on the top platform of this stepladder, he holds the fuel-tank above him for a firm grip to balance his body. Then, he enters his upper body (head and shoulders) about two-feet in an enclosed area (empty fuel tank) to inspect the fuel tank. However, the metal floor-surface area under this fuel tank was slightly sloped where ladder was placed. Employee #1 stated that on the day of the incident, as he stood on the top platform of the stepladder, he noticed that the ladder was jiggling and it was not secure. Before Employee #1 stepped off the ladder, it tipped over to its left side (towards down-slope) and made him fall. During the fall, Employee #1 first landed on the metal-floor where the ladder had been standing then landed on another adjacent lower metal-floor, which was about fourteen-inches below. As a result, Employee # 1 suffered a laceration on his lip and fracture on his right ankle. Employee #1 was taken to the hospital where he was hospitalized for two days and surgery was performed on his ankle. Two coworkers were standing near Employee #1 and they witnessed the fall. Both coworkers stated that they saw the ladder falling off its side (towards down slope) while Employee #1 was standing on it. The coworkers stated that they had used this ladder several times in the past and when it was placed on the sloped surface. Employee #1 stated that he was trained and experienced, had worked for last twenty-six years for the same Employer.