Narrative:

The first officer and I were operating an aircraft with multiple maintenance deferrals; several of which increased our normal workload. We were operating 1 1/2 hours late due to additional maintenance. They had been called out to fix a problem with the #1 remote tuning unit (the primary interface with communication #1; navigation #1; transponder #1; TCASII). The fix was to replace the rtu which failed as we were preparing to push back. Maintenance reset the unit and cleared us to push again. After pushback; ATC told us to expect runway 9L; instead of runway 8R (this was due to numerous thunderstorms at the north boundary of the airport). I asked the first officer to reprogram the FMS for the new runway and associated departure fixes. When tower cleared us for takeoff; we were told to fly heading 065 degrees (normal heading is 095 degrees to 110 degrees). When cleared to contact departure; I realized that the #1 rtu had again failed. I selected departure frequency on rtu #2 (normally used for company communication) and checked in. Before I could pull out the checklist for the rtu failure; ATC assigned us present heading direct to the first fix for a runway 8R departure. I advised that we had the appropriate fixes selected for runway 9L and we were told to reload the northern fixes and to expect vectors around WX until we would be able to go direct. At this point; I was observing a lot of lightning to our left and between dealing with the radar; rtu failure and trying to reprogram the FMS; I lost the big picture and elected to return to ZZZ. I contacted company dispatch and advised them of the decision; then told ATC the same. ATC provided vectors around WX while I set the approach up and prepared the aircraft for the return. I realized that we would be overweight; so I declared an emergency to allow for the overweight landing. The first officer flew the ILS to a visual and after we returned to the gate; we turned the aircraft back over to maintenance. I believe that this relatively benign failure triggering me into such a drastic solution was caused by several factors. First; I feel that the deferrals plus the previous problems with the rtu put me into a mental state of not believing the aircraft was safe to fly near WX. Second; I think that the abnormal departure procedures necessitating an FMS reprogram after departure put me into tunnel vision and I lost the situational awareness needed to pull out the applicable checklist and bypass the affected system. Third; I believe that fatigue played a factor in the loss of situational awareness. We did not have that busy of a duty day; but the fact that this happened late in the evening did play a part. In the future; I need to remember that first we fly the airplane (including running necessary checklists). When ATC asks for something I can't give; I need to advise them and do what is needed. Also; I need to be cautious when abnormal sits (different runway; different departure heading are assigned) crop up and to clarify ATC intentions. I feel that had ATC left us on our original runway with its respective fixes or let us fly the fixes that were correct for the departing runway that I would not have gotten overloaded and as a result; we would have gotten through the checklist to rectify the problem.

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Original NASA ASRS Text

Title: AFTER THE PRIMARY RADIO TUNING UNIT FAILED ON TKOF; A FATIGUED CL65 CAPT EXPERIENCED A SITUATIONAL AWARENESS LOSS; DECLARED AN EMER; AND RETURNED FOR AN OVERWT LNDG.

Narrative: THE FO AND I WERE OPERATING AN ACFT WITH MULTIPLE MAINT DEFERRALS; SEVERAL OF WHICH INCREASED OUR NORMAL WORKLOAD. WE WERE OPERATING 1 1/2 HRS LATE DUE TO ADDITIONAL MAINT. THEY HAD BEEN CALLED OUT TO FIX A PROB WITH THE #1 REMOTE TUNING UNIT (THE PRIMARY INTERFACE WITH COM #1; NAV #1; XPONDER #1; TCASII). THE FIX WAS TO REPLACE THE RTU WHICH FAILED AS WE WERE PREPARING TO PUSH BACK. MAINT RESET THE UNIT AND CLRED US TO PUSH AGAIN. AFTER PUSHBACK; ATC TOLD US TO EXPECT RWY 9L; INSTEAD OF RWY 8R (THIS WAS DUE TO NUMEROUS TSTMS AT THE N BOUNDARY OF THE ARPT). I ASKED THE FO TO REPROGRAM THE FMS FOR THE NEW RWY AND ASSOCIATED DEP FIXES. WHEN TWR CLRED US FOR TKOF; WE WERE TOLD TO FLY HDG 065 DEGS (NORMAL HDG IS 095 DEGS TO 110 DEGS). WHEN CLRED TO CONTACT DEP; I REALIZED THAT THE #1 RTU HAD AGAIN FAILED. I SELECTED DEP FREQ ON RTU #2 (NORMALLY USED FOR COMPANY COM) AND CHKED IN. BEFORE I COULD PULL OUT THE CHKLIST FOR THE RTU FAILURE; ATC ASSIGNED US PRESENT HDG DIRECT TO THE FIRST FIX FOR A RWY 8R DEP. I ADVISED THAT WE HAD THE APPROPRIATE FIXES SELECTED FOR RWY 9L AND WE WERE TOLD TO RELOAD THE NORTHERN FIXES AND TO EXPECT VECTORS AROUND WX UNTIL WE WOULD BE ABLE TO GO DIRECT. AT THIS POINT; I WAS OBSERVING A LOT OF LIGHTNING TO OUR L AND BTWN DEALING WITH THE RADAR; RTU FAILURE AND TRYING TO REPROGRAM THE FMS; I LOST THE BIG PICTURE AND ELECTED TO RETURN TO ZZZ. I CONTACTED COMPANY DISPATCH AND ADVISED THEM OF THE DECISION; THEN TOLD ATC THE SAME. ATC PROVIDED VECTORS AROUND WX WHILE I SET THE APCH UP AND PREPARED THE ACFT FOR THE RETURN. I REALIZED THAT WE WOULD BE OVERWT; SO I DECLARED AN EMER TO ALLOW FOR THE OVERWT LNDG. THE FO FLEW THE ILS TO A VISUAL AND AFTER WE RETURNED TO THE GATE; WE TURNED THE ACFT BACK OVER TO MAINT. I BELIEVE THAT THIS RELATIVELY BENIGN FAILURE TRIGGERING ME INTO SUCH A DRASTIC SOLUTION WAS CAUSED BY SEVERAL FACTORS. FIRST; I FEEL THAT THE DEFERRALS PLUS THE PREVIOUS PROBS WITH THE RTU PUT ME INTO A MENTAL STATE OF NOT BELIEVING THE ACFT WAS SAFE TO FLY NEAR WX. SECOND; I THINK THAT THE ABNORMAL DEP PROCS NECESSITATING AN FMS REPROGRAM AFTER DEP PUT ME INTO TUNNEL VISION AND I LOST THE SITUATIONAL AWARENESS NEEDED TO PULL OUT THE APPLICABLE CHKLIST AND BYPASS THE AFFECTED SYS. THIRD; I BELIEVE THAT FATIGUE PLAYED A FACTOR IN THE LOSS OF SITUATIONAL AWARENESS. WE DID NOT HAVE THAT BUSY OF A DUTY DAY; BUT THE FACT THAT THIS HAPPENED LATE IN THE EVENING DID PLAY A PART. IN THE FUTURE; I NEED TO REMEMBER THAT FIRST WE FLY THE AIRPLANE (INCLUDING RUNNING NECESSARY CHKLISTS). WHEN ATC ASKS FOR SOMETHING I CAN'T GIVE; I NEED TO ADVISE THEM AND DO WHAT IS NEEDED. ALSO; I NEED TO BE CAUTIOUS WHEN ABNORMAL SITS (DIFFERENT RWY; DIFFERENT DEP HDG ARE ASSIGNED) CROP UP AND TO CLARIFY ATC INTENTIONS. I FEEL THAT HAD ATC LEFT US ON OUR ORIGINAL RWY WITH ITS RESPECTIVE FIXES OR LET US FLY THE FIXES THAT WERE CORRECT FOR THE DEPARTING RWY THAT I WOULD NOT HAVE GOTTEN OVERLOADED AND AS A RESULT; WE WOULD HAVE GOTTEN THROUGH THE CHKLIST TO RECTIFY THE PROB.

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.