|37000 Feet||Browse and search NASA's
Aviation Safety Reporting System
|Local Time Of Day||1801 To 2400|
|Locale Reference||atc facility : hnl|
|Altitude||msl bound lower : 9000|
msl bound upper : 9000
|Operator||common carrier : air carrier|
|Make Model Name||ATR 42|
|Operating Under FAR Part||Part 121|
|Navigation In Use||Other |
|Flight Phase||cruise other|
|Route In Use||enroute airway : hnl|
|Affiliation||company : air carrier|
|Function||flight crew : first officer|
|Qualification||pilot : atp|
pilot : cfi
|Experience||flight time last 90 days : 128|
flight time total : 2175
flight time type : 128
|Affiliation||company : air carrier|
|Function||flight crew : captain|
oversight : pic
|Qualification||pilot : atp|
|Anomaly||aircraft equipment problem : critical|
other anomaly other
|Independent Detector||other flight crewa|
|Resolutory Action||none taken : unable|
|Air Traffic Incident||other|
At about 11 mins into the flight, after an uneventful takeoff and departure, and established at cruise, the automatic flight control system gave us a roll left wing down message. Captain reacted by disengaging the autoplt and added left aileron and rudder trim. Upon re-engaging the autoplt the aircraft was still out of trim, so additional aileron trim was added. In the process of adding the additional aileron trim, captain noticed that he was unable to decrease trim and asked me my observation. Initially, I noticed that it was intermittently working properly, but for the most part would give only left wing down trim. He gave me the controls, and I tried them myself. I was also unable to decrease left aileron trim. At this point captain looked at the abnormal checklists regarding aileron mistrim and aileron jam malfunctions and surmised that there was nothing else we could do but continue on flying the aircraft manually. He then took back the control of the aircraft and told me to look at the abnormal checklist. I drew the same conclusion. He also advised me to try to recycle the appropriate circuit breakers, which did not remedy the problem. Since we were past the halfway point and in range of kahului we continued the flight with captain at the controls of the aircraft. The remainder of the flight was uneventful. While the mechanic was trying to fix the aircraft we were able to get the trim to read wings level. The mechanic proceeded to check the ailerons and the respective trim tabs to make sure trims were zero and no jams had occurred. At this point we decided to fly the aircraft back without autoplt and without the aileron trim function. After obtaining the appropriate permits and signoffs we brought the aircraft back to hnl with captain at the controls. The flight was uneventful. In retrospect I feel that we should have notified ATC of our problem and returned to hnl immediately after the problem had occurred, instead of continuing to kahului while dealing with the problem. Secondly, after landing at kahului the aircraft should not have been flown back until the aircraft was repaired. Callback conversation with reporter revealed the following information: the aileron trim is electrical on this ATR42-300. When the afcs (automatic flight control system) gave a wing down message, the captain disengaged the autoplt and added left aileron and rudder trim, but when re-engaging the autoplt, it was still out of trim, so more trim was added. It was then noticed that the trim could not be decreased (trimmed the opposite direction). Since there was no irregular or emergency checklist associated with that problem, the flight crew continued to fly manually without using the aileron trim. Because the trim was displaced, it took greater control force to fly the aircraft manually to counteract the trim. Since rudder trim is used much more, particularly with power changes, it helped to counter the offset aileron. After landing, the mechanic was able to get the trim back to zero and he surmised that the problem of 1-WAY aileron trim was due to a faulty relay. The flight crew decided to fly the aircraft back to hnl. Reporter first officer had not heard of any similar problems with the ATR42 aileron trim, but he had heard of a similar problem with the horizontal stabilizer trim.
Original NASA ASRS Text
Title: AILERON TRIM FAILURE. THE TRIM WOULD ONLY TRIM IN ONE DIRECTION. CREATED EXTRA FORCE ON THE CTLS. MECH SUSPECTS FAULTY RELAY.
Narrative: AT ABOUT 11 MINS INTO THE FLT, AFTER AN UNEVENTFUL TKOF AND DEP, AND ESTABLISHED AT CRUISE, THE AUTOMATIC FLT CTL SYS GAVE US A ROLL L WING DOWN MESSAGE. CAPT REACTED BY DISENGAGING THE AUTOPLT AND ADDED L AILERON AND RUDDER TRIM. UPON RE-ENGAGING THE AUTOPLT THE ACFT WAS STILL OUT OF TRIM, SO ADDITIONAL AILERON TRIM WAS ADDED. IN THE PROCESS OF ADDING THE ADDITIONAL AILERON TRIM, CAPT NOTICED THAT HE WAS UNABLE TO DECREASE TRIM AND ASKED ME MY OBSERVATION. INITIALLY, I NOTICED THAT IT WAS INTERMITTENTLY WORKING PROPERLY, BUT FOR THE MOST PART WOULD GIVE ONLY L WING DOWN TRIM. HE GAVE ME THE CTLS, AND I TRIED THEM MYSELF. I WAS ALSO UNABLE TO DECREASE L AILERON TRIM. AT THIS POINT CAPT LOOKED AT THE ABNORMAL CHKLISTS REGARDING AILERON MISTRIM AND AILERON JAM MALFUNCTIONS AND SURMISED THAT THERE WAS NOTHING ELSE WE COULD DO BUT CONTINUE ON FLYING THE ACFT MANUALLY. HE THEN TOOK BACK THE CTL OF THE ACFT AND TOLD ME TO LOOK AT THE ABNORMAL CHKLIST. I DREW THE SAME CONCLUSION. HE ALSO ADVISED ME TO TRY TO RECYCLE THE APPROPRIATE CIRCUIT BREAKERS, WHICH DID NOT REMEDY THE PROB. SINCE WE WERE PAST THE HALFWAY POINT AND IN RANGE OF KAHULUI WE CONTINUED THE FLT WITH CAPT AT THE CTLS OF THE ACFT. THE REMAINDER OF THE FLT WAS UNEVENTFUL. WHILE THE MECH WAS TRYING TO FIX THE ACFT WE WERE ABLE TO GET THE TRIM TO READ WINGS LEVEL. THE MECH PROCEEDED TO CHK THE AILERONS AND THE RESPECTIVE TRIM TABS TO MAKE SURE TRIMS WERE ZERO AND NO JAMS HAD OCCURRED. AT THIS POINT WE DECIDED TO FLY THE ACFT BACK WITHOUT AUTOPLT AND WITHOUT THE AILERON TRIM FUNCTION. AFTER OBTAINING THE APPROPRIATE PERMITS AND SIGNOFFS WE BROUGHT THE ACFT BACK TO HNL WITH CAPT AT THE CTLS. THE FLT WAS UNEVENTFUL. IN RETROSPECT I FEEL THAT WE SHOULD HAVE NOTIFIED ATC OF OUR PROB AND RETURNED TO HNL IMMEDIATELY AFTER THE PROB HAD OCCURRED, INSTEAD OF CONTINUING TO KAHULUI WHILE DEALING WITH THE PROB. SECONDLY, AFTER LNDG AT KAHULUI THE ACFT SHOULD NOT HAVE BEEN FLOWN BACK UNTIL THE ACFT WAS REPAIRED. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: THE AILERON TRIM IS ELECTRICAL ON THIS ATR42-300. WHEN THE AFCS (AUTOMATIC FLT CTL SYS) GAVE A WING DOWN MESSAGE, THE CAPT DISENGAGED THE AUTOPLT AND ADDED L AILERON AND RUDDER TRIM, BUT WHEN RE-ENGAGING THE AUTOPLT, IT WAS STILL OUT OF TRIM, SO MORE TRIM WAS ADDED. IT WAS THEN NOTICED THAT THE TRIM COULD NOT BE DECREASED (TRIMMED THE OPPOSITE DIRECTION). SINCE THERE WAS NO IRREGULAR OR EMER CHKLIST ASSOCIATED WITH THAT PROB, THE FLC CONTINUED TO FLY MANUALLY WITHOUT USING THE AILERON TRIM. BECAUSE THE TRIM WAS DISPLACED, IT TOOK GREATER CTL FORCE TO FLY THE ACFT MANUALLY TO COUNTERACT THE TRIM. SINCE RUDDER TRIM IS USED MUCH MORE, PARTICULARLY WITH PWR CHANGES, IT HELPED TO COUNTER THE OFFSET AILERON. AFTER LNDG, THE MECH WAS ABLE TO GET THE TRIM BACK TO ZERO AND HE SURMISED THAT THE PROB OF 1-WAY AILERON TRIM WAS DUE TO A FAULTY RELAY. THE FLC DECIDED TO FLY THE ACFT BACK TO HNL. RPTR FO HAD NOT HEARD OF ANY SIMILAR PROBS WITH THE ATR42 AILERON TRIM, BUT HE HAD HEARD OF A SIMILAR PROB WITH THE HORIZ STABILIZER TRIM.
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.