A PA32 PLT DSNDS 1000 FT BELOW HIS ASSIGNED ALT WHILE APCHING CHS; SC.

Narrative

ON A FEB/XA/99 IFR FLT FROM MYR TO CHS; I VIOLATED ASSIGNED ALT INADVERTENTLY. DEP FROM MYR WAS ROUTINE AND WAS IMC AT 1200 FT AND THEN ON TOP AT 4500 FT. AS FORECAST; I WAS FLYING INTO IMPROVING CONDITIONS AND CHS WAS ALREADY GOOD VFR. I COULD SEE 20-30 MI AND AS FORECAST; THE OVCST WAS BREAKING UP TO SCATTERED TO CLR. I WAS GIVEN A DSCNT FROM 6000 FT TO WHAT I HEARD TO BE 2000 FT BY ATC. I REPEATED THE DSCNT CLRNC AND RESET MY ALT HOLD BUG TO 2000 FT. ABOUT 20 DME FROM CHS I NOTICED THAT I WAS FLYING AT ABOUT THE SAME HT AS THE 3 RADIO TWRS ON MT PLEASANT (I FLY THIS RTE REGULARLY); AND ABOUT THE SAME TIME ATC CALLED TO ADVISE ME I WAS ASSIGNED 3000 FT AND NOT THE 2000 FT I WAS MAINTAINING. CONCLUSION: I DO NOT KNOW WHETHER THE ATC TAPES SHOW ME CLRED TO 2000 FT OR 3000 FT; BUT THE ERROR WAS THAT I MENTALLY TRANSITIONED TO VFR WHILE STILL ON AN IFR FLT PLAN. HAD I KEPT MY MIND IN THE COCKPIT AND NOT WATCHING THE COAST AND DISTRACTED BY THE MODERATE TURB; I WOULD HAVE NOTED MY DSCNT CLRNC VIOLATED THE 2400 FT MEA ON THE IFR AIRWAY AND CALLED ATC FOR CLARIFICATION PRIOR TO DSCNT. LESSON: FLY YOUR IFR FLT PLAN UNTIL YOU CAN AND GO VFR. NEVER MIX OR CONFUSE THE OPS OF THE TWO! ALT INCURSION WHILE ON IFR FLT PLAN; DUE TO LACK OF CAREFUL CONSIDERATION OF MAINTAINING IFR RULES WHEN WX GOES TO CAVU. UPON DISCOVERY BY ATC; ADVISED TO MAINTAIN DSCNT ALT AND MAINTAIN OBSTACLE CLRNC. ATC DID NOT REQUEST A CLB BACK TO 3000 FT.