What was found
APPROXIMATELY 50 MINUTES INTO FLIGHT, ANNUNCIATION, HYD 3 OFF. HYD 3 SYS SHOWED 2.0 AT THAT TIME. LEVEL CONTINUED TO DECREASE UNTIL 0.0. RECEIVED ANNUNCIATION, HYD 3 FAIL. USED ALTERNATE GEAR EXTENSION. TROUBLE SHOT ITEM & FOUND LEAK COMING FROM INBD STAB TRIM BRAKE. R & R BRAKE & STAB TRIM MOTOR. ALL OPERATIONAL & LEAK CHECK NORMAL. AMM 27-43-04-4, 27-43-30-4 R & R ENG 3, NR 2 EDP. STILL NEEDS OPERATIONS & LEAK CHECK. AMM 29-11-20-4-1 R & R NR 3 ENG 1 HYD PUMP. NEEDS OPERATIONS & LEAK CHECK. AMM 29-11-20-4-1 COMPLETED NR 3 ENG NR 1 & 2 ENG DRIVEN HYD OPERATIONS & LEAK CHECKED IAW AMM 29-11-20-4-1. ALL OPERATIONAL CHECKED NORMAL & NO LEAKS NOTED.