Abstract: Employee #1 and coworkers were disassembling a 100 ton FMC Linkbelt model HC218 truck crane, #TC63, in preparation for reassembling and adding additional boom sections by the self erection method, using the crane's own live mast. The head section was put on an empty trailer. A coworker was standing atop the heel section after he had knocked the topping out. Another coworker was picking up parts while a third coworker was looking for the nylon straps to support the heel section. There were four pins that secured the heel section to the head section and Employee #1 told a fourth coworker not to knock out the bottom pins before the heel was supported by the mast. Unknown to the others, he then got under the heel section and knocked out the bottom pins. The heel section fell 3 to 4 ft on him, causing skull, pelvic, and internal injuries. He was hospitalized. All employees were experienced in the operation; Employee #1 had done it 15 times.