Narrative:

During climb segment to FL200 on flight between mdt and pit, reporter's flight was given a report of traffic at 10-11 O'clock, several mi (do not remember exactly) at 17000'. Both crew members noticed 17000' set in MCP altitude selector and commented that we were climbing to that altitude, and were curious that there would be conflicting traffic at the same altitude. We observed the traffic passing well clear to our left and behind us, and soon thereafter ny ARTCC asked that we confirm our altitude as being 16000'. We answered that we had been cleared to, and read back the clearance to climb to 17000'. The controller insisted he had cleared us to only 16000', because of the opposing traffic at 17000'. (Because of the visibility and horizontal sep, it is the reporter's opinion that neither aircraft was in danger, but the potential certainly existed.) the following factors contributed to the incident: the flight segment was the fourth of the day--a day which originated in calif at xx:00 (EDT) and sent the flight crew through their home base (a high density hub), further east, and back again. The altitude clearance by ny ARTCC was given along with a turn off of the published route (requiring re-entry of data into FMC, and verifying route on charts), and while aircraft and crew were facing into the sun. As a result of this high workload, neither crew member remembered exactly who set the altitude indicator, or what clearance he actually been read back. The reporter's type aircraft has had a history of unscheduled altitude deviations (series). (Not that this is what definitely occurred, but the history suggests the possibility certainly exists.) supplemental information from acn 149078: we had been on duty 11 hours at the time of the occurrence. It was the fourth segment on our day which began in the pacific time zone, and the last leg of a 3 day trip. We had already flown 6+50 block smf-lax-pit-mdt. We were climbing into a very bright sun with lots of glare from multiple cloud layers and build-ups. This captain has only flown mdt-pit once ad I not that well-acquainted with NAVAID names and locations. It takes just a bit longer to look them up and program the FMC. The first officer had never flown this segment before. We were flying a type that has a history of altitude deviations either accidentally induced or system induced.

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Original NASA ASRS Text

Title: POTENTIAL CONFLICT LESS THAN STANDARD SEPARATION.

Narrative: DURING CLB SEGMENT TO FL200 ON FLT BTWN MDT AND PIT, RPTR'S FLT WAS GIVEN A RPT OF TFC AT 10-11 O'CLOCK, SEVERAL MI (DO NOT REMEMBER EXACTLY) AT 17000'. BOTH CREW MEMBERS NOTICED 17000' SET IN MCP ALT SELECTOR AND COMMENTED THAT WE WERE CLBING TO THAT ALT, AND WERE CURIOUS THAT THERE WOULD BE CONFLICTING TFC AT THE SAME ALT. WE OBSERVED THE TFC PASSING WELL CLR TO OUR LEFT AND BEHIND US, AND SOON THEREAFTER NY ARTCC ASKED THAT WE CONFIRM OUR ALT AS BEING 16000'. WE ANSWERED THAT WE HAD BEEN CLRED TO, AND READ BACK THE CLRNC TO CLB TO 17000'. THE CTLR INSISTED HE HAD CLRED US TO ONLY 16000', BECAUSE OF THE OPPOSING TFC AT 17000'. (BECAUSE OF THE VISIBILITY AND HORIZ SEP, IT IS THE RPTR'S OPINION THAT NEITHER ACFT WAS IN DANGER, BUT THE POTENTIAL CERTAINLY EXISTED.) THE FOLLOWING FACTORS CONTRIBUTED TO THE INCIDENT: THE FLT SEGMENT WAS THE FOURTH OF THE DAY--A DAY WHICH ORIGINATED IN CALIF AT XX:00 (EDT) AND SENT THE FLT CREW THROUGH THEIR HOME BASE (A HIGH DENSITY HUB), FURTHER E, AND BACK AGAIN. THE ALT CLRNC BY NY ARTCC WAS GIVEN ALONG WITH A TURN OFF OF THE PUBLISHED RTE (REQUIRING RE-ENTRY OF DATA INTO FMC, AND VERIFYING RTE ON CHARTS), AND WHILE ACFT AND CREW WERE FACING INTO THE SUN. AS A RESULT OF THIS HIGH WORKLOAD, NEITHER CREW MEMBER REMEMBERED EXACTLY WHO SET THE ALT INDICATOR, OR WHAT CLRNC HE ACTUALLY BEEN READ BACK. THE RPTR'S TYPE ACFT HAS HAD A HISTORY OF UNSCHEDULED ALT DEVIATIONS (SERIES). (NOT THAT THIS IS WHAT DEFINITELY OCCURRED, BUT THE HISTORY SUGGESTS THE POSSIBILITY CERTAINLY EXISTS.) SUPPLEMENTAL INFO FROM ACN 149078: WE HAD BEEN ON DUTY 11 HRS AT THE TIME OF THE OCCURRENCE. IT WAS THE FOURTH SEGMENT ON OUR DAY WHICH BEGAN IN THE PACIFIC TIME ZONE, AND THE LAST LEG OF A 3 DAY TRIP. WE HAD ALREADY FLOWN 6+50 BLOCK SMF-LAX-PIT-MDT. WE WERE CLBING INTO A VERY BRIGHT SUN WITH LOTS OF GLARE FROM MULTIPLE CLOUD LAYERS AND BUILD-UPS. THIS CAPT HAS ONLY FLOWN MDT-PIT ONCE AD I NOT THAT WELL-ACQUAINTED WITH NAVAID NAMES AND LOCATIONS. IT TAKES JUST A BIT LONGER TO LOOK THEM UP AND PROGRAM THE FMC. THE F/O HAD NEVER FLOWN THIS SEGMENT BEFORE. WE WERE FLYING A TYPE THAT HAS A HISTORY OF ALT DEVIATIONS EITHER ACCIDENTALLY INDUCED OR SYS INDUCED.

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.