On 4 July 2007, the pilot of a Beech Aircraft Corporation B58 (Baron), registered VH-VEG, was conducting a charter flight in accordance with the instrument flight rules from Sydney, NSW to Shepparton, Vic. At about 1415 Eastern Standard Time, the pilot departed Sydney Airport with one passenger on board. The flight was planned via overhead Canberra, ACT and Albury, NSW. The weather forecasts obtained by the pilot indicated that in the Canberra area the freezing level would be about 6,000 ft above mean sea level (AMSL) and that broken cumulus or stratocumulus cloud could be expected to extend between 5,000 and 10,000 ft with moderate icing in cloud. The aircraft was not equipped for flight into icing conditions.
The pilot climbed the aircraft to the planned cruise altitude of 10,000 ft AMSL and was generally clear of cloud until over Canberra at 1532. At about 50 km to the south-west of Canberra the aircraft entered cloud with high moisture content at a temperature below 0 degrees C, resulting in the rapid accumulation of clear ice on the airframe. The pilot continued on track, but the build-up of ice eventually forced the pilot to descend below 7,500 ft, the published lowest safe altitude for the route. After maintaining 7,100 ft in cloud for a short time the pilot was cleared to descend to 4,900 ft. The pilot became visual and was able to descend further and to dislodge the ice.
The investigation found that the pilot was inexperienced operating in conditions conducive to icing and had not assimilated the guidance provided by the operator and the aircraft manufacturer.
While on this occasion the aircraft did not get very close to terrain, the circumstances of the occurrence are a salutary reminder of the hazard that winter weather in southern Australia can present to pilots of aircraft not equipped for flight in icing conditions.
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