Narrative:

On initial climb aircraft power setting of TO2 was not sufficient to make ord 4000 ft MSL by 8 DME restr. ATC commented on slow climb at approximately 6.5 DME. Higher climb power was selected and we believe that we cleared the 5 by 8 DME restr. Departure was planned and briefed for ord; runway 32R. 10005 ft available runway. Runway was dry. Day VFR flight conditions. Takeoff was planned and briefed as standard power; TO2 with an assumed temperature of 26 degrees C. Start and taxi were normal. During taxi; crew requested and received new performance numbers via ACARS. Data was basically unchanged; except for a 1 degree change (to 30 degrees) in assumed temperature (at). Bugs and power were inserted and verified again. Approaching the #1 position for runway 32R we informed the tower controller that we were not yet ready for takeoff; since we had not received our load closeout. The controller replied; 'that's ok; I still need you to hold in position on runway 32R.' we accepted that clearance to hold in position; based on information the relief pilot (who had been communicating with the load room) that load closeout would be ready shortly. Runway 32R was not being used for approachs. After a short wait; the load closeout was received along with a new FMC uplink of takeoff data. Since our numbers were basically unchanged; we accepted the new uplinked takeoff data. Shortly thereafter we received takeoff clearance. During takeoff roll the captain; who was flying; decided he did not like the thrust setting and increased thrust to takeoff (full power). Takeoff was continued uneventfully. After takeoff we discussed the event and concluded that our thrust was lower than it should have been. We surmised that the assumed temperature had changed; and we did not catch it. Unfortunately; the FMS deletes the takeoff thrust settings used immediately after takeoff; and we were unable to review the data we used after the event. This was a very experienced crew. Nonetheless; we missed an important check. Although our data was virtually unchanged; the last FMC uplink of the takeoff reference data apparently introduced a change and an error. This is what we missed. In our cockpit debrief the relief pilot mentioned that he had not received a takeoff data uplink during the preflight loading of the FMS. Knowing this; we suspect that the data that was uplinked may have been from the previous (domestic) leg. This problem was addressed last year in a bulletin as a caution. Although the previously mentioned caution refers to partial uplinks; we all concur that the uplink we received did not appear to be incomplete and therefore the caution would not have applied.

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Original NASA ASRS Text

Title: LATE MODIFICATIONS TO FMC PERFORMANCE DATA WHILE HOLDING IN POSITION FOR TKOF MAY HAVE RESULTED IN ERRONEOUS THRUST SETTINGS FOR DEP FROM ORD FOR B777 FLT CREW. MAY NOT HAVE MET CROSSING RESTRICTION AT EIGHT DME.

Narrative: ON INITIAL CLB ACFT PWR SETTING OF TO2 WAS NOT SUFFICIENT TO MAKE ORD 4000 FT MSL BY 8 DME RESTR. ATC COMMENTED ON SLOW CLB AT APPROX 6.5 DME. HIGHER CLB PWR WAS SELECTED AND WE BELIEVE THAT WE CLRED THE 5 BY 8 DME RESTR. DEP WAS PLANNED AND BRIEFED FOR ORD; RWY 32R. 10005 FT AVAILABLE RWY. RWY WAS DRY. DAY VFR FLT CONDITIONS. TKOF WAS PLANNED AND BRIEFED AS STANDARD PWR; TO2 WITH AN ASSUMED TEMP OF 26 DEGS C. START AND TAXI WERE NORMAL. DURING TAXI; CREW REQUESTED AND RECEIVED NEW PERFORMANCE NUMBERS VIA ACARS. DATA WAS BASICALLY UNCHANGED; EXCEPT FOR A 1 DEG CHANGE (TO 30 DEGS) IN ASSUMED TEMP (AT). BUGS AND PWR WERE INSERTED AND VERIFIED AGAIN. APCHING THE #1 POS FOR RWY 32R WE INFORMED THE TWR CTLR THAT WE WERE NOT YET READY FOR TKOF; SINCE WE HAD NOT RECEIVED OUR LOAD CLOSEOUT. THE CTLR REPLIED; 'THAT'S OK; I STILL NEED YOU TO HOLD IN POS ON RWY 32R.' WE ACCEPTED THAT CLRNC TO HOLD IN POS; BASED ON INFO THE RELIEF PLT (WHO HAD BEEN COMMUNICATING WITH THE LOAD ROOM) THAT LOAD CLOSEOUT WOULD BE READY SHORTLY. RWY 32R WAS NOT BEING USED FOR APCHS. AFTER A SHORT WAIT; THE LOAD CLOSEOUT WAS RECEIVED ALONG WITH A NEW FMC UPLINK OF TKOF DATA. SINCE OUR NUMBERS WERE BASICALLY UNCHANGED; WE ACCEPTED THE NEW UPLINKED TKOF DATA. SHORTLY THEREAFTER WE RECEIVED TKOF CLRNC. DURING TKOF ROLL THE CAPT; WHO WAS FLYING; DECIDED HE DID NOT LIKE THE THRUST SETTING AND INCREASED THRUST TO TKOF (FULL PWR). TKOF WAS CONTINUED UNEVENTFULLY. AFTER TKOF WE DISCUSSED THE EVENT AND CONCLUDED THAT OUR THRUST WAS LOWER THAN IT SHOULD HAVE BEEN. WE SURMISED THAT THE ASSUMED TEMP HAD CHANGED; AND WE DID NOT CATCH IT. UNFORTUNATELY; THE FMS DELETES THE TKOF THRUST SETTINGS USED IMMEDIATELY AFTER TKOF; AND WE WERE UNABLE TO REVIEW THE DATA WE USED AFTER THE EVENT. THIS WAS A VERY EXPERIENCED CREW. NONETHELESS; WE MISSED AN IMPORTANT CHK. ALTHOUGH OUR DATA WAS VIRTUALLY UNCHANGED; THE LAST FMC UPLINK OF THE TKOF REF DATA APPARENTLY INTRODUCED A CHANGE AND AN ERROR. THIS IS WHAT WE MISSED. IN OUR COCKPIT DEBRIEF THE RELIEF PLT MENTIONED THAT HE HAD NOT RECEIVED A TKOF DATA UPLINK DURING THE PREFLT LOADING OF THE FMS. KNOWING THIS; WE SUSPECT THAT THE DATA THAT WAS UPLINKED MAY HAVE BEEN FROM THE PREVIOUS (DOMESTIC) LEG. THIS PROB WAS ADDRESSED LAST YEAR IN A BULLETIN AS A CAUTION. ALTHOUGH THE PREVIOUSLY MENTIONED CAUTION REFERS TO PARTIAL UPLINKS; WE ALL CONCUR THAT THE UPLINK WE RECEIVED DID NOT APPEAR TO BE INCOMPLETE AND THEREFORE THE CAUTION WOULD NOT HAVE APPLIED.

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.