AFTER TAKEOFF FM THE PRIVATE AIRSTRIP NEAR GOVE, KANSAS, THE AIRCRAFT WAS WITNESSED TO DESCEND TOWARDS THE GROUND UNTIL IMPACT. THE WITNESS TO THE ACCIDENT, WHO IS A PLT AND THE OWNER OF THE AIRSTRIP, STATED THAT AFTER THE ACFT CLRD THE AIRSTRIP ENVIRONMENT WHICH WAS WELL LIT, THE ACFT WAS SEEN MAKING A TURN AND DESCENDING. THE WITNESS STATED THAT AFTER YOU LEAVE THE LIGHTED AREA OF THE AIRSTRIP IT BECOMES EXTREMELY DARK AND HORIZON REFERENCES ARE LOST AND HE THOUGHT THAT THE PLT PROBABLY EXPERIENCED A LOSS OF VISUAL CUES AND FLEW THE ACFT INTO THE GROUND. THE WITNESS STATED THAT ON NIGHT DEPARTURES FROM THAT AIRSTRIP, HE HAS HAD TO FLY HIS ACFT SOLELY BY REFERENCE TO INSTRUMENTS, BECAUSE OF THE LACK OF VISUAL CUES ON THE HORIZON. NEITHER THE PLT OR WITNESS INDICATED THERE WAS ANY PROBLEM WITH THE ACFT DURING ANY PHASE OF THE FLT. THE PLT WAS UNABLE TO REMEMBER ANYTHING AFTER DEPARTING AND CLEARING ALL OBSTACLES NEAR THE AIRSTRIP.