Narrative:

Vector given to join runway 18R ILS, all checklists done and aircraft descending, set up, and configured for phase of flight, on autoplt. When cleared for approach, first officer selected LNAV instead of 'approach mode.' aircraft promptly made hard turn to the left to fly to last waypoint (off left wing). Crew momentarily surprised by wrong turn and its cause. Captain hit heading select to return to original heading assigned for intercept, but autoplt was very slow in stopping turn and starting right turn. First officer clicked off autoplt to lighten turn and was distraction by events to the point that he added power for the 3000 ft leveloff with speed brake still up. Captain lowered speed brake for first officer but aircraft descended 200-300 ft below 3000 ft assigned and crossed runway centerline at around 75 degrees off inbound course. We definitely violated the runway 18L approach path during corrections. (Runway 18L not in use for lndgs at the time.) captain requested and received clearance for visual approach during corrections. Lessons learned: 1) program autoflt system properly to start. 2) don't troubleshoot system when close in -- kick it off and be prepared to hand fly it. 3) don't be complacent because of routine nature of approach, WX and crew performance.

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Original NASA ASRS Text

Title: AN FK100 FLC FINDS THAT THE ATTITUDE OF THE ZID ENRTE CTLR IS RATHER STRANGE WHEN CTLR PERSISTS IN ACCUSING CREW OF DEVIATING FROM THE AMENDED CLRNC DURING TSTM AVOIDANCE NEAR J-6 NE OF LIT, AR.

Narrative: VECTOR GIVEN TO JOIN RWY 18R ILS, ALL CHKLISTS DONE AND ACFT DSNDING, SET UP, AND CONFIGURED FOR PHASE OF FLT, ON AUTOPLT. WHEN CLRED FOR APCH, FO SELECTED LNAV INSTEAD OF 'APCH MODE.' ACFT PROMPTLY MADE HARD TURN TO THE L TO FLY TO LAST WAYPOINT (OFF L WING). CREW MOMENTARILY SURPRISED BY WRONG TURN AND ITS CAUSE. CAPT HIT HDG SELECT TO RETURN TO ORIGINAL HDG ASSIGNED FOR INTERCEPT, BUT AUTOPLT WAS VERY SLOW IN STOPPING TURN AND STARTING R TURN. FO CLICKED OFF AUTOPLT TO LIGHTEN TURN AND WAS DISTR BY EVENTS TO THE POINT THAT HE ADDED PWR FOR THE 3000 FT LEVELOFF WITH SPD BRAKE STILL UP. CAPT LOWERED SPD BRAKE FOR FO BUT ACFT DSNDED 200-300 FT BELOW 3000 FT ASSIGNED AND CROSSED RWY CTRLINE AT AROUND 75 DEGS OFF INBOUND COURSE. WE DEFINITELY VIOLATED THE RWY 18L APCH PATH DURING CORRECTIONS. (RWY 18L NOT IN USE FOR LNDGS AT THE TIME.) CAPT REQUESTED AND RECEIVED CLRNC FOR VISUAL APCH DURING CORRECTIONS. LESSONS LEARNED: 1) PROGRAM AUTOFLT SYS PROPERLY TO START. 2) DON'T TROUBLESHOOT SYS WHEN CLOSE IN -- KICK IT OFF AND BE PREPARED TO HAND FLY IT. 3) DON'T BE COMPLACENT BECAUSE OF ROUTINE NATURE OF APCH, WX AND CREW PERFORMANCE.

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.