The pilot intended to transport two passengers and their equipment along the Katherine Gorge. The helipad used for take-off was on the side of the gorge, some 40 feet above the river level. The pilot initiated a running take-off on the skids, but the helicopter began to sink as it left the river bank. Full throttle was applied, but without effect. As the helicopter approached the opposite bank at tree-top level, the pilot raised the collective lever in an attempt to clear the trees. The aircraft did not respond and as it continued to sink, the pilot recalled seeing the engine and rotor rpm decay towards the lower limit of the operating range. The helicopter descended into the trees and came to rest on its left side about 400 metres from the take-off point. The pilot subsequently advised that the helicopter had not been performing as well as he had expected during previous flights. Investigation revealed that the engine had been unable to develop rated power output and that the helicopter was some 114 kilograms over the maximum permissible all-up weight. Detailed examination of the turbocharger revealed that various components had suffered severe deterioration. The unit had exceeded its authorised life by nearly 400 hours. It was also likely that pilot operating techniques had contributed to the faults in the turbocharger, in that insufficient engine idling time prior to shutdown had been allowed.
