An Airbus A320-200 was being refueled at an aerodrome in England. After the refueling was completed, the refueling vehicle was driven away. But the refueling hose was not disconnected from the airplane. The refueling hose was torn out of the aircraft and dragged along the ground to the vehicle parking lot. Then the problem was finally discovered. The airplane was taken out of service for repairs to its refueling adapter ring and was returned to service the next day. An investigation by the refueling organization showed that the refueler had not complied with the vehicle’s checklist or with the refueling organization’s operations manual. Both the checklist and the manual required that he make sure all hoses were secure on the refueling vehicle before driving the vehicle away from an aircraft. Examination of the refueling vehicle showed a bent actuating rod on the vehicle’s refueling nozzle. This defect existed prior to this incident, and caused the nozzle detection system not to function. When working properly, the detection system prevents the vehicle’s engine from being started unless all nozzles are stowed correctly. This interlock system had been damaged sometime in the recent past. It was checked about ten days prior to the accident and was found to function properly. The refueler stated that his normal routine had been interrupted by a paperwork problem. As a result, he was distracted by filling out the paperwork, and then drove away, believing he had disconnected the refueling hoses and nozzle even though he had not really done so. The company repaired the refueling vehicle and agreed to further training for the driver. 4. Why did the nozzle detection system fail?