A RETURN LAND IS MANDATED BY MULTIPLE ACFT EQUIP PROBS MALFUNCTIONS IN A COMMUTER ACFT.

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SHORTLY AFTER ROTATION AND PRIOR TO 400 FT MSL I NOTICED THAT MY ALTIMETER (L SIDE) APPEARED TO HAVE FAILED AND I LOOKED TO R TO SEE IF IT CONCURRED AND WHAT OUR ACTUAL ALT WAS. WHEN I MENTIONED THIS TO MY FO HE RESPONDED THAT HIS WAS WORKING. AS WE DID OUR 400 FT AFTER TKOF CHKS OTHER HDG AND NAV FLAG FAILURE INDICATIONS APPEARED. WHILE I CONTINUED TO ASSESS THE SIT AND DECIDE ON A COURSE OF ACTION IN CONSULTATION WITH MY FO; ATC ASKED US TO TURN L TO A NEW HDG. AFTER A SLIGHT L TURN I REALIZED MY HDG INDICATOR WAS NOT RESPONDING PROPERLY. WHEREAS WE WERE IN DETERIORATING VMC CONDITIONS I ELECTED TO RETURN TO THE ARPT AND HAVE THE FO FLY THE ACFT. AT THIS TIME DEP ADVISED US THAT OUR HDG WAS 30 DEGS L OF WHAT THEY WANTED. WE FURTHER APPRISED ATC OF OUR NEED TO RETURN TO THE ARPT. THE DEP CTLR FURTHER ADVISED ME THAT OUR CURRENT HDG WAS ALMOST IN DIRECT CONFLICT WITH SCHEDULED TFC TO APCH ON RWY 15 ILS AND CIRCLE TO RWY 4L. BUT THIS ACTION HAD YET TO COMMENCE AND WAS ONLY PLANNED. I REITERATED OUR SIT AND NEED TO RETURN WHICH WE DID WITHOUT FURTHER INCIDENT.