NTSB Probable Cause

FUEL CONTAMINATION BY WATER DUE TO THE; 1) FAILURE OF THE FUEL CAPS TO PROPERLY SEAL AGAINST WATER INGESTION, 2) THE PILOTS FAILURE TO ADEQUATELY PERFORM A PREFLIGHT INSPECTION OF THE AIRCRAFT SUFFICIENT TO DETECT THE PRESENCE OF WATER IN THE FUEL TANKS. FACTORS IN THE ACCIDENT WERE THE INADEQUATE FUEL CAP/WELL DESIGN BY THE MANUFACTURER AND THE PILOTS REDUCED ABILITY TO VISUALLY SEE AND AVOID THE POWER POLE DUE TO THE PREVAILING LIGHT CONDITIONS.