A GAR WAS EXECUTED BECAUSE OF AN UNSTABLE APCH FOLLOWING A LATE RWY CHANGE AT LAX AND NO ILS ACQUISITION. ACFT PITCHED UP DURING GAR LEVEL OFF.

Narrative

DURING GO AROUND FROM ILS RWY 07R APCH AT LAX WE WERE ASSIGNED 3000 FT AND A HDG OF 070. BETWEEN 2500 AND 3000 FT THE AUTOPILOT FAILED. A LARGE NOSE UP FORCE EXISTED WHEN AUTOPILOT FAILED. CAPT (PF) A LITTLE SLOW TO APPLY LARGE NOSE DOWN FORCE REQUIRED TO LEVEL AT ASSIGNED ALTITUDE. WE EXCEEDED ALTITUDE BY 200 TO 300 FT. ACFT WAS ALSO ALLOWED TO DRIFT 20 DEGS TO THE L (APPROX 050 HDG). RETURNED TO ASSIGNED ALTITUDE AND HDG. THE EVENTS STARTED BY ACCEPTING A LATE CLRNC FOR A RWY CHANGE. DUE TO ILS EQUIPMENT PROBLEMS ON BOARD AND POSSIBLY AT THE FIELD WE NEVER GOT A SOLID LOCALIZER CAPTURE FOR RWY 07R. CONTINUED APCH TO ABOUT 1000 FT AT WHICH TIME WE HAD THE RWY IN SIGHT BUT WERE NOT IN A POSITION TO LAND SAFELY. INITIATED A GAR AND RETURNED TO LAND ON RWY 06L. I WAS NOT PREPARED FOR THE LARGE FORCE REQUIRED TO LEVEL OFF WHEN THE AUTOPILOT FAILED. A LARGE CONTRIBUTING FACTOR WAS MY ACCEPTANCE OF A LATE RWY CHANGE. THE WORKLOAD FOR BOTH CREWMEMBERS INCREASED TO A VERY HIGH LEVEL WHEN WE SHOULD HAVE BEEN IN A STABLE APCH MONITORING SITUATION. THIS IS WHAT LED TO THE GAR. THE MISSED APCH GAR WAS A GOOD DECISION BUT I COULD HAVE AVOIDED IT BY STAYING WITH THE ORIGINAL CLRNC. THE MAJOR FACTOR CONTRIBUTING TO THE ACTUAL DEVIATION WAS PROBABLY FATIGUE. MY REACTION TO THE AUTOPILOT FAILURE WAS ONE OF SURPRISE AND A LITTLE BIT OF DELAY TAKING OVER THE FLYING FROM THE AUTOPILOT.