Australia

The exact cause of the accident could not be determined with certainty. However, it was probably the result of severe turbulences and reduced performance due to a high density altitude.

Failure of the right engine caused by a fuel line that was blocked by a hornet's nest.

The report confirmed that the crash occurred because the aircraft stalled and the pilots were unable to regain control. However, the evidence was not sufficient to allow determination of what caused the stall. The report conceded that over-loading of the aircraft's rear baggage compartment may have contributed to the stall. The inquiry was critical of the operator and the Department of Civil Aviation. In particular, it was critical of the operator's poor standards of maintenance of aircraft instruments. For this reason, the inquiry recommended the operator's airline licence should be suspended or cancelled. It also considered the Department should have made more checks of the operator's methods and record keeping. The Minister declined to take action against the operator, saying its maintenance record keeping had improved significantly since the accident. He also cited the hardship that would be inflicted on many remote communities in Western Australia if the operator's airline licence were to be suspended or cancelled.

The crew attempted a flapless landing under unsuitable meteorological and wind conditions.

The accident was caused by the aircraft being loaded so its centre of gravity was behind the rear limit. The report also stated that incorrect setting of the elevator trim tab may have been a contributory cause. The rear limit for the centre of gravity was 39% of Mean Aerodynamic Chord. The load sheet prepared for the fatal flight indicated the centre of gravity of VH-BAG was at 39.2% of Mean Aerodynamic Chord. The load sheet was based on a load chart prepared by the Department of Civil Aviation and based on information supplied by the RAAF. During the investigation, inquiries were made with the US Civil Aeronautics Administration and this revealed an error in the load chart. The main undercarriage of the Lockheed Lodestar retracted to the rear so that retraction caused the centre of gravity to move rearwards but this was not taken into account in the design of the load chart. Other errors also came to light. The passenger seats were 1 inch (25 mm) further apart than shown on the load chart, causing the centre of gravity to be further to the rear than calculated, especially when the aircraft was fully loaded. Up to 18 kilograms (40 lb) of food and beverages for the passengers were stored at the rear of the passenger cabin but were not taken into account on the load chart. Investigation of the accident concluded that after the aircraft's undercarriage retracted, the centre of gravity would have been at about 43.4% of Mean Aerodynamic Chord. With the centre of gravity 4% of MAC behind the rear limit the aircraft would have been tail-heavy and longitudinally unstable. The aircraft had been in daily civil operations in Australia since November 1946 so the investigators assumed there must have been numerous flights with the centre of gravity significantly more than 39% of Mean Aerodynamic Chord. It was necessary for the investigators to find something unique about the fatal flight of VH-BAG that would explain its sudden climb immediately after take-off and the pilot's inability to regain control and prevent the aircraft crashing. The aircraft's tail was one of the few parts of the aircraft not destroyed by fire. The position of the elevator trim tab spool appeared to be in the normal position for landing rather than a typical position for take-off. The investigators concluded that on the final takeoff it was likely that the elevator trim tab was still set for landing. This, coupled with the aircraft being tail-heavy and longitudinally unstable after undercarriage retraction, caused the aircraft to pitch nose-up so strongly that the pilot was unable to retain control or prevent the aircraft stalling. Minister for Civil Aviation Arthur Drakeford made a public announcement that the accident had occurred because the aircraft was tail-heavy and unstable as the result of incorrect loading. The Minister said the operator had not taken adequate steps to ensure safe loading of its aircraft and he hinted that stricter regulation of the loading of aircraft was being considered.

Poor judgement on part of the pilot who continued the approach at an unsafe altitude.

The cause of the aircraft striking high ground whilst flying in cloud at a height of approximately 3,000 feet was that:
a) The pilot failed to follow the track specified in his flight plan and deviated about nine miles to port of the correct track. This deviation was either deliberate or due to an error in navigation.
b) The pilot failed to comply with the visual flight rules' requirements, thus violating the conditions of his flight clearance.

Investigations were unable to determine the exact cause of the accident. However, the inquiry found that the probable cause of the crash was interference with the airplane's magnetic compass due to a nearby electrical storm and a defect in the navigational signals sent by the Government-maintained Kempsey low-frequency radio range station, an important navigational aid to flights in the area. Errors and deficiencies in the aeronautical charts used to navigate the mountainous area were also found.