Narrative:

During takeoff roll from sfo; after the 80 KTS call by the first officer; the primary relief pilot observed that the v-spds were not displayed on either pilot's pfd. The first officer (PNF) pulled up the takeoff reference page and the v-spds were blank. V2 speed was set on the MCP in the speed window. Because the v-spds were not displayed anywhere in the cockpit; the crew did not know what the V1 or vr speeds were. As a result; the V1 and vr callouts were not made. The decision was made to get as close to V2 before rotation. The captain (PF) rotated a few KTS before V2 with about 2000-3000 ft remaining on runway 28R. We were lucky that we did not encounter any airplane malfunction during takeoff roll that would have required an abort; as we would not have been able to determine if we were below or above V1. We were lucky that we were lightweight and could use the available runway to get closer to V2 before rotation. If we had been at maximum gross TOGW; we would have had smaller window for error. Luckily; our crew was very experienced and knew not to rotate early. Other inexperienced crews encountering the same problem at maximum TOGW may not be so lucky. If a crew does not know what V1 or vr is during takeoff; the possibility for sustaining aircraft damage and/or loss of life during the takeoff exists.

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Original NASA ASRS Text

Title: B747-400 FLT CREW ON TKOF ROLL DISCOVERS TKOF SAFETY SPDS ARE NOT DISPLAYED ON EITHER PLT'S PFD IAS TAPE.

Narrative: DURING TKOF ROLL FROM SFO; AFTER THE 80 KTS CALL BY THE FO; THE PRIMARY RELIEF PLT OBSERVED THAT THE V-SPDS WERE NOT DISPLAYED ON EITHER PLT'S PFD. THE FO (PNF) PULLED UP THE TKOF REF PAGE AND THE V-SPDS WERE BLANK. V2 SPD WAS SET ON THE MCP IN THE SPD WINDOW. BECAUSE THE V-SPDS WERE NOT DISPLAYED ANYWHERE IN THE COCKPIT; THE CREW DID NOT KNOW WHAT THE V1 OR VR SPDS WERE. AS A RESULT; THE V1 AND VR CALLOUTS WERE NOT MADE. THE DECISION WAS MADE TO GET AS CLOSE TO V2 BEFORE ROTATION. THE CAPT (PF) ROTATED A FEW KTS BEFORE V2 WITH ABOUT 2000-3000 FT REMAINING ON RWY 28R. WE WERE LUCKY THAT WE DID NOT ENCOUNTER ANY AIRPLANE MALFUNCTION DURING TKOF ROLL THAT WOULD HAVE REQUIRED AN ABORT; AS WE WOULD NOT HAVE BEEN ABLE TO DETERMINE IF WE WERE BELOW OR ABOVE V1. WE WERE LUCKY THAT WE WERE LIGHTWEIGHT AND COULD USE THE AVAILABLE RWY TO GET CLOSER TO V2 BEFORE ROTATION. IF WE HAD BEEN AT MAX GROSS TOGW; WE WOULD HAVE HAD SMALLER WINDOW FOR ERROR. LUCKILY; OUR CREW WAS VERY EXPERIENCED AND KNEW NOT TO ROTATE EARLY. OTHER INEXPERIENCED CREWS ENCOUNTERING THE SAME PROB AT MAX TOGW MAY NOT BE SO LUCKY. IF A CREW DOES NOT KNOW WHAT V1 OR VR IS DURING TKOF; THE POSSIBILITY FOR SUSTAINING ACFT DAMAGE AND/OR LOSS OF LIFE DURING THE TKOF EXISTS.

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.