Glasflugel Standard Libelle Glider, VH-GSJ, Kingaroy, Qld, 26 November 1972

At the time of the flight Kingaroy was under the influence of a cold front. Although conditions were suitable for gliding operations, the turbulence was moderate to severe and some convection cloud was present, mainly to the west of the aerodrome. The glider was launched by aero-tow and, shortly after lift-off, the tug/glider combination encountered moderate turbulence. The turbulence became stronger as the two aircraft proceeded towards an area to the west of the aerodrome and, at a height of about 1600 feet, good lift was experienced and the glider pilot released the tow rope. After release the glider was observed by the tug pilot to be orbiting to the left, clear of cloud and apparently climbing. Shortly afterwards persons on the ground heard a report and the wings of the glider were then observed tumbling earthward. The fuselage was found to have struck the ground approximately two miles south west of Kingaroy. The wings were subsequently located 205 feet apart and some 1600 feet to the south of the wreckage of the fuselage. Examination of the wreckage revealed that the aircraft had been subjected to a positive aerodynamic load in excess of its designed strength. This had caused the failure of the metal end-fitting on the inboard end of the starboard wing spar. The horizontal rigging pin locking the two main plane assemblies in position sheared and both wings separated from the fuselage. The excessive load may have arisen in an encounter with a severe turbulence gust; it may have been produced by a severe control input by the pilot or by a combination of both factors. Post-mortem examination indicated that the pilot had been suffering from heart disease and it was found that drugs had been prescribed for its treatment. It has not been possible to determine whether this medical condition or the treatment specified contributed to the accident, but neither possibility can be completely excluded.