SEA91FA156

The student plt was the owner/operator of the acft. He and the passenger were on a pleasure flt in an area of mountainous terrain. The acft was seen to turn into a valley where it subsequently collided with the ground at an elevation of about 5500 ft. during impact, the wings were bent down and forward; there was a 45 deg crush line on the leading edges of the wings. No ground scars were found to indicate movement after ground impact. The acft's last annual inspn was dated 7/22/87; however, the student plt continued to operate the acft; he performed oil changes himself. No preimpact mechanical failure or malfunction of the engine was found. The student's last medical exam was dated 11/25/87. A toxicology exam of the student plt's blood showed a saturation of 20% carboxyhemoglobin. A flt surgeon reported that this percentage could cause a headache, a state of confusion, dizziness and visual disturbance. The investigation did not determine if the acft heater system could have been the source of carbon monoxide.