Narrative:

This problem was discovered after the fact when a controller asked if we were the same aircraft who had crossed a certain fix at 13500 ft instead of the assigned 12000 ft earlier. The chain of events had gone like this: we were air carrier X en route from sea-tac to sacramento metropolitan descending on the tudor 1 arrival, lmt transition with a clearance to cross bowls at 12000 ft. The FMC was programmed for this and the aircraft was on the VNAV path descent. Approaching bowls, ZOA asked if we could be 12000 ft at bowls. After checking the instruments we replied 'yes.' later, and prior to bowls, we were handed off to approach who cleared us 'direct metre (OM runway 16R), descend and maintain 4000 ft.' the previously assigned crossing restr was not mentioned. Since our altitude (as well as our routing) had been changed without restatement of the restr, we took this to mean that the bowls restr was no longer applicable and that we were now on a different plan for the arrival. Selecting 'direct metre' on the FMC/CDU eliminated the bowls fix and the VNAV path was now being computed on a 3 degree flight path angle to the end of the runway. Since this path was initially above the aircraft, the descent rate reduced to capture the path. This is what caused the aircraft to be above 12000 ft crossing bowls, causing some sort of problem regarding another aircraft. I believe the problem arose with controller-controller communications during the handoff to approach control. Approach's newly issued instructions cancelled the restrs that center apparently wanted to be honored. In replying to center's comments about what he thought was an altitude bust, and explaining that we had received a revised clearance, he sounded surprised and didn't have anything else to say about it over the radio.

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Original NASA ASRS Text

Title: ACR X ALT RESTR NOT ADHERED TO. OPDEV.

Narrative: THIS PROB WAS DISCOVERED AFTER THE FACT WHEN A CTLR ASKED IF WE WERE THE SAME ACFT WHO HAD CROSSED A CERTAIN FIX AT 13500 FT INSTEAD OF THE ASSIGNED 12000 FT EARLIER. THE CHAIN OF EVENTS HAD GONE LIKE THIS: WE WERE ACR X ENRTE FROM SEA-TAC TO SACRAMENTO METRO DSNDING ON THE TUDOR 1 ARR, LMT TRANSITION WITH A CLRNC TO CROSS BOWLS AT 12000 FT. THE FMC WAS PROGRAMMED FOR THIS AND THE ACFT WAS ON THE VNAV PATH DSCNT. APCHING BOWLS, ZOA ASKED IF WE COULD BE 12000 FT AT BOWLS. AFTER CHKING THE INSTS WE REPLIED 'YES.' LATER, AND PRIOR TO BOWLS, WE WERE HANDED OFF TO APCH WHO CLRED US 'DIRECT METRE (OM RWY 16R), DSND AND MAINTAIN 4000 FT.' THE PREVIOUSLY ASSIGNED XING RESTR WAS NOT MENTIONED. SINCE OUR ALT (AS WELL AS OUR ROUTING) HAD BEEN CHANGED WITHOUT RESTATEMENT OF THE RESTR, WE TOOK THIS TO MEAN THAT THE BOWLS RESTR WAS NO LONGER APPLICABLE AND THAT WE WERE NOW ON A DIFFERENT PLAN FOR THE ARR. SELECTING 'DIRECT METRE' ON THE FMC/CDU ELIMINATED THE BOWLS FIX AND THE VNAV PATH WAS NOW BEING COMPUTED ON A 3 DEG FLT PATH ANGLE TO THE END OF THE RWY. SINCE THIS PATH WAS INITIALLY ABOVE THE ACFT, THE DSCNT RATE REDUCED TO CAPTURE THE PATH. THIS IS WHAT CAUSED THE ACFT TO BE ABOVE 12000 FT XING BOWLS, CAUSING SOME SORT OF PROB REGARDING ANOTHER ACFT. I BELIEVE THE PROB AROSE WITH CTLR-CTLR COMS DURING THE HDOF TO APCH CTL. APCH'S NEWLY ISSUED INSTRUCTIONS CANCELLED THE RESTRS THAT CTR APPARENTLY WANTED TO BE HONORED. IN REPLYING TO CTR'S COMMENTS ABOUT WHAT HE THOUGHT WAS AN ALT BUST, AND EXPLAINING THAT WE HAD RECEIVED A REVISED CLRNC, HE SOUNDED SURPRISED AND DIDN'T HAVE ANYTHING ELSE TO SAY ABOUT IT OVER THE RADIO.

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.