A WITNESS STATED THE ACFT VEERED APRX 30 DEGS DURING THE LANDING ROLL AND WAS HEADING TOWARD THE NORTH EDGE OF THE RWY WHEN FULL PWR WAS ADDED TO ABORT THE LANDING. THE ACFT TOOK OFF AND TRAVELED OVER A GRASS AND WHEAT FIELD, WHICH BORDERS THE RWY, WITH THE LANDING GEAR TOUCHING THE TOPS OF THE WHEAT. WITNESS CONTINUED TO REPORT, 'THE PILOT THEN GAINED AN ESTIMATED 40 FEET OF ALTITUDE AGL BUT ALSO APPEARED TO BE, IN MY OPINION, CLOSE TO FULL STALL.' THE ACFT CONTINUED TO FLY ALONG THE NORTH SIDE OF THE RWY FOR APRX 2500 FT BEFORE IT ENTERED A STEEP RIGHT BANK AND COLLIDED WITH THE GROUND RIGHT WING TIP FIRST. POST ACCIDENT EXAMINATION OF THE ACFT DISCLOSED A BROKEN MAIN AILERON BELLCRANK. METALLURGICAL EXAMINATION REVEALED THE BELLCRANK FAILURE RESULTED FROM A SUDDEN OVERLOAD. THE PLT HAD A TOTAL OF 5 HRS FLT TIME IN THIS MAKE AND MODEL ACFT.