Accident Overview
During an early morning night flight, the aircraft encountered deteriorating weather conditions at the destination, characterized by a low overcast ceiling and rapidly decreasing visibility due to fog. The airplane was cleared for the RNAV (GPS) Runway 18 instrument approach. The approach minimum visibility was 7/8 of a mile.
Weather Conditions
A few minutes before the scheduled arrival time, the weather changed from clear with 10 statute miles visibility to 300 ft overcast with 3/4 statute miles visibility. Within the next 20 minutes, visibility further decreased to about 1/2 statute mile with fog.
Approach and Descent
During the first approach, on final, the pilot executed a missed approach and requested to attempt another instrument approach. On the second approach, while on final, the pilot failed to maintain a stabilized approach; the airplane's descent rate and airspeed were excessive. Subsequently, the airplane descended below the decision altitude without appropriate visual references and impacted terrain approximately 810 ft short of the runway threshold. The circumstances of the accident were consistent with controlled flight into terrain.
Postaccident Examination
Postaccident examination of the airplane and engines revealed no evidence of mechanical failures or malfunctions that would have precluded normal operation.
Toxicology Findings
The pilot had very low levels of ethanol detected in postmortem vitreous fluid and cavity blood. Some or all of this small amount may have been from sources other than alcohol consumption. Although it is uncertain whether the pilot consumed alcohol overnight, it is unlikely that the pilot’s performance was significantly affected by ethanol. The copilot’s ethanol levels were high in all tested postmortem specimens. Based on toxicology results and circumstances, it is likely that the copilot had consumed alcohol. However, due to the extent of his injuries, presence of microbial decomposition indicators, and relative differences in ethanol levels across specimens, some of the detected ethanol was likely from other sources. The copilot’s blood alcohol level at the time of the crash could not be reliably determined. Alcohol-related impairment may have limited the copilot’s ability to make a positive contribution to flight safety, but whether alcohol use by the copilot contributed to the accident could not be determined.