A recreational vessel with 6 occupants onboard allided with a rock canyon wall on Lake Mead, resulting in multiple injuries and one fatality. The operator claimed that the vessel was headed for the canyon wall and he was unable to steer away from the wall because the steering wheel was locked or stuck, and that the steering wheel was jerked out of his hands, allegedly by the vessel’s autopilot system. The steering system, and specifically the autopilot system, had allegedly been recently maintained by a marine mechanic.
Explico was hired to investigate the incident, and specifically evaluate the vessel’s steering system. Inspection of the subject vessel revealed that the autopilot pump was, at the time of the accident, completely disconnected from the steering system hydraulicly but still connected to electrical power.
The subject vessel was first evaluated for possible force feedback at the helm by applying torque to the rudders; results showed that feedback from the rudder to the steering wheel was properly blocked by the steering system check valves and could not have caused movement of the steering wheel. The entire hydraulic steering system was removed and re-assembled in a lab to bench test all components’ functions.
The lab testing not only showed that all components were in working order, but also that even when the autopilot system was connected and attempting to turn the boat, the operator could easily overpower the autopilot pump by continuously turning the steering wheel in the desired direction of travel.
Hydraulic fluid from the steering system was collected at various locations in the steering system during removal. Lab examination of the subject hydraulic fluid came back with a significant number of large particulates which could cause valves in the hydraulic system to intermittently stick or lock. This intermittent locking was consistent with the witness testimony that attempts to steer away from the canyon wall in one direction failed because the wheel simply would not turn in that direction.
Interestingly, the vessel’s steering system had allegedly just been serviced, and the service routine should have included a full flush and fill of the steering system with fresh hydraulic fluid. This was inconsistent with the findings of particulate-filled hydraulic fluid in the steering system, which exceeded the manufacturer recommended limit by 4x to 16x.
A thorough analysis of the subject vessel as well as a comprehensive evaluation of the hydraulic steering system showed that:
1) There were no defects within any of the hydraulic steering components.
2) The testimony that the steering wheel was locked when the operator tried to steer away from the collision was shown to be scientifically valid.
3) Claims that the wheel jerked out of the operator’s hands or that the autopilot somehow contributed to the collision were not scientifically plausible.
4) The operator could have avoided the allision by slowing down or stopping.
5) The hydraulic fluid was shown to have significant presence of particulates, which may affect the performance of the steering system.
6) If the steering locked due to particulates in the hydraulic fluid, it would have un-locked if the operator had rotated the steering wheel slightly in the other direction, thereby forcing the particulate free from the check valve. Once freed, the steering wheel would have allowed the operator to steer away from the collision.
Explico was able to dissect the system and break it down into simple yet effective diagrams and figures to explain exactly how the steering system on the subject vessel worked and why certain claims were invalid based on features inherent in the subject system.