Narrative:

Takeoff was made with only 1 air conditioning pack operating (it is impossible to cool an large transport with only 1 pack on the ground). Assigned altitude 3000 ft MSL, outside temperature 86 degrees, inside aircraft about the same. Departed from runway 9L, miami departure assigned a northwest heading and 5000 ft MSL. Power was reduced passing 4000 ft for pending level off, also checking radar scope and outside view for thunderstorm buildups in area. Altitude alert went off at 5300 ft and departure called to ask our altitude. I immediately returned to 5000 ft. Distrs: very warm humid cockpit and several thunderstorms in our path. Apparently I allowed possible evasive action to eliminate my concentration on level off. Not a good excuse! I guess that's why we have altitude alerts.

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Original NASA ASRS Text

Title: FLC OF AN LGT ACR ACFT OVERSHOT ASSIGNED ALT ON CLB DUE TO ACFT EQUIP AND WX DISTR.

Narrative: TKOF WAS MADE WITH ONLY 1 AIR CONDITIONING PACK OPERATING (IT IS IMPOSSIBLE TO COOL AN LGT WITH ONLY 1 PACK ON THE GND). ASSIGNED ALT 3000 FT MSL, OUTSIDE TEMP 86 DEGS, INSIDE ACFT ABOUT THE SAME. DEPARTED FROM RWY 9L, MIAMI DEP ASSIGNED A NW HDG AND 5000 FT MSL. PWR WAS REDUCED PASSING 4000 FT FOR PENDING LEVEL OFF, ALSO CHKING RADAR SCOPE AND OUTSIDE VIEW FOR TSTM BUILDUPS IN AREA. ALT ALERT WENT OFF AT 5300 FT AND DEP CALLED TO ASK OUR ALT. I IMMEDIATELY RETURNED TO 5000 FT. DISTRS: VERY WARM HUMID COCKPIT AND SEVERAL TSTMS IN OUR PATH. APPARENTLY I ALLOWED POSSIBLE EVASIVE ACTION TO ELIMINATE MY CONCENTRATION ON LEVEL OFF. NOT A GOOD EXCUSE! I GUESS THAT'S WHY WE HAVE ALT ALERTS.

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.