A FORCED LANDING IN UNSUITABLE TERRAIN DUE TO AN INTERNAL ENGINE FAILURE. THE ENGINE FAILURE SEQUENCE WAS INITIATED BY A FAILED OIL PRESSURE RELIEF SPRING WHICH HAD FAILED IN FATIGUE DUE TO IMPROPER PLATING OF THE SPRING. THE SPRING FAILURE CAUSED OIL STARVATION TO THE ENGINE CRANKSHAFT AND RESULTING FAILURE OF A CONNECTING ROD.