Narrative:

Flying started at late evening from mci to sdf. 4 hour layover in sdf. Continued trip at AM30 EDT to abq with 45 mins on ground. Flight continued on to san. During cruise, the captain and I debated on how fatigued we were and that we needed to fly to be awake for the localizer 27 approach at san. Approach started normally and done in VNAV and localizer. After passing swatt, the aircraft computers sensed a 'beam error' in the localizer. Raw data indications showed erratic movement of the CDI. Computers then regained localizer signal and approach was continued (5 seconds of signal loss). At 2400 ft MSL, prior to reebo, signal was again lost. Captain initiated the missed approach and missed approach was announced. Controller instructed us to 'fly the published missed.' the initial missed approach altitude is 2500 ft MSL. With go around thrust selected in the tmc and no altitude for the FMC to go to, the aircraft climbed rapidly upon gear retraction and flap retraction to 2800 ft MSL. Aircraft control was regained as quickly as possible by overpwring trim and selecting climb in the tmc. A subsequent approach was done to runway 27 using raw data only and a landing made without incident. Localizer identification monitored during vectors on second approach attempt. Signal was lost on 5 occasions for 5-15 seconds at a time. Found out from local personnel that equipment trucks are moving in the vicinity of the localizer beam. The incident of beam error has happened to me a number of times at san. I feel that if our flight pairing (mci-sdf-abq-san) had not disturbed our rhythm so much, we would have been more aware and responsive to the situation. (Pairing start time XY06Z, end time ZZ38Z, duty 10:47.)

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Original NASA ASRS Text

Title: LGT HAS LOSS OF LOC SIGNAL ON APCH. MISSED APCH EXECUTED BUT CLBED ABOVE PUBLISHED ALT.

Narrative: FLYING STARTED AT LATE EVENING FROM MCI TO SDF. 4 HR LAYOVER IN SDF. CONTINUED TRIP AT AM30 EDT TO ABQ WITH 45 MINS ON GND. FLT CONTINUED ON TO SAN. DURING CRUISE, THE CAPT AND I DEBATED ON HOW FATIGUED WE WERE AND THAT WE NEEDED TO FLY TO BE AWAKE FOR THE LOC 27 APCH AT SAN. APCH STARTED NORMALLY AND DONE IN VNAV AND LOC. AFTER PASSING SWATT, THE ACFT COMPUTERS SENSED A 'BEAM ERROR' IN THE LOC. RAW DATA INDICATIONS SHOWED ERRATIC MOVEMENT OF THE CDI. COMPUTERS THEN REGAINED LOC SIGNAL AND APCH WAS CONTINUED (5 SECONDS OF SIGNAL LOSS). AT 2400 FT MSL, PRIOR TO REEBO, SIGNAL WAS AGAIN LOST. CAPT INITIATED THE MISSED APCH AND MISSED APCH WAS ANNOUNCED. CTLR INSTRUCTED US TO 'FLY THE PUBLISHED MISSED.' THE INITIAL MISSED APCH ALT IS 2500 FT MSL. WITH GAR THRUST SELECTED IN THE TMC AND NO ALT FOR THE FMC TO GO TO, THE ACFT CLBED RAPIDLY UPON GEAR RETRACTION AND FLAP RETRACTION TO 2800 FT MSL. ACFT CTL WAS REGAINED AS QUICKLY AS POSSIBLE BY OVERPWRING TRIM AND SELECTING CLB IN THE TMC. A SUBSEQUENT APCH WAS DONE TO RWY 27 USING RAW DATA ONLY AND A LNDG MADE WITHOUT INCIDENT. LOC ID MONITORED DURING VECTORS ON SECOND APCH ATTEMPT. SIGNAL WAS LOST ON 5 OCCASIONS FOR 5-15 SECONDS AT A TIME. FOUND OUT FROM LCL PERSONNEL THAT EQUIP TRUCKS ARE MOVING IN THE VICINITY OF THE LOC BEAM. THE INCIDENT OF BEAM ERROR HAS HAPPENED TO ME A NUMBER OF TIMES AT SAN. I FEEL THAT IF OUR FLT PAIRING (MCI-SDF-ABQ-SAN) HAD NOT DISTURBED OUR RHYTHM SO MUCH, WE WOULD HAVE BEEN MORE AWARE AND RESPONSIVE TO THE SIT. (PAIRING START TIME XY06Z, END TIME ZZ38Z, DUTY 10:47.)

Data retrieved from NASA's ASRS site as of July 2007 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.