Narrative:

Our day started in ZZZ and we flew to las; city; and finished back in las over 4 hours late due to WX related delays in both cities. While on vectors by las approach control; on the last leg of the day; we were given a low altitude alert by las approach control. I was the captain and PNF on this leg. We were on a heading of 080 degrees at 8000 ft; approximately abeam from the field on a wide downwind when we started a descent to 6000 ft after what we understood and read back to be a descent clearance to 6000 ft. Prior to reaching 6500 ft; the controller said; 'company number; low altitude alert; climb immediately to 8000 ft.' the PF immediately and aggressively added power and started the climb to 8000 ft. The controller asked what altitude we were descending to and we responded 6000 ft. He said he had given us a heading of 060 degrees and not a descent to 6000 ft. Nothing further was said about the incident by the controller and we never got a GPWS warning. The rest of the approach was uneventful. I think fatigue played a major role in what happened. We were approaching the end of a very long duty day which included several hours of ground delays; passenger issues; moderate turbulence and holding on every leg; icing and all the other challenges associated with flying in bad WX all day long. The lesson I learned is that on days like this; as we get more and more fatigued; we need to constantly remind ourselves to stay on our toes at all times in order to avoid making mistakes and also to catch other people's potential mistakes; which are probably operating under the same types of pressures and stress.

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Original NASA ASRS Text

Title: A FATIGUED ACR PILOT REPORTS CONFUSING A HDG ASSIGNMENT FOR AN ALT. THE ACFT DESCENDED TO 6000 FT ON AN APCH GOING BELOW MIN VECTORING ALT.

Narrative: OUR DAY STARTED IN ZZZ AND WE FLEW TO LAS; CITY; AND FINISHED BACK IN LAS OVER 4 HRS LATE DUE TO WX RELATED DELAYS IN BOTH CITIES. WHILE ON VECTORS BY LAS APCH CTL; ON THE LAST LEG OF THE DAY; WE WERE GIVEN A LOW ALT ALERT BY LAS APCH CTL. I WAS THE CAPT AND PNF ON THIS LEG. WE WERE ON A HDG OF 080 DEGS AT 8000 FT; APPROX ABEAM FROM THE FIELD ON A WIDE DOWNWIND WHEN WE STARTED A DSCNT TO 6000 FT AFTER WHAT WE UNDERSTOOD AND READ BACK TO BE A DSCNT CLRNC TO 6000 FT. PRIOR TO REACHING 6500 FT; THE CTLR SAID; 'COMPANY NUMBER; LOW ALT ALERT; CLB IMMEDIATELY TO 8000 FT.' THE PF IMMEDIATELY AND AGGRESSIVELY ADDED PWR AND STARTED THE CLB TO 8000 FT. THE CTLR ASKED WHAT ALT WE WERE DSNDING TO AND WE RESPONDED 6000 FT. HE SAID HE HAD GIVEN US A HDG OF 060 DEGS AND NOT A DSCNT TO 6000 FT. NOTHING FURTHER WAS SAID ABOUT THE INCIDENT BY THE CTLR AND WE NEVER GOT A GPWS WARNING. THE REST OF THE APCH WAS UNEVENTFUL. I THINK FATIGUE PLAYED A MAJOR ROLE IN WHAT HAPPENED. WE WERE APCHING THE END OF A VERY LONG DUTY DAY WHICH INCLUDED SEVERAL HRS OF GND DELAYS; PAX ISSUES; MODERATE TURB AND HOLDING ON EVERY LEG; ICING AND ALL THE OTHER CHALLENGES ASSOCIATED WITH FLYING IN BAD WX ALL DAY LONG. THE LESSON I LEARNED IS THAT ON DAYS LIKE THIS; AS WE GET MORE AND MORE FATIGUED; WE NEED TO CONSTANTLY REMIND OURSELVES TO STAY ON OUR TOES AT ALL TIMES IN ORDER TO AVOID MAKING MISTAKES AND ALSO TO CATCH OTHER PEOPLE'S POTENTIAL MISTAKES; WHICH ARE PROBABLY OPERATING UNDER THE SAME TYPES OF PRESSURES AND STRESS.

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.