On 12 December 2008, a DHC-6-300 Twin Otter aircraft, registered PK-BRS, was being operated by Aviastar Mandiri on a series of scheduled flights from Timika, Papua. The last flight of the day was a return flight from Timika to Ewer, about 36 minutes each way. The copilot was the handling pilot for the flight sector from Ewer to Timika, and the PIC was the support/monitoring pilot. The PIC reported that the aircraft commenced sliding before brakes release, and shortly after commencing the takeoff roll the aircraft veered to the right, so he took over control from the copilot. However, he was unable to prevent the aircraft from swinging to the left and it rolled through the centreline to the left side of the runway. The PIC aborted the take off and attempted to regain the runway centreline from the left using nose-wheel steering. That attempt was unsuccessful, and the aircraft veered further left and slid off the runway into wet soft ground on the edge of the marsden matting runway. It came to a stop 360 meters from the departure end of the runway on a heading of 190 degrees. The PIC shut down the engines and instructed the copilot to disembark the passengers. None of the aircraft’s occupants were injured. The Ewer runway was constructed on swampy ground, using the marsden matting to give a solid surface. CAUSE: “The investigation was unable to determine why the pilots were unable to maintain directional control during the take-off roll. It is likely that in taking control from the co-pilot, and using nose-wheel steering, the PIC may have over corrected, resulting in a loss of directional control.”