Narrative:

We had been cleared to descend via the korry one arrival. As per our training I selected 10000 ft on our altitude selector (we were currently at fl 270) armed the VNAV function or our autoplt and checked all altitudes in the FMS to ensure they matched the crossing restrs published in the arrival. The autoplt captured the 'vpath' and began descending on schedule and my first officer and I continued with our descent duties. A few mins later while my first officer was briefing the approach at lea. We both looked up and noticed the autoplt had held us at 13000 ft (the 'at our above altitude' at holey) even though we were currently passing over brand and should have been at 11000 ft. I informed the controller that our FMS was giving us problems and that we were unsure if we could make the 10000 ft restr at korry at this point. She told us to simply descend to 8000 ft with a good rate down. We complied using vs mode (vertical speed mode, independent of the FMS). I am unsure why the FMS locked us up at 13000 ft. Upon further troubleshooting it may have been due to the fact that the 'performance initialization' page had a descent angle programmed in which was too shallow to allow both 13000 ft at holey and 11000 ft at brand. The FMS was aware that it had become too high since it's glide slope indication was full-scale at the bottom of the flight display. The ultimate cause of the failure to adhere to the crossing restr is of course the flight crew. It is easy to become complacent in a state-of-the-art cockpit. Indeed I have flown this arrival with the FMS dozens of times without a mishap.

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Original NASA ASRS Text

Title: D328 CREW DID NOT COMPLY WITH A CHARTED CROSSING ALT RESTR WHILE FLYING A VNAV DESCENT, ON THE KORRY ONE STAR, INTO LGA.

Narrative: WE HAD BEEN CLRED TO DESCEND VIA THE KORRY ONE ARR. AS PER OUR TRAINING I SELECTED 10000 FT ON OUR ALTITUDE SELECTOR (WE WERE CURRENTLY AT FL 270) ARMED THE VNAV FUNCTION OR OUR AUTOPLT AND CHKED ALL ALTITUDES IN THE FMS TO ENSURE THEY MATCHED THE CROSSING RESTRS PUBLISHED IN THE ARRIVAL. THE AUTOPLT CAPTURED THE 'VPATH' AND BEGAN DESCENDING ON SCHEDULE AND MY FO AND I CONTINUED WITH OUR DESCENT DUTIES. A FEW MINS LATER WHILE MY FO WAS BRIEFING THE APCH AT LEA. WE BOTH LOOKED UP AND NOTICED THE AUTOPLT HAD HELD US AT 13000 FT (THE 'AT OUR ABOVE ALTITUDE' AT HOLEY) EVEN THOUGH WE WERE CURRENTLY PASSING OVER BRAND AND SHOULD HAVE BEEN AT 11000 FT. I INFORMED THE CTLR THAT OUR FMS WAS GIVING US PROBS AND THAT WE WERE UNSURE IF WE COULD MAKE THE 10000 FT RESTR AT KORRY AT THIS POINT. SHE TOLD US TO SIMPLY DESCEND TO 8000 FT WITH A GOOD RATE DOWN. WE COMPLIED USING VS MODE (VERTICAL SPEED MODE, INDEPENDENT OF THE FMS). I AM UNSURE WHY THE FMS LOCKED US UP AT 13000 FT. UPON FURTHER TROUBLESHOOTING IT MAY HAVE BEEN DUE TO THE FACT THAT THE 'PERFORMANCE INITIALIZATION' PAGE HAD A DESCENT ANGLE PROGRAMMED IN WHICH WAS TOO SHALLOW TO ALLOW BOTH 13000 FT AT HOLEY AND 11000 FT AT BRAND. THE FMS WAS AWARE THAT IT HAD BECOME TOO HIGH SINCE IT'S GLIDE SLOPE INDICATION WAS FULL-SCALE AT THE BOTTOM OF THE FLT DISPLAY. THE ULTIMATE CAUSE OF THE FAILURE TO ADHERE TO THE CROSSING RESTR IS OF COURSE THE FLT CREW. IT IS EASY TO BECOME COMPLACENT IN A STATE-OF-THE-ART COCKPIT. INDEED I HAVE FLOWN THIS ARR WITH THE FMS DOZENS OF TIMES WITHOUT A MISHAP.

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.