During the descent the pilot heard a loud bang, following which the engine stopped. An autorotational descent was carried out for a landing onto the clearest available area, a dry river bed. The helicopter touched down with some forward speed on the soft sand, pitched forward and rolled over. An inspection of the wreckage revealed that a connecting rod big-end had failed due to fatigue. These fatigue cracks had initiated in the area of the recesses for the big end bolt nuts, where production machining was found to be quite coarse. This accident was not the subject of an on-site investigation.