Narrative:

En route mia to mco nwbnd along V531, given pilot's discretion descent clearance from 9000 to 5000' to cross barin at 5000'. Inadvertently descended to 4000', trying to 'make our crossing altitude.' 15 seconds after level off at 4000' we realized we were low and at the same time we received a call from ZMA questioning our altitude. We notified them we were climbing back up to 5000'. Conditions were day VMC with normal cockpit duties in progress. Aircraft (small transport) had no altitude deviation warning system. Both pilots monitored the descent trying to make the crossing and both pilots misread their altimeters allowing the descent to go 1000' too low.

Google
 

Original NASA ASRS Text

Title: COMMUTER FLT CREW DESCENDS 1000' LOW FOR ALT CROSSING RESTRICTION.

Narrative: ENRTE MIA TO MCO NWBND ALONG V531, GIVEN PLT'S DISCRETION DSNT CLRNC FROM 9000 TO 5000' TO CROSS BARIN AT 5000'. INADVERTENTLY DSNDED TO 4000', TRYING TO 'MAKE OUR XING ALT.' 15 SECS AFTER LEVEL OFF AT 4000' WE REALIZED WE WERE LOW AND AT THE SAME TIME WE RECEIVED A CALL FROM ZMA QUESTIONING OUR ALT. WE NOTIFIED THEM WE WERE CLBING BACK UP TO 5000'. CONDITIONS WERE DAY VMC WITH NORMAL COCKPIT DUTIES IN PROGRESS. ACFT (SMT) HAD NO ALT DEVIATION WARNING SYS. BOTH PLTS MONITORED THE DSNT TRYING TO MAKE THE XING AND BOTH PLTS MISREAD THEIR ALTIMETERS ALLOWING THE DSNT TO GO 1000' TOO LOW.

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.