scope:

Description of Driving Event:

A 5-ton mobile A-Frame was being used to lift a 8450 No. piece of research hardware from a lower floor level to the wind tunnel floor through a slot in the wind tunnel floor. Due to the constrained operational space and complex geometry of the hardware, the lift was not through the C.G. of the hardware. During the lift operation, the C.G. rapidly shifted causing the lift line to fall outside of the A-frame base dimension. This caused the A-frame to rapidly topple over and inflict fatal injuries to a bystander. This same lift had been successfully completed on a previous occasion using lateral movement restraints, but there appeared to be no loading on these restraints; therefore, they were not used for this lift.

During the mishap investigation, an observation was made that the wheels were only rated for 3000 No. each which implies that all four wheels must be equally loaded to safely support the 10000 No. rated load. If the lift line moved from a vertical position (e.g. load swinging during transit) the wheels would be unequally loaded and the load could exceed the wheel rated loading.