What was found
AIR TURNBACK, & ENG SHUTDOWN: FLT 8813 CPR TO JAC: ON CLIMBOUT FROM CPR AT APPROXIMATELY 500 FT AGL. THE CREW NOTICED FLUCTUATING OIL PRESSURE ON THE NR 1 ENG FOLLOWED BY AN AUDIO MASTER WARNING AND LOW OIL PRESSURE LIGHT. A PRECAUTIONARY ENG SHUTDOWN OF NR 1 ENG WAS PERFORMED. THE RETURN TO CPR WAS MADE WITHOUT INCIDENT. INSPECTION OF THE NR 1 ENG FOUND THE ENG OIL CAP PARTIALLY OFF. AN ENG LOW OIL PRESSURE INSPECTION WAS PERFORMED. INSPECTION OF THE OIL CAP FOUND NO DEFECTS. SERVICED ENG OIL SYSTEM & REINSTALLED OIL CAP. (S)