B747-400 FLC CLBED IN RESPONSE TO TCASII RA AND APCH CTLR CLB INSTRUCTIONS. IN ADDITION; THE ACFT'S HYD SYS WAS MALFUNCTIONING AGAIN AFTER BEING CLRED BY MAINT FOR PREVIOUS WRITE-UPS.

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ACFT LANDED AT DELHI WITH A HYD OVERHEAT SYS #3 LOGBOOK ENTRY. SYS COMPONENTS WERE INSPECTED; AN IDLE ENG RUN CONDUCTED; AND THE DISCREPANCY CLRED BY MAINT PERSONNEL. ON SUBSEQUENT FLT TO STANSTED; AT FL280; THE EICAS MESSAGE HYD OVERHEAT SYS #3 WAS DISPLAYED. THE QRH CHKLIST WAS COMPLETED. THE MESSAGE REMAINED DISPLAYED; SO BOTH HYD PUMPS WERE LEFT OFF. REDUCED STABILIZER TRIM RATE AND REDUCED SPOILER CAPABILITY WERE BRIEFED FROM THE QRH. DSCNT AND APCH TO STANSTED WERE BRIEFED BY THE PF; THE FO. THE AUTOPLT PERFORMED SEVERAL INTERMEDIATE LEVELOFFS NORMALLY. WHILE SLOWING THE ACFT ON RADAR VECTORS TO DOWNWIND TO RWY 5; DSCNT CLRNC TO 6000 FT ON QNH 1001 WAS RECEIVED AND INITIATED ON AUTOPLT IN FLT LEVEL CHANGE. FMA PROGRESS WAS NOTED NORMAL; SPD AND ALT; UPON APCHING 6000 FT; WHEN OUR ATTN WAS DIVERTED TO A TA. WE SIGHTED; BELOW TO OUR L; A B737 ALSO ON RADAR VECTORS TO STANSTED; WITH BOTH ACFT ABOVE A SOLID UNDERCAST. I THEN NOTICED THE PFD WHITE ALT BOX TURN AMBER; NOTED APPROX 5700 FT DSNDING; AND CALLED FOR IMMEDIATE CLB. AT THE SAME TIME; THE FO WAS DISCONNECTING THE AUTOPLT TO CLB AND OUR ESSEX CTLR CALLED WITH CLB INSTRUCTIONS. IN MANUAL FLT; HVY ACFT NOSE DOWN TRIM WAS NOTED; DUE TO THE REDUCED STABILIZER TRIM RATE; WHICH THE AUTOPLT WAS APPARENTLY NOT ABLE TO COUNTER. THE ACFT WAS TRIMMED AND AUTOPLT RE-ENGAGED UNTIL ON ILS FINAL. A NORMAL LNDG WAS CONDUCTED.