DRG DEP FM RWY 24 WITH AN IFR CLNC, AN ATLANTIC SOUTHEAST AIRLINE FLT (EMBRAER EMB-120, N217AS) ENTERED A LEFT TURN TO A HDG OF EAST & CLIMBED TO AN ASSIGNED ALT OF 5000' MSL. BEFORE RADAR CONTACT WAS ESTABLISHED WITH ATC, THE EMB-120 CONVERGED WITH A CAP CESSNA 172, N99501. THE CESSNA WAS HDG WESTBOUND TOWARD THE SETTING SUN. SUBSEQUENTLY, A HEAD-ON COLLISION OCCURRED ABOUT 2-1/2 MI SOUTH OF THE ARPT. DRG IMPACT, THE RGT HORIZONTAL STABILIZER OF THE EMB-120 SEPD FROM THE ACFT, BUT IT CONTD FLYING TO A SAFE LNDG. THE CESSNA, HOWEVER, ENTERED AN UNCTLD DSCNT & CRASHED. A WITNESS, WHO SAW THE COLLISION, DID NOT NOTE ANY EVASIVE ACTION BY EITHER ACFT BEFORE IMPACT. THE CREW OF THE EMB-120 RPRTD THAT THEY SAW THE CESSNA MOMENTS BEFORE IMPACT. THE CAPT OF THE EMB-120 SAID HE TOOK IMMEDIATE EVASIVE ACTION BY 'PUSHING' THE NOSE DOWN, BUT WAS UNABLE TO AVOID A COLLISION. A FLT ATTENDANT ON THE EMB-120 RECALLED A 'THUMP' BEFORE THE ACFT STARTED A DSCNT.