Narrative:

First officer was flying on autoplt during descent with center instructions to cross the VOR at 9000', while I performed the 'in range' checklist. I was satisfied that the crossing restriction would be met and left the radio frequency to make the required arrival public address and in range call to company operations. During my absence from the radio, center instructed our flight to level at 11,000' and make a turn for traffic separation. Then in rapid succession, a turn back toward the VOR and descent to 9000. The first officer apparently pushed the 'climb' mode button instead of 'descent', possibly due to the light turbulence. Believing the autoplt had malfunctioned, he first overrode it with force on the yoke, causing the autoplt to trim more nose up, then disconnected the autoplt with the yoke button. Due to the heavy control force required to stop the climb, he thought it had not disengaged and pushed the pedestal mounted button, actually reengaging the autoplt, adding more nose up trim. I became aware of situation due to his frantic efforts and overrode with my electric trim, initiating descent after a 700' accidental climb. Factors: 1) first officer new to airplane and had only a few hours experience with autoplt/flight director of any type. 2) bad timing on my part to be off frequency at a busy time, causing slow recognition. 3) close vertical proximity of 'climb' and 'descent' buttons. 4) unusual rams horn yoke and array of buttons is cumbersome at first and takes time to adjust to.

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Original NASA ASRS Text

Title: NEW FO ON COMMUTER ACFT UNFAMILIAR WITH AUTOPLT OPERATION, CAUSING ALT DEVIATION.

Narrative: F/O WAS FLYING ON AUTOPLT DURING DSCNT WITH CENTER INSTRUCTIONS TO CROSS THE VOR AT 9000', WHILE I PERFORMED THE 'IN RANGE' CHECKLIST. I WAS SATISFIED THAT THE XING RESTRICTION WOULD BE MET AND LEFT THE RADIO FREQ TO MAKE THE REQUIRED ARR PUBLIC ADDRESS AND IN RANGE CALL TO COMPANY OPS. DURING MY ABSENCE FROM THE RADIO, CENTER INSTRUCTED OUR FLT TO LEVEL AT 11,000' AND MAKE A TURN FOR TFC SEPARATION. THEN IN RAPID SUCCESSION, A TURN BACK TOWARD THE VOR AND DSCNT TO 9000. THE F/O APPARENTLY PUSHED THE 'CLIMB' MODE BUTTON INSTEAD OF 'DESCENT', POSSIBLY DUE TO THE LIGHT TURBULENCE. BELIEVING THE AUTOPLT HAD MALFUNCTIONED, HE FIRST OVERRODE IT WITH FORCE ON THE YOKE, CAUSING THE AUTOPLT TO TRIM MORE NOSE UP, THEN DISCONNECTED THE AUTOPLT WITH THE YOKE BUTTON. DUE TO THE HEAVY CTL FORCE REQUIRED TO STOP THE CLIMB, HE THOUGHT IT HAD NOT DISENGAGED AND PUSHED THE PEDESTAL MOUNTED BUTTON, ACTUALLY REENGAGING THE AUTOPLT, ADDING MORE NOSE UP TRIM. I BECAME AWARE OF SITUATION DUE TO HIS FRANTIC EFFORTS AND OVERRODE WITH MY ELECTRIC TRIM, INITIATING DESCENT AFTER A 700' ACCIDENTAL CLIMB. FACTORS: 1) F/O NEW TO AIRPLANE AND HAD ONLY A FEW HOURS EXPERIENCE WITH AUTOPLT/FLT DIRECTOR OF ANY TYPE. 2) BAD TIMING ON MY PART TO BE OFF FREQ AT A BUSY TIME, CAUSING SLOW RECOGNITION. 3) CLOSE VERTICAL PROX OF 'CLIMB' AND 'DESCENT' BUTTONS. 4) UNUSUAL RAMS HORN YOKE AND ARRAY OF BUTTONS IS CUMBERSOME AT FIRST AND TAKES TIME TO ADJUST TO.

Data retrieved from NASA's ASRS site as of August 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.