Narrative:

During our descent from cruise altitude into the terminal area of cvg we were instructed to leave FL260 for FL240. The altitude control for the autoplt in this aircraft has 2 knobs like a communications radio. I set the new altitude into the autoplt with the big outer knob (thousands of ft); then pulled the inset smaller knob out to set our rate of descent (hundreds of ft). Due to a bad glare on the display from the sun I did not notice that I hadn't pulled the small knob out completely before setting the vertical speed mode and inadvertently changed the altitude itself to 23800 ft. During the descent I was drawn into a conversation with my copilot explaining the pressurization system on our aircraft. As we descended through FL240 I saw the error and thought we were supposed to go down to FL230; since the bug on the altimeter was on the 3000 mark; our initial altitude at our departure airport. When ATC asked us to verify our altitude I immediately noticed the problem and prepared to climb back up to FL240. The controller advised us not to worry about it and we continued our descent into the terminal area. Contributing factors were my incorrect input into the autoplt; lighting conditions in the cockpit that made viewing the display difficult; an inexperienced copilot who either didn't notice the error or wasn't comfortable notifying me of it; and my distraction during the descent. CRM was a major issue since I had never flown with my copilot before and she had very little experience in the aircraft. This increased my workload because I had to explain how and why everything was being done. Due to this incident I have learned to be much more careful and precise when inputting new altitudes or headings; to verify with ATC any time something looks out of place (such as an incongruous number like 23800); and to make sure my copilot; regardless of experience; is comfortable questioning my actions or judgment. As PIC I need to worry more about flying the aircraft and less about being a flight instructor to a new copilot.

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Original NASA ASRS Text

Title: DISTRACTED BY OTHER EVENTS; PC12 FLT CREW MISSET ALTITUDE CONTROLS AND DESCEND THROUGH CLRED ALT.

Narrative: DURING OUR DSCNT FROM CRUISE ALT INTO THE TERMINAL AREA OF CVG WE WERE INSTRUCTED TO LEAVE FL260 FOR FL240. THE ALT CTL FOR THE AUTOPLT IN THIS ACFT HAS 2 KNOBS LIKE A COMS RADIO. I SET THE NEW ALT INTO THE AUTOPLT WITH THE BIG OUTER KNOB (THOUSANDS OF FT); THEN PULLED THE INSET SMALLER KNOB OUT TO SET OUR RATE OF DSCNT (HUNDREDS OF FT). DUE TO A BAD GLARE ON THE DISPLAY FROM THE SUN I DID NOT NOTICE THAT I HADN'T PULLED THE SMALL KNOB OUT COMPLETELY BEFORE SETTING THE VERT SPD MODE AND INADVERTENTLY CHANGED THE ALT ITSELF TO 23800 FT. DURING THE DSCNT I WAS DRAWN INTO A CONVERSATION WITH MY COPLT EXPLAINING THE PRESSURIZATION SYS ON OUR ACFT. AS WE DSNDED THROUGH FL240 I SAW THE ERROR AND THOUGHT WE WERE SUPPOSED TO GO DOWN TO FL230; SINCE THE BUG ON THE ALTIMETER WAS ON THE 3000 MARK; OUR INITIAL ALT AT OUR DEP ARPT. WHEN ATC ASKED US TO VERIFY OUR ALT I IMMEDIATELY NOTICED THE PROB AND PREPARED TO CLB BACK UP TO FL240. THE CTLR ADVISED US NOT TO WORRY ABOUT IT AND WE CONTINUED OUR DSCNT INTO THE TERMINAL AREA. CONTRIBUTING FACTORS WERE MY INCORRECT INPUT INTO THE AUTOPLT; LIGHTING CONDITIONS IN THE COCKPIT THAT MADE VIEWING THE DISPLAY DIFFICULT; AN INEXPERIENCED COPLT WHO EITHER DIDN'T NOTICE THE ERROR OR WASN'T COMFORTABLE NOTIFYING ME OF IT; AND MY DISTR DURING THE DSCNT. CRM WAS A MAJOR ISSUE SINCE I HAD NEVER FLOWN WITH MY COPLT BEFORE AND SHE HAD VERY LITTLE EXPERIENCE IN THE ACFT. THIS INCREASED MY WORKLOAD BECAUSE I HAD TO EXPLAIN HOW AND WHY EVERYTHING WAS BEING DONE. DUE TO THIS INCIDENT I HAVE LEARNED TO BE MUCH MORE CAREFUL AND PRECISE WHEN INPUTTING NEW ALTS OR HDGS; TO VERIFY WITH ATC ANY TIME SOMETHING LOOKS OUT OF PLACE (SUCH AS AN INCONGRUOUS NUMBER LIKE 23800); AND TO MAKE SURE MY COPLT; REGARDLESS OF EXPERIENCE; IS COMFORTABLE QUESTIONING MY ACTIONS OR JUDGMENT. AS PIC I NEED TO WORRY MORE ABOUT FLYING THE ACFT AND LESS ABOUT BEING A FLT INSTRUCTOR TO A NEW COPLT.

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