Failure Analysis of a Jet Boat Steering Linkage

As part of a steering linkage mechanism in a jet boat, two D-ring shackle pins were safety wired together in order to prevent either of the shackle pins from falling out. Relative movement of the D-ring shackles from maneuvering the boat caused fluctuating stresses in the stainless steel safety wire, resulting in a fatigue fracture of the wire. Without the constraint of the safety wire, a pin from one of the D-ring shackles became dislodged, resulting in the failure of the steering mechanism, loss of control and crash of the boat. As well as a demonstration of the key features of the components that led to the determination of a fatigue fracture, the significant flaws in the installation and configuration of the steering linkage are discussed.