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Investigators determined that a coolant leak, which led to a digital control system error, caused the loss of the MQ-1B Predator that ditched in the Mediterranean Sea on Jan 17, Air Combat Command officials announced. The remotely piloted aircraft was airborne for 10 hours before spiking a high engine temperature, causing a loss of thrust and uncommanded decent from 14,000 feet, according to the accident investigation's executive summary. The RPA operator diverted the Predator to the nearest available airfield, consulted with an instructor pilot, and conducted proper troubleshooting procedures. A loss of engine coolant then exposed a temperature sensor to the ambient air, causing the aircraft's computer to misinterpret the condition as a cold-start and override pilot commands.  The digital control increased and enriched the fuel flow, forcing the crew to guide the RPA to a forced landing at sea. Loss of the RPA and mission equipment is estimated at $4.6 million, according to the July 10 report. (AIB report.)