IMPROPER PREFLIGHT BY THE PILOT, HIS FAILURE TO ABORT THE TAKEOFF WHILE THERE WAS SUFFICIENT RUNWAY REMAINING, AND HIS FAILURE TO ASSURE THAT THE AIRCRAFT ATTAINED SUFFICIENT AIRSPEED FOR LIFT-OFF AND CLIMB. FACTORS RELATED TO THE ACCIDENT WERE: THE PILOT'S FAILURE TO ASSURE THE AIRCRAFT WAS WITHIN ITS MAXIMUM WEIGHT LIMITATION, HIS IMPROPER USE OF THE PARKING BRAKE, AND INSUFFICIENT INFORMATION IN THE PILOT OPERATING HANDBOOK CONCERNING THE AIRCRAFT PARKING BRAKE.