THE AIRCRAFT TOOK OFF FROM RUNWAY 18 WITH 4 OCCUPANTS AND ABOUT 98 GAL OF FUEL ON BOARD. THE WIND WAS FROM 210 DEG AT 8, GUSTING 20 KTS, THE PRESSURE ALTITUDE WAS ABOUT 8900 FT AND MODERATE TURBULENCE WAS REPORTED. ACCORDING TO WITNESSES, THE AIRCRAFT MADE A LONGER THAN NORMAL TAKEOFF ROLL AND NEVER GAINED MUCH ALTITUDE. A LEFT TURN WAS MADE JUST SOUTH OF THE RUNWAY WHILE STILL AT A VERY LOW ALTITUDE AND THE AIRCRAFT WAS UNABLE TO CLEAR THE TREES IN A WOODED AREA. ABOUT 365 FT PAST THE FIRST CONTACT WITH THE TREES, THE PLANE IMPACTED THE GROUND. AN INVESTIGATION REVEALED NO PREIMPACT MALFUNCTION OR FAILURE. A VISUAL OBSEVATION OF THE SPARK PLUGS REVEALED INDICATIONS OF A RICH MIXTURE AND THE MIXTURE CONTROL WAS FOUND IN THE FULL RICH POSITION. THE AIRPORT ELEVATION WAS 6911 FT, THE ELEVATION OF THE CRASH SITE WAS REPORTED TO BE 7133 FT IN THE VICINITY OF HILLY/MOUNTAINOUS TERRAIN. THE CONFIGURATION OF THE GEAR AND FLAPS AFTER LIFT-OFF WAS NOT VERIFIED.