Narrative:

8/thur/90. Our small aircraft had an elevator trim kit installed that is designed to limit the forward and aft movement, this preventing the trim from getting stuck in these extreme position. The aircraft was tested and seemed to be working properly. 8/fri/90, I departed from 3v5 and contacted denver center requesting IFR clearance to salina, ks. I discovered that the elevator trim had to be in full down position to maintain level flight. I told center that I had a mechanical problem and was returning to 3v5. My IFR flight plan was set back one hour. My mechanic made a 2 degree adjustment. After a test flight, I departed from 3v5 again and activated my IFR flight around noon. At cruise altitude the F/D, autoplt (ap), heading bug (hb) and altitude hold (ah) were engaged. There were no altitude changes en route. Upon nearing the destination airport I was given a lower altitude by center. I turned off all of the automatic equipment and hand flew the aircraft through the descent, approach and landing. Everything seemed to be working properly. 8/sun/90, after departure from salina municipal airport, I flew to cruise altitude and engaged the FD, ap, hb, and ah. When center gave my a higher altitude, I disengaged the ah and pressed the console switch that allows the aircraft to climb. Nothing happened. The elevator trim did not move. I reached down and tried to turn the trim wheel but it was completely immobile. The ap was turned off and the electric trim control that is located on the yoke was used to establish climb. When the desired altitude was reached, the FD, ap, hb and ah were re-engaged. The trim wheel continued to turn and the ah did not hold the altitude. The FD, ap, hb, ah and electric trim rocker switch on the panel were all turned off while I stablized the aircraft by reaching down and turning the trim wheel manually. The FD, ap, hg and ah were all re-engaged and everything seemed to be working just fine. I tried the console switch that controls the up and down elevator action and it still didn't respond. I knew then that all future trim adjustments would have to be done by turning off the autoplt and using the electric trimctl located on the yoke. Center advised me to climb prior to reaching goodland, ks. I disengaged the autoplt, increased the propeller and mixture, added some power and used the electric trim control located on the yoke. The aircraft climbed and it was not apparent that we had a runway elevator trim until reaching the desired altitude. After reducing the power, and pushing the electric trim control located on the yoke forward the aircraft continued to climb. Forward pressure was applied to the yoke to reduce the climb. Center called asking me to verify my altitude. Because I was holding heavy forward pressure on the yoke with my left hand while continuing to press the trim control forward (to stop the climb), I could not release the yoke to pick up the hand-held microphone and could not respond to ctrs call. I reached down to the trim wheel and it was turning fast in the direction that was causing the climb. Center called again asking me to verify my altitude. With my right hand, I reached over to the microphone that is located on the left side of the cabin and told center I was out of 8000' and requesting 10000' while continuing to hold forward pressure on the yoke with my left hand, I used my right hand to turn off the electric trim rocker switch on the panel. Then I started manually turning the trim wheel down to stop the climb. Center called again requesting altitude verification. I again requested 10000' and stated that I had elevator problems and I was fighting a runaway trim control. Center cleared me to 10000' (which I was already at by this time) and asked me to write down the telephone number at that time because I was in solid IFR, and flying an airplane that had a runaway trim, had red flashing lights and beepers going off. Meanwhile the aircraft was manually leveled off and stablized. I requested 8000' MSL so we would be below the cloud layer instead of 'in the soup'. This request was granted. Leaving the FD, ap, hb, ah and electric trim rocker switch off, I descended to 8000'. After establishing stablized level flight, I checked the WX at our destination airport and the WX was good. No instrument approach would be needed, so the decision was made to proceed to our destination airport. Callback conversation with reporter revealed the following information.reporter stated that she did cal denver center and that they were very understanding of her problem. Apparently, there was no traffic conflict resulting from the incident. Reporter said that trim problem was caused by a worn part in the electric trim system, and that they were able to replicate the runaway condition on the ground.

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Original NASA ASRS Text

Title: SMA PLT FLYING ON AN IFR FLT PLAN ON V4 JUST EAST OF GLD EXPERIENCED A RUNAWAY TRIM CONDITION DURING CLIMB WHICH RESULTED IN A 2000' ALT DEVIATION.

Narrative: 8/THUR/90. OUR SMA HAD AN ELEVATOR TRIM KIT INSTALLED THAT IS DESIGNED TO LIMIT THE FORWARD AND AFT MOVEMENT, THIS PREVENTING THE TRIM FROM GETTING STUCK IN THESE EXTREME POS. THE ACFT WAS TESTED AND SEEMED TO BE WORKING PROPERLY. 8/FRI/90, I DEPARTED FROM 3V5 AND CONTACTED DENVER CTR REQUESTING IFR CLRNC TO SALINA, KS. I DISCOVERED THAT THE ELEVATOR TRIM HAD TO BE IN FULL DOWN POS TO MAINTAIN LEVEL FLT. I TOLD CTR THAT I HAD A MECHANICAL PROB AND WAS RETURNING TO 3V5. MY IFR FLT PLAN WAS SET BACK ONE HR. MY MECH MADE A 2 DEG ADJUSTMENT. AFTER A TEST FLT, I DEPARTED FROM 3V5 AGAIN AND ACTIVATED MY IFR FLT AROUND NOON. AT CRUISE ALT THE F/D, AUTOPLT (AP), HDG BUG (HB) AND ALT HOLD (AH) WERE ENGAGED. THERE WERE NO ALT CHANGES ENRTE. UPON NEARING THE DEST ARPT I WAS GIVEN A LOWER ALT BY CTR. I TURNED OFF ALL OF THE AUTOMATIC EQUIP AND HAND FLEW THE ACFT THROUGH THE DSNT, APCH AND LNDG. EVERYTHING SEEMED TO BE WORKING PROPERLY. 8/SUN/90, AFTER DEP FROM SALINA MUNICIPAL ARPT, I FLEW TO CRUISE ALT AND ENGAGED THE FD, AP, HB, AND AH. WHEN CTR GAVE MY A HIGHER ALT, I DISENGAGED THE AH AND PRESSED THE CONSOLE SWITCH THAT ALLOWS THE ACFT TO CLB. NOTHING HAPPENED. THE ELEVATOR TRIM DID NOT MOVE. I REACHED DOWN AND TRIED TO TURN THE TRIM WHEEL BUT IT WAS COMPLETELY IMMOBILE. THE AP WAS TURNED OFF AND THE ELECTRIC TRIM CTL THAT IS LOCATED ON THE YOKE WAS USED TO ESTABLISH CLB. WHEN THE DESIRED ALT WAS REACHED, THE FD, AP, HB AND AH WERE RE-ENGAGED. THE TRIM WHEEL CONTINUED TO TURN AND THE AH DID NOT HOLD THE ALT. THE FD, AP, HB, AH AND ELECTRIC TRIM ROCKER SWITCH ON THE PANEL WERE ALL TURNED OFF WHILE I STABLIZED THE ACFT BY REACHING DOWN AND TURNING THE TRIM WHEEL MANUALLY. THE FD, AP, HG AND AH WERE ALL RE-ENGAGED AND EVERYTHING SEEMED TO BE WORKING JUST FINE. I TRIED THE CONSOLE SWITCH THAT CTLS THE UP AND DOWN ELEVATOR ACTION AND IT STILL DIDN'T RESPOND. I KNEW THEN THAT ALL FUTURE TRIM ADJUSTMENTS WOULD HAVE TO BE DONE BY TURNING OFF THE AUTOPLT AND USING THE ELECTRIC TRIMCTL LOCATED ON THE YOKE. CTR ADVISED ME TO CLB PRIOR TO REACHING GOODLAND, KS. I DISENGAGED THE AUTOPLT, INCREASED THE PROP AND MIXTURE, ADDED SOME PWR AND USED THE ELECTRIC TRIM CTL LOCATED ON THE YOKE. THE ACFT CLBED AND IT WAS NOT APPARENT THAT WE HAD A RWY ELEVATOR TRIM UNTIL REACHING THE DESIRED ALT. AFTER REDUCING THE PWR, AND PUSHING THE ELECTRIC TRIM CTL LOCATED ON THE YOKE FORWARD THE ACFT CONTINUED TO CLB. FORWARD PRESSURE WAS APPLIED TO THE YOKE TO REDUCE THE CLB. CTR CALLED ASKING ME TO VERIFY MY ALT. BECAUSE I WAS HOLDING HVY FORWARD PRESSURE ON THE YOKE WITH MY L HAND WHILE CONTINUING TO PRESS THE TRIM CTL FORWARD (TO STOP THE CLB), I COULD NOT RELEASE THE YOKE TO PICK UP THE HAND-HELD MICROPHONE AND COULD NOT RESPOND TO CTRS CALL. I REACHED DOWN TO THE TRIM WHEEL AND IT WAS TURNING FAST IN THE DIRECTION THAT WAS CAUSING THE CLB. CTR CALLED AGAIN ASKING ME TO VERIFY MY ALT. WITH MY R HAND, I REACHED OVER TO THE MIKE THAT IS LOCATED ON THE L SIDE OF THE CABIN AND TOLD CTR I WAS OUT OF 8000' AND REQUESTING 10000' WHILE CONTINUING TO HOLD FORWARD PRESSURE ON THE YOKE WITH MY L HAND, I USED MY R HAND TO TURN OFF THE ELECTRIC TRIM ROCKER SWITCH ON THE PANEL. THEN I STARTED MANUALLY TURNING THE TRIM WHEEL DOWN TO STOP THE CLB. CTR CALLED AGAIN REQUESTING ALT VERIFICATION. I AGAIN REQUESTED 10000' AND STATED THAT I HAD ELEVATOR PROBS AND I WAS FIGHTING A RUNAWAY TRIM CTL. CTR CLRED ME TO 10000' (WHICH I WAS ALREADY AT BY THIS TIME) AND ASKED ME TO WRITE DOWN THE TELEPHONE NUMBER AT THAT TIME BECAUSE I WAS IN SOLID IFR, AND FLYING AN AIRPLANE THAT HAD A RUNAWAY TRIM, HAD RED FLASHING LIGHTS AND BEEPERS GOING OFF. MEANWHILE THE ACFT WAS MANUALLY LEVELED OFF AND STABLIZED. I REQUESTED 8000' MSL SO WE WOULD BE BELOW THE CLOUD LAYER INSTEAD OF 'IN THE SOUP'. THIS REQUEST WAS GRANTED. LEAVING THE FD, AP, HB, AH AND ELECTRIC TRIM ROCKER SWITCH OFF, I DSNDED TO 8000'. AFTER ESTABLISHING STABLIZED LEVEL FLT, I CHKED THE WX AT OUR DEST ARPT AND THE WX WAS GOOD. NO INSTRUMENT APCH WOULD BE NEEDED, SO THE DECISION WAS MADE TO PROCEED TO OUR DEST ARPT. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO.RPTR STATED THAT SHE DID CAL DENVER CTR AND THAT THEY WERE VERY UNDERSTANDING OF HER PROB. APPARENTLY, THERE WAS NO TFC CONFLICT RESULTING FROM THE INCIDENT. RPTR SAID THAT TRIM PROB WAS CAUSED BY A WORN PART IN THE ELECTRIC TRIM SYS, AND THAT THEY WERE ABLE TO REPLICATE THE RUNAWAY CONDITION ON THE GND.

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.