B747-400 FLT CREW REPORTS TAT PROBE HEAT FAILURE AFTER TKOF AND NUMEROUS OTHER UNRELATED FAILURES DURING FUEL DUMPING AND RETURN FOR LANDING.

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A WRITE-UP WAS NOTED IN THE FLT PAPERS RELATING TO 'L TAT HEAT FAILURE.' THIS WAS CARRIED OVER FROM PREVIOUS FLTS -- SEVERAL WKS. DISCUSSED A REPAIR WITH MAINT AND FIRST THEY SAID THAT PART WAS NOT AVAILABLE. THEN COMEBACK WITH ATTACHMENT SCREWS WERE MISSING. CAPT REQUESTED THAT AIRPLANE BE REPLACED WITH ANOTHER ONE WHICH WOULD HAVE CAUSED A DELAY FOR AN INBOUND ACFT. MAINT CLAIMED THAT THEY REPAIRED THE UNIT BUT LEFT THE MEL DEFERRED TAGS IN THE AIRPLANE FOR THE CREW TO REMOVE AFTER A CONTACT PRIOR TO PUSHBACK. THE CREW WAS BRIEFED BY MAINT FOLLOWING THE REPAIR REGARDING THE BITE TEST OR THE REPLACEMENT OF THE UNIT. THE FO CALLED NUMEROUS TIMES REQUESTING ADDITIONAL VERIFICATION OF THE PROC WHICH WAS IGNORED. THE CAPT CONFERRED WITH THE DISPATCHER THAT A FAILURE OF THE TAT HEAT DIDN'T HAVE THE PROPER MEL NOTED RELATING TO INFLT ICING AND THE EMER PROC FOR ERRATIC FLT INST INDICATION IN FLT; AND A REQUIREMENT FOR DIVERSION. THIS PROC WAS IN THE B747 FLT MANUAL. SHORTLY AFTER TKOF THE TAT HEAT L FAILURE OCCURRED. THE CREW CONTACTED DISPATCH AND MAINT RELATING TO THE FAILURE. IT WAS NOTED THAT THE FLT WAS REQUESTED TO RETURN TO ZZZ WHICH REQUIRED HOLDING AND TO DUMP 200000 LBS OF FUEL TO REACH MAX LNDG WT. DURING THE DUMP PROC WE GOT 'STAB XFER SIG' MESSAGE. ON THE WAY BACK TO ZZZ WE GOT 'ELEC IDG 3 VALVE' MESSAGE. ON THE DSCNT TO ZZZ THE CAPT PUT OUT THE FLT SPOILERS AND THE R SPOILERS FAILED; CAUSING A YAW TO THE L. THIS IS A CHRONIC PROB ON THIS ACFT. WHEN THE CAPT PUT OUT FLAPS FOR LNDG WE GOT A 'FLAPS PRIMARY' FLAP FAILURE MESSAGE THEN FOLLOWED BY A 'FLAPS DRIVE' FAILURE MESSAGE. THE CAPT DECLARED A FLT EMER AND HELD TO DUMP ANOTHER 90000 LBS OF FUEL TO MAKE A PARTIAL FLAP LNDG ON THE RWY. THERE WAS AN ADDITIONAL 'FLAP SYS MONITOR' MESSAGE AND A 'LE MULTI DRIVE' MESSAGE DISPLAYED. ACFT BLOCKED OUT AT XA37Z AND RETURNED AT BLOCK TIME XE27Z. MAINT DID NOT INPUT ANY MESSAGES TO THE COMPUTER DURING THIS EMER. CAPT BRIEF FLT ATTENDANTS ON THE SITUATION FOR LNDG AND THEY PREPARED THE CABIN PER SOP. CREW WAS EXTREMELY FATIGUED FOLLOWING THIS EMER ORDEAL AND RESCHEDULED TO FLY THE SAME TRIP; EXTENDING THIS TRIP TO A 7 DAY ONE WITH MINIMUM REST TO ANOTHER 6 DAY TRIP SHORTLY THEREAFTER. THE LACK OF MAINT PERFORMED OR QUALITY OF MAINT IS LACKING SEVERELY IN THE PAST YR ON THE B747-400 FLEET AND HAS BECOME A CHRONIC SAFETY PROB CAUSING GREAT CONCERN AND EXTREME WASTE OF MONEY -- FOR EXAMPLE: FUEL DUMPING TODAY COST A LOT OF MONEY PLUS PAX GRIEF AND INCONVENIENCE.