FLC OF A BEECH 1900 AIRLINER (BE02); FAILED TO NOTE THAT THE ACFT WAS GROUNDED DUE TO THE FO ATTITUDE GYRO WAS WRITTEN UP BY THE PREVIOUS FLC AS NOT WORKING PROPERLY. IN ADDITION; THE DISPATCHER WAS NOTIFIED BY MAINT OF THE GROUNDING BUT HAD NOT PASSED ON THE INFO TO THE RPTR. THE GROUNDING WAS DISCOVERED WHEN THE RPTR RPTED THE GYRO PROBLEM TO MAINT AFTER THE FIRST LEG LANDING.

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I AM A CAPT FOR A PART 121 OP. ON 4/XA/98 I WAS SCHEDULED TO FLY A TRIP. THE ACFT I WAS SCHEDULED TO DEP WITH WAS 'GROUNDED' BY THE CREW THAT FLEW IT PREVIOUSLY. IT WAS GROUNDED DUE TO THE CO-PLT GYRO BECOMING INOP. THIS ACFT WAS GROUNDED AT APPROX XA00 HRS ON 4/XA/98. THE MAINT DEPT WAS NOTIFIED BY THE CREW THAT WROTE UP THE GYRO. MAINT THEN NOTIFIED DISPATCH THAT THE ACFT WAS GROUNDED AND CONSIDERED UNAIRWORTHY. DISPATCH KNEW THE ACFT HAD BEEN GROUNDED AND WAS AWARE THAT IT WAS AWAITING A PART TO BE REPLACED ON THE ACFT. OPERATIONS KNEW THE ACFT WAS GROUNDED AS WELL. THE ACFT HAD BEEN GROUNDED APPROX. 8-9 HRS PRIOR TO MY ARRIVAL AT THE ARPT. AT XI50 I ARRIVED AND WAS GIVEN A DISPATCH RELEASE FROM OPS. I ASSUMED EVERYTHING WAS NORMAL. AS I REVIEWED MY RELEASE I ASKED OPS HOW MANY PEOPLE WOULD BE TRAVELING AND HOW MUCH FUEL WAS ON BOARD THE ACFT. I WAS TOLD THE FUEL WAS ALREADY IN THE ACFT AND IT WAS READY TO GO. I NEVER WAS TOLD THE ACFT HAD BEEN GROUNDED. I WALKED OUT TO THE AIRPLANE AND GREETED MY FO WHO WAS PERFORMING THE PREFLT. I ASKED HIM HOW THE ACFT LOOKED AND HE TOLD ME ABOUT THE MEL ON THE ACFT (STROBE LIGHT INOP) AND HE ALSO INFORMED ME OF 2- WATCH CARRY OVER ITEMS. I REVIEWED THE MEL PROC FOR THE STROBE LIGHT AND PICKED UP THE LOGBOOK AND SIGNED IT. AT THIS POINT MY ATTENTION WAS DIRECTED TO PERFORMING THE WT AND BAL. MY ATTENTION WAS ON THIS MORE THAN IT NORMALLY WOULD BE BECAUSE IT WAS THE FIRST TIME THE COMPANY HAD US START WITH A NEW WT AND BAL SHEET AND WHIZ WHEEL FOR DETERMINING THE CG. IT SHOULD BE NOTED WE HAD NEVER RECEIVED FORMAL TRAINING ON THE USE OF THE NEW PROC FOR WT AND BAL. WE DEPARTED AND EVERYTHING SEEMED NORMAL; AS WE WERE CLBING MY FO INFORMED ME HIS GYRO HAD STOPPED WORKING. WE THEN DSNDED TO VFR CONDITIONS AND CONTINUED THE FLT TO OUR DESTINATION. IT WAS MY LEG AND MY GYRO WORKED FINE. ONCE ON THE GND; I CALLED MAINT AND INFORMED THEM OF THE INOP GYRO. THEY THEN INFORMED ME THAT THE ACFT WAS NOT SUPPOSED TO BE RELEASED BECAUSE IT WAS GROUNDED. AT THIS TIME I HAD REALIZED I HAD TAKEN AN UNAIRWORTHY ACFT; DUE TO IT HAVING AN 'OPEN WRITE-UP.' DISPATCH SHOULDN'T HAVE SENT THE RELEASE. THIS ERROR SHOULD NOT HAVE HAPPENED BECAUSE MAINT; DISPATCH; AND OPS ALL KNEW FOR APPROX 9 HOURS THE ACFT WAS GROUNDED. I HAD 30 MINS PRIOR TO DEP AND 'MISSED' THE WRITE UP IN THE LOG AND MY FO HAD ALSO. I LEARNED NOT TO TRUST ANYONE THAT THE ACFT IS SAFE AND AIRWORTHY. I WAS SUSPENDED FROM FLYING ON LINE FOR 2 DAYS WITHOUT PAY AS A RESULT AFTER SITTING DOWN AND DISCUSSING THIS MATTER WITH MY CHIEF PLT AND VP OF OPS AND FO.