What was found
UPON PREFLIGHT OF THE AIRCRAFT, AND AFTER SITTING OUTSIDE OF THE HANGAR DURING A RAINSTORM, 2 TO 3 SUMP GLASSES WERE FILLED WITH WATER FROM EACH WING FUEL TANK SUMP DRAIN. FURTHER INSPECTION OF 9 OTHER AIRCRAFT OF THE SAME MAKE AND MODEL FOUND 2 OTHER AIRCRAFT WITH SIMILAR AMOUNTS OF WATER IN THE SUMP DRAINS. ALL 3 OF THESE AIRCRAFT WERE TIED DOWN OUTSIDE DURING WEATHER ABOVE STATED. INSPECTION OF THE FUEL FILLER FLANGE/CAP ASSEMBLY OF ALL TWELVE AIRCRAFT REVEALED THE SAME LOOSE FUEL CAP CONDITION. ALL AIRCRAFT FUEL CAPS WERE TIGHTEN AS A PRECAUTION. THE O-RING SEALS DID NOT APPEAR TO BE DAMAGED.