THE ACFT WAS ON A SCHEDULED COMMUTER FLT FROM UTICA, NY TO WASHINGTON, DC WITH A STOP AT ITHACA, NY. THE EN ROUTE PORTION OF THE FLT FROM UTICA TO ITHACA WAS NORMAL. AT 0735 EST, THE ACFT WAS AT 6000 FT MSL WHEN APCH CONTROL INFORMED THE AIRCREW TO EXPECT AN ILS APCH TO RWY 32 AT ITHACA. AT 0739, AN EMERG WAS DECLARED CONCERNING A SPLIT FLAP COND WITH 1 FLAP DWN. DRG THE NEXT 5 MIN, THE CREW RETAINED CONTROL OF THE ACFT WHILE DSCNDG FROM APRX 2500 TO 1900 FT. AT 0744:40, THE CREW RPRTD ON THE LOCALIZER COURSE AT 9 MI FROM THE ARPT, THEN RPRTD MAINTAINING CONTROL WITH FULL RGT AILERON. SHORTLY AFTER RPRTG THE GND IN SIGHT, THE PLANE CRASHED & BURNED IN A WOODED AREA, 6.7 MI FROM THE ARPT. IT DESCENDED THRU THE TREES IN AN 80 TO 90 DEG L BANK, APRX 24 DEG NOSE DWN. FND R FLAP 34 DEG DWN & L FLAP UP. THE INBOARDFEMALE SPLINE COMPONENT OF THE L FLAP FLEX CABLE WAS WORN & THE MALE FITTING WOULD ROTATE WITHIN. CAR 3.339 REQD A MECHANICAL FLAP INTERCONNECT WHEN ACFT CAN NOT BE CONTROLLED W SPLIT FLAPS. MOD LOW ALT TURBC & LOW LVL WND SHEAR ENCTRD