The aircraft was engaged in an operation involving the aerial sowing of bulk fertiliser. The Lodestar had made a straight sowing run after which it was seen to cross a ridge. It turned slightly to starboard and followed the line of the ridge before entering a comparatively steep left-hand turn apparently initiated to bring it back toward a suitable position from which another sowing run could be started. When about two-thirds of the turn had been completed, the aircraft was seen to flick suddenly into a left-hand spin which continued very rapidly for one and a half to two and a half turns until the aircraft impacted on bush-clad terrain near the top of the ridge it had formerly crossed, exploded, disintegrated and burned. PROBABLE CAUSE: “The accident resulted from irretrievable loss of control occasioned by the unintentional incurrence of a stall and spin in conditions of turbulence and at a height which did not permit recovery before the aircraft struck the ground.”