Narrative:

In cruise at FL410 over cap VOR, we were issued a clearance to cross 30 NM east of cap at FL330. The FMS was properly programmed for the crossing restr and the descent initiated approximately 6 NM short of the top of descent point, figured by the FMS and mentally calculated by myself. There should have been plenty of room to make the descent in a timely manner even considering the 50 KT tailwind. The aircraft correctly responded to the descent command and showed 'on path' at FL390. At this time, with everything seeming to be running normally, I became distracted by other cockpit duties and events. I was attempting to look up the ATIS frequency and get the information, get out the approach plates to cvg, had the flight attendant call on the interphone and enter the cockpit, etc. Unnoticed by myself or the PNF, the aircraft shallowed the descent rate for some still unknown reason and went above descent path. At approximately FL370, the controller called us to ask if we'd be able to make the altitude restr. A glance at the instruments showed about 5.0 NM to the restr point and about 4000 ft to lose. I immediately disengaged the autoplt, extended the speed brake and greatly steepened the descent rate. It looked as though we would still be able to make the restr so I responded to the controller with those expectations. In fact, with the lag time in increasing the descent, we were a little late in getting down and I estimate we passed over the point of restr about 2000-3000 ft high. The controller did issue us a 90 degree right turn for traffic avoidance and did likewise to the other aircraft. Due to the workload at the moment, I am not sure of the horizontal/vertical clearance we finally had with the other aircraft. In retrospect, the lessons I learned from this experience are: don't trust the FMS too much. Constantly monitor aircraft performance and situation. Never let other duties and distractions interfere with the primary job of flying the aircraft. Downloading the automation to a lower level in order to produce the proper performance may be necessary but must be down early enough to get the required outcome.

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Original NASA ASRS Text

Title: FO FLYING WDB UNDERSHOOTS DSCNT XING RESTR DUE TO ACFT FMC NOT FOLLOWING NECESSARY DSCNT RATE.

Narrative: IN CRUISE AT FL410 OVER CAP VOR, WE WERE ISSUED A CLRNC TO CROSS 30 NM E OF CAP AT FL330. THE FMS WAS PROPERLY PROGRAMMED FOR THE XING RESTR AND THE DSCNT INITIATED APPROX 6 NM SHORT OF THE TOP OF DSCNT POINT, FIGURED BY THE FMS AND MENTALLY CALCULATED BY MYSELF. THERE SHOULD HAVE BEEN PLENTY OF ROOM TO MAKE THE DSCNT IN A TIMELY MANNER EVEN CONSIDERING THE 50 KT TAILWIND. THE ACFT CORRECTLY RESPONDED TO THE DSCNT COMMAND AND SHOWED 'ON PATH' AT FL390. AT THIS TIME, WITH EVERYTHING SEEMING TO BE RUNNING NORMALLY, I BECAME DISTRACTED BY OTHER COCKPIT DUTIES AND EVENTS. I WAS ATTEMPTING TO LOOK UP THE ATIS FREQ AND GET THE INFO, GET OUT THE APCH PLATES TO CVG, HAD THE FLT ATTENDANT CALL ON THE INTERPHONE AND ENTER THE COCKPIT, ETC. UNNOTICED BY MYSELF OR THE PNF, THE ACFT SHALLOWED THE DSCNT RATE FOR SOME STILL UNKNOWN REASON AND WENT ABOVE DSCNT PATH. AT APPROX FL370, THE CTLR CALLED US TO ASK IF WE'D BE ABLE TO MAKE THE ALT RESTR. A GLANCE AT THE INSTS SHOWED ABOUT 5.0 NM TO THE RESTR POINT AND ABOUT 4000 FT TO LOSE. I IMMEDIATELY DISENGAGED THE AUTOPLT, EXTENDED THE SPD BRAKE AND GREATLY STEEPENED THE DSCNT RATE. IT LOOKED AS THOUGH WE WOULD STILL BE ABLE TO MAKE THE RESTR SO I RESPONDED TO THE CTLR WITH THOSE EXPECTATIONS. IN FACT, WITH THE LAG TIME IN INCREASING THE DSCNT, WE WERE A LITTLE LATE IN GETTING DOWN AND I ESTIMATE WE PASSED OVER THE POINT OF RESTR ABOUT 2000-3000 FT HIGH. THE CTLR DID ISSUE US A 90 DEG R TURN FOR TFC AVOIDANCE AND DID LIKEWISE TO THE OTHER ACFT. DUE TO THE WORKLOAD AT THE MOMENT, I AM NOT SURE OF THE HORIZ/VERT CLRNC WE FINALLY HAD WITH THE OTHER ACFT. IN RETROSPECT, THE LESSONS I LEARNED FROM THIS EXPERIENCE ARE: DON'T TRUST THE FMS TOO MUCH. CONSTANTLY MONITOR ACFT PERFORMANCE AND SIT. NEVER LET OTHER DUTIES AND DISTRACTIONS INTERFERE WITH THE PRIMARY JOB OF FLYING THE ACFT. DOWNLOADING THE AUTOMATION TO A LOWER LEVEL IN ORDER TO PRODUCE THE PROPER PERFORMANCE MAY BE NECESSARY BUT MUST BE DOWN EARLY ENOUGH TO GET THE REQUIRED OUTCOME.

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.