What was found
(CAN) SHORTLY AFTER LEVELING AT CRUISE FL410, THE NR 2 ENGINE N1 ROLLED BACK FROM ABOUT 90 PERCENT TO 70 PERCENT WITH ASSOCIATED FUEL FLOW DECREASE. THE CREW INITIATED A DESCENT, NOTICED A KNOB SPLIT BETWEEN THE 2 ENGINES, DID NOT SHUTDOWN THE ENGINE AND A NORMAL LANDING WAS MADE. POST FLIGHT INSPECTION FOUND THE CHIP DETECTOR LIGHT ON AND A SIGNIFIGANT FUEL LEAK WAS SEEN AT THE NR 2 FCU WITH LARGE AMOUNT OF FUEL IN THE COWLING. THERE WAS NO EVIDENCE OF FIRE. A CUT O-RING WAS FOUND ON 1 OF THE FCU FITTINGS.