Over the past five years, two of the Slocum underwater gliders operated by the UK National Oceanography Centre have lost a wing mid-mission without the pilot being aware of the problem until the point of vehicle retrieval. In this study, the steady-state data collected by gliders during the two deployments has been analysed to develop a fault detection system. From the data analysis, it is clear that the loss of the wing was a sudden event for both gliders. The main changes to the system

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... s associated with the event are an increase in the positive buoyancy of the glider and the occurrence of a roll angle on the side of the lost wing, with significant difference between dives and climbs. Hence, a simple effective system for the detection of the wing loss has been designed using the roll angle. Since sensors are known to fail and the roll sensor is non-critical to the operation of the glider, a back-up diagnostics system has been developed based on the dynamic model of the vehicle, capturing the change in buoyancy. Both systems are able to correctly detect the loss of the wing and notify pilots, who can re-plan missions to safely recover the vehicle.