A Bristol 170 Freighter 21E cargo plane was destroyed when it crashed at sea off Cape Paterson, Australia. Both crew members were killed. The flight departed Melbourne-Essendon Airport (MEB) shortly after about 00:50 at night on an over water flight to Launceston Airport (LST) on the island of Tasmania. It was carrying 4200 kg of mixed freight. At 01:45 hours VH-SJQ advised the Melbourne Flight Service Unit (FSU) “we have an engine failure on the port side, we have it feathered and are returning to Melbourne.” At 01:51 hours the flight advised the Melbourne FSU “we are making a slow descent to one five zero zero” and, in answer to a query, reported “we’re unable to maintain our height with our rated power”. The pilot was given vectors for Wonthaggi. The altitude of 1500 feet also could not be maintained. The crew continuously transmitted their position relative to Wonthaggi. A mayday call was issued at 02:15, at which time one of the altimeters was already displaying zero feet. The airplane struck the surface of the sea shortly afterwards. It broke up and sank to a depth of 40 m. The cause of the accident could not be established. Weight and centre of gravity were within limits. Analysis of the information available indicates that the flight profile flown by VH-SJQ is compatible with the aircraft having been flown at an indicated airspeed of 95 knots, and a power output from the starboard engine of 1250 BHP, i.e. 26 per cent less than the normal maximum power available in the conditions which prevailed. The conditions were not conducive to the formation of airframe or carburettor icing, and search aircraft in the area did not encounter any such icing. CAUSE: “The cause of the accident has not been determined.”