Narrative:

On the grnpa one arrival into las. We were told to expect runway 19L for landing. Runway 25L had already been selected in the FMC; so we changed the arrival runway. During this change we lost navigation points on the arrival without realizing it. We tracked off course a few miles and we were told by ATC to 'turn right 20 degrees and re-intercept the arrival. Track to trrop then lemnz; cleared for the visual.' the visual was completed with no further incident. I will pay closer attention to assure that the remaining points are correct for the remainder of the arrival being flown.supplemental information from acn 762983: before commencing the grnpa one arrival into las; all checklists were completed and the visual runway 25L was briefed and entered into the FMC by the first officer. While descending via the arrival; passing dublx intersection; we were given runway 19L for our arrival runway. After making the crossing restriction of frawg at 8000 ft first officer entered runway 19L into the FMC and confirmed with captain. With first officer being new to the company and aircraft; complicated by the first time to arrive into las using runway 19L/right; I was thinking through this visual approach (altitudes; course; terrain; etc). During the same timeframe first officer noticed parallel traffic and captain inquired first officer if we were on a heading. I observed at that point the aircraft was in cws roll and the arrival was not shown on the du. ATC notified us that we were deviating off course and asked us to turn 20 degrees right to rejoin the arrival. Captain entered the trrop and lemnz intersections in the FMC and first officer used heading mode to turn back on course. Approach then cleared us for the visual runway 19L via the lemnz intersection and switched us to las tower. On check-in with tower; arrival runway was changed to runway 19R and our landing clearance was issued. Aircraft arrived in las without further event. While being new to this FMC; I apparently dropped the arrival when entering the new runway. Complicating matters; the captain did not notice the error when crosschecking the FMC entry. This input error coupled with poor monitoring with the distraction from the runway change caused the mode change with the autopilot and the lateral deviation. In conclusion; first officer should have just continued the arrival and proceeded with the visual runway 19L without changing the runway in the FMC. By changing the FMC during a high workload time it started the chain of events. Furthermore; I as the first officer (PF) should have asked the captain (pm) to make the FMC change if there was one to be made.

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Original NASA ASRS Text

Title: LGT INBOUND TO LAS RECEIVES LATE RWY CHANGE. REPROGRAMMING OF FMS RESULTS IN LOSS OF WAYPOINTS ON ASSIGNED RNAV STAR.

Narrative: ON THE GRNPA ONE ARRIVAL INTO LAS. WE WERE TOLD TO EXPECT RWY 19L FOR LANDING. RWY 25L HAD ALREADY BEEN SELECTED IN THE FMC; SO WE CHANGED THE ARRIVAL RWY. DURING THIS CHANGE WE LOST NAV POINTS ON THE ARRIVAL WITHOUT REALIZING IT. WE TRACKED OFF COURSE A FEW MILES AND WE WERE TOLD BY ATC TO 'TURN RIGHT 20 DEGREES AND RE-INTERCEPT THE ARRIVAL. TRACK TO TRROP THEN LEMNZ; CLEARED FOR THE VISUAL.' THE VISUAL WAS COMPLETED WITH NO FURTHER INCIDENT. I WILL PAY CLOSER ATTENTION TO ASSURE THAT THE REMAINING POINTS ARE CORRECT FOR THE REMAINDER OF THE ARRIVAL BEING FLOWN.SUPPLEMENTAL INFO FROM ACN 762983: BEFORE COMMENCING THE GRNPA ONE ARRIVAL INTO LAS; ALL CHECKLISTS WERE COMPLETED AND THE VISUAL RWY 25L WAS BRIEFED AND ENTERED INTO THE FMC BY THE FO. WHILE DESCENDING VIA THE ARRIVAL; PASSING DUBLX INTERSECTION; WE WERE GIVEN RWY 19L FOR OUR ARRIVAL RWY. AFTER MAKING THE CROSSING RESTRICTION OF FRAWG AT 8000 FT FO ENTERED RWY 19L INTO THE FMC AND CONFIRMED WITH CAPTAIN. WITH FO BEING NEW TO THE COMPANY AND AIRCRAFT; COMPLICATED BY THE FIRST TIME TO ARRIVE INTO LAS USING RWY 19L/R; I WAS THINKING THROUGH THIS VISUAL APPROACH (ALTITUDES; COURSE; TERRAIN; ETC). DURING THE SAME TIMEFRAME FO NOTICED PARALLEL TRAFFIC AND CAPTAIN INQUIRED FO IF WE WERE ON A HEADING. I OBSERVED AT THAT POINT THE AIRCRAFT WAS IN CWS ROLL AND THE ARRIVAL WAS NOT SHOWN ON THE DU. ATC NOTIFIED US THAT WE WERE DEVIATING OFF COURSE AND ASKED US TO TURN 20 DEGREES RIGHT TO REJOIN THE ARRIVAL. CAPTAIN ENTERED THE TRROP AND LEMNZ INTERSECTIONS IN THE FMC AND FO USED HEADING MODE TO TURN BACK ON COURSE. APPROACH THEN CLEARED US FOR THE VISUAL RWY 19L VIA THE LEMNZ INTERSECTION AND SWITCHED US TO LAS TOWER. ON CHECK-IN WITH TOWER; ARRIVAL RWY WAS CHANGED TO RWY 19R AND OUR LANDING CLEARANCE WAS ISSUED. AIRCRAFT ARRIVED IN LAS WITHOUT FURTHER EVENT. WHILE BEING NEW TO THIS FMC; I APPARENTLY DROPPED THE ARRIVAL WHEN ENTERING THE NEW RWY. COMPLICATING MATTERS; THE CAPTAIN DID NOT NOTICE THE ERROR WHEN CROSSCHECKING THE FMC ENTRY. THIS INPUT ERROR COUPLED WITH POOR MONITORING WITH THE DISTRACTION FROM THE RWY CHANGE CAUSED THE MODE CHANGE WITH THE AUTOPILOT AND THE LATERAL DEVIATION. IN CONCLUSION; FO SHOULD HAVE JUST CONTINUED THE ARRIVAL AND PROCEEDED WITH THE VISUAL RWY 19L WITHOUT CHANGING THE RWY IN THE FMC. BY CHANGING THE FMC DURING A HIGH WORKLOAD TIME IT STARTED THE CHAIN OF EVENTS. FURTHERMORE; I AS THE FO (PF) SHOULD HAVE ASKED THE CAPTAIN (PM) TO MAKE THE FMC CHANGE IF THERE WAS ONE TO BE MADE.

Data retrieved from NASA's ASRS site as of January 2009 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.