Narrative:

Scheduled flight from jfk to hou in a centerline thrust medium large transport, about 2 hours after takeoff, cruising at 35000 ft at mach .75 in smooth air, a sudden small jolt was felt throughout the aircraft. A passenger in a first class window seat on left side reported it sounded like something fell loudly in cargo compartment, under floor. There were no other abnormal indications. I thought maybe we had struck a WX balloon, or just maybe we were hit by remote chance by returning space debris. We landed normally. I had the forward cargo compartment immediately checked for a possible culprit with no results. Then on the external walkaround I noticed that on the left side the forward lavatory service door was leaking, and there were long, light blue stains along the fuselage glistening and still wet, from the lavatory service door along and up over the wing. I requested a mechanic to chkout the engines for compressor damage. Standing on the ramp with the first officer discussing the situation he mentioned the further possibility of it hitting the tail. It was then we saw it. Dimly illuminated in the terminal lights, a dent in the leading edge of the horizontal stabilizer on the opposite side from the lavatory door. Closer inspection showed it to be about 2 ft across, starting about 3 ft out from the vertical stabilizer. It had hit on a rib and tore the skin along side. Clearly the forward lavatory fluid leaked and built up a glob of ice which eventually was large enough to tear off, maybe impinging on the fuselage near that first class seat. If the aerodynamics of the glob had been different, it might have destroyed an engine. What also alarms me is how I missed seeing the damage to the stabilizer on the walkaround, except it was night, and one does not normally expect to have to give a close inspection to that high tail plane for damage on 'through flight' walkarounds. Recommend 1. Ensure forward lavatory service areas not leaking. (2. Maybe fund a study of glob aerodynamics with a view to controling same!) 'the culprit had flown, but not without leaving a trace!'

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Original NASA ASRS Text

Title: LEAKING FLUID FROM LAVATORY SVC DOOR CAUSES 'BLUE ICE' ACCUMULATION WHICH BREAKS OFF DURING FLT AND CAUSES SIGNIFICANT DAMAGE TO LEADING EDGE OF ACFT'S HORIZ STABILIZER.

Narrative: SCHEDULED FLT FROM JFK TO HOU IN A CTRLINE THRUST MLG, ABOUT 2 HRS AFTER TKOF, CRUISING AT 35000 FT AT MACH .75 IN SMOOTH AIR, A SUDDEN SMALL JOLT WAS FELT THROUGHOUT THE ACFT. A PAX IN A FIRST CLASS WINDOW SEAT ON L SIDE RPTED IT SOUNDED LIKE SOMETHING FELL LOUDLY IN CARGO COMPARTMENT, UNDER FLOOR. THERE WERE NO OTHER ABNORMAL INDICATIONS. I THOUGHT MAYBE WE HAD STRUCK A WX BALLOON, OR JUST MAYBE WE WERE HIT BY REMOTE CHANCE BY RETURNING SPACE DEBRIS. WE LANDED NORMALLY. I HAD THE FORWARD CARGO COMPARTMENT IMMEDIATELY CHKED FOR A POSSIBLE CULPRIT WITH NO RESULTS. THEN ON THE EXTERNAL WALKAROUND I NOTICED THAT ON THE L SIDE THE FORWARD LAVATORY SVC DOOR WAS LEAKING, AND THERE WERE LONG, LIGHT BLUE STAINS ALONG THE FUSELAGE GLISTENING AND STILL WET, FROM THE LAVATORY SVC DOOR ALONG AND UP OVER THE WING. I REQUESTED A MECH TO CHKOUT THE ENGS FOR COMPRESSOR DAMAGE. STANDING ON THE RAMP WITH THE FO DISCUSSING THE SITUATION HE MENTIONED THE FURTHER POSSIBILITY OF IT HITTING THE TAIL. IT WAS THEN WE SAW IT. DIMLY ILLUMINATED IN THE TERMINAL LIGHTS, A DENT IN THE LEADING EDGE OF THE HORIZ STABILIZER ON THE OPPOSITE SIDE FROM THE LAVATORY DOOR. CLOSER INSPECTION SHOWED IT TO BE ABOUT 2 FT ACROSS, STARTING ABOUT 3 FT OUT FROM THE VERT STABILIZER. IT HAD HIT ON A RIB AND TORE THE SKIN ALONG SIDE. CLRLY THE FORWARD LAVATORY FLUID LEAKED AND BUILT UP A GLOB OF ICE WHICH EVENTUALLY WAS LARGE ENOUGH TO TEAR OFF, MAYBE IMPINGING ON THE FUSELAGE NEAR THAT FIRST CLASS SEAT. IF THE AERODYNAMICS OF THE GLOB HAD BEEN DIFFERENT, IT MIGHT HAVE DESTROYED AN ENG. WHAT ALSO ALARMS ME IS HOW I MISSED SEEING THE DAMAGE TO THE STABILIZER ON THE WALKAROUND, EXCEPT IT WAS NIGHT, AND ONE DOES NOT NORMALLY EXPECT TO HAVE TO GIVE A CLOSE INSPECTION TO THAT HIGH TAIL PLANE FOR DAMAGE ON 'THROUGH FLT' WALKAROUNDS. RECOMMEND 1. ENSURE FORWARD LAVATORY SVC AREAS NOT LEAKING. (2. MAYBE FUND A STUDY OF GLOB AERODYNAMICS WITH A VIEW TO CTLING SAME!) 'THE CULPRIT HAD FLOWN, BUT NOT WITHOUT LEAVING A TRACE!'

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.