Narrative:

I took off for a medical transport operation. I had 2 medical attendants and 1 patient and his wife in the airplane. During the climb and cruise, everything looked normal. But before I started descent, I found the aileron trim indicator showed a little offset. After I started descent, suddenly I heard a very loud bang noise then the airplane started to turn to the right. I tried to control the airplane to fly straight and checked all engine instruments. All engine gauges showed fine. When I checked left aileron, I found an aileron trim stuck at full up position. Airplane still trying to turn into right, fortunately, I still had an aileron control and tried to fly airplane straight. Even if it was very heavy, I could fly. I called ATC and explained what happened to my airplane. I told them I had to land airplane as soon as possible. I saw the closest airfield, which was dillingham airfield, about 20 more mi ahead, and I flew the airplane into it. All landing gear and flaps worked fine. Then I landed at dillingham airfield without any problem. After I landed, I called ATC to report we landed safely and thank them for their help. Also, I called to company operations to explain about a situation and arranged for other transportation for the patient. Next day, one of our mechanics checked the airplane and he found that a rod connected to the aileron trim was broken. I never heard such a thing before. He said likely a metal fatigue must be the cause of this. However, flight control is very important. I hope they will check and inspect these flight control system more closely and carefully and this thing will never happen again.

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Original NASA ASRS Text

Title: PLT OF SMT EXPERIENCES FAILURE OF AILERON TRIM MECHANISM RESULTING IN FULL L AILERON TRIM. MANUAL AILERON INPUTS RESULT IN LESS THAN ACCEPTABLE CTL. PLT LANDS AT NEAREST SUITABLE ARPT.

Narrative: I TOOK OFF FOR A MEDICAL TRANSPORT OP. I HAD 2 MEDICAL ATTENDANTS AND 1 PATIENT AND HIS WIFE IN THE AIRPLANE. DURING THE CLB AND CRUISE, EVERYTHING LOOKED NORMAL. BUT BEFORE I STARTED DSCNT, I FOUND THE AILERON TRIM INDICATOR SHOWED A LITTLE OFFSET. AFTER I STARTED DSCNT, SUDDENLY I HEARD A VERY LOUD BANG NOISE THEN THE AIRPLANE STARTED TO TURN TO THE R. I TRIED TO CTL THE AIRPLANE TO FLY STRAIGHT AND CHKED ALL ENG INSTS. ALL ENG GAUGES SHOWED FINE. WHEN I CHKED L AILERON, I FOUND AN AILERON TRIM STUCK AT FULL UP POS. AIRPLANE STILL TRYING TO TURN INTO R, FORTUNATELY, I STILL HAD AN AILERON CTL AND TRIED TO FLY AIRPLANE STRAIGHT. EVEN IF IT WAS VERY HVY, I COULD FLY. I CALLED ATC AND EXPLAINED WHAT HAPPENED TO MY AIRPLANE. I TOLD THEM I HAD TO LAND AIRPLANE ASAP. I SAW THE CLOSEST AIRFIELD, WHICH WAS DILLINGHAM AIRFIELD, ABOUT 20 MORE MI AHEAD, AND I FLEW THE AIRPLANE INTO IT. ALL LNDG GEAR AND FLAPS WORKED FINE. THEN I LANDED AT DILLINGHAM AIRFIELD WITHOUT ANY PROB. AFTER I LANDED, I CALLED ATC TO RPT WE LANDED SAFELY AND THANK THEM FOR THEIR HELP. ALSO, I CALLED TO COMPANY OPS TO EXPLAIN ABOUT A SIT AND ARRANGED FOR OTHER TRANSPORTATION FOR THE PATIENT. NEXT DAY, ONE OF OUR MECHS CHKED THE AIRPLANE AND HE FOUND THAT A ROD CONNECTED TO THE AILERON TRIM WAS BROKEN. I NEVER HEARD SUCH A THING BEFORE. HE SAID LIKELY A METAL FATIGUE MUST BE THE CAUSE OF THIS. HOWEVER, FLT CTL IS VERY IMPORTANT. I HOPE THEY WILL CHK AND INSPECT THESE FLT CTL SYS MORE CLOSELY AND CAREFULLY AND THIS THING WILL NEVER HAPPEN AGAIN.

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.