Narrative:

On approach to phx runway 25L. I remember getting a descent clearance to 6000 ft. Approach was busy pointing out traffic and I noticed we leveled at 5000 ft. Myself and the captain do not remember reading back a 5000 ft clearance. It was the right altitude for the position on approach. 5 and 6 look very close on the LCD panel. I could have set 5 instead of 6. We may have received a 5000 ft clearance and don't recall the readback due to the high workload. The biggest factor was fatigue. We both had been awake 16 hours. On duty over 12 hours and just below 8 hours of flight for the day. The FARS are very dangerous in the flight time/duty area. We still do not know if we had a deviation. ATC did not question our altitude.

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Original NASA ASRS Text

Title: AT THE END OF A LONG DUTY DAY; A FATIGUED B737-300 FLT CREW FIND THEMSELVES AT 5000 FT MSL WHILE ONLY REMEMBERING RECEIVING A CLRNC TO 6000 FT. ATC SAYS NOTHING.

Narrative: ON APCH TO PHX RWY 25L. I REMEMBER GETTING A DSCNT CLRNC TO 6000 FT. APCH WAS BUSY POINTING OUT TFC AND I NOTICED WE LEVELED AT 5000 FT. MYSELF AND THE CAPT DO NOT REMEMBER READING BACK A 5000 FT CLRNC. IT WAS THE RIGHT ALT FOR THE POSITION ON APCH. 5 AND 6 LOOK VERY CLOSE ON THE LCD PANEL. I COULD HAVE SET 5 INSTEAD OF 6. WE MAY HAVE RECEIVED A 5000 FT CLRNC AND DON'T RECALL THE READBACK DUE TO THE HIGH WORKLOAD. THE BIGGEST FACTOR WAS FATIGUE. WE BOTH HAD BEEN AWAKE 16 HOURS. ON DUTY OVER 12 HOURS AND JUST BELOW 8 HOURS OF FLT FOR THE DAY. THE FARS ARE VERY DANGEROUS IN THE FLT TIME/DUTY AREA. WE STILL DO NOT KNOW IF WE HAD A DEV. ATC DID NOT QUESTION OUR ALT.

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