Narrative:

While climbing to FL290 through approximately FL180. I noticed a 200 pounds fuel imbal between the left and right wing tank. I attempted to correct by transferring fuel. This did not initially seem to correct the problem. The aircraft started to yaw left and after a period of a few mins I was having to apply a lot of left roll control to hold the aircraft level. I disengaged the autoplt and asked center to block my altitude by 1000 ft above and below. While trying to maintain a level attitude and at the same time find a solution to my out of balance and control problem. My altitude deviated by more than my blocked altitude, however, I felt at the time that it was safer to give up some altitude so as to be able to maintain control of the airplane. The controls were very difficult to move, I believe because of the aerodynamic loads on them. After what seemed like an eternity and after I cycled the fuel xfeed a few times and insured that the aircraft was in proper trim the situation began to be corrected and the aircraft returned to a proper confign and climb profile. I have flown this aircraft for 300 hours within the last 7 months and I have never experienced anything like this before. In fact, in my 27 yrs of flying I have never seen these same conditions before. I still do not know exactly why the aircraft behaved this way. Was it the autoplt mis-trimming? Was it a stuck fuel xfeed valve? Was my initial attempt to correct the fuel imbal improperly executed? I don't know the answers to these questions. As a side note, I personally feel that I would have better roll authority if the aircraft had ailerons as opposed to spoilers. I am still not comfortable with this particular design. I also feel strongly that all aircraft should have manual trimming devices, not just electric trim motors and a button. Callback conversation with reporter revealed the following information: the reporter stated the lateral imbal is still a mystery, whether the problem was fuel or electric trim he still has not been able to resolve. He has not experienced the phenomena again. The first officer and the reporter worked together to resolve the problem. To feel the severity the captain with autoplt off had the first officer hold the aircraft for a few moments. Otherwise, after the autoplt was disconnected the captain flew the aircraft. The first officer called at the captain's request for a block altitude. It seemed the aircraft was easier to control laterally if it were allowed to vary in altitude vertically. After a while the problem seemed to correct itself. There are automatic fuel pumps and valves and sensors that ration fuel from the 2 fuselage auxiliary tanks into the 2 main wing tanks. The possibility exists the problem was a result of a temperature fuel automatic transfer system anomaly.

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Original NASA ASRS Text

Title: PLT FAILS TO MAINTAIN ASSIGNED ALT.

Narrative: WHILE CLBING TO FL290 THROUGH APPROX FL180. I NOTICED A 200 LBS FUEL IMBAL BTWN THE L AND R WING TANK. I ATTEMPTED TO CORRECT BY TRANSFERRING FUEL. THIS DID NOT INITIALLY SEEM TO CORRECT THE PROB. THE ACFT STARTED TO YAW L AND AFTER A PERIOD OF A FEW MINS I WAS HAVING TO APPLY A LOT OF L ROLL CTL TO HOLD THE ACFT LEVEL. I DISENGAGED THE AUTOPLT AND ASKED CTR TO BLOCK MY ALT BY 1000 FT ABOVE AND BELOW. WHILE TRYING TO MAINTAIN A LEVEL ATTITUDE AND AT THE SAME TIME FIND A SOLUTION TO MY OUT OF BAL AND CTL PROB. MY ALT DEVIATED BY MORE THAN MY BLOCKED ALT, HOWEVER, I FELT AT THE TIME THAT IT WAS SAFER TO GIVE UP SOME ALT SO AS TO BE ABLE TO MAINTAIN CTL OF THE AIRPLANE. THE CTLS WERE VERY DIFFICULT TO MOVE, I BELIEVE BECAUSE OF THE AERODYNAMIC LOADS ON THEM. AFTER WHAT SEEMED LIKE AN ETERNITY AND AFTER I CYCLED THE FUEL XFEED A FEW TIMES AND INSURED THAT THE ACFT WAS IN PROPER TRIM THE SIT BEGAN TO BE CORRECTED AND THE ACFT RETURNED TO A PROPER CONFIGN AND CLB PROFILE. I HAVE FLOWN THIS ACFT FOR 300 HRS WITHIN THE LAST 7 MONTHS AND I HAVE NEVER EXPERIENCED ANYTHING LIKE THIS BEFORE. IN FACT, IN MY 27 YRS OF FLYING I HAVE NEVER SEEN THESE SAME CONDITIONS BEFORE. I STILL DO NOT KNOW EXACTLY WHY THE ACFT BEHAVED THIS WAY. WAS IT THE AUTOPLT MIS-TRIMMING? WAS IT A STUCK FUEL XFEED VALVE? WAS MY INITIAL ATTEMPT TO CORRECT THE FUEL IMBAL IMPROPERLY EXECUTED? I DON'T KNOW THE ANSWERS TO THESE QUESTIONS. AS A SIDE NOTE, I PERSONALLY FEEL THAT I WOULD HAVE BETTER ROLL AUTHORITY IF THE ACFT HAD AILERONS AS OPPOSED TO SPOILERS. I AM STILL NOT COMFORTABLE WITH THIS PARTICULAR DESIGN. I ALSO FEEL STRONGLY THAT ALL ACFT SHOULD HAVE MANUAL TRIMMING DEVICES, NOT JUST ELECTRIC TRIM MOTORS AND A BUTTON. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: THE RPTR STATED THE LATERAL IMBAL IS STILL A MYSTERY, WHETHER THE PROB WAS FUEL OR ELECTRIC TRIM HE STILL HAS NOT BEEN ABLE TO RESOLVE. HE HAS NOT EXPERIENCED THE PHENOMENA AGAIN. THE FO AND THE RPTR WORKED TOGETHER TO RESOLVE THE PROB. TO FEEL THE SEVERITY THE CAPT WITH AUTOPLT OFF HAD THE FO HOLD THE ACFT FOR A FEW MOMENTS. OTHERWISE, AFTER THE AUTOPLT WAS DISCONNECTED THE CAPT FLEW THE ACFT. THE FO CALLED AT THE CAPT'S REQUEST FOR A BLOCK ALT. IT SEEMED THE ACFT WAS EASIER TO CTL LATERALLY IF IT WERE ALLOWED TO VARY IN ALT VERTLY. AFTER A WHILE THE PROB SEEMED TO CORRECT ITSELF. THERE ARE AUTOMATIC FUEL PUMPS AND VALVES AND SENSORS THAT RATION FUEL FROM THE 2 FUSELAGE AUX TANKS INTO THE 2 MAIN WING TANKS. THE POSSIBILITY EXISTS THE PROB WAS A RESULT OF A TEMP FUEL AUTO TRANSFER SYS ANOMALY.

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.