A C310 PLT IN IMC EXPERIENCES A PARTIAL LOSS OF ACFT CTL WHILE ATTEMPTING TO OVERRIDE THE AUTOPLT FOLLOWING INCORRECT GPS/AUTOPLT PROGRAMMING. AN ALT EXCURSION AND TRACK DEV ENSUED.

Narrative

UPON DEPARTING DALLAS LOVE (DAL) ON AN IFR FLT PLAN VIA THE TEXOMA 7; WILL ROGERS TRANSITION TO 2DT; I LEVELED OFF AT 6000 FT MSL IN IMC RAIN AND WAS GIVEN DIRECT TO 2DT FROM A HDG. UPON ENTERING DEST (2DT) IN GPS; I MISTAKENLY COMMANDED THE GPS AND AUTOPLT TO NAV DIRECT TO A WAYPOINT ON THE TEXOMA 7; WILL ROGERS TRANSITION RATHER THAN TO 2DT. AS THE AUTOPLT (GPS MODE) BEGAN A L TURN TOWARD THE WAYPOINT I REALIZED THAT A MISTAKE HAD BEEN MADE. AT A HDG OF 270 DEGS I BEGAN TO OVERRIDE THE AUTOPLT MANUALLY WHILE TRYING TO REPROGRAM THE AUTOPLT. THIS LED TO FALSE SENSE OF CTL INPUTS RELATIVE TO THE ATTITUDE OF THE ACFT WHICH WAS NOTICED AS THE ACFT ENTERED A 45 DEG R BANK AND 1500 FPM DSCNT. AT 5500 FT MSL I DISENGAGED THE AUTOPLT AND THE DSCNT WAS STOPPED AND WINGS LEVELED. I THEN BEGAN AN ASCENT WHICH REACHED AN UNANTICIPATED 2000 FPM UNTIL THE ACFT WAS LEVELED OFF AT 6500 FT MSL ON A 350 DEG HDG WHERE I RE-ENGAGED THE AUTOPLT IN HDG MODE. I THEN ADVISED ATC THAT I WAS MOMENTARILY HAVING DIFFICULTY MAINTAINING ALT AND STATED THAT I WOULD BE LEVELING AT 6400 FT MSL AND BACK ON HDG 350 DEGS FOR A MOMENT. UPON ONCE AGAIN REACHING 6000 FT MSL I REPROGRAMMED THE GPS AND ACTIVATED THE AUTOPLT (GPS MODE) RESUMING DIRECT NAV TO 2DT AND INFORMED ATC THAT I WAS BACK ON COURSE. THE MOMENTARY LOSS OF SITUATIONAL AWARENESS AND ENTRY INTO AN UNUSUAL ATTITUDE WHILE IN IMC WAS A RESULT OF LESS THAN COMPLETE FAMILIARIZATION WITH THE INTEGRATION OF GPS/AUTOPLT; AND THE INCORRECT DECISION TO MANUALLY OVERRIDE THE AUTOPLT RATHER THAN EITHER DISENGAGING IT OR CORRECTLY REPROGRAMMING THE AUTOPLT AND GPS TO THE INTENDED NAV. ALSO A FACTOR WAS MY DIVISION OF ATTN BTWN THE MANUAL MANIPULATION OF THE CTLS WHILE MANUALLY OVERRIDING THE AUTOPLT WHILE SIMULTANEOUSLY TRYING TO REPROGRAM THE GPS. THE VIOLATION WAS EXCEEDING MORE THAN 300 FT BELOW AND ABOVE MY ASSIGNED ALT AND TURNING NEARLY 90 DEGS OFF OF ASSIGNED HDG.