20030401005799I

(-23) ON APRIL 1, 2003, AIRCRAFT N175UA, OPERATING AS UA FLT 896-1 HKG TO ORD DECLARED AN EMERGENCY ON DESCENT AND APPROACH INTO ORD DUE TO A RESTRICTION IN THE ABILITY TO ROLL THE AIRPLANE TO THE LEFT WITH THE CONTROL WHEE. THE CREW WAS CLEARED FOR A LONG STRAIGHT IN APPROACH TO RUNWAY 14R AND HAD AN UNEVENTFUL LANDING AND ROLLOUT. AFTER TAXIING INTO THE GATE, THE CREW WAS ABLE TO OPERATE THE CONTROL WHEEL IN BOTH DIRECTIONS WITH NO RESTRICTIONS. ABOUT 4 HOURS OUTSIDE OF ORD THEY NOTED THAT THEIR PORTABLE WATER TANKS WERE EMPTY AND THAT WATER WAS DRAINING INTO THE PASSENGER CABIN FROM THE CEILING ALONG THE RIGHT HAND AISLE, BETWEEN DOORS 2R AND 3R. UPON PARKING AT THE GATE, THE AIRCRAFT HAD A SIGNIFICANT AMOUNT OF WATER DRAINING FROM THE FUSELAGE DRAIN MASTS AND THE MAIN DECK FLOOR BETWEEN DOOR 2R AND 3R WAS COMPLETELY SATURATED. THE UPPER DECK CART LIFT SHAFT HAD WATER ALONG THE BASE ON THE MAIN DECK. ONCE THE AIRCRAFT ARRIVED IN THE HANGAR, THE TROUBLESHOOTING PLAN FOCUSED ON THE POSSIBILITY THAT THE AILERON CONTROL EVENT AND THE WATER DRAINAGE ISSUE COULD BE RELATED. IT WAS THEORIZED THAT THIS COULD HAVE BEEN THE RESULT OF WATER FREEZING ON THE AILERON CONTROL CABLES IN THE MAIN LANDING GEAR WHEEL WELL, BASED ON SIMILAR IN-FLIGHT EVENTS FROM OTHER OPERATORS AS PER BOEING SERVICE BULLETIN 747-51A2057, INSPECTION OF THE "CANTED PRESSURE DECK DRAINAGE SYSTEM." DURING THE ISOLATION AND TROUBLESHOOTING OF A POSSIBLE WATER LEAK IN THE PASSENGER CABIN AREA AND THE UPPER DECK GALLEY, THE FOLLOWING CIRCUIT BREAKERS ON THE P414 PANEL IN THE E&E (ELECTRICAL/ELECTRONIC COMPARTMENT) WERE FOUND OPEN AND NOT TAGGED: 1. 414L22 FWD DRAIN MAST HEATER AIR MODE 2. 414L23 CENTER DRAIN MAST HEATER AIR MODE 3. 414L24 AFT DRAIN MAST HEATER AIR MODE 4. 414C21 DRAIN MAST HEATER GROUND MODE THE ABOVE NOTED CIRCUIT BREAKERS WERE PULLED AS PART OF A MAINTENANCE TASK TO SUPPORT THE CLEANING OF THE OVERBOARD DRAIN LINES TO THE AIRCRAFT EXTERIOR DRAIN MAST. THIS WAS ACCOMPLISHED AT HKG (HONG KONG) ON MARCH 31, 2003. DURING THE SUBSEQUENT TROUBLESHOOTING BY MAINTENANCE AND ENGINEERING IT WAS NOTED THAT WHEN THE DRAIN MASTS WERE PLUGGED (SIMULATING A FROZEN CONDITION), WATER BACKED UP THROUGH THE UPPER DECK GALLEY CHILLER DRAIN AND BEGAN TO OVERFLOW INTO THE CABIN THROUGH THE CEILING PANELS ALONG THE RIGHT HAND AISLE IN BUSINESS CLASS. THIS WATER WOULD EVENTUALLY WORK ITS WAY DOWN TO THECENTER FUSELAGE UNDER FLOOR AREA AND INTO THE CANTED PRESSURE DECK AREA THAT ALSO SERVES LIKE A SUMP AREA. IN ADDITION DURING THE INSPECTION AND TROUBLESHOOTING, THE MAIN LANDING GEAR WHEEL WELL DRAINS THAT LEAD FROM THE CANTED PRESSURE DECK AREA WERE FOUND TO BE CLEAN AND CLEAR BUT A 6" X 0.125" GAP WAS FOUND ON THE RIGHT SIDE ALONG THE OUTBOARD EDGE OF THE CANTED PRESSURE BULKHEAD PANEL AT RBL 100. THIS GAP WAS DUE TO A LACK OF SEALANT AND WOULD ALLOW ANY ACCUMULATED WATER TO BE FORCED OUT BY CABIN PRESSURE. ONCE FORCED OUT AS A SPRAY INTO THE RIGHT WHEEL WELL, THE WATER WOULD COAT AND FREEZE ON THE AILERON CONTROL CABLES THAT ARE POSITIONED ON THE AFT SIDE OF THIS BULKHEAD PANEL. MAINTENANCE SUBSEQUENTLY RESEALED THE CANTED PRESSURE BULKHEAD AT RBL 100, WHICH WAS DETERMINED TO BE THE REASON FOR WATER SPRAYING ONTO THE AILERON CABLES. THE DRAIN MAST CIRCUIT BREAKERS WERE ALSO RESET AND NO LEAKS WERE EVER FOUND IN THE POTABLE WATER SYSTEM TO EXPLAIN WHY THE TANKS WERE EMPTY AS ORIGINALLY NOTED BY THE AIRCREW. MAINTENANCE AND ENGINEERING SPECULATE THAT THE TANKS MAY NOT HAVE BEEN FULL TO BEGIN WITH AND THE REMAINING WATER WAS CONSUMED NORMALLY. IN CONCLUSION THE AIRCRAFT WAS RETURNED TO ITS NORMAL CONFIGURATION AND A VERIFICATION TEST FLIGHT WAS FLOWN ON APRIL 4, 2003. THE AIRCRAFT WAS FLOWN FOR 3 HOURS WITH MINIMUM CONTROL INPUTS ON A CONSTANT HEADING FOR AN APPROXIMATE SIMULATION OF THE ORIGINAL PROBLEM FLIGHT. THE TEST FLIGHT WAS SATISFACTORY WITH NO DISCREPANCIES NOTED. AS TO THE PROBLEM OF THE DRAIN MAST CIRCUIT BREAKERS,^PRIVACY DATA OMITTED^