Narrative:

This report is being submitted after discussing the incident with my first officer's and my chief pilot. My concern is that the new procedure; wherein MEL cards are no longer required to be carried; lessens the likelihood of the flight crew catching maintenance mistakes. On flight to ZZZZ on jul/sun/07; we had about a 2 1/2 hour departure delay. It started with an inbound log item concerning a stabilizer trim EICAS message and accompanying cockpit indications on the inbound from ZZZZ. It was the third gripe and although the first time the problem occurred there was no visual indication of stabilizer trim controller module malfunction; a visual indicator was found when the problem occurred before departure from ZZZZ2. The problem then occurred again on the flight from ZZZZ2 to ZZZ. On boarding the late inbound aircraft in ZZZ; I looked into the problem. I had seen almost the same gripe only 3 weeks ago so I was familiar with some of the troubleshooting procedures. First; I received permission from maintenance to energize the hydraulic system and run the trim. Trimming nose down activated the stabilizer trim caution message and half-rate was noted. Trimming nose-up cleared the message and occurred at normal rate. I determined that when the left stabilizer trim controller module was isolated; it would not trim downward from any trim setting and only the manual/alternate switches would work. Trimming nose-up worked at half-rate which is normal when 1 side is isolated. Unfortunately; this was one of those intermittent gripes and by the time a maintenance supervisor showed up; the problem had cleared itself. Also; there was no visual indication of a problem on the stabilizer trim controller module itself. But the problem returned and I demonstrated the problem with the left side to the supervisor. He said he would need his avionics guy to run a CAT III check to isolate the problem. When the avionics mechanic showed up; he said he only validated CAT III and wasn't a troubleshooter. Still; he ran the check and reported that the right FCC failed the test and would have to be changed or deferred. Either would take 30 mins or less and we were told we could board. Half way through boarding the maintenance supervisor decided he wanted a different avionics mechanic to perform a second CAT III check to ensure everything was alright. While waiting for that to occur; the original trim problem occurred and this time I demonstrated the problem to the supervisor and another mechanic. The problem then went away. Because of this intermittent problem the supervisor decided to have the CAT III check done a third time. Finally; the decision was made to defer the right FCC and also to defer the trim system malfunction. According to the CAT III check; however; it is the center hydraulic stabilizer trim controller module which is degraded; not the left stabilizer trim controller module. We point out that we twice showed him that it was the left side that was acting up but he explains that the system somehow 'cross' (something new to us). However; the trim problem has stopped occurring (they ran it several times stop-to-stop to 'clear out the gunk') and we can't show him something that is no longer happening. We checked with them to make sure that the only thing they have deactivated is the right FCC (done by collaring the appropriate circuit breaker) so as to make sure that they did not deactivate the 'solid' trim system as it appeared to us. Deferral decals were posted and a new mrd was received. Per the new procedure; we complied with the operations placard and did not pull up the MEL; as we were quite late by this time. Later; in-flight; when we had time; we pulled up the MEL to see if we could learn anything more about what had transpired on the ground. We were surprised to see that the stabilizer trim deferral required a lengthy maintenance procedure; which was never accomplished. The procedure would have clearly shown that the problem; as we demonstrated several times; was with the left stabilizer trim controller module. Also importantly; a check of the manual trim handles/alternate system was not performed to ensure that neither channel had failed to the 'energize' position (as in possible unscheduled stabilizer trim problem). This check is only on the maintenance placard. The trim problem never resurfaced in-flight and the flight itself was nominal; which is lucky; because it seems to me that had the problem recurred and stayed; with the right FCC deferred and the left and center FCC not able to activate their respective stabilizer trim channel; we would have found ourselves 1/2 way across the atlantic in rvsm airspace without a single working autoplt. For what it is worth; between this stabilizer trim problem and the previous stabilizer trim event I encountered wherein maintenance had tried to fix a stabilizer trim controller module problem by changing out the center FCC; I think more maintenance training in this area is needed.

Related reports:

Google
 

Original NASA ASRS Text

Title: A B767-300 ACFT STAB TRIM MALFUNCTION WAS DEFERRED WITHOUT REQUIRED CHECK OF STAB SYS INCLUDING MANUAL TRIM HANDLES. PILOT BELIEVES NEW MEL CARD PROCEDURE LESSENS AWARENESS OF MAINT MISTAKES.

Narrative: THIS RPT IS BEING SUBMITTED AFTER DISCUSSING THE INCIDENT WITH MY FO'S AND MY CHIEF PLT. MY CONCERN IS THAT THE NEW PROC; WHEREIN MEL CARDS ARE NO LONGER REQUIRED TO BE CARRIED; LESSENS THE LIKELIHOOD OF THE FLT CREW CATCHING MAINT MISTAKES. ON FLT TO ZZZZ ON JUL/SUN/07; WE HAD ABOUT A 2 1/2 HR DEP DELAY. IT STARTED WITH AN INBOUND LOG ITEM CONCERNING A STABILIZER TRIM EICAS MESSAGE AND ACCOMPANYING COCKPIT INDICATIONS ON THE INBOUND FROM ZZZZ. IT WAS THE THIRD GRIPE AND ALTHOUGH THE FIRST TIME THE PROB OCCURRED THERE WAS NO VISUAL INDICATION OF STABILIZER TRIM CONTROLLER MODULE MALFUNCTION; A VISUAL INDICATOR WAS FOUND WHEN THE PROB OCCURRED BEFORE DEP FROM ZZZZ2. THE PROB THEN OCCURRED AGAIN ON THE FLT FROM ZZZZ2 TO ZZZ. ON BOARDING THE LATE INBOUND ACFT IN ZZZ; I LOOKED INTO THE PROB. I HAD SEEN ALMOST THE SAME GRIPE ONLY 3 WKS AGO SO I WAS FAMILIAR WITH SOME OF THE TROUBLESHOOTING PROCS. FIRST; I RECEIVED PERMISSION FROM MAINT TO ENERGIZE THE HYD SYS AND RUN THE TRIM. TRIMMING NOSE DOWN ACTIVATED THE STABILIZER TRIM CAUTION MESSAGE AND HALF-RATE WAS NOTED. TRIMMING NOSE-UP CLRED THE MESSAGE AND OCCURRED AT NORMAL RATE. I DETERMINED THAT WHEN THE L STABILIZER TRIM CONTROLLER MODULE WAS ISOLATED; IT WOULD NOT TRIM DOWNWARD FROM ANY TRIM SETTING AND ONLY THE MANUAL/ALTERNATE SWITCHES WOULD WORK. TRIMMING NOSE-UP WORKED AT HALF-RATE WHICH IS NORMAL WHEN 1 SIDE IS ISOLATED. UNFORTUNATELY; THIS WAS ONE OF THOSE INTERMITTENT GRIPES AND BY THE TIME A MAINT SUPVR SHOWED UP; THE PROB HAD CLRED ITSELF. ALSO; THERE WAS NO VISUAL INDICATION OF A PROB ON THE STABILIZER TRIM CONTROLLER MODULE ITSELF. BUT THE PROB RETURNED AND I DEMONSTRATED THE PROB WITH THE L SIDE TO THE SUPVR. HE SAID HE WOULD NEED HIS AVIONICS GUY TO RUN A CAT III CHK TO ISOLATE THE PROB. WHEN THE AVIONICS MECH SHOWED UP; HE SAID HE ONLY VALIDATED CAT III AND WASN'T A TROUBLESHOOTER. STILL; HE RAN THE CHK AND REPORTED THAT THE R FCC FAILED THE TEST AND WOULD HAVE TO BE CHANGED OR DEFERRED. EITHER WOULD TAKE 30 MINS OR LESS AND WE WERE TOLD WE COULD BOARD. HALF WAY THROUGH BOARDING THE MAINT SUPVR DECIDED HE WANTED A DIFFERENT AVIONICS MECH TO PERFORM A SECOND CAT III CHK TO ENSURE EVERYTHING WAS ALRIGHT. WHILE WAITING FOR THAT TO OCCUR; THE ORIGINAL TRIM PROB OCCURRED AND THIS TIME I DEMONSTRATED THE PROB TO THE SUPVR AND ANOTHER MECH. THE PROB THEN WENT AWAY. BECAUSE OF THIS INTERMITTENT PROB THE SUPVR DECIDED TO HAVE THE CAT III CHK DONE A THIRD TIME. FINALLY; THE DECISION WAS MADE TO DEFER THE R FCC AND ALSO TO DEFER THE TRIM SYS MALFUNCTION. ACCORDING TO THE CAT III CHK; HOWEVER; IT IS THE CTR HYD STABILIZER TRIM CONTROLLER MODULE WHICH IS DEGRADED; NOT THE L STABILIZER TRIM CONTROLLER MODULE. WE POINT OUT THAT WE TWICE SHOWED HIM THAT IT WAS THE L SIDE THAT WAS ACTING UP BUT HE EXPLAINS THAT THE SYS SOMEHOW 'CROSS' (SOMETHING NEW TO US). HOWEVER; THE TRIM PROB HAS STOPPED OCCURRING (THEY RAN IT SEVERAL TIMES STOP-TO-STOP TO 'CLR OUT THE GUNK') AND WE CAN'T SHOW HIM SOMETHING THAT IS NO LONGER HAPPENING. WE CHKED WITH THEM TO MAKE SURE THAT THE ONLY THING THEY HAVE DEACTIVATED IS THE R FCC (DONE BY COLLARING THE APPROPRIATE CIRCUIT BREAKER) SO AS TO MAKE SURE THAT THEY DID NOT DEACTIVATE THE 'SOLID' TRIM SYS AS IT APPEARED TO US. DEFERRAL DECALS WERE POSTED AND A NEW MRD WAS RECEIVED. PER THE NEW PROC; WE COMPLIED WITH THE OPS PLACARD AND DID NOT PULL UP THE MEL; AS WE WERE QUITE LATE BY THIS TIME. LATER; INFLT; WHEN WE HAD TIME; WE PULLED UP THE MEL TO SEE IF WE COULD LEARN ANYTHING MORE ABOUT WHAT HAD TRANSPIRED ON THE GND. WE WERE SURPRISED TO SEE THAT THE STABILIZER TRIM DEFERRAL REQUIRED A LENGTHY MAINT PROC; WHICH WAS NEVER ACCOMPLISHED. THE PROC WOULD HAVE CLRLY SHOWN THAT THE PROB; AS WE DEMONSTRATED SEVERAL TIMES; WAS WITH THE L STABILIZER TRIM CONTROLLER MODULE. ALSO IMPORTANTLY; A CHK OF THE MANUAL TRIM HANDLES/ALTERNATE SYS WAS NOT PERFORMED TO ENSURE THAT NEITHER CHANNEL HAD FAILED TO THE 'ENERGIZE' POS (AS IN POSSIBLE UNSCHEDULED STABILIZER TRIM PROB). THIS CHK IS ONLY ON THE MAINT PLACARD. THE TRIM PROB NEVER RESURFACED INFLT AND THE FLT ITSELF WAS NOMINAL; WHICH IS LUCKY; BECAUSE IT SEEMS TO ME THAT HAD THE PROB RECURRED AND STAYED; WITH THE R FCC DEFERRED AND THE L AND CTR FCC NOT ABLE TO ACTIVATE THEIR RESPECTIVE STABILIZER TRIM CHANNEL; WE WOULD HAVE FOUND OURSELVES 1/2 WAY ACROSS THE ATLANTIC IN RVSM AIRSPACE WITHOUT A SINGLE WORKING AUTOPLT. FOR WHAT IT IS WORTH; BTWN THIS STABILIZER TRIM PROB AND THE PREVIOUS STABILIZER TRIM EVENT I ENCOUNTERED WHEREIN MAINT HAD TRIED TO FIX A STABILIZER TRIM CONTROLLER MODULE PROB BY CHANGING OUT THE CTR FCC; I THINK MORE MAINT TRAINING IN THIS AREA IS NEEDED.

Data retrieved from NASA's ASRS site as of January 2009 and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.