SMA PLT MAY HAVE ENTERED CLASS C AIRSPACE WHILE ON A SIGHTSEEING FLT.

Narrative

DEPARTED 1C5 ENRTE TO CHICAGO LAKEFRONT AREA (SIGHTSEEING TRIP FOR SON AND NEPHEW). FLEW S TO ARRIVE AT LAKEFRONT AREA WITHOUT VIOLATING MDW AIRSPACE. ALT VARIED FROM 2000 FT TO 2300 FT MSL. VMC CONDITIONS; USING SECTIONAL MAP. DURING CRUISE; I NOTED SOME INACCURATE INDICATIONS ON ATTITUDE INDICATOR. UPON REACHING THE LAKEFRONT; I TURNED N AND PROCEEDED ALONG THE LAKEFRONT. ON THE N SIDE OF CHICAGO; I TURNED AROUND AND HEADED S ALONG THE SHORE (2000 FT MSL). AT THIS TIME THE ATTITUDE INDICATOR AND DIRECTIONAL GYRO FAILED (VACUUM SYS FAILURE). I RETURNED TO CLOW WITHOUT INCIDENT. ON THE RETURN; I FLEW CLOSER TO MDW AT 1800 FT MSL TO BE ASSURED TO BE BELOW THE AIRSPACE. AFTER MY RETURN UPON REVIEWING THE FLT; I FELT THAT I MAY HAVE BEEN FURTHER N ON THE OUTBOUND LEG THAN I HAD ORIGINALLY THOUGHT. I AM NOT POSITIVE OF THIS; BUT FELT THE INCIDENT WORTH RPTING. THIS WOULD HAVE CAUSED ME TO HAVE VIOLATED MDW'S AIRSPACE WITHOUT PERMISSION. DURING THE FLT; THERE WERE FEW ACFT ENCOUNTERED; AND NONE NEAR MDW. I FEEL THAT DISTR CAUSED BY THE ATTITUDE INDICATOR CONTRIBUTED TO THIS INCIDENT AS WELL AS ERROR IN READING THE SECTIONAL (I.E.; VISUAL NAV).