Narrative:

While climbing out runway heading and then given a turn to 320 degrees (right turn). When turn was completed and a constant 7 degree pitch up deck angle maintained, I engaged the autoplt with heading and altitude preselect. The autoplt annunciator lights confirmed engagement to selected options. I did not 'feel' any abnormal movement of aircraft, but the flight instruments indicated a sudden uncommanded pitch down and left turn. I disengaged the autoplt and manually rolled wings level and returned to a climb attitude and returned to assigned heading. During this period, ATC advised immediate right turn and climb to assigned heading and altitude. I acknowledged and resumed course. Upon reaching heading and altitude, I had the copilot re-engaged autoplt and it appeared to work fine. We were handed off to another controling agency and nothing further was said. Upon completion of the flight, the copilot and myself debriefed the situation. At first, I thought I had made an error and that looking away from the instruments in night IMC to engage autoplt caused altitude loss (approximately 400 ft and 45 degree heading change). However, both pilots agree that the autoplt was engaged for a few seconds before the uncommanded pitch and roll. On final conclusions, I decided that it would be best and safest if I flew the instruments and the copilot would engage the autoplt on my requested settings. I could firstly see autoplt annunciators engaging to my requested settings and if there was a malfunction my eyes were never off the instruments and recovery could be accomplished almost instantly.

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Original NASA ASRS Text

Title: TEMPORARY LOSS OF ACFT CTL ASSOCIATED WITH AN AUTOPLT PROB DURING A NIGHT OP BY THE FLT CREW OF A BE100 WHEN DEP CLE.

Narrative: WHILE CLBING OUT RWY HDG AND THEN GIVEN A TURN TO 320 DEGS (R TURN). WHEN TURN WAS COMPLETED AND A CONSTANT 7 DEG PITCH UP DECK ANGLE MAINTAINED, I ENGAGED THE AUTOPLT WITH HDG AND ALT PRESELECT. THE AUTOPLT ANNUNCIATOR LIGHTS CONFIRMED ENGAGEMENT TO SELECTED OPTIONS. I DID NOT 'FEEL' ANY ABNORMAL MOVEMENT OF ACFT, BUT THE FLT INSTS INDICATED A SUDDEN UNCOMMANDED PITCH DOWN AND L TURN. I DISENGAGED THE AUTOPLT AND MANUALLY ROLLED WINGS LEVEL AND RETURNED TO A CLB ATTITUDE AND RETURNED TO ASSIGNED HDG. DURING THIS PERIOD, ATC ADVISED IMMEDIATE R TURN AND CLB TO ASSIGNED HDG AND ALT. I ACKNOWLEDGED AND RESUMED COURSE. UPON REACHING HDG AND ALT, I HAD THE COPLT RE-ENGAGED AUTOPLT AND IT APPEARED TO WORK FINE. WE WERE HANDED OFF TO ANOTHER CTLING AGENCY AND NOTHING FURTHER WAS SAID. UPON COMPLETION OF THE FLT, THE COPLT AND MYSELF DEBRIEFED THE SIT. AT FIRST, I THOUGHT I HAD MADE AN ERROR AND THAT LOOKING AWAY FROM THE INSTS IN NIGHT IMC TO ENGAGE AUTOPLT CAUSED ALT LOSS (APPROX 400 FT AND 45 DEG HDG CHANGE). HOWEVER, BOTH PLTS AGREE THAT THE AUTOPLT WAS ENGAGED FOR A FEW SECONDS BEFORE THE UNCOMMANDED PITCH AND ROLL. ON FINAL CONCLUSIONS, I DECIDED THAT IT WOULD BE BEST AND SAFEST IF I FLEW THE INSTS AND THE COPLT WOULD ENGAGE THE AUTOPLT ON MY REQUESTED SETTINGS. I COULD FIRSTLY SEE AUTOPLT ANNUNCIATORS ENGAGING TO MY REQUESTED SETTINGS AND IF THERE WAS A MALFUNCTION MY EYES WERE NEVER OFF THE INSTS AND RECOVERY COULD BE ACCOMPLISHED ALMOST INSTANTLY.

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.