Narrative:

Flight dtw-ord on jun/xx/94. Flight was hold on the ground at dtw for about 2 hours due to WX at ord. After airborne and having been turned over to ZAU from ZOB we were cleared 'direct' to pappi intersection which is on the pullman STAR. I pushed the 'direct to' button and selected pappi. The airplane started a turn on autoplt and I thought it was making an excessive turn. In fact it turned too far to go direct to pappi and just as I started to 'deselect' the managed navigation feature and go to a selected heading to fly direct pappi we rolled out of the turn and I thought the airplane was making its own correction. At that point I was distracted by something or someone and didn't 'follow up' on what the airplane was doing. The next thing I know, ATC calls us and asks us if we are going direct pappi as previously cleared. I looked and the airplane was on about a 230 degree heading as though it were trying to intercept a course, not on a 280 degree heading direct to pappi. ATC gave us a 310 degree heading and said we were 'getting too close' to the chicago departure corridor. I don't know why the FMS did not take us direct pappi. When I pushed the 'direct to' push button it gave me a solid line from present position to pappi but then it made too large a turn and when I thought it was making its own correction it obviously wasn't. I've never seen that or a similar situation occur before. My error was to allow myself to be distracted before I finished following up on what the airplane was doing when it rolled out of its turn after turning too far for a direct pappi.

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Original NASA ASRS Text

Title: MLG HAS HDG DEV DUE TO MALFUNCTION OF THE FMS.

Narrative: FLT DTW-ORD ON JUN/XX/94. FLT WAS HOLD ON THE GND AT DTW FOR ABOUT 2 HRS DUE TO WX AT ORD. AFTER AIRBORNE AND HAVING BEEN TURNED OVER TO ZAU FROM ZOB WE WERE CLRED 'DIRECT' TO PAPPI INTXN WHICH IS ON THE PULLMAN STAR. I PUSHED THE 'DIRECT TO' BUTTON AND SELECTED PAPPI. THE AIRPLANE STARTED A TURN ON AUTOPLT AND I THOUGHT IT WAS MAKING AN EXCESSIVE TURN. IN FACT IT TURNED TOO FAR TO GO DIRECT TO PAPPI AND JUST AS I STARTED TO 'DESELECT' THE MANAGED NAV FEATURE AND GO TO A SELECTED HDG TO FLY DIRECT PAPPI WE ROLLED OUT OF THE TURN AND I THOUGHT THE AIRPLANE WAS MAKING ITS OWN CORRECTION. AT THAT POINT I WAS DISTRACTED BY SOMETHING OR SOMEONE AND DIDN'T 'FOLLOW UP' ON WHAT THE AIRPLANE WAS DOING. THE NEXT THING I KNOW, ATC CALLS US AND ASKS US IF WE ARE GOING DIRECT PAPPI AS PREVIOUSLY CLRED. I LOOKED AND THE AIRPLANE WAS ON ABOUT A 230 DEG HDG AS THOUGH IT WERE TRYING TO INTERCEPT A COURSE, NOT ON A 280 DEG HDG DIRECT TO PAPPI. ATC GAVE US A 310 DEG HDG AND SAID WE WERE 'GETTING TOO CLOSE' TO THE CHICAGO DEP CORRIDOR. I DON'T KNOW WHY THE FMS DID NOT TAKE US DIRECT PAPPI. WHEN I PUSHED THE 'DIRECT TO' PUSH BUTTON IT GAVE ME A SOLID LINE FROM PRESENT POS TO PAPPI BUT THEN IT MADE TOO LARGE A TURN AND WHEN I THOUGHT IT WAS MAKING ITS OWN CORRECTION IT OBVIOUSLY WASN'T. I'VE NEVER SEEN THAT OR A SIMILAR SIT OCCUR BEFORE. MY ERROR WAS TO ALLOW MYSELF TO BE DISTRACTED BEFORE I FINISHED FOLLOWING UP ON WHAT THE AIRPLANE WAS DOING WHEN IT ROLLED OUT OF ITS TURN AFTER TURNING TOO FAR FOR A DIRECT PAPPI.

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.