TKOF ABORTED WHEN PLT OF AN SA227 COULD NOT MAINTAIN CTRLINE ALIGNMENT.

Narrative

I WAS A FO ON A FLT DEPARTING SEATTLE ON RWY 16L AT LIMA INTXN. THE ACFT WAS AN SA227. OUR COMPANY HAS HAD THE ACFT OVER 12 YRS AND THOUSANDS OF TKOFS; HOWEVER RWY EXCURSIONS HAVE BEEN A CHECKERED PART OF OUR PAST. I WAS THE PF. THE CAPT TURNED OFF THE NOSEWHEEL STEERING PRIOR TO TURNING ON THE RWY; CTRED THE ACFT ON THE CTRLINE; AND WE TRANSFERRED CTL. I ADVANCED THE PWR LEVERS; THEY WERE COMING UP THROUGH 40 PERCENT AND THE ACFT TURNED ABOUT 10-20 DEGS TO THE R. I TRIED TO CTL IT WITH DIFFERENTIAL BRAKING; BUT WAS UNABLE TO KEEP THE DIVERSION FROM HAPPENING. I ABORTED THE TKOF WHICH IS NOT STANDARD. OUR CAPTS ARE SUPPOSED TO ABORT. HE WAS GLAD THAT I DID; HOWEVER. ALSO; HE WAS UNABLE TO STRAIGHTEN THE ACFT UNTIL AT TAXI SPD. WE TOLD THE TWR WE WERE ON ABORT; TAXIED TO AN AREA TO RUN CHKLISTS AND PREPARED FOR ANOTHER TKOF. WE RAN THE EMER 'NOSEWHEEL STEERING FAIL CHKLIST;' AND PULLED THE NOSEWHEEL STEERING CIRCUIT BREAKER. HE ELECTED TO DO THE NEXT TKOF. WE PROCEEDED WITHOUT INCIDENT. WE WROTE UP THE NOSEWHEEL STEERING AT OUR DEST; FERRIED THE ACFT BACK TO OUR BASE. DISCUSSING THE INCIDENT; NEITHER ONE OF US COULD FIGURE OUT EXACTLY WHAT HAPPENED. IT WAS IFR AT SEATTLE; 700 FT BROKEN; 1-2 MI VISIBILITY; RAIN AND GUSTY WINDS (190 DEGS 15 KTS GUSTING TO 25 KTS). THE WINDS COULD HAVE BEEN WHAT CAUSED IT; BUT WE DON'T KNOW. WE NEVER RAN OFF THE RWY WHICH WAS FORTUNATE. WE HAD FLOWN TOGETHER AND WERE FAMILIAR WITH ONE ANOTHER (AT LEAST 70 HRS). THE CAPT IS THE PINNACLE OF A STANDARDIZED PLT; NEVER RUSHES; ALWAYS 'BY THE BOOK.' WE USED TKOF SETTINGS FOR A CONTAMINATED RWY. NOTHING WAS OUT OF THE ORDINARY FOR A TYPICAL WINTER; CRUDDY DAY IN SEATTLE. NO WINDSHEAR WAS BEING RPTED; BUT THAT MIGHT HAVE BEEN WHAT CAUSED IT. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: RPTR FEELS THAT RWY EXCURSIONS ARE A COMMON PROB WITH THE DIFFICULT HANDLING CHARACTERISTICS OF THE METRO III. THE FO STILL DOES NOT KNOW WHY HE WAS NOT ABLE TO MAINTAIN CTRLINE. HE STILL BELIEVES THAT THIS MIGHT HAVE BEEN RELATED TO A MALFUNCTION IN THE NOSEWHEEL STEERING; BUT HAS NOT SINCE QUERIED MAINT.