B757; CREW ON DEP; OVERSHOT ASSIGNED HDG.

Narrative

CLRED FOR TKOF ON MDW RWY 22 AND GIVEN A HDG ON DEP OF 250 DEGS; WHICH IS CUSTOMARY. I WAS PF. FO STATED HE WOULD GET HDG SELECTOR TO 250 DEGS. WE BEGAN TKOF. AFTER LIFTOFF; FO WAS DIALING HDG AND FLT DIRECTOR COMMANDED A R TURN; WHICH WAS NORMAL. WE WERE TURNING DIRECTLY INTO THE SUN WHICH COMPLICATED MY SCAN; AND I OBSERVED THAT I HAD PAST THE BUG AND HDG OF 250 DEGS. I STOPPED TURN AT 300 DEGS. I WAS CONFUSED BECAUSE THE FLT DIRECTOR WAS STILL COMMANDING A R TURN. WE WERE IN HDG MODE AND HDG WAS SET CORRECTLY. WE LATER DETERMINED THE PROB WAS PLT ERROR IN THAT THE FO DIALED IN A TURN GREATER THAN 180 DEGS (WENT ALL THE WAY AROUND) AND I WAS UNAWARE OF THIS. I HAD TURNED PAST 250 DEGS BY THE TIME HE SET 250 DEGS IN THE WINDOW; SO THE FLT DIRECTOR WAS STILL COMMANDING A R TURN. I BEGAN A L TURN SLOWLY BECAUSE I WASN'T SURE AT THAT TIME WHAT WAS WRONG. (WE WERE GIVEN ANOTHER HDG TO 270 DEGS; GUT FLT DIRECTOR STILL COMMANDED A R TURN). MITIGATING FACTORS WERE A LATE DEP DUE TO WX DELAYS; DEP RWY CHANGE FROM INITIAL PLANNING; AND FO FELT FATIGUED DUE TO BODY CLOCK CHANGE (WAKE-UP AT XA00 WHERE HE RESIDES).