Narrative:

On a flight from dtw to rfd, dtw's departure handed us off to ZOB. My first officer was flying and I, the captain, was working the radios. I checked in with center and reported out of 8000 for 11000', which was our clearance limit. I was looking down, away from the flight INS, at the winds aloft forecast deciding on what altitude would work best. Then I looked up and saw my altimeter approaching 11300'. I immediately turned the transponder on standby and instructed my first officer to descend immediately to 11000'. The controller said he had lost our transponder. I reported that we had been having problems with that particular transponder and said I would try resetting it. I simply turned it back on. The controller mentioned nothing about my altitude deviation. I had him give me 1 more transponder check before going to ZAU. He said he had 3 good hits on me before losing the transponder over ann arbor, mi, and that it was working properly after that. I again had a transponder check down with ZAU. I believe to avoid any such situations, neither pilot should be looking down or doing anything else in the cockpit except looking at the flight and engine INS, when the aircraft is within 1000' of the assigned altitude. I immediately incorporated this into my practice.

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Original NASA ASRS Text

Title: COMMUTER LTT ALT DEVIATION OVERSHOT DURING CLIMB. PIC SHUT OFF MODE C UNTIL BACK ON CLRNC ALT.

Narrative: ON A FLT FROM DTW TO RFD, DTW'S DEP HANDED US OFF TO ZOB. MY F/O WAS FLYING AND I, THE CAPT, WAS WORKING THE RADIOS. I CHKED IN WITH CENTER AND RPTED OUT OF 8000 FOR 11000', WHICH WAS OUR CLRNC LIMIT. I WAS LOOKING DOWN, AWAY FROM THE FLT INS, AT THE WINDS ALOFT FORECAST DECIDING ON WHAT ALT WOULD WORK BEST. THEN I LOOKED UP AND SAW MY ALTIMETER APCHING 11300'. I IMMEDIATELY TURNED THE XPONDER ON STANDBY AND INSTRUCTED MY F/O TO DSND IMMEDIATELY TO 11000'. THE CTLR SAID HE HAD LOST OUR XPONDER. I RPTED THAT WE HAD BEEN HAVING PROBS WITH THAT PARTICULAR XPONDER AND SAID I WOULD TRY RESETTING IT. I SIMPLY TURNED IT BACK ON. THE CTLR MENTIONED NOTHING ABOUT MY ALT DEVIATION. I HAD HIM GIVE ME 1 MORE XPONDER CHK BEFORE GOING TO ZAU. HE SAID HE HAD 3 GOOD HITS ON ME BEFORE LOSING THE XPONDER OVER ANN ARBOR, MI, AND THAT IT WAS WORKING PROPERLY AFTER THAT. I AGAIN HAD A XPONDER CHK DOWN WITH ZAU. I BELIEVE TO AVOID ANY SUCH SITUATIONS, NEITHER PLT SHOULD BE LOOKING DOWN OR DOING ANYTHING ELSE IN THE COCKPIT EXCEPT LOOKING AT THE FLT AND ENG INS, WHEN THE ACFT IS WITHIN 1000' OF THE ASSIGNED ALT. I IMMEDIATELY INCORPORATED THIS INTO MY PRACTICE.

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.