An aircraft cleaner reported finding significant damage to the landing gear and wing spars of the aircraft during a routine cleaning operation on the afternoon of Sunday the 17 October 1988. The damage to the aircraft indicated that the aircraft had probably been stalled at a significant height above the ground descended vertically and touched down heavily on the left wheel followed by the right wheel. Damage to the left wing was readily visible on the upper skin surface. Six pilots had been involved in the operation of the aircraft over the two days preceding the report by the aircraft cleaner. All six indicated that they had not done or had not observed a landing which could have caused the damage found. None of the pilots had observed any damage to the aircraft during their pre or post flight inspections. The damage was such that continued operation of the aircraft could have resulted in a serious air safety occurrence.
