Narrative:

The first officer was flying and doing his own CPU/FMC work. He is very proficient in the use of the FMS, AFDS, etc. He has several thousand hours in the B767-200. Between us we had flown this particular arrival into phl 300-325 times. We were at FL280 awaiting further stepdown. A fairly standard clearance was given to be at FL200 35 mi northeast of the manta intersection. We were on a direct course to manta. The first officer informed me that he had built in an additional buffer of 10 mi to 45 total mi for the descent. I glanced at the progress page and saw the 10 mi spread between the 'MAN02' which was the waypoint he had built and the next fix. I did not check further. The 10 or a 5 mi buffer has almost become standard procedure because the aircraft has a tendency not to make the selected altitude restr. Shortly thereafter the first officer got out of his seat to go to the lavatory. He informed me the aircraft would be starting down shortly. I glanced down and saw to top of descent at 10 mi. Almost simultaneously a change to ZNY was given. I checked in with 'FL280 cleared to FL200.' the center immediately asked if we were in a descent and I stated we would be starting down in about 10 mi. The center replied that we were 43 mi from manta (8 mi from the restr). I immediately began an idle descent with speed brakes extended. The first officer turned back and climbed into his seat stating we had plenty of room. There was no time to discuss the situation and I continued the descent. Ny then advised us no problem, a normal descent would be ok. We crossed manta at approximately FL210. It was difficult to fully assess what had occurred until after arrival at phl. There I realized the system had been programmed to arrive at FL200 10 mi from manta. The original 35 mi fix had not been entered which would have given a total of 45 mi. Conclusions: I did not check the programming completely. I relied completely on the ability of someone I knew and had worked with many times previously. I now think it is imperative when any entries of any sort are made there should be no exceptions to double-checking of those entries by the other pilot or pilots.

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Original NASA ASRS Text

Title: B767 FLC FAILED TO MEET XING RESTR DUE TO A PROGRAMMING ERROR.

Narrative: THE FO WAS FLYING AND DOING HIS OWN CPU/FMC WORK. HE IS VERY PROFICIENT IN THE USE OF THE FMS, AFDS, ETC. HE HAS SEVERAL THOUSAND HRS IN THE B767-200. BTWN US WE HAD FLOWN THIS PARTICULAR ARR INTO PHL 300-325 TIMES. WE WERE AT FL280 AWAITING FURTHER STEPDOWN. A FAIRLY STANDARD CLRNC WAS GIVEN TO BE AT FL200 35 MI NE OF THE MANTA INTXN. WE WERE ON A DIRECT COURSE TO MANTA. THE FO INFORMED ME THAT HE HAD BUILT IN AN ADDITIONAL BUFFER OF 10 MI TO 45 TOTAL MI FOR THE DSCNT. I GLANCED AT THE PROGRESS PAGE AND SAW THE 10 MI SPREAD BTWN THE 'MAN02' WHICH WAS THE WAYPOINT HE HAD BUILT AND THE NEXT FIX. I DID NOT CHK FURTHER. THE 10 OR A 5 MI BUFFER HAS ALMOST BECOME STANDARD PROC BECAUSE THE ACFT HAS A TENDENCY NOT TO MAKE THE SELECTED ALT RESTR. SHORTLY THEREAFTER THE FO GOT OUT OF HIS SEAT TO GO TO THE LAVATORY. HE INFORMED ME THE ACFT WOULD BE STARTING DOWN SHORTLY. I GLANCED DOWN AND SAW TO TOP OF DSCNT AT 10 MI. ALMOST SIMULTANEOUSLY A CHANGE TO ZNY WAS GIVEN. I CHKED IN WITH 'FL280 CLRED TO FL200.' THE CTR IMMEDIATELY ASKED IF WE WERE IN A DSCNT AND I STATED WE WOULD BE STARTING DOWN IN ABOUT 10 MI. THE CTR REPLIED THAT WE WERE 43 MI FROM MANTA (8 MI FROM THE RESTR). I IMMEDIATELY BEGAN AN IDLE DSCNT WITH SPD BRAKES EXTENDED. THE FO TURNED BACK AND CLBED INTO HIS SEAT STATING WE HAD PLENTY OF ROOM. THERE WAS NO TIME TO DISCUSS THE SIT AND I CONTINUED THE DSCNT. NY THEN ADVISED US NO PROB, A NORMAL DSCNT WOULD BE OK. WE CROSSED MANTA AT APPROX FL210. IT WAS DIFFICULT TO FULLY ASSESS WHAT HAD OCCURRED UNTIL AFTER ARR AT PHL. THERE I REALIZED THE SYS HAD BEEN PROGRAMMED TO ARRIVE AT FL200 10 MI FROM MANTA. THE ORIGINAL 35 MI FIX HAD NOT BEEN ENTERED WHICH WOULD HAVE GIVEN A TOTAL OF 45 MI. CONCLUSIONS: I DID NOT CHK THE PROGRAMMING COMPLETELY. I RELIED COMPLETELY ON THE ABILITY OF SOMEONE I KNEW AND HAD WORKED WITH MANY TIMES PREVIOUSLY. I NOW THINK IT IS IMPERATIVE WHEN ANY ENTRIES OF ANY SORT ARE MADE THERE SHOULD BE NO EXCEPTIONS TO DOUBLE-CHKING OF THOSE ENTRIES BY THE OTHER PLT OR PLTS.

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.