Narrative:

Approaching phx on the karlo 6 arrival, first officer flying, descending to assigned altitude to 9000 ft. First officer suggested we ask for the north runway, assuming by our altitude assignment of 9000 ft so close in that we were being vectored for the south runway. (Our gate was on the north side.) just after I made our request to approach and received a response, I looked down at our altitude which was passing through about 8800 ft. I immediately responded verbally to first officer as I reached for the controls. First officer reacted immediately with power and pulled the nose up. As we both were reacting, approach told us to climb to 9000 ft. By the time we noticed the deviation and then reacted, our altitude bottomed out around 8650 ft. We are normally turned in on the north side of the airport for a right downwind to the south runway while on the karlo 6 arrival. Our discussion as to what exactly approach was going to do with us, distracted us from leveling off at assigned altitude. Personally, my fix for the problem will be simple. When the altitude warning (1000 ft to go) comes on, I will not allow myself to be distracted until level off. Having a definite plan prior to the airport is a plus. Had we known for sure what approach control had in mind, this discussion would probably not have even taken place and the altitude excursion not happened. Most of the time, accomplishing multiple tasks all at the same time is a standard while flying. Throw in a little non normal at just the wrong moment, it's not difficult to get distracted.

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Original NASA ASRS Text

Title: AN ACR B737-200 FLC GETS DISTRACTED WHILE DSNDING AND GOES BELOW 9000 FT ASSIGNED.

Narrative: APCHING PHX ON THE KARLO 6 ARR, FO FLYING, DSNDING TO ASSIGNED ALT TO 9000 FT. FO SUGGESTED WE ASK FOR THE N RWY, ASSUMING BY OUR ALT ASSIGNMENT OF 9000 FT SO CLOSE IN THAT WE WERE BEING VECTORED FOR THE S RWY. (OUR GATE WAS ON THE N SIDE.) JUST AFTER I MADE OUR REQUEST TO APCH AND RECEIVED A RESPONSE, I LOOKED DOWN AT OUR ALT WHICH WAS PASSING THROUGH ABOUT 8800 FT. I IMMEDIATELY RESPONDED VERBALLY TO FO AS I REACHED FOR THE CTLS. FO REACTED IMMEDIATELY WITH PWR AND PULLED THE NOSE UP. AS WE BOTH WERE REACTING, APCH TOLD US TO CLB TO 9000 FT. BY THE TIME WE NOTICED THE DEV AND THEN REACTED, OUR ALT BOTTOMED OUT AROUND 8650 FT. WE ARE NORMALLY TURNED IN ON THE N SIDE OF THE ARPT FOR A R DOWNWIND TO THE S RWY WHILE ON THE KARLO 6 ARR. OUR DISCUSSION AS TO WHAT EXACTLY APCH WAS GOING TO DO WITH US, DISTRACTED US FROM LEVELING OFF AT ASSIGNED ALT. PERSONALLY, MY FIX FOR THE PROB WILL BE SIMPLE. WHEN THE ALT WARNING (1000 FT TO GO) COMES ON, I WILL NOT ALLOW MYSELF TO BE DISTRACTED UNTIL LEVEL OFF. HAVING A DEFINITE PLAN PRIOR TO THE ARPT IS A PLUS. HAD WE KNOWN FOR SURE WHAT APCH CTL HAD IN MIND, THIS DISCUSSION WOULD PROBABLY NOT HAVE EVEN TAKEN PLACE AND THE ALT EXCURSION NOT HAPPENED. MOST OF THE TIME, ACCOMPLISHING MULTIPLE TASKS ALL AT THE SAME TIME IS A STANDARD WHILE FLYING. THROW IN A LITTLE NON NORMAL AT JUST THE WRONG MOMENT, IT'S NOT DIFFICULT TO GET DISTRACTED.

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.