Narrative:

I departed runway 34 at ZZZ, with ceilings approximately 1500 ft AGL and a clearance limit of 5000 ft. Approximately 2 mins after departing, ZSE told me they could turn me north earlier if I could accept ZZZ VOR, then portland. I told seattle that would work, and started refolding the en route chart to see what radial was off of the ZZZ VOR. At the same time, while I was about halfway through the climbing 200 degree left turn back to the VOR, I noticed the DME quit working. I then turned on the autoplt to reduce some of my workload. I switched the DME to the #2 navigation and still nothing, so I started wondering about the integrity of the VOR signal. The autoplt was acting a little erratic (slight oscillations in the pitching axis), but with the moderate turbulence we were in, I didn't feel it would be noticeable to the patient, nurse or paramedic who were located in the center of the aircraft, closer to the pivoting point. By stabilizing the yoke, I felt I was dampening the oscillations, and decided to leave the autoplt on for a few more mins. With my right hand, I started checking the detents on the navigation radios to make sure they were not inbtwn frequencys. At this point, I was coming up on 4800 ft, so I decided to use the electric elevator trim on the yoke with my left thumb to level the airplane, even though that would turn the autoplt off. When I started trimming the nose down, the airplane abruptly pitched up -- at least 20 degrees, and I immediately turned the autoplt off with the disconnect on the yoke with my left thumb, and also at the autoplt control head on the lower center console with my right hand. Then with both hands, I pushed the nose down to get back to 5000 ft. As I was doing all of this while in IMC conditions, I notified seattle that I was through 5300 ft or something like that, but I'm not exactly sure, as I was trying to get the airplane back under control and understand what was happening. After what I think was only 1 oscillation, I got the airplane back level and manually trimmed out, and continued the flight to portland, where I MEL'ed the autoplt and DME. The patient on this part 135 air ambulance fl was next to me getting sick during all of this, (she threw-up twice on this flight), but I have learned to tune these little distrs out. I feel the cause of this deviation was the autoplt trimming the airplane to a very high nose up attitude, along with the failure of the DME and a change in my clearance all occurring at the same time, while in IMC conditions with moderate turbulence.

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Original NASA ASRS Text

Title: ALT OVERSHOT BY THE SINGLE PLT OF AN AC90 PART 135 CHARTER EXPERIENCING AN ELEVATOR TRIM PROB ON CLBOUT FROM ZZZ, US.

Narrative: I DEPARTED RWY 34 AT ZZZ, WITH CEILINGS APPROX 1500 FT AGL AND A CLRNC LIMIT OF 5000 FT. APPROX 2 MINS AFTER DEPARTING, ZSE TOLD ME THEY COULD TURN ME N EARLIER IF I COULD ACCEPT ZZZ VOR, THEN PORTLAND. I TOLD SEATTLE THAT WOULD WORK, AND STARTED REFOLDING THE ENRTE CHART TO SEE WHAT RADIAL WAS OFF OF THE ZZZ VOR. AT THE SAME TIME, WHILE I WAS ABOUT HALFWAY THROUGH THE CLBING 200 DEG L TURN BACK TO THE VOR, I NOTICED THE DME QUIT WORKING. I THEN TURNED ON THE AUTOPLT TO REDUCE SOME OF MY WORKLOAD. I SWITCHED THE DME TO THE #2 NAV AND STILL NOTHING, SO I STARTED WONDERING ABOUT THE INTEGRITY OF THE VOR SIGNAL. THE AUTOPLT WAS ACTING A LITTLE ERRATIC (SLIGHT OSCILLATIONS IN THE PITCHING AXIS), BUT WITH THE MODERATE TURB WE WERE IN, I DIDN'T FEEL IT WOULD BE NOTICEABLE TO THE PATIENT, NURSE OR PARAMEDIC WHO WERE LOCATED IN THE CTR OF THE ACFT, CLOSER TO THE PIVOTING POINT. BY STABILIZING THE YOKE, I FELT I WAS DAMPENING THE OSCILLATIONS, AND DECIDED TO LEAVE THE AUTOPLT ON FOR A FEW MORE MINS. WITH MY R HAND, I STARTED CHKING THE DETENTS ON THE NAV RADIOS TO MAKE SURE THEY WERE NOT INBTWN FREQS. AT THIS POINT, I WAS COMING UP ON 4800 FT, SO I DECIDED TO USE THE ELECTRIC ELEVATOR TRIM ON THE YOKE WITH MY L THUMB TO LEVEL THE AIRPLANE, EVEN THOUGH THAT WOULD TURN THE AUTOPLT OFF. WHEN I STARTED TRIMMING THE NOSE DOWN, THE AIRPLANE ABRUPTLY PITCHED UP -- AT LEAST 20 DEGS, AND I IMMEDIATELY TURNED THE AUTOPLT OFF WITH THE DISCONNECT ON THE YOKE WITH MY L THUMB, AND ALSO AT THE AUTOPLT CTL HEAD ON THE LOWER CTR CONSOLE WITH MY R HAND. THEN WITH BOTH HANDS, I PUSHED THE NOSE DOWN TO GET BACK TO 5000 FT. AS I WAS DOING ALL OF THIS WHILE IN IMC CONDITIONS, I NOTIFIED SEATTLE THAT I WAS THROUGH 5300 FT OR SOMETHING LIKE THAT, BUT I'M NOT EXACTLY SURE, AS I WAS TRYING TO GET THE AIRPLANE BACK UNDER CTL AND UNDERSTAND WHAT WAS HAPPENING. AFTER WHAT I THINK WAS ONLY 1 OSCILLATION, I GOT THE AIRPLANE BACK LEVEL AND MANUALLY TRIMMED OUT, AND CONTINUED THE FLT TO PORTLAND, WHERE I MEL'ED THE AUTOPLT AND DME. THE PATIENT ON THIS PART 135 AIR AMBULANCE FL WAS NEXT TO ME GETTING SICK DURING ALL OF THIS, (SHE THREW-UP TWICE ON THIS FLT), BUT I HAVE LEARNED TO TUNE THESE LITTLE DISTRS OUT. I FEEL THE CAUSE OF THIS DEV WAS THE AUTOPLT TRIMMING THE AIRPLANE TO A VERY HIGH NOSE UP ATTITUDE, ALONG WITH THE FAILURE OF THE DME AND A CHANGE IN MY CLRNC ALL OCCURRING AT THE SAME TIME, WHILE IN IMC CONDITIONS WITH MODERATE TURB.

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.