Narrative:

At FL330 about 110 NM south of dpk VOR, we were given a crossing restr, 40 NM south of dpk at FL250. Captain wanted to try out VNAV on GPS and set up descent profile. He began descent about 80 NM from dpk where prompted by GPS VNAV at 1500 FPM rate. Since our airspeed increased (and thus ground speed) 1500 FPM was insufficient to meet restr. I advised captain twice that we were not going to make our restr at that rate, but he continued on. He seemed to have more faith in the GPS than in his own sense, and so we missed the restr by about 2 NM. Automation is a great tool for reducing workload, but it is only as good as the pilot operating it. GPS's cannot work miracles!

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Original NASA ASRS Text

Title: FO RPT REGARDING USE OF GPS ON DSCNT. CAPT CHOOSES TO RELY ON GPS INDICATIONS EVEN THOUGH REMINDED TWICE BY FO THAT THEY WILL MISS THE XING RESTR. THEY MISS THE XING RESTR.

Narrative: AT FL330 ABOUT 110 NM S OF DPK VOR, WE WERE GIVEN A XING RESTR, 40 NM S OF DPK AT FL250. CAPT WANTED TO TRY OUT VNAV ON GPS AND SET UP DSCNT PROFILE. HE BEGAN DSCNT ABOUT 80 NM FROM DPK WHERE PROMPTED BY GPS VNAV AT 1500 FPM RATE. SINCE OUR AIRSPD INCREASED (AND THUS GND SPD) 1500 FPM WAS INSUFFICIENT TO MEET RESTR. I ADVISED CAPT TWICE THAT WE WERE NOT GOING TO MAKE OUR RESTR AT THAT RATE, BUT HE CONTINUED ON. HE SEEMED TO HAVE MORE FAITH IN THE GPS THAN IN HIS OWN SENSE, AND SO WE MISSED THE RESTR BY ABOUT 2 NM. AUTOMATION IS A GREAT TOOL FOR REDUCING WORKLOAD, BUT IT IS ONLY AS GOOD AS THE PLT OPERATING IT. GPS'S CANNOT WORK MIRACLES!

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.