THE ACFT WAS SEEN BY WITNESSES IN A DIVE FROM APRX 1000 FT AGL. IT APPEARED TO NOT CHANGE ATTITUDE NOR WAIVER AS IT CONTINUED TOWARD THE GRND. IMPACT WITH THE GRND OCCURRED WITH THE WINGS LEVEL IN APRX 15 DEG DIVE ON A HDG OF 118 DEGREES. A MARK ON THE A/S INDICATOR INDICATED 194 KTS IAS AT IMPACT. INVEST AFTER THE ACCIDENT REVEALED NO FAILURE OR MALFUNCTION IN EQUIP EXCEPT DIFFICULTIES IN USING ALT MODE OF THE AUTO-PLT. THIS EQUIP WAS NOTED AS UNRELIABLE AND NOT TO BE USED. THRU INTERVIEWS IT WAS DETERMINED THAT THE PLT HAD INJURED HIS LEG 5 DAYS BEFORE THE ACCIDENT WHILE DEPLANING IN OZONA, TX. THE RT SHIN LACERATION WAS ABOUT 3 INCHES LONG REQUIRING SEVERAL SUTURES FOR CLOSING. DURING AUTOPSY THE WOUND WAS FOUND OPEN AND BLOODY BANDAGES FOUND IN THE PLANE WRECKAGE SUGGESTS THAT THE WOUND HAD REOPENED IN FLT. THE ONLY OTHER SIGNIFICANT FINDINGS OF THE AUTOPSY WAS THE ABSENCE OF BROKEN BONES IN THE HANDS & WRISTS. IN DISCUSSIONS WITH THE PLTS WIFE SHE SAID THAT SHE OBSERVED THE BANDAGED AREA BEFORE THE FLT AS BEING CLEAN & NOT BLOODY.