Narrative:

While en route to lal on jan/xx/95, approximately XX00 pm, I was given clearance to descend to 6000 ft. At the time I was circumnavigating a line of embedded thunderstorms of level 3-4 intensity on my radar, I was penetrating a small cell on the weak light rain side. The turbulence the last few mi was continuous moderate, occasionally heavy. As I started the descent, I reset the altitude alert and I presume the arm button. At the same time, traffic was called out approximately 10 mi away at 5000 ft. At that time I noticed I was descending through 5400 ft. I immediately climbed back up to 6000 ft, looked at the alerter and saw 6000 ft set but the armed light not on. The autoplt which was on at the time didn't capture altitude! Why? 1) I didn't arm it or 2) it didn't capture because of turbulence or me bumping the trim in the turbulence knocking it off? Whatever, I believe it's my responsibility to monitor all functions and in the midst of all that was happening, I missed the altitude capture. I failed to monitor the engagement and didn't hear the bell. Center asked me if I was level 6000 ft, which now I was, I replied affirmative level 6000 ft. They said mode C indicated 5400 ft. I said roger and said I'll try another transponder, which I did. They said it showed 6000 ft, and asked me to verify I was level at 6000 ft, as they have to write it down. I said I was level 6000 ft. Nothing else was said as I was handed off to another controller. In conclusion, in a high workload environment, situational awareness can easily be lost. Pilot must be sure to reverify all pertinent items.

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Original NASA ASRS Text

Title: CORP SMT HAS ALTDEV ON DSCNT.

Narrative: WHILE ENRTE TO LAL ON JAN/XX/95, APPROX XX00 PM, I WAS GIVEN CLRNC TO DSND TO 6000 FT. AT THE TIME I WAS CIRCUMNAVIGATING A LINE OF EMBEDDED TSTMS OF LEVEL 3-4 INTENSITY ON MY RADAR, I WAS PENETRATING A SMALL CELL ON THE WEAK LIGHT RAIN SIDE. THE TURB THE LAST FEW MI WAS CONTINUOUS MODERATE, OCCASIONALLY HVY. AS I STARTED THE DSCNT, I RESET THE ALT ALERT AND I PRESUME THE ARM BUTTON. AT THE SAME TIME, TFC WAS CALLED OUT APPROX 10 MI AWAY AT 5000 FT. AT THAT TIME I NOTICED I WAS DSNDING THROUGH 5400 FT. I IMMEDIATELY CLBED BACK UP TO 6000 FT, LOOKED AT THE ALERTER AND SAW 6000 FT SET BUT THE ARMED LIGHT NOT ON. THE AUTOPLT WHICH WAS ON AT THE TIME DIDN'T CAPTURE ALT! WHY? 1) I DIDN'T ARM IT OR 2) IT DIDN'T CAPTURE BECAUSE OF TURB OR ME BUMPING THE TRIM IN THE TURB KNOCKING IT OFF? WHATEVER, I BELIEVE IT'S MY RESPONSIBILITY TO MONITOR ALL FUNCTIONS AND IN THE MIDST OF ALL THAT WAS HAPPENING, I MISSED THE ALT CAPTURE. I FAILED TO MONITOR THE ENGAGEMENT AND DIDN'T HEAR THE BELL. CTR ASKED ME IF I WAS LEVEL 6000 FT, WHICH NOW I WAS, I REPLIED AFFIRMATIVE LEVEL 6000 FT. THEY SAID MODE C INDICATED 5400 FT. I SAID ROGER AND SAID I'LL TRY ANOTHER XPONDER, WHICH I DID. THEY SAID IT SHOWED 6000 FT, AND ASKED ME TO VERIFY I WAS LEVEL AT 6000 FT, AS THEY HAVE TO WRITE IT DOWN. I SAID I WAS LEVEL 6000 FT. NOTHING ELSE WAS SAID AS I WAS HANDED OFF TO ANOTHER CTLR. IN CONCLUSION, IN A HIGH WORKLOAD ENVIRONMENT, SITUATIONAL AWARENESS CAN EASILY BE LOST. PLT MUST BE SURE TO REVERIFY ALL PERTINENT ITEMS.

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.