C525 HAS ALT EXCURSION DURING VECTORS AROUND WX ON INITIAL APCH TO BHM.

Narrative

ON JUN/THU/01 AT APPROX XA30 HRS; 2 QUALIFIED PLTS; ONE FLYING AS PIC AND THE OTHER AS SIC; WERE WORKING WITH THE APCH CTLRS AT BHM; DSNDING FROM 11000 FT TO AN ASSIGNED ALT OF 6000 FT. SEVERAL TSTMS PLUS NUMEROUS CUMULUS BUILDUPS COVERED THE DSCNT AREA. THE CUMULUS BUILDUPS WERE CLOSE TOGETHER AND NEAR A TSTM BEING CIRCUMNAVED. IN AN EFFORT TO AVOID TURBULENT AIR AND MAINTAIN PAX COMFORT; THE AUTOPLT WAS DISCONNECTED AND THE ACFT WAS HAND FLOWN TO INCREASE MANEUVERABILITY. DURING A SERIES OF RAPID TURNS; THE ACFT WAS ALLOWED TO DSND BELOW THE ASSIGNED ALT OF 6000 FT AS WE DODGED BUILDUPS. WHEN THIS WAS RECOGNIZED; IMMEDIATE CORRECTION WAS MADE AND THE FLT CONTINUED WITHOUT FURTHER INCIDENT. THE PROB WAS CAUSED BY THE PLT'S INTENSE CONCENTRATION ON AVOIDING VERY TURBULENT AIR AND FAILING TO MAINTAIN THE PROPER ALT. IT COULD HAVE BEEN PREVENTED BY FLYING A MORE CIRCUITOUS; THOUGH LONGER; RTE AROUND THE AREA OF STORMS AND BUILDUPS. THE PLT SHOULD HAVE CONCENTRATED ON ALT AS WELL AS DIRECTION.