The pilot reported that on commencing descent at 50 nautical miles from Cairns engine power was reduced to 3,000 pounds of torque. At approximately 40 nautical miles a further reduction was made to 2,700 pounds. When the next reduction was made at 30 nautical miles the left engine did not respond to throttle movement and remained at 2,700 pounds. Right hand engine response was normal. The crew considered shutting down the left engine, but with weather and terrain circumstances taken into account, it was decided to leave the engine going. After arrival in the circuit area, speed was reduced and movement of the power lever was checked. The torque on the left engine had then reduced to approximately 2,400 pounds. After selection of landing gear and flap, propeller revolutions per minute were reduced to 1,400, and a normal approach profile was maintained. After selection of maximum propeller revolutions per minute, engine torque reduced to approximately 2,000 pounds, and as a normal profile could be maintained, it was decided not to shut the left engine down.
Power was reduced on the right engine to maintain profile on the approach. After touchdown on the damp runway, the power levers were retarded by the pilot and the aircraft immediately swung to the right. Corrective action was taken with flight controls and brakes. Directional control was regained and as the aircraft decelerated the crew became aware that the right main tyre had blown. The aircraft was stopped on the runway and rescue and fire services attended the aircraft.
Investigation revealed that the left engine power control cambox had jammed and this had prevented the power lever from transmitting movement to the fuel control unit via a teleflex cable. The cam mechanism appears to have been sticking due to inadequate lubrication, and hardened grease. The power lever could still be moved due to the flexibility in the teleflex cable.