Narrative:

Nearing, but not into, the sea TCA, a clearance was received to descend from 13000 to 8000'. The copilot was flying. Out of 9000' sea approach control reported traffic at 1 O'clock climbing to maintain 7000'. Flight conditions were between layers, in and out of IMC. I was simultaneously looking for the traffic and monitoring the copilot's descent to 8000'. The next moment I recall is the visibility annunciator of the altitude alerter blinking on and off, signifying descent below 8000'. (I do not recall hearing the audible annunciator, perhaps because it came at the same time as the controller's transmission pointing out the other traffic.) I immediately called out to the copilot, '8000'.' he responded immediately, stopping descent at 7650 and climbing back to 8000'. No verbal communication re: this altitude bust came from the approach controller. The conflicting traffic was a good 5 mi (estimated) in front of us. The controller's next communication was to 'descend and maintain 4000'.' I reported, 'leaving 8000'.' we then landed west/O further incident. In retrospect, I believe the controller's transmission re: the traffic climbing to 7000' came at the same time we were descending out of 9000 for 8000', a thousand ft to go, a callout which I would normally have made, but don't believe I did because of my diverted attention to the controller's transmission at the same time and then the subsequent looking for and sighting of the aforementioned traffic. The copilot mentioned to me later that for some reason he had 7000' in his mind for level off--perhaps from after hearing that particular altitude clearance given to the other traffic. With the increasing complexity of thought processes and resolutions required in coping with today's crowded airspace system, ATC demands on pilot's attention, the PNF's surveillance of the PF, not to mention the preponderance of bells, whistles, lights and gauges in today's modern jetliner competing for our attention as well, with an infraction seemingly as small as an altitude bust of 350', when or at what point does the human mind finally reach the saturation point and relax, if only for a few seconds to protect itself from overload?

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Original NASA ASRS Text

Title: ACR LGT OVERSHOT ALT ON DESCENT.

Narrative: NEARING, BUT NOT INTO, THE SEA TCA, A CLRNC WAS RECEIVED TO DSND FROM 13000 TO 8000'. THE COPLT WAS FLYING. OUT OF 9000' SEA APCH CTL RPTED TFC AT 1 O'CLOCK CLBING TO MAINTAIN 7000'. FLT CONDITIONS WERE BTWN LAYERS, IN AND OUT OF IMC. I WAS SIMULTANEOUSLY LOOKING FOR THE TFC AND MONITORING THE COPLT'S DSCNT TO 8000'. THE NEXT MOMENT I RECALL IS THE VIS ANNUNCIATOR OF THE ALT ALERTER BLINKING ON AND OFF, SIGNIFYING DSCNT BELOW 8000'. (I DO NOT RECALL HEARING THE AUDIBLE ANNUNCIATOR, PERHAPS BECAUSE IT CAME AT THE SAME TIME AS THE CTLR'S XMISSION POINTING OUT THE OTHER TFC.) I IMMEDIATELY CALLED OUT TO THE COPLT, '8000'.' HE RESPONDED IMMEDIATELY, STOPPING DSCNT AT 7650 AND CLBING BACK TO 8000'. NO VERBAL COM RE: THIS ALT BUST CAME FROM THE APCH CTLR. THE CONFLICTING TFC WAS A GOOD 5 MI (ESTIMATED) IN FRONT OF US. THE CTLR'S NEXT COM WAS TO 'DSND AND MAINTAIN 4000'.' I RPTED, 'LEAVING 8000'.' WE THEN LANDED W/O FURTHER INCIDENT. IN RETROSPECT, I BELIEVE THE CTLR'S XMISSION RE: THE TFC CLBING TO 7000' CAME AT THE SAME TIME WE WERE DSNDING OUT OF 9000 FOR 8000', A THOUSAND FT TO GO, A CALLOUT WHICH I WOULD NORMALLY HAVE MADE, BUT DON'T BELIEVE I DID BECAUSE OF MY DIVERTED ATTN TO THE CTLR'S XMISSION AT THE SAME TIME AND THEN THE SUBSEQUENT LOOKING FOR AND SIGHTING OF THE AFOREMENTIONED TFC. THE COPLT MENTIONED TO ME LATER THAT FOR SOME REASON HE HAD 7000' IN HIS MIND FOR LEVEL OFF--PERHAPS FROM AFTER HEARING THAT PARTICULAR ALT CLRNC GIVEN TO THE OTHER TFC. WITH THE INCREASING COMPLEXITY OF THOUGHT PROCESSES AND RESOLUTIONS REQUIRED IN COPING WITH TODAY'S CROWDED AIRSPACE SYS, ATC DEMANDS ON PLT'S ATTN, THE PNF'S SURVEILLANCE OF THE PF, NOT TO MENTION THE PREPONDERANCE OF BELLS, WHISTLES, LIGHTS AND GAUGES IN TODAY'S MODERN JETLINER COMPETING FOR OUR ATTN AS WELL, WITH AN INFRACTION SEEMINGLY AS SMALL AS AN ALT BUST OF 350', WHEN OR AT WHAT POINT DOES THE HUMAN MIND FINALLY REACH THE SATURATION POINT AND RELAX, IF ONLY FOR A FEW SECS TO PROTECT ITSELF FROM OVERLOAD?

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