WITNESSES REPORTED THAT THE AIRCRAFT APPEARED TO TAKEOFF AND CLIMB NORMALLY UNTIL IT REACHED AN ALTITUDE OF ABOUT 100 FT AGL. IT THEN PITCHED UP ABRUPTLY TO ABOUT A 70 DEG NOSE HIGH ATTITUDE. AFTER THE PITCH-UP, THE AIRCRAFT CLIMBED TO ABOUT 175 TO 200 FT AGL, STALLED, ROTATED ABOUT THE LEFT WING TIP AND ENTERED A SPIN. THE PLANE ROTATED ABOUT 270 DEG BEFORE CRASHING. NO PREIMPACT MALFUNCTION OR FAILURES OF THE ENGINE OR FLIGHT CONTROLS WERE FOUND. TWO METALLURGICAL EXAMINATIONS OF THE SEAT TRACKS AND SEAT LOCKING MECHANISMS WERE MADE. REPORTS OF THESE EXAMINATIONS CONCLUDED THAT THE LEFT (STUDENT PILOT'S) SEAT WAS NOT IN A FIXED POSITION DURING IMPACT. THERE WAS EVIDENCE THAT IT HAD TRAVELED TO AN EXTREME AFT POSITION BEFORE THE PLANE CRASH. THE LEFT SEAT LOCKING MECHANISM OPERATED NORMALLY WHEN CHECKED AFTER THE ACCIDENT.