Narrative:

The aircraft was filed on victor arwys below FL180 for a flight from alb to phl. The flight required frequent heading changes, nv and communication frequency changes and altitude changes during a short period of time. The WX was IMC in icing conditions on route and low IFR at the destination. This required additional attention being paid to the aircraft's anti-icing system and briefing for the INS approach. North of east tx VOR, which I was briefing the approach to the PNF, the aircraft was cleared to '1-1-thousand' ft (11000) and 250 KTS. '1-1-thousand' was read back by the PNF and set in the altitude alerter. (The altitude alerter on this aircraft was set off to the right side of the cockpit which is not its usual position and produces a less audible. Also, only the top 1/2 of the #'south set in the alerter can easily be seen from the left seat.) I, PF, thought that I heard '1-0-thousand' (10000), repeated back to the PNF '1-0-thousand,' and scanned the alerter for the altitude. The PNF during this heavy workload period did not catch my error, nor did I distinguish between 10 and 11-000 set in the alerter. Following the approach briefing the descent checklist was being run. It was during the running of this checklist that the aircraft was approaching 12000 for 11000'. Again during the heavy workload the call of '12 for 11' by the PNF went unnoticed by me, the PF. I did call out '11 for 10' when going through 11000', but this went unnoticed by the PNF. (It should be noted here that the heavy vol of communication with both ATC and between ourselves contributed to our missing each other's callouts.) at approximately 10400' the PNF advised me that we should be at 11000'. I took a hard look at 11000 set in the altitude alerter and climbed immediately back up to 11000'. It was simultaneously at this pint in time that ATC advised us of our altitude deviation. To help prevent this type of occurrence, crew coordination procedures should require the '1000' to go callout' to be acknowledged by both crew members. In addition, I feel that steps must continue to be taken to simplify the routing and arrs of all jet aircraft in the congested northeast, and to avoid the exposure of such flts to multiple legs of short segments that go from VOR to VOR. Additionally, efforts should continue to be made to standardize equipment in cockpits.

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Original NASA ASRS Text

Title: DESCENT BELOW ASSIGNED ALT BY MLG FLT CREW.

Narrative: THE ACFT WAS FILED ON VICTOR ARWYS BELOW FL180 FOR A FLT FROM ALB TO PHL. THE FLT REQUIRED FREQUENT HDG CHANGES, NV AND COM FREQ CHANGES AND ALT CHANGES DURING A SHORT PERIOD OF TIME. THE WX WAS IMC IN ICING CONDITIONS ON RTE AND LOW IFR AT THE DEST. THIS REQUIRED ADDITIONAL ATTN BEING PAID TO THE ACFT'S ANTI-ICING SYS AND BRIEFING FOR THE INS APCH. N OF E TX VOR, WHICH I WAS BRIEFING THE APCH TO THE PNF, THE ACFT WAS CLRED TO '1-1-THOUSAND' FT (11000) AND 250 KTS. '1-1-THOUSAND' WAS READ BACK BY THE PNF AND SET IN THE ALT ALERTER. (THE ALT ALERTER ON THIS ACFT WAS SET OFF TO THE RIGHT SIDE OF THE COCKPIT WHICH IS NOT ITS USUAL POS AND PRODUCES A LESS AUDIBLE. ALSO, ONLY THE TOP 1/2 OF THE #'S SET IN THE ALERTER CAN EASILY BE SEEN FROM THE LEFT SEAT.) I, PF, THOUGHT THAT I HEARD '1-0-THOUSAND' (10000), REPEATED BACK TO THE PNF '1-0-THOUSAND,' AND SCANNED THE ALERTER FOR THE ALT. THE PNF DURING THIS HEAVY WORKLOAD PERIOD DID NOT CATCH MY ERROR, NOR DID I DISTINGUISH BTWN 10 AND 11-000 SET IN THE ALERTER. FOLLOWING THE APCH BRIEFING THE DSNT CHKLIST WAS BEING RUN. IT WAS DURING THE RUNNING OF THIS CHKLIST THAT THE ACFT WAS APCHING 12000 FOR 11000'. AGAIN DURING THE HEAVY WORKLOAD THE CALL OF '12 FOR 11' BY THE PNF WENT UNNOTICED BY ME, THE PF. I DID CALL OUT '11 FOR 10' WHEN GOING THROUGH 11000', BUT THIS WENT UNNOTICED BY THE PNF. (IT SHOULD BE NOTED HERE THAT THE HEAVY VOL OF COM WITH BOTH ATC AND BTWN OURSELVES CONTRIBUTED TO OUR MISSING EACH OTHER'S CALLOUTS.) AT APPROX 10400' THE PNF ADVISED ME THAT WE SHOULD BE AT 11000'. I TOOK A HARD LOOK AT 11000 SET IN THE ALT ALERTER AND CLBED IMMEDIATELY BACK UP TO 11000'. IT WAS SIMULTANEOUSLY AT THIS PINT IN TIME THAT ATC ADVISED US OF OUR ALT DEVIATION. TO HELP PREVENT THIS TYPE OF OCCURRENCE, CREW COORD PROCS SHOULD REQUIRE THE '1000' TO GO CALLOUT' TO BE ACKNOWLEDGED BY BOTH CREW MEMBERS. IN ADDITION, I FEEL THAT STEPS MUST CONTINUE TO BE TAKEN TO SIMPLIFY THE ROUTING AND ARRS OF ALL JET ACFT IN THE CONGESTED NE, AND TO AVOID THE EXPOSURE OF SUCH FLTS TO MULTIPLE LEGS OF SHORT SEGMENTS THAT GO FROM VOR TO VOR. ADDITIONALLY, EFFORTS SHOULD CONTINUE TO BE MADE TO STANDARDIZE EQUIP IN COCKPITS.

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.