Narrative:

Preparing to depart las, I put all active runways and current ATIS into the opc. ATIS was calling light winds, with runways 19 and 25 in use, well below maximum ATOG for both runways 25R and 25L. ATIS called low level windshear advisory, so that box was active in the opc. On taxi out, ground called new winds for us, 130 degrees/12 KTS. I put those winds into the opc, deselecting all runways except the one we were taxiing to runway 25R, so that the opc could quickly recalculate. No problems noted with these winds. No change in v-spds (125-15-130), still maximum N1 (due to 'LLWS' box). We were cleared into position and hold on runway 25R. Long delay ensued due to departures and arrs on runways 19L and 19R. Tower called winds 130 degrees/12 KTS gusting 24 KTS, then offered us a runway 25L departure. Captain answered 'yes' and we were cleared position and hold on runway 25L. I pulled out the opc, but realized that the time it would take for it to calculate everything, after I would back out to enter the new winds and new runway, would be excessive. I rationalize that 1) we were already using maximum N1, 2)we had 6000-7000 ft stopping margin on runway 25R, 3) the flight path is similar for the 2 runways and 4) we're in a fairly light B-700. ('We have great performance!'), so it'll work fine. Bottom line, though, we hurried, and I didn't have the captain wait for me to run the numbers. At cruise altitude, I did run the numbers, and discovered that the last winds tower had given us had a 12 KT tailwind gust component. Also realized we hadn't changed the departure runway in the FMC to runway 25L. I'm confident I'd have put everything in if it had been a 'big' change (ie, to runway 19), but I missed 2 key actions (FMC and opc) when it was a 'small' (runways 25L to runway 25R) change. Lessons learned: 1) every runway change is a 'red flag' event -- don't rush through it! 2) pull out the chart with wind components to check for tail/xwinds out of limits -- much quicker than the opc! 3) when las is using runway 19's as well as runway 25's, they may assign runway 25L since it doesn't intersect the runways 19's as runway 25 does. Always keep runway 25L in the opc. 4) don't rush!

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Original NASA ASRS Text

Title: ACCEPTING AN OFFER FROM THE TWR TO DEPART RWY 25L INSTEAD OF RWY 25R, AS PLANNED. TO PREVENT FURTHER DELAY A B737-700 CREW DOES NOT RE-COMPUTE THEIR PERFORMANCE. ONCE AIRBORNE THEY DO RE-COMPUTE FINDING THEY HAVE EXCEEDED THE TAILWIND LIMIT FOR TKOF.

Narrative: PREPARING TO DEPART LAS, I PUT ALL ACTIVE RWYS AND CURRENT ATIS INTO THE OPC. ATIS WAS CALLING LIGHT WINDS, WITH RWYS 19 AND 25 IN USE, WELL BELOW MAX ATOG FOR BOTH RWYS 25R AND 25L. ATIS CALLED LOW LEVEL WINDSHEAR ADVISORY, SO THAT BOX WAS ACTIVE IN THE OPC. ON TAXI OUT, GND CALLED NEW WINDS FOR US, 130 DEGS/12 KTS. I PUT THOSE WINDS INTO THE OPC, DESELECTING ALL RWYS EXCEPT THE ONE WE WERE TAXIING TO RWY 25R, SO THAT THE OPC COULD QUICKLY RECALCULATE. NO PROBS NOTED WITH THESE WINDS. NO CHANGE IN V-SPDS (125-15-130), STILL MAX N1 (DUE TO 'LLWS' BOX). WE WERE CLRED INTO POS AND HOLD ON RWY 25R. LONG DELAY ENSUED DUE TO DEPS AND ARRS ON RWYS 19L AND 19R. TWR CALLED WINDS 130 DEGS/12 KTS GUSTING 24 KTS, THEN OFFERED US A RWY 25L DEP. CAPT ANSWERED 'YES' AND WE WERE CLRED POS AND HOLD ON RWY 25L. I PULLED OUT THE OPC, BUT REALIZED THAT THE TIME IT WOULD TAKE FOR IT TO CALCULATE EVERYTHING, AFTER I WOULD BACK OUT TO ENTER THE NEW WINDS AND NEW RWY, WOULD BE EXCESSIVE. I RATIONALIZE THAT 1) WE WERE ALREADY USING MAX N1, 2)WE HAD 6000-7000 FT STOPPING MARGIN ON RWY 25R, 3) THE FLT PATH IS SIMILAR FOR THE 2 RWYS AND 4) WE'RE IN A FAIRLY LIGHT B-700. ('WE HAVE GREAT PERFORMANCE!'), SO IT'LL WORK FINE. BOTTOM LINE, THOUGH, WE HURRIED, AND I DIDN'T HAVE THE CAPT WAIT FOR ME TO RUN THE NUMBERS. AT CRUISE ALT, I DID RUN THE NUMBERS, AND DISCOVERED THAT THE LAST WINDS TWR HAD GIVEN US HAD A 12 KT TAILWIND GUST COMPONENT. ALSO REALIZED WE HADN'T CHANGED THE DEP RWY IN THE FMC TO RWY 25L. I'M CONFIDENT I'D HAVE PUT EVERYTHING IN IF IT HAD BEEN A 'BIG' CHANGE (IE, TO RWY 19), BUT I MISSED 2 KEY ACTIONS (FMC AND OPC) WHEN IT WAS A 'SMALL' (RWYS 25L TO RWY 25R) CHANGE. LESSONS LEARNED: 1) EVERY RWY CHANGE IS A 'RED FLAG' EVENT -- DON'T RUSH THROUGH IT! 2) PULL OUT THE CHART WITH WIND COMPONENTS TO CHK FOR TAIL/XWINDS OUT OF LIMITS -- MUCH QUICKER THAN THE OPC! 3) WHEN LAS IS USING RWY 19'S AS WELL AS RWY 25'S, THEY MAY ASSIGN RWY 25L SINCE IT DOESN'T INTERSECT THE RWYS 19'S AS RWY 25 DOES. ALWAYS KEEP RWY 25L IN THE OPC. 4) DON'T RUSH!

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.