Narrative:

I departed ZZZ in new aircraft I just purchased. I was talking to approach; who assigned me; 'right turn to 120 degrees; climb 2000 ft.' moments later an additional vector; 'right turn 270 degrees.' this was a 150 degree turn; which I think caused the autoplt to malfunction. The autoplt; an s-tec 55X; did not stop at the altitude pre-select altitude setting of 2000 ft but rather climbed to 2900 ft. At this point; the autoplt seemed to register the altitude; and subsequently put the plane into a steep dive. I immediately disconnected the autoplt and corrected the altitude with no delay. One problem that stands out is that when turning to 270 degrees; which was the 150 degree turn; the autoplt put the plane into a bank; much steeper than usually experienced; and seemingly delaying the altitude pre-select setting. Later in the flight while in level cruise; the autoplt seemed to constantly rock the wings. I subsequently checked with someone who has flown the plane and they had the same problem.callback conversation with reporter revealed the following information: reporter stated he recently purchased his new mooney 'acclaim;' and installed the s-tec 55X autoplt because the G-1000 garmin panel; which incorporates the garmin gfc -700 autopilot system with a new multi-functional display unit; was not certified for the mooney 'acclaim' at the time. Reporter also stated; as a result of his experience with the s-tec 55X and a recent previous user of his aircraft having the same experience; he is replacing the s-tec 55X with the now available garmin 1000 (GFC700).

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Original NASA ASRS Text

Title: A NEW MOONEY ACCLAIM M20TN ACFT WITH S-TEC MODEL 55X AUTOPILOT COMPUTER EXPERIENCED UNCOMMANDED ALTITUDE CLIMB AND STEEP DIVE DURING TKOF CLIMB AND WINGS ROCKING DURING LEVEL CRUISE.

Narrative: I DEPARTED ZZZ IN NEW ACFT I JUST PURCHASED. I WAS TALKING TO APCH; WHO ASSIGNED ME; 'RIGHT TURN TO 120 DEGS; CLB 2000 FT.' MOMENTS LATER AN ADDITIONAL VECTOR; 'RIGHT TURN 270 DEGS.' THIS WAS A 150 DEG TURN; WHICH I THINK CAUSED THE AUTOPLT TO MALFUNCTION. THE AUTOPLT; AN S-TEC 55X; DID NOT STOP AT THE ALT PRE-SELECT ALT SETTING OF 2000 FT BUT RATHER CLBED TO 2900 FT. AT THIS POINT; THE AUTOPLT SEEMED TO REGISTER THE ALT; AND SUBSEQUENTLY PUT THE PLANE INTO A STEEP DIVE. I IMMEDIATELY DISCONNECTED THE AUTOPLT AND CORRECTED THE ALT WITH NO DELAY. ONE PROB THAT STANDS OUT IS THAT WHEN TURNING TO 270 DEGS; WHICH WAS THE 150 DEG TURN; THE AUTOPLT PUT THE PLANE INTO A BANK; MUCH STEEPER THAN USUALLY EXPERIENCED; AND SEEMINGLY DELAYING THE ALT PRE-SELECT SETTING. LATER IN THE FLT WHILE IN LEVEL CRUISE; THE AUTOPLT SEEMED TO CONSTANTLY ROCK THE WINGS. I SUBSEQUENTLY CHECKED WITH SOMEONE WHO HAS FLOWN THE PLANE AND THEY HAD THE SAME PROB.CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: REPORTER STATED HE RECENTLY PURCHASED HIS NEW MOONEY 'ACCLAIM;' AND INSTALLED THE S-TEC 55X AUTOPLT BECAUSE THE G-1000 GARMIN PANEL; WHICH INCORPORATES THE GARMIN GFC -700 AUTOPILOT SYSTEM WITH A NEW MULTI-FUNCTIONAL DISPLAY UNIT; WAS NOT CERTIFIED FOR THE MOONEY 'ACCLAIM' AT THE TIME. REPORTER ALSO STATED; AS A RESULT OF HIS EXPERIENCE WITH THE S-TEC 55X AND A RECENT PREVIOUS USER OF HIS ACFT HAVING THE SAME EXPERIENCE; HE IS REPLACING THE S-TEC 55X WITH THE NOW AVAILABLE GARMIN 1000 (GFC700).

Data retrieved from NASA's ASRS site as of January 2009 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.