About 5 minutes after take off the engine began to run roughly. The aircraft returned to Hoxton Park and after landing the pilot found the fuel strainer full of water. The aircraft had been refuelled about 10 days before from a ground installation and had remained in the open since then. Investigation revealed that no other operators who had refuelled from the same installation had suffered from water contamination. The fuel installation is a modern style appliance with a water sensing element which automatically shuts itself down if water is detected.
It was not determined how the water got into the fuel system but there had been periods of heavy rainfall whilst the aircraft had remained in the open and it is possible that water had leaked in through the fuel caps.