The aircraft was being used to conduct parachuting operations from Hamilton Island. On this flight, an instructor was to carry out a tandem jump and another parachutist was to make a solo jump. As the aircraft was climbing to altitude the pilot parachute on the instructor's rig opened. The pilot parachute was drawn out of the aircraft and the instructor managed to exit the aircraft and deploy his main parachute. He made a successful water landing. The solo parachutist jumped from the aircraft to render any necessary assistance to the instructor. The parachutist who was to jump in tandem with the instructor remained in the aircraft which was landed successfully at Hamilton Island. Subsequent inspection of the aircraft found that the right stabliser and elevator were bent upward and the elevator horn balance torn off. The reason for the inadvertent deployment of the pilot parachute is unknown.