ACCORDING TO WITNESSES, THE ACFT MADE A NORMAL APCH TO RWY 33 WITH NO APPARENT ABNORMALITIES. HOWEVER, WHEN IT WAS ABOUT 200 FT OVER THE APCH LIGHTS, THEY HEARD AN INCREASE IN THE ENG THRUST & THE ACFT'S DESCENT STOPPED. TWO PLT WITNESSES THOUGHT THE AIRCREW INITIATED A GO-AROUND. IMMEDIATELY THEREAFTER, THE ACFT BEGAN AN APPARENT LEVEL TURN TO THE RIGHT. AS IT TURNED THRU ABOUT 90 DEG OF TURN, THE BANK ANGLE HAD INCREASED TO NEARLY 90 DEG, THE ACFT'S NOSE DROPPED & THE PLANE CRASHED IN A NOSE LOW ATTITUDE & BURNED. AN INVESTIGATION REVEALED THE LANDING GEAR WAS EXTENDED & THE FLAPS WERE PARTIALLY EXTENDED. THE AILERON TRIM ACTUATOR WAS IN A FULL LEFT WING DOWN POSITION & THE ELEVATOR WAS TRIMMED NEAR A FULL NOSE UP POSITION. THE RIGHT SPOILER ACTUATOR WAS FOUND IN A FULL EXTENDED POSITION & THE LEFT WAS IN A RETRACTED POSITION, WHICH WAS INDICATIVE OF AN ASYMMETRIC SPOILER CONFIGURATION. RADAR DATA INDICATED THE CREW HAD EXTENDED THE SPOILERS DURING THE LAST PART OF THE DESCENT & APCH. NO REASON FOUND FOR IMPROPER SPOILER OPERATION.