DEN91FA135

Drg taxi after a x-country flt, a prop blade was nicked by flying gravel. The plt had the prop dressed by a mech, then he made an eng run-up & took off on a test flt. Witnesses rprtd that as the acft was depg, it remained at a lower alt than expected, but the eng sounded smooth. The acft was turned dwnwnd & mnvrd for final apch to the same rwy. However, it overshot the turn & collided with trees at the edge of the clear way about 1200' short of the rwy. The acft remained airborne for about 500', then it collided with the gate of a hi fence, crashed & burned. No preimpact part failure or malfunction, of the acft or eng was fnd, but the mixture ctl was fnd at a mid-range psn, rather than full forward. For takeoffs below 17,000' in this acft, the mixture should have been full rich. The plt had been issued a 3rd class med cert on 3/14/91, but it was rescinded ltr, when a cardiovascular abnormality of the plt was noted. A check of the plt's blood showed a chlorpheniramine (antihistamine) level of 0.073 ug/ml. Density alt was abt 9300'.