Narrative:

As PNF, one of my preflight duties is to ensure that the FMC is properly loaded. One item is to verify that the captain has loaded our cleared route. This is often done during a somewhat busy time when we are dealing with maintenance items and flight attendant's needs. Our filed route from seattle to washington dulles began with: sea J70 lwt MLS J90 abr. The revised segment of our pre-departure clearance was: 'BLUIT3 bluit mlp.' bluit intersection lies along J70, and the airway leads to mlp. A direct routing of bluit to mlp is slightly north of the J70 airway. Around spokane the controller queried whether we were proceeding direct to mlp. I quickly looked at the pre departure clearance and the FMC and saw that we had not programmed the revised routing. Although the deviation was only a few mi (at most), the captain had programmed MLS instead of mlp after bluit intersection. Therefore, we were headed to miles city (MLS) instead of mullan pass (mlp) after bluit intersection. The cause of the error was incorrect programming and verification of a revised pre-departure clearance. Also, I feel that the similarity between the designators 'MLS' and 'mlp' may have lead to the oversight. It is not uncommon to see that a revised segment is actually the original filed route, which might have led to complacency.

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Original NASA ASRS Text

Title: FMS PROGRAMMED INCORRECTLY AND ACR GOES OFF COURSE A LITTLE.

Narrative: AS PNF, ONE OF MY PREFLT DUTIES IS TO ENSURE THAT THE FMC IS PROPERLY LOADED. ONE ITEM IS TO VERIFY THAT THE CAPT HAS LOADED OUR CLRED RTE. THIS IS OFTEN DONE DURING A SOMEWHAT BUSY TIME WHEN WE ARE DEALING WITH MAINT ITEMS AND FLT ATTENDANT'S NEEDS. OUR FILED RTE FROM SEATTLE TO WASHINGTON DULLES BEGAN WITH: SEA J70 LWT MLS J90 ABR. THE REVISED SEGMENT OF OUR PRE-DEP CLRNC WAS: 'BLUIT3 BLUIT MLP.' BLUIT INTXN LIES ALONG J70, AND THE AIRWAY LEADS TO MLP. A DIRECT ROUTING OF BLUIT TO MLP IS SLIGHTLY N OF THE J70 AIRWAY. AROUND SPOKANE THE CTLR QUERIED WHETHER WE WERE PROCEEDING DIRECT TO MLP. I QUICKLY LOOKED AT THE PDC AND THE FMC AND SAW THAT WE HAD NOT PROGRAMMED THE REVISED ROUTING. ALTHOUGH THE DEV WAS ONLY A FEW MI (AT MOST), THE CAPT HAD PROGRAMMED MLS INSTEAD OF MLP AFTER BLUIT INTXN. THEREFORE, WE WERE HEADED TO MILES CITY (MLS) INSTEAD OF MULLAN PASS (MLP) AFTER BLUIT INTXN. THE CAUSE OF THE ERROR WAS INCORRECT PROGRAMMING AND VERIFICATION OF A REVISED PRE-DEP CLRNC. ALSO, I FEEL THAT THE SIMILARITY BTWN THE DESIGNATORS 'MLS' AND 'MLP' MAY HAVE LEAD TO THE OVERSIGHT. IT IS NOT UNCOMMON TO SEE THAT A REVISED SEGMENT IS ACTUALLY THE ORIGINAL FILED RTE, WHICH MIGHT HAVE LED TO COMPLACENCY.

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.