Narrative:

We received that arlin 8 STAR into phoenix, it was my leg the autoplt was on. We were in an medium large transport advanced technology non EFIS aircraft. In the aircraft our primary mode of navigation is an inertial navigation system with a flight management computer (FMC) and a computer display unit (CDU) for entering commands into the FMC. On the arlin 8 you proceed outbnd from mohak intersection to a fix that is designated by only latitude and longitude coords followed by a turn to hydrr intersection. Prior to mohak I went to the arrival page on the CDU to put in the active runway at phoenix. From there you go to the legs page, this is where the order and the name of all fixes that will be flown are listed. The legs page showed a gap prior to hydrr, what is called a 'route discontinuity' this is normal after selecting a different runway or path then what was preprogrammed at our departure airport. Since that latitude/long fix did not have a name it was not listed on the legs page. The CDU showed us going to our active fix mohak then a row of empty boxes (route discontinuity) then hydrr intersection, paynt, arlin and so on. So instinctively, I closed up the gap by selecting the next fix after the empty boxes, hydrr intersection, this was incorrect. What the autoplt flew was from mohak direct to hydrr intersection bypassing the latitude/long fix. We went about 8 mi north of course when ATC advise us of our path and gave us a heading to get back on course. As we were making the turn the controller said we had just entered restr airspace. There are several factors I feel that caused this deviation. The first being no name on that latitude/long fix after mohak, every other fix on this STAR had coords and a name, why not this one. If there was a name for this fix it would have been entered into the FMC's data base. Secondly, our flight operations manual does not require the PNF to back up the inertial navigation computer with raw data. If the captain would have had his VOR receiver tuned for that outbnd right from mohak we would have caught the error.

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Original NASA ASRS Text

Title: ACR MLG EXPERIENCES TRACK DEVIATION ON ARLIN EIGHT STAR TO PHX THROUGH MISPROGRAMMING OF FMC.

Narrative: WE RECEIVED THAT ARLIN 8 STAR INTO PHOENIX, IT WAS MY LEG THE AUTOPLT WAS ON. WE WERE IN AN MLG ADVANCED TECHNOLOGY NON EFIS ACFT. IN THE ACFT OUR PRIMARY MODE OF NAV IS AN INERTIAL NAV SYS WITH A FLT MGMNT COMPUTER (FMC) AND A COMPUTER DISPLAY UNIT (CDU) FOR ENTERING COMMANDS INTO THE FMC. ON THE ARLIN 8 YOU PROCEED OUTBND FROM MOHAK INTXN TO A FIX THAT IS DESIGNATED BY ONLY LATITUDE AND LONGITUDE COORDS FOLLOWED BY A TURN TO HYDRR INTXN. PRIOR TO MOHAK I WENT TO THE ARR PAGE ON THE CDU TO PUT IN THE ACTIVE RWY AT PHOENIX. FROM THERE YOU GO TO THE LEGS PAGE, THIS IS WHERE THE ORDER AND THE NAME OF ALL FIXES THAT WILL BE FLOWN ARE LISTED. THE LEGS PAGE SHOWED A GAP PRIOR TO HYDRR, WHAT IS CALLED A 'RTE DISCONTINUITY' THIS IS NORMAL AFTER SELECTING A DIFFERENT RWY OR PATH THEN WHAT WAS PREPROGRAMMED AT OUR DEP ARPT. SINCE THAT LAT/LONG FIX DID NOT HAVE A NAME IT WAS NOT LISTED ON THE LEGS PAGE. THE CDU SHOWED US GOING TO OUR ACTIVE FIX MOHAK THEN A ROW OF EMPTY BOXES (RTE DISCONTINUITY) THEN HYDRR INTXN, PAYNT, ARLIN AND SO ON. SO INSTINCTIVELY, I CLOSED UP THE GAP BY SELECTING THE NEXT FIX AFTER THE EMPTY BOXES, HYDRR INTXN, THIS WAS INCORRECT. WHAT THE AUTOPLT FLEW WAS FROM MOHAK DIRECT TO HYDRR INTXN BYPASSING THE LAT/LONG FIX. WE WENT ABOUT 8 MI N OF COURSE WHEN ATC ADVISE US OF OUR PATH AND GAVE US A HDG TO GET BACK ON COURSE. AS WE WERE MAKING THE TURN THE CTLR SAID WE HAD JUST ENTERED RESTR AIRSPACE. THERE ARE SEVERAL FACTORS I FEEL THAT CAUSED THIS DEV. THE FIRST BEING NO NAME ON THAT LAT/LONG FIX AFTER MOHAK, EVERY OTHER FIX ON THIS STAR HAD COORDS AND A NAME, WHY NOT THIS ONE. IF THERE WAS A NAME FOR THIS FIX IT WOULD HAVE BEEN ENTERED INTO THE FMC'S DATA BASE. SECONDLY, OUR FLT OPS MANUAL DOES NOT REQUIRE THE PNF TO BACK UP THE INERTIAL NAV COMPUTER WITH RAW DATA. IF THE CAPT WOULD HAVE HAD HIS VOR RECEIVER TUNED FOR THAT OUTBND R FROM MOHAK WE WOULD HAVE CAUGHT THE ERROR.

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.