Narrative:

I was second officer on flight from sydney, australia to hnl. During flight, the F/a's several times reported a 'thunking noise,' loud at times, from the vicinity of door 2L (just ahead of left wing). I visited the area several times during the flight, but never heard the noise nor could find anything unusual from a visibility inspection. After landing, it was found that the left inboard slat had a basketball sized hole in it approximately 1 1/2' outboard of wing root. At least 3 slat ribs were damaged, but the slat spar appeared intact and, to our knowledge, the slat functioned normally during approach and landing. It was determined that potable water leaking from the potable water fill port on left side of fuselage approximately 30' forward of wing root was forming ice chunks and breaking off during flight and striking the slat leading edge. Water was leaking in a steady stream from the port, even 1 hour after landing. During preflight walkaround in syd I had noticed the area around the fill port and ground under it to be wet, but assumed that the aircraft had recently been serviced and did not call maintenance. It is not uncommon to see water from overfills in that area. During flight, all 3 of us in the cockpit thought that the most probable cause of the noise was a cargo pallet shifting in the forward cargo hold. There were no injuries or use of abnormal procedures during this incident. Contributing factor: aircraft design that put fill port in line with wing leading edge.

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Original NASA ASRS Text

Title: LEAK IN POTABLE WATER SYSTEM ON ACR WDB ON OVERWATER PACIFIC FLT LEADS TO EXTERNAL ICE CHUNK FORMATION AT CRUISE AND SUBSEQUENT AIRFRAME DAMAGE.

Narrative: I WAS S/O ON FLT FROM SYDNEY, AUSTRALIA TO HNL. DURING FLT, THE F/A'S SEVERAL TIMES RPTED A 'THUNKING NOISE,' LOUD AT TIMES, FROM THE VICINITY OF DOOR 2L (JUST AHEAD OF LEFT WING). I VISITED THE AREA SEVERAL TIMES DURING THE FLT, BUT NEVER HEARD THE NOISE NOR COULD FIND ANYTHING UNUSUAL FROM A VIS INSPECTION. AFTER LNDG, IT WAS FOUND THAT THE LEFT INBOARD SLAT HAD A BASKETBALL SIZED HOLE IN IT APPROX 1 1/2' OUTBOARD OF WING ROOT. AT LEAST 3 SLAT RIBS WERE DAMAGED, BUT THE SLAT SPAR APPEARED INTACT AND, TO OUR KNOWLEDGE, THE SLAT FUNCTIONED NORMALLY DURING APCH AND LNDG. IT WAS DETERMINED THAT POTABLE WATER LEAKING FROM THE POTABLE WATER FILL PORT ON LEFT SIDE OF FUSELAGE APPROX 30' FORWARD OF WING ROOT WAS FORMING ICE CHUNKS AND BREAKING OFF DURING FLT AND STRIKING THE SLAT LEADING EDGE. WATER WAS LEAKING IN A STEADY STREAM FROM THE PORT, EVEN 1 HR AFTER LNDG. DURING PREFLT WALKAROUND IN SYD I HAD NOTICED THE AREA AROUND THE FILL PORT AND GND UNDER IT TO BE WET, BUT ASSUMED THAT THE ACFT HAD RECENTLY BEEN SERVICED AND DID NOT CALL MAINT. IT IS NOT UNCOMMON TO SEE WATER FROM OVERFILLS IN THAT AREA. DURING FLT, ALL 3 OF US IN THE COCKPIT THOUGHT THAT THE MOST PROBABLE CAUSE OF THE NOISE WAS A CARGO PALLET SHIFTING IN THE FORWARD CARGO HOLD. THERE WERE NO INJURIES OR USE OF ABNORMAL PROCS DURING THIS INCIDENT. CONTRIBUTING FACTOR: ACFT DESIGN THAT PUT FILL PORT IN LINE WITH WING LEADING EDGE.

Data retrieved from NASA's ASRS site as of July 2007 and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.