DEP TURN OVERSHOT IN A SNOWSTORM DURING AN EQUIP MALFUNCTION ON A DEPARTING F100 FROM ORD; IL.

Narrative

TAKING OFF ON RWY 4L AT ORD DURING A SNOWSTORM; WE WERE ASSIGNED AN INITIAL HDG OF 070 DEGS. THE WX WAS IMC AND THE FO WAS FLYING. AS WE INITIATED THE TURN; WE RECEIVED MULTIPLE WARNINGS ABOUT THE FLT INSTS. I SCANNED ALL 3 ATTITUDE AND SPD INDICATIONS AND FOUND THEY WERE ALL IN AGREEMENT. BY THE TIME I CHKED HDGS; WE HAD OVERSHOT OUR ASSIGNED 070 DEG HDG BY 40 DEGS. JUST AS I CAUGHT THIS; THE TWR CTLR GAVE US A 160 DEG HDG AND TURNED US OVER TO DEP CTL. WE QUICKLY DETERMINED THAT THE INSTS ON MY SIDE WERE FUNCTIONING PROPERLY; SO I TOOK CTL OF THE ACFT. THE MALFUNCTION WAS THE FO'S FLT CTL COMPUTER (FCC). WE HAD SEVERAL VISUAL AND AURAL WARNINGS ASSOCIATED WITH THIS FAILURE. FO'S FLT DIRECTOR FAILURE; #2 AUTOTHROTTLE FAILURE; SPD LIMIT FLAGS ON BOTH PFD'S; NO WINDSHEAR GUIDANCE; NO AUTOLAND; AND AN FCC FAULT. SUPPLEMENTAL INFO FROM ACN 607081: RIGHT AT THE MOMENT I BEGAN MY TURN; THE FO'S FLT CTL COMPUTER (FCC) FAILED CAUSING MULTIPLE INSTRUMENTATION FAILURES; AND SEVERAL ANNUNCIATORS TO ILLUMINATE (FLASHING). I WAS MOMENTARILY DISTR BY THE IMMEDIATE FAILURE AND I TURNED PAST MY HDG OF 070 DEGS TO ABOUT 110 DEGS. ORD TWR NEVER MADE ANY MENTION OF THE ERROR.