The aircraft was on a flight from Bandana Station Authorised Landing Area (ALA) to Gunnedah in company with two Airtourer 150 aircraft. Landings were planned at Roma, St. George and Moree. VH-MVL took off first into a moderate south-westerly wind. After a long takeoff roll the aircraft became airborne and, at low altitude, maintained runway heading for some considerable distance. During the completion of a 90 degree left turn, the aircraft failed to climb then entered a steep descent and crashed two kilometres south-west of the strip. Impacting the ground in a level attitude, the aircraft was destroyed and the two occupants seriously injured. The pilot's head struck the instrument panel when his shoulder harness restraint failed. The Bandana ALA is 820 metres long, aligned 04/22, and slopes two percent down toward the south-west. The surface is uneven and covered with long grass. About 3.5 kilometres to the west is an escarpment, almost 2000 feet high. The escarpment forms part of the eastern edge of the Carnarvon Range. In conjunction with the escarpment, the fresh, cool and stable south-westerly airstream produced appropriate conditions for significant leeside downdraughts or standing waves. The pilot was very familiar with VH-MVL, having logged most of his experience on type in that aircraft. He had recent experience in operating from ALAs and had expressed some concern about takeoff performance from Bandana. He considered flying VH-MVL to nearby Ingelara to load his passenger and baggage and then depart from its 1250 metre grass strip. He subsequently decided to depart from Bandana. The aircraft had been refuelled to 108 litres (24 Imperial gallons) at Emerald before the 74 minute flight to Bandana. Combined with the weights of occupants and baggage, the aircraft was 33 kilograms over maximum gross for takeoff. Even at the highest rate of fuel consumption, the weight of the remaining fuel was sufficient to result in the aircraft being marginally over maximum gross weight for takeoff from Bandana. The aircraft had been operating from other airfields with the two occupants, the baggage and fuel loads up to 108 litres. It seems likely that the critical terrain and meteorological conditions requiring performance beyond the aircraft's capability were not encountered until this flight. With their additional power the two Airtourer 150s were able to climb safely in the prevailing meteorological conditions. Examination of the aircraft and engine failed to reveal any pre-existing mechanical abnormalities which could be considered as factors contributing to the accident. Examination of the failed shoulder harness restraint cable revealed that one third of its steel wire strands had been broken or partially fatigued before the accident. The broken strands had paint on the fracture surfaces, indicating that they were broken before or when the aircraft interior was last painted. The number of intact strands was insufficient to absorb the loads in the impact, causing failure of the cable and serious head injury to the pilot.