Reliability Case Notes No. 10. Board of Inquiry: Circumstances surrounding the stranding of the AutoNaut ‘Gordon’ on the Plymouth coast on 7th November 2014.

The Marine Autonomous Systems in Support of Marine Operations (MASSMO) was a project funded by the Natural Environment Research Council, United Kingdom. Autonaut ‘Gordon’ met all objectives set out in MASSMO mission plan. The vehicle has survived extreme storms in phase 1, whilst gathering valuable science data using state of the art sensors, such as novel passive acoustic devices. In phase 2, the vehicle was successfully deployed to detect tagged fish. In phase 2, Autonaut ‘Gordon’ was deployed on 4th November 2014, at 11.10 am, from Plymouth bay, and transited out 7.2 km East to position 50.337°Latitude, ‐ 4.13367°Longitude, to start ranging tests and the campaign. The mission was terminated, under NERC’s instructions, on November 6th. During recovery, in the early hours of November 7th, Autonaut ‘Gordon’ was grounded. This resulted in severe damage to the vessel. This Inquiry report looks at the circumstances that have led to the grounding of Autonaut ‘Gordon’ with the aim of diagnosing the most likely root cause for the accident. The grounding of Autonaut ‘Gordon’ was caused by severe weather. However, this report concludes that planning error was the most influential root cause for the accident. The last waypoint, WPT1, was approximately 0.5 miles from Shagstone and lee shore on east side of Harbour entrance. This has put the vehicle in a vulnerable position. The report also concludes that rushed planning was the second most influential root cause for planning error. This report presents analysis of all other potential root causes considered by the Inquiry panel and raises recommendations to mitigate the risk of marine autonomous systems grounding in future deployments.