Narrative:

I was departing on an IFR flight in a family owned C-310. I was departing out of agc (pittsburgh, PA) and going to toledo, oh. Upon departing agc I noticed the airplane yawing to the right and initially thought I was having engine problems but I was climbing at 1500 FPM and all engine gauges were in the green. I was cleared to 6000 ft , so I continued my climb and tried to determine my problem. I checked all trims were in the neutral position and again verified both engines producing power. Once in cruse the airplane wanted to yaw even more and the ball was about 1 1/2 its diameter out of center when no rudder was used and considerable rudder pressure was needed to keep the ball in the center. At this point, I decided to return to agc and pittsburgh approach gave me a vector and lower altitude. When I called tower they asked me if I wanted the fire truck waiting and, since I was unsure about the seriousness of the problem, I asked to have them out. The landing went without incident and I taxied to the ramp and parked. Looking at the airplane, I noticed the rudder trim tab deflected to the left which could have caused the right yawing tendency. Yet the trim position indicator was in the neutral position. We took the airplane for a test flight after the mechanic had checked it out and found it to work fine. I was embarrassed about what had happened and couldn't believe that it was only a trim problem. We recently had some work done on a mixture lever and apparently the mechanic also lubed the trim and them worked the trim and returned it to the neutral position (what he thought was neutral). The following are what I believe are the factors involved in my problem. 1) I have over 250 hours in this C-310. I am in the plane 80 percent of the time it flies. I assumed the trim was in the same place it was last time I flew it and I was the last person to fly it. 2) the trim indicator not correctly indicating position. I believe the trim might have been rigged incorrectly during annual which was only 1 1/2 months ago and I never noticed it. Because of the amount of pressure on the rudder I couldn't believe it was a trim problem. 3) I had very little sleep the night before so I wasn't as sharp as I would have liked to have been. For your information I never believed the flight to be in danger and never declared an emergency. But I found it an interesting experience that I don't believe should have happened an I hope you found it useful.

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Original NASA ASRS Text

Title: SMT ACFT HAS A YAWING TENDENCY ONCE AIRBORNE. RETURN LAND.

Narrative: I WAS DEPARTING ON AN IFR FLT IN A FAMILY OWNED C-310. I WAS DEPARTING OUT OF AGC (PITTSBURGH, PA) AND GOING TO TOLEDO, OH. UPON DEPARTING AGC I NOTICED THE AIRPLANE YAWING TO THE R AND INITIALLY THOUGHT I WAS HAVING ENG PROBS BUT I WAS CLBING AT 1500 FPM AND ALL ENG GAUGES WERE IN THE GREEN. I WAS CLRED TO 6000 FT , SO I CONTINUED MY CLB AND TRIED TO DETERMINE MY PROB. I CHKED ALL TRIMS WERE IN THE NEUTRAL POS AND AGAIN VERIFIED BOTH ENGS PRODUCING PWR. ONCE IN CRUSE THE AIRPLANE WANTED TO YAW EVEN MORE AND THE BALL WAS ABOUT 1 1/2 ITS DIAMETER OUT OF CTR WHEN NO RUDDER WAS USED AND CONSIDERABLE RUDDER PRESSURE WAS NEEDED TO KEEP THE BALL IN THE CTR. AT THIS POINT, I DECIDED TO RETURN TO AGC AND PITTSBURGH APCH GAVE ME A VECTOR AND LOWER ALT. WHEN I CALLED TWR THEY ASKED ME IF I WANTED THE FIRE TRUCK WAITING AND, SINCE I WAS UNSURE ABOUT THE SERIOUSNESS OF THE PROB, I ASKED TO HAVE THEM OUT. THE LNDG WENT WITHOUT INCIDENT AND I TAXIED TO THE RAMP AND PARKED. LOOKING AT THE AIRPLANE, I NOTICED THE RUDDER TRIM TAB DEFLECTED TO THE L WHICH COULD HAVE CAUSED THE R YAWING TENDENCY. YET THE TRIM POS INDICATOR WAS IN THE NEUTRAL POS. WE TOOK THE AIRPLANE FOR A TEST FLT AFTER THE MECH HAD CHKED IT OUT AND FOUND IT TO WORK FINE. I WAS EMBARRASSED ABOUT WHAT HAD HAPPENED AND COULDN'T BELIEVE THAT IT WAS ONLY A TRIM PROB. WE RECENTLY HAD SOME WORK DONE ON A MIXTURE LEVER AND APPARENTLY THE MECH ALSO LUBED THE TRIM AND THEM WORKED THE TRIM AND RETURNED IT TO THE NEUTRAL POS (WHAT HE THOUGHT WAS NEUTRAL). THE FOLLOWING ARE WHAT I BELIEVE ARE THE FACTORS INVOLVED IN MY PROB. 1) I HAVE OVER 250 HRS IN THIS C-310. I AM IN THE PLANE 80 PERCENT OF THE TIME IT FLIES. I ASSUMED THE TRIM WAS IN THE SAME PLACE IT WAS LAST TIME I FLEW IT AND I WAS THE LAST PERSON TO FLY IT. 2) THE TRIM INDICATOR NOT CORRECTLY INDICATING POS. I BELIEVE THE TRIM MIGHT HAVE BEEN RIGGED INCORRECTLY DURING ANNUAL WHICH WAS ONLY 1 1/2 MONTHS AGO AND I NEVER NOTICED IT. BECAUSE OF THE AMOUNT OF PRESSURE ON THE RUDDER I COULDN'T BELIEVE IT WAS A TRIM PROB. 3) I HAD VERY LITTLE SLEEP THE NIGHT BEFORE SO I WASN'T AS SHARP AS I WOULD HAVE LIKED TO HAVE BEEN. FOR YOUR INFO I NEVER BELIEVED THE FLT TO BE IN DANGER AND NEVER DECLARED AN EMER. BUT I FOUND IT AN INTERESTING EXPERIENCE THAT I DON'T BELIEVE SHOULD HAVE HAPPENED AN I HOPE YOU FOUND IT USEFUL.

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.