This Day in History: 1978-04-19

Hughes 369HS VH-CHD crashed 6km NW of Harrietville, VIC on 19 April 1978. The helicopter was engaged on a program of controlled burning of forest floor debris for the Victorian Forests Commission. In carrying out this operation, it was flown some 250 feet above the forest at a forward speed of about 35 knots while delayed action incendiary devices (DAIDS) were dropped on selected areas. The DAIDS were about 18cm long and were like large matches. The pilot flew the helicopter from the left control seat; the bombardier, who was responsible for dropping the DAIDS, occupied the front right seat; and the navigator, who directed the pilot to the areas to be burned, occupied the rear seat. The pilot had radio communication with Melbourne Flight Service Unit (FSU) and the bombardier with a Forests Commission base at Bright. The door of the helicopter adjacent to the bombardier was modified to permit external attachment of a steel box as a container for 700 to 800 DAIDS. The door modification permitted the bombardier ready access to the box so that he could remove the DAIDS individually from the box, ignite them by striking their heads on a striker plate, and drop them to the forest floor below. The attachment mechanism also permitted the bombardier to jettison the box in flight if necessary. The helicopter arrived at Bright and commenced forest burning-off operations in the area on the day prior to the accident. On the morning of the day of the accident, it operated in the Beechworth and Bright areas and these operations were completed about 1300 hours. It was then refuelled to capacity and a container box filled with DAIDS was attached to the right door. Another container box full of DAIDS was placed in the rear passenger compartment. After the three crew members had lunch, the helicopter departed from Bright for a further burn-off operation to the south-east. The pilot, at 1346 hours, advised Melbourne FSU that he had departed Bright and, at 1415 hours, that he was 15 miles south of Bright and operations were normal. At about 1430 hours, the bombardier advised the Forests Commission base that they were looking for a place to land in order to replace the now empty DAIDS box attached to the right door with the full box in the passenger compartment. No further radio communications were received from the helicopter. The helicopter was seen to land in a field at about 1430 hours and, some five minutes later, return towards the burn-off area. When there was no response to attempted communication checks by Melbourne FSU, Search and Rescue action was initiated. The burnt out wreckage of the helicopter was located on the following day. The helicopter had struck a large tree at a low forward speed and a low rate of descent. It then fell vertically to the ground and was virtually destroyed by fire. Detailed examination of the wreckage did not reveal evidence of any defect or malfunction of the helicopter which might have contributed to the accident. There was evidence, however, to indicate that ignition of a substantial number of DAIDS had occurred in the container box while it was attached to the door of the helicopter and that the box had been jettisoned shortly before the helicopter struck the tree. There were 3 fatalities. Sources: ATSB; aviation-safety.net website