Abstract: At approximately 3:30 a.m. on December 13, 1991, Employee #1, of United Airlines, was repairing engine #4 of a 747 aircraft (#8316) at the Los Angeles Airport, gate #76. He had used a ladder to access the engine. Employee #1 was closing the engine cover (cowling) when it came off at its hinge point and fell on Employee #1, knocking him from the ladder to the ground. Employee #1 required hospitalization. According to the supervisor, a manlift was available but was not used. The employer's investigation revealed that the safety pip pin failed, causing the cowling to come off at its hinge point.