The pilot was operating a NOSAR NO DETAILS flight and he did not establish the time of last light at Esperance prior to departure from Lake King. In flight the pilot's only navigation was to check that he passed over known features whilst enroute. At a point approximately half way into the 50 minute flight the pilot became concerned about the failing light and he increased power in an attempt to reduce the remaining time interval to his destination. When the aircraft was approximately 15 km short of Esperance the pilot who was unsure of his exact position decided to land in a paddock rather then continue with the flight. The pilot carried out an Authorised Landing Area (ALA) inspection under the constraints of reducing time and light and he did not observe any obstructions other than some trees near the approach end of the paddock. Because of the trees the aircraft touched down well into the paddock and the pilot was unable to avoid colliding with a fence and water trough which he had not seen prior to landing. The collision occurred approximately 30 minutes prior to last light. The light was poor due to an extensive cloud cover. Esperance airfield was fitted with a Pilot Activated Lighting (PAL) system but the pilot who was aware that the system was there did not know the frequency needed to operate it. The pilot did not seek help from Flight Service prior to his precautionary landing.
