that was unaffected by the fatigue crack at the time of the accident and calculated that the wing was capable of supporting loads up to about 2.5 times the weight of the aircraft on its fatal flight. This suggested the gusting winds prevailing at the time, and the turbulence associated with the low altitude at which the aircraft was flying, were partly responsible for the failure. The matching socket in the spar in the right wing was also examined and found to be affected by a similar fatigue crack in the interior of the weld metal. This crack was detected by magnaflux inspection but could not be seen by visual examination. The Investigation Panel determined that the conversion from three-engine to two-engine configuration was not a cause of the accident. It found that fatigue failure of the wing was inevitable, and this modification and subsequent operation at a higher weight caused only slight shortening of the time before the failure occurred. In its report, the Investigation Panel wrote: "The crash is, as far as is known to the Panel, the first example of a failure inflight of an aircraft structure attributable directly to fatigue. "In the type of construction embodied in these aircraft, where concentrated loads are carried by a small number of heavy members, a single fatigue failure can, and in fact has caused, a complete structural collapse. "The Panel feels impelled to assert that neither the original design nor the original manufacture was at fault ... the tragedy has several new lessons to teach all concerned with aviation, and that learning provides some small degree of compensation for the loss of valuable human lives." The Investigation Panel's report was completed in two weeks and included five recommendations: Critical joints of all heat treated, welded steel tube aircraft structures should be examined annually by the magnaflux method. The unique nature of the accident should be drawn to the attention of the Australian Council for Aeronautics. The Council should be asked to study the phenomenon of metal fatigue in aircraft structures. The certificate of airworthiness of VH-UKK Binana, the sole Stinson Model A surviving in Australia, should be cancelled immediately. Both wings of VH-UKK should be sent to the Division of Aeronautics laboratories for test and examination to advance the knowledge of fatigue of aircraft structures. The Department of Civil Aviation should obtain a suitable number of V-G recorders and