Narrative:

Had been in cruise for 1 1/2 hours. PIC noticed what was first perceived to be water dripping from underneath copilot's INS panel. Touching and smelling liquid revealed it was fuel. With a small puddle of fuel on the floor already, an emergency was initiated (7700 on squawk) and an emergency descent and VOR-C approach was accomplished into st george airport. Ice accumulation on descent melted at about 8000' MSL. Boost pumps were left off and flaps left up during landing to avoid further fire hazard (flaps microswitch operated and boost pump would cause greater fuel leakage). Uneventful landing made at st george. Upon post-flight investigation, following factors and causes were found. Aircraft sat for 1-2 days in rain in south calif, loading airframe with moisture. Condensation was noticed on windshield before takeoff. Upon reaching FL230 heater failed. Shortly thereafter, moisture condensed on the INS panel and gauges (noticed in flight), and on the back of the gauges in the panel. The fuel pressure gauges (located on copilot's panel) were found to have ice on the back of the gauge and and on the low pressure fuel lines to the gauge. While these lines were cold and ice was present, fuel would leak from the right hand gauge line when pulled or pushed with a side load. PIC feels that water soaked the b-nut and nipple assembly on the end of this line. When cold temperatures were reached, they added inflexibility of the line (at cold temperatures) and ice forming between the b-nut and line sleeve opened a path for fuel to escape by the sleeve at a rate of 3-5 drops per second. Leak stopped when lines warmed to above freezing. PIC suggests replacing fuel pressure gauge lines with new every 5 yrs or replacing the existing low pressure type lines wit high pressure type which are of a heavier construction.

Google
 

Original NASA ASRS Text

Title: FUEL LEAKING INTO COCKPIT OF SMT AT FL230. FLT CREW DECLARED EMERGENCY AND LANDED SGU.

Narrative: HAD BEEN IN CRUISE FOR 1 1/2 HRS. PIC NOTICED WHAT WAS FIRST PERCEIVED TO BE WATER DRIPPING FROM UNDERNEATH COPLT'S INS PANEL. TOUCHING AND SMELLING LIQUID REVEALED IT WAS FUEL. WITH A SMALL PUDDLE OF FUEL ON THE FLOOR ALREADY, AN EMER WAS INITIATED (7700 ON SQUAWK) AND AN EMER DSNT AND VOR-C APCH WAS ACCOMPLISHED INTO ST GEORGE ARPT. ICE ACCUMULATION ON DSNT MELTED AT ABOUT 8000' MSL. BOOST PUMPS WERE LEFT OFF AND FLAPS LEFT UP DURING LNDG TO AVOID FURTHER FIRE HAZARD (FLAPS MICROSWITCH OPERATED AND BOOST PUMP WOULD CAUSE GREATER FUEL LEAKAGE). UNEVENTFUL LNDG MADE AT ST GEORGE. UPON POST-FLT INVESTIGATION, FOLLOWING FACTORS AND CAUSES WERE FOUND. ACFT SAT FOR 1-2 DAYS IN RAIN IN S CALIF, LOADING AIRFRAME WITH MOISTURE. CONDENSATION WAS NOTICED ON WINDSHIELD BEFORE TKOF. UPON REACHING FL230 HEATER FAILED. SHORTLY THEREAFTER, MOISTURE CONDENSED ON THE INS PANEL AND GAUGES (NOTICED IN FLT), AND ON THE BACK OF THE GAUGES IN THE PANEL. THE FUEL PRESSURE GAUGES (LOCATED ON COPLT'S PANEL) WERE FOUND TO HAVE ICE ON THE BACK OF THE GAUGE AND AND ON THE LOW PRESSURE FUEL LINES TO THE GAUGE. WHILE THESE LINES WERE COLD AND ICE WAS PRESENT, FUEL WOULD LEAK FROM THE RIGHT HAND GAUGE LINE WHEN PULLED OR PUSHED WITH A SIDE LOAD. PIC FEELS THAT WATER SOAKED THE B-NUT AND NIPPLE ASSEMBLY ON THE END OF THIS LINE. WHEN COLD TEMPS WERE REACHED, THEY ADDED INFLEXIBILITY OF THE LINE (AT COLD TEMPS) AND ICE FORMING BTWN THE B-NUT AND LINE SLEEVE OPENED A PATH FOR FUEL TO ESCAPE BY THE SLEEVE AT A RATE OF 3-5 DROPS PER SEC. LEAK STOPPED WHEN LINES WARMED TO ABOVE FREEZING. PIC SUGGESTS REPLACING FUEL PRESSURE GAUGE LINES WITH NEW EVERY 5 YRS OR REPLACING THE EXISTING LOW PRESSURE TYPE LINES WIT HIGH PRESSURE TYPE WHICH ARE OF A HEAVIER CONSTRUCTION.

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.