Narrative:

Clearance from ft myers approach controller was descend to 5000 ft and turn left to 140 degrees. First officer was flying. We put correct altitude into altitude alerter. However the first officer was hand flying the aircraft and thought the clearance was to 4000 ft. We caught the mistake at 4600 ft and immediately climbed back up to 5000 ft. No conflict occurred with other aircraft. The first officer thought the 4000 ft clearance was correct, probably because of the 140 degree heading clearance that was also given by the controller. It was a mistake of misplacing a '4.'

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Original NASA ASRS Text

Title: B737-400 CLRED DSND 5000 FT. ACKNOWLEDGED AND SET IN ALT ALERTER. CLRED TO TURN L 140 DEGS. FO WAS HAND FLYING THE ACFT AND THOUGHT CLRED TO 4000 FT. GOT TO 4600 FT WHEN REALIZED ERROR. CORRECTED BACK TO 5000 FT. NO CONFLICT.

Narrative: CLRNC FROM FT MYERS APCH CTLR WAS DSND TO 5000 FT AND TURN L TO 140 DEGS. FO WAS FLYING. WE PUT CORRECT ALT INTO ALT ALERTER. HOWEVER THE FO WAS HAND FLYING THE ACFT AND THOUGHT THE CLRNC WAS TO 4000 FT. WE CAUGHT THE MISTAKE AT 4600 FT AND IMMEDIATELY CLBED BACK UP TO 5000 FT. NO CONFLICT OCCURRED WITH OTHER ACFT. THE FO THOUGHT THE 4000 FT CLRNC WAS CORRECT, PROBABLY BECAUSE OF THE 140 DEG HDG CLRNC THAT WAS ALSO GIVEN BY THE CTLR. IT WAS A MISTAKE OF MISPLACING A '4.'

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.