Narrative:

Upon arriving at the aircraft for preflight; I became aware that we had a #2 tank fuel quantity problem. The gauge indicated 13.9K pounds which was correct for the flight planned load. All fueling paperwork checked good. When the test button for the gauge was depressed everything checked fine except a soft error code was present. Maintenance was called and the MEL was checked. Maintenance person followed the MEL procedures which stated that for 'digital indicator error codes...a. Any error code with gauge display normal: gauge is operative; no further action needed.' the MEL further states '2. See B-727 QRH for fuel indicator error codes.' the B-727 QRH says 'when an error is sensed in a tank quantity indicating system; the quantity indicator will display an appropriate numerical err code. If the system fault disappears; the err code is removed and normal quantity display resumes. Some of the fault codes represent an inoperative system; while others represent an operative system. Whenever the indicator displays a normal display with an error code; the system is operative and requires no dispatch penalties. Whenever the fuel indicator displays a zero with any error code; the system is inoperative. A soft error allows the indicator to continue functioning with a degraded accuracy of + or - 3%. Normal operations may continue. Make a maintenance log entry stating; fuel indicator error tank no. ____.' The gauge display was normal. Maintenance made the entry in the open item list of the maintenance log and the gauge was determined to be operative; no further action...in accordance with MEL. Takeoff was normal; and I was unaware of any further problems until prior to descent. Approximately 100 miles from destination; two low pressure fuel boost pump lights in the #2 tank illuminated followed by a third light. The QRH was consulted and procedures followed. We requested a descent below FL260 and set up crossfeed to #2 engine. A few isolated thundershowers and circuit breaker's in the arrival area. No factor. We conducted a visual approach to runway 01L at ZZZ; and landed with no incident. I think the wing tanks indicated approximately 16.0K pounds of fuel at block in. Maintenance personnel at ZZZ measured the fuel in #2 tank and it was found to be virtually dry. No engines flamed out; and no emergencies were declared. MEL procedures were followed verbatim.supplemental information from acn 784516: after my arrival to the aircraft during a check of the aircraft systems; one of the fuel gauges indicated a 'soft error code' but otherwise appeared to be indicating normally. Maintenance was called and agreed the gauge was indicating normally. An aircraft logbook entry was made according to my company's MEL procedures and the flight departed. During the climb; the quantity in the gauge began to fluctuate our presumed amount of fuel and around 4000 pounds. A fuel log was begun according to company procedures. We leveled at FL320. Approximately 20 minutes later one of the aft boost pump lights came on; followed by the other one. Now the amount of fuel indicated less than 3000 pounds steadily. The entire crew was thinking a fuel leak was a possibility. The crew decided to descend to FL240 to guarantee the flow of fuel to the engine in the event all the boost pumps failed. Level at FL240; we determined that there was not a fuel leak based on the amount of fuel burned out of tanks 1 and 3 with all of the fuel crossfeeds open. The third (forward) boost pump light illuminated in the descent. The amount of fuel indicated in the #2 tank was less than 1000 pounds. After landing; the #2 tank indicated about 300 pounds of fuel. Another aircraft logbook entry was made. Maintenance at our destination attempted to pump out all of the fuel out of the #2 tank according to their procedures. There was no fuel in the tank. The gauge failed from the time the aircraft blocked in with the previous crew; to the time the fuelers showed up to fuel our flight. Since the gauge failed between the flts; the amount of fuel that showed on the fuel ticket versus the number of gallons pumped checked out correctly. I could not find a fuel ticket from the inbound crew and the fuel ticket for my flight had a notation that the fueler could not find the fuel ticket either. The maintenance procedures have been changed. Any fuel gauge with a 'soft error code' will make the gauge inoperative requiring the more rigorous fueling procedures.supplemental information from acn 784517: I arrived at the aircraft with a student for a line check. At 1000 ft AGL; we went tank to engine and landed with all low pressure boost pump lights on. The error requires new procedures for maintenance so this will not occur again. Supplemental information from acn 784518: #2 gauge must have been off at this time as the fueler filled #2 tank to about 6500 pounds; not 14000 pounds.callback conversation with reporter 784448 revealed the following information: reporter stated the cause of these soft error codes has not been determined at this time. The # 2 fuel tank has two fwd and two aft fuel boost pumps. Reporter stated he felt something was seriously wrong; when they noticed the # 2 fuel tank boost pump low pressure lights come on at cruise level attitude. He was very concerned about the #2 engine flaming out inflight for lack of fuel or serious fuel leak. Reporter stated he has been told the MEL maintenance procedure is being changed to address the soft code indication issue and preventing any further low fuel loads under their MEL.

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Original NASA ASRS Text

Title: A B727-200 ACFT #2 FUEL TANK HAS A 'SOFT' DIGITAL FUEL INDICATOR ERROR CODE FOR TANK #2 WHICH WAS ACCEPTABLE PER MEL FOR DISPATCH. ACFT LANDED WITH THREE FUEL BOOST PUMP LOW PRESS LIGHTS ON; AND TANK #2 VIRTUALLY DRY.

Narrative: UPON ARRIVING AT THE AIRCRAFT FOR PREFLT; I BECAME AWARE THAT WE HAD A #2 TANK FUEL QUANTITY PROBLEM. THE GAUGE INDICATED 13.9K LBS WHICH WAS CORRECT FOR THE FLIGHT PLANNED LOAD. ALL FUELING PAPERWORK CHECKED GOOD. WHEN THE TEST BUTTON FOR THE GAUGE WAS DEPRESSED EVERYTHING CHECKED FINE EXCEPT A SOFT ERROR CODE WAS PRESENT. MAINT WAS CALLED AND THE MEL WAS CHECKED. MAINT PERSON FOLLOWED THE MEL PROCEDURES WHICH STATED THAT FOR 'DIGITAL INDICATOR ERROR CODES...A. ANY ERROR CODE WITH GAUGE DISPLAY NORMAL: GAUGE IS OPERATIVE; NO FURTHER ACTION NEEDED.' THE MEL FURTHER STATES '2. SEE B-727 QRH FOR FUEL INDICATOR ERROR CODES.' THE B-727 QRH SAYS 'WHEN AN ERROR IS SENSED IN A TANK QUANTITY INDICATING SYSTEM; THE QUANTITY INDICATOR WILL DISPLAY AN APPROPRIATE NUMERICAL ERR CODE. IF THE SYSTEM FAULT DISAPPEARS; THE ERR CODE IS REMOVED AND NORMAL QUANTITY DISPLAY RESUMES. SOME OF THE FAULT CODES REPRESENT AN INOPERATIVE SYSTEM; WHILE OTHERS REPRESENT AN OPERATIVE SYSTEM. WHENEVER THE INDICATOR DISPLAYS A NORMAL DISPLAY WITH AN ERROR CODE; THE SYSTEM IS OPERATIVE AND REQUIRES NO DISPATCH PENALTIES. WHENEVER THE FUEL INDICATOR DISPLAYS A ZERO WITH ANY ERROR CODE; THE SYSTEM IS INOPERATIVE. A SOFT ERROR ALLOWS THE INDICATOR TO CONTINUE FUNCTIONING WITH A DEGRADED ACCURACY OF + OR - 3%. NORMAL OPERATIONS MAY CONTINUE. MAKE A MAINT LOG ENTRY STATING; FUEL INDICATOR ERROR TANK NO. ____.' THE GAUGE DISPLAY WAS NORMAL. MAINT MADE THE ENTRY IN THE OPEN ITEM LIST OF THE MAINT LOG AND THE GAUGE WAS DETERMINED TO BE OPERATIVE; NO FURTHER ACTION...IAW MEL. TAKEOFF WAS NORMAL; AND I WAS UNAWARE OF ANY FURTHER PROBLEMS UNTIL PRIOR TO DESCENT. APPROX 100 MILES FROM DESTINATION; TWO LOW PRESSURE FUEL BOOST PUMP LIGHTS IN THE #2 TANK ILLUMINATED FOLLOWED BY A THIRD LIGHT. THE QRH WAS CONSULTED AND PROCEDURES FOLLOWED. WE REQUESTED A DESCENT BELOW FL260 AND SET UP CROSSFEED TO #2 ENGINE. A FEW ISOLATED THUNDERSHOWERS AND CB'S IN THE ARRIVAL AREA. NO FACTOR. WE CONDUCTED A VISUAL APPROACH TO RUNWAY 01L AT ZZZ; AND LANDED WITH NO INCIDENT. I THINK THE WING TANKS INDICATED APPROX 16.0K LBS OF FUEL AT BLOCK IN. MAINT PERSONNEL AT ZZZ MEASURED THE FUEL IN #2 TANK AND IT WAS FOUND TO BE VIRTUALLY DRY. NO ENGINES FLAMED OUT; AND NO EMERGENCIES WERE DECLARED. MEL PROCEDURES WERE FOLLOWED VERBATIM.SUPPLEMENTAL INFO FROM ACN 784516: AFTER MY ARRIVAL TO THE ACFT DURING A CHK OF THE ACFT SYSTEMS; ONE OF THE FUEL GAUGES INDICATED A 'SOFT ERROR CODE' BUT OTHERWISE APPEARED TO BE INDICATING NORMALLY. MAINT WAS CALLED AND AGREED THE GAUGE WAS INDICATING NORMALLY. AN ACFT LOGBOOK ENTRY WAS MADE ACCORDING TO MY COMPANY'S MEL PROCS AND THE FLT DEPARTED. DURING THE CLB; THE QUANTITY IN THE GAUGE BEGAN TO FLUCTUATE OUR PRESUMED AMOUNT OF FUEL AND AROUND 4000 LBS. A FUEL LOG WAS BEGUN ACCORDING TO COMPANY PROCS. WE LEVELED AT FL320. APPROX 20 MINUTES LATER ONE OF THE AFT BOOST PUMP LIGHTS CAME ON; FOLLOWED BY THE OTHER ONE. NOW THE AMOUNT OF FUEL INDICATED LESS THAN 3000 POUNDS STEADILY. THE ENTIRE CREW WAS THINKING A FUEL LEAK WAS A POSSIBILITY. THE CREW DECIDED TO DESCEND TO FL240 TO GUARANTEE THE FLOW OF FUEL TO THE ENGINE IN THE EVENT ALL THE BOOST PUMPS FAILED. LEVEL AT FL240; WE DETERMINED THAT THERE WAS NOT A FUEL LEAK BASED ON THE AMOUNT OF FUEL BURNED OUT OF TANKS 1 AND 3 WITH ALL OF THE FUEL CROSSFEEDS OPEN. THE THIRD (FORWARD) BOOST PUMP LIGHT ILLUMINATED IN THE DESCENT. THE AMOUNT OF FUEL INDICATED IN THE #2 TANK WAS LESS THAN 1000 LBS. AFTER LANDING; THE #2 TANK INDICATED ABOUT 300 POUNDS OF FUEL. ANOTHER ACFT LOGBOOK ENTRY WAS MADE. MAINT AT OUR DEST ATTEMPTED TO PUMP OUT ALL OF THE FUEL OUT OF THE #2 TANK ACCORDING TO THEIR PROCS. THERE WAS NO FUEL IN THE TANK. THE GAUGE FAILED FROM THE TIME THE ACFT BLOCKED IN WITH THE PREVIOUS CREW; TO THE TIME THE FUELERS SHOWED UP TO FUEL OUR FLT. SINCE THE GAUGE FAILED BETWEEN THE FLTS; THE AMOUNT OF FUEL THAT SHOWED ON THE FUEL TICKET VERSUS THE NUMBER OF GALLONS PUMPED CHECKED OUT CORRECTLY. I COULD NOT FIND A FUEL TICKET FROM THE INBOUND CREW AND THE FUEL TICKET FOR MY FLT HAD A NOTATION THAT THE FUELER COULD NOT FIND THE FUEL TICKET EITHER. THE MAINT PROCS HAVE BEEN CHANGED. ANY FUEL GAUGE WITH A 'SOFT ERROR CODE' WILL MAKE THE GAUGE INOP REQUIRING THE MORE RIGOROUS FUELING PROCS.SUPPLEMENTAL INFO FROM ACN 784517: I ARRIVED AT THE ACFT WITH A STUDENT FOR A LINE CHK. AT 1000 FT AGL; WE WENT TANK TO ENGINE AND LANDED WITH ALL LOW PRESSURE BOOST PUMP LIGHTS ON. THE ERROR REQUIRES NEW PROCS FOR MAINT SO THIS WILL NOT OCCUR AGAIN. SUPPLEMENTAL INFO FROM ACN 784518: #2 GAUGE MUST HAVE BEEN OFF AT THIS TIME AS THE FUELER FILLED #2 TANK TO ABOUT 6500 LBS; NOT 14000 LBS.CALLBACK CONVERSATION WITH RPTR 784448 REVEALED THE FOLLOWING INFO: REPORTER STATED THE CAUSE OF THESE SOFT ERROR CODES HAS NOT BEEN DETERMINED AT THIS TIME. THE # 2 FUEL TANK HAS TWO FWD AND TWO AFT FUEL BOOST PUMPS. REPORTER STATED HE FELT SOMETHING WAS SERIOUSLY WRONG; WHEN THEY NOTICED THE # 2 FUEL TANK BOOST PUMP LOW PRESSURE LIGHTS COME ON AT CRUISE LEVEL ATTITUDE. HE WAS VERY CONCERNED ABOUT THE #2 ENG FLAMING OUT INFLIGHT FOR LACK OF FUEL OR SERIOUS FUEL LEAK. REPORTER STATED HE HAS BEEN TOLD THE MEL MAINT PROCEDURE IS BEING CHANGED TO ADDRESS THE SOFT CODE INDICATION ISSUE AND PREVENTING ANY FURTHER LOW FUEL LOADS UNDER THEIR MEL.

Data retrieved from NASA's ASRS site as of May 2009 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.