Narrative:

On a flight from sjc to hio. While climbing through approximately FL310 in the vicinity of rbl VOR, I noticed a fuel imbal of approximately 300 pounds. The left wing had the excess fuel. Both tip tanks were empty. I performed the normal procedures required to balance the fuel by turning the standby fuel pump in the heavy left wing on and opening the xflow valve. After a few mins passed, I noticed that the fuel was not balancing. I checked the fuel panel confign and determined that it was correct. After a few more mins, I noticed that the fuel was still not balanced. I asked the copilot to verify the fuel imbal and to verify that the fuel panel was in the correct confign. He verified that the fuel was out of balance and the fuel panel settings were in the correct position to balance the fuel. I thought that perhaps the standby fuel pump in the left wing was not working. I checked the circuit breaker and it was in. This did not correct the problem. I then asked the copilot to check his circuit breakers. He did. They were all in. At this point I decided to return to hwd, which is our maintenance base. Then I asked the copilot to consult the checklist for fuel abnormalities while I flew the aircraft. He consulted the abnormal checklist for the fuel system. We were approximately 15 mins from hwd. At this point the copilot began working on the fuel situation. The fuel became more unbalanced. There was approximately 900 pounds of fuel in the left wing and 100 pounds in the right wing. At this point I told the copilot to declare an emergency in order to get priority handling back to hwd. The copilot suggested that I use differential power to help balance the fuel. Which I did. He then suggested that he xfer fuel to the fuselage tank in order to lighten the load in the left wing. Which he did. I told the copilot to inform ATC that we would be single engine. He did. We then briefed the single engine landing and consulted the single engine landing checklist. Then I pulled the right engine back to idle. We then asked ATC if we could fly faster than 250 KTS below 10000 ft in order to aid stability and to keep a high power setting on the left engine which would burn more fuel and help the balance. ATC approved this. After this we considered landing at a closer airport. But came to the conclusion that if we flew longer the fuel imbal would lessen and the aircraft would become easier to control. And we were very familiar with hwd and the surrounding area. When we were about 15 mi from hwd, I determined that the aircraft was ctlable enough to land. The right engine did not flame out but we left it in idle for the approach. The landing at hwd was uneventful. My major error was not identing the problem correctly. This led me to not directing the copilot to the proper checklist. There is a checklist for fuel imbal during fuel xfer. I should have been more familiar with the checklist and the fuel system. Another error was when I did not find a checklist for our situation we should have returned the fuel panel to the position it was in before the imbal began getting worse. The corrective action for this would have been to close the xflow valve and turn the left standby pump off. The learjet has a kit available that indicates when the standby pump is receiving power. If our aircraft had this modification we could have idented the problem sooner. I am asking my employer to consider modifying the aircraft with this kit.

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Original NASA ASRS Text

Title: LEARJET CREW HAS MAJOR FUEL IMBAL.

Narrative: ON A FLT FROM SJC TO HIO. WHILE CLBING THROUGH APPROX FL310 IN THE VICINITY OF RBL VOR, I NOTICED A FUEL IMBAL OF APPROX 300 LBS. THE L WING HAD THE EXCESS FUEL. BOTH TIP TANKS WERE EMPTY. I PERFORMED THE NORMAL PROCS REQUIRED TO BAL THE FUEL BY TURNING THE STANDBY FUEL PUMP IN THE HVY L WING ON AND OPENING THE XFLOW VALVE. AFTER A FEW MINS PASSED, I NOTICED THAT THE FUEL WAS NOT BALANCING. I CHKED THE FUEL PANEL CONFIGN AND DETERMINED THAT IT WAS CORRECT. AFTER A FEW MORE MINS, I NOTICED THAT THE FUEL WAS STILL NOT BALANCED. I ASKED THE COPLT TO VERIFY THE FUEL IMBAL AND TO VERIFY THAT THE FUEL PANEL WAS IN THE CORRECT CONFIGN. HE VERIFIED THAT THE FUEL WAS OUT OF BAL AND THE FUEL PANEL SETTINGS WERE IN THE CORRECT POS TO BAL THE FUEL. I THOUGHT THAT PERHAPS THE STANDBY FUEL PUMP IN THE L WING WAS NOT WORKING. I CHKED THE CIRCUIT BREAKER AND IT WAS IN. THIS DID NOT CORRECT THE PROB. I THEN ASKED THE COPLT TO CHK HIS CIRCUIT BREAKERS. HE DID. THEY WERE ALL IN. AT THIS POINT I DECIDED TO RETURN TO HWD, WHICH IS OUR MAINT BASE. THEN I ASKED THE COPLT TO CONSULT THE CHKLIST FOR FUEL ABNORMALITIES WHILE I FLEW THE ACFT. HE CONSULTED THE ABNORMAL CHKLIST FOR THE FUEL SYS. WE WERE APPROX 15 MINS FROM HWD. AT THIS POINT THE COPLT BEGAN WORKING ON THE FUEL SIT. THE FUEL BECAME MORE UNBALANCED. THERE WAS APPROX 900 LBS OF FUEL IN THE L WING AND 100 LBS IN THE R WING. AT THIS POINT I TOLD THE COPLT TO DECLARE AN EMER IN ORDER TO GET PRIORITY HANDLING BACK TO HWD. THE COPLT SUGGESTED THAT I USE DIFFERENTIAL PWR TO HELP BAL THE FUEL. WHICH I DID. HE THEN SUGGESTED THAT HE XFER FUEL TO THE FUSELAGE TANK IN ORDER TO LIGHTEN THE LOAD IN THE L WING. WHICH HE DID. I TOLD THE COPLT TO INFORM ATC THAT WE WOULD BE SINGLE ENG. HE DID. WE THEN BRIEFED THE SINGLE ENG LNDG AND CONSULTED THE SINGLE ENG LNDG CHKLIST. THEN I PULLED THE R ENG BACK TO IDLE. WE THEN ASKED ATC IF WE COULD FLY FASTER THAN 250 KTS BELOW 10000 FT IN ORDER TO AID STABILITY AND TO KEEP A HIGH PWR SETTING ON THE L ENG WHICH WOULD BURN MORE FUEL AND HELP THE BAL. ATC APPROVED THIS. AFTER THIS WE CONSIDERED LNDG AT A CLOSER ARPT. BUT CAME TO THE CONCLUSION THAT IF WE FLEW LONGER THE FUEL IMBAL WOULD LESSEN AND THE ACFT WOULD BECOME EASIER TO CTL. AND WE WERE VERY FAMILIAR WITH HWD AND THE SURROUNDING AREA. WHEN WE WERE ABOUT 15 MI FROM HWD, I DETERMINED THAT THE ACFT WAS CTLABLE ENOUGH TO LAND. THE R ENG DID NOT FLAME OUT BUT WE LEFT IT IN IDLE FOR THE APCH. THE LNDG AT HWD WAS UNEVENTFUL. MY MAJOR ERROR WAS NOT IDENTING THE PROB CORRECTLY. THIS LED ME TO NOT DIRECTING THE COPLT TO THE PROPER CHKLIST. THERE IS A CHKLIST FOR FUEL IMBAL DURING FUEL XFER. I SHOULD HAVE BEEN MORE FAMILIAR WITH THE CHKLIST AND THE FUEL SYS. ANOTHER ERROR WAS WHEN I DID NOT FIND A CHKLIST FOR OUR SIT WE SHOULD HAVE RETURNED THE FUEL PANEL TO THE POS IT WAS IN BEFORE THE IMBAL BEGAN GETTING WORSE. THE CORRECTIVE ACTION FOR THIS WOULD HAVE BEEN TO CLOSE THE XFLOW VALVE AND TURN THE L STANDBY PUMP OFF. THE LEARJET HAS A KIT AVAILABLE THAT INDICATES WHEN THE STANDBY PUMP IS RECEIVING PWR. IF OUR ACFT HAD THIS MODIFICATION WE COULD HAVE IDENTED THE PROB SOONER. I AM ASKING MY EMPLOYER TO CONSIDER MODIFYING THE ACFT WITH THIS KIT.

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.