MD80 CREW TOOK OFF WITH BOTH IRS SYS IN ATTITUDE.

Narrative

WHEN WE WERE TAXIING TO DEICE; I NOTICED BOTH THE #1 AND #2 IRS ATTITUDE MODE LIGHTS WERE ILLUMINATED. I ALSO NOTICED THE MAP DISPLAY HAD FAILED. I WAS UNSUCCESSFUL IN GETTING THE LIGHTS TO GO OUT. IT APPEARED THAT THE FMS WAS INOP. THE #1; #2 AND THE STANDBY COMPASSES WERE IN AGREEMENT. #1; #2 AND STANDBY ATTITUDE INDICATORS WERE OPERATING NORMALLY. I DECIDED TO CHANGE OUR FLT PLAN SUFFIX FROM /F TO /A AND CONTINUE ON TO DFW. WHEN WE TOOK THE RWY; ALL 3 COMPASSES WERE CHKED TO INSURE THAT THEY CORRESPONDED TO THE RWY HDG. ATTITUDE INDICATORS AND FLT DIRECTORS WERE NORMAL. AFTER TKOF; WE TURNED TO A HDG OF 255 DEGS. DEP CTL ASKED WHAT OUR HDG WAS. THEY INSTRUCTED US TO TURN R 20 DEGS. WE WERE THEN CLRED DIRECT TO THE MXE VOR AND ON COURSE. AFTER XING MXE; WE TURNED L TO INTERCEPT THE 278 DEG RADIAL. CTR ASKED OUR HDG. THEY SAID WE WERE 40 DEGS OFF ON OUR HDG. I CONFIRMED THIS WITH THE STANDBY COMPASS. I ASKED FOR RADAR VECTORS AND TO MAINTAIN FL260. ABOUT THIS TIME; THE AUTOPLT AND AUTOTHROTTLES DISENGAGED. WE LOST THE FLT DIRECTORS; ATTITUDE INDICATORS; NAV DISPLAYS AND THE RMI'S. I DECLARED AN EMER AND ASKED TO MAINTAIN FL260 AND OUR CURRENT HDG WHILE I SOLVED THE PROBS. ALL THE FLT INSTS STARTED WORKING AFTER ABOUT 30 SECONDS. I THOUGHT THE PROB WAS RELATED TO OUR FMS FAILURE. I ALSO NOTED THAT WE NOW HAD A FLASHING 'ALIGN' LIGHT. I RAN THE 'ALIGN LIGHT FLASHING' CHKLIST. THIS CORRECTED THE COMPASS PROBS WE HAD BEEN EXPERIENCING. THE COMPASSES AND THE FMS HDGS AS WELL AS THE STANDBY COMPASS ALL STAYED IN AGREEMENT FOR THE REST OF THE FLT TO DFW.