To avoid turbulence over the mountain area near Launceston, the cruising level was maintained prior to entry into the airport circuit pattern. Just prior to turning for finals, trouble was experienced in the pitch-lock mechanism of the no. 1 prop. The prop was feathered and the approach was continued with full flaps, but without immediately increasing power on the remaining engine. The high rate of descent was not arrested during the turn, resulting in a slightly low altitude. Power was added and speed reduced to control the descent rate, but the crew were unable to maintain runway heading. An overshoot was attempted, but the speed had dropped below minimum control speed. The left wing dropped as full power was applied to the no. 2 engine. The wing struck the ground and the aircraft crashed, coming to rest 740 feet abeam the runway threshold. Fuel tanks ruptured and caused a fire, which was quickly extinguished.