EMB170 FLT CREW REJECTS TWO TKOFS AFTER SPEEDS DROP OUT OF FMC DURING TKOF ROLL. THE THIRD ATTEMPT IS SUCCESSFUL AFTER COMPLETE POWER DOWN AND RESTART.

Narrative

ACFT HAD NEW LOAD IN FMS. WE WERE ORIGINALLY GIVEN XXR FOR DEP; BUT THAT WAS THEN CHANGED TO XXL. THE TKOF ROLL BEGAN NORMALLY WITH THE FO AS PF. AROUND 100 KTS THE FO DECLARED THAT THE SPDS HAD DROPPED OUT. I CONFIRMED THAT AND CALLED FOR THE ABORT. THE ABORT ITSELF WAS UNEVENTFUL. WE CLRED THE RWY COMPLETED THE CHKLIST AND ASKED ATC FOR A MINUTE TO TROUBLESHOOT THE PROB. WE OBSERVED THAT RWY XXR HAD BEEN INADVERTENTLY LEFT IN THE FMS. WE COULD SEE NO OTHER ERRORS OR ABNORMALITIES. EVERYTHING WAS DOUBLE-CHKED AND THE CORRECT RWY FOR DEP (XXR THIS TIME) WAS PROGRAMMED INTO THE FMS. ALL CHKLISTS WERE COMPLETED AND WE INITIATED A TKOF ON RWY XXR. THE SAME PROB WAS OBSERVED; AND THE TKOF WAS ONCE AGAIN ABORTED UNEVENTFULLY. THIS TIME THE ACFT WAS PARKED ON THE RAMP AT THE DIRECTION OF ATC; THE #2 ENG WAS SHUT DOWN TO CONSERVE FUEL AND I CALLED MAINT CTL. AT THE DIRECTION OF MAINT ALL ENGS WERE SHUT DOWN AND ALL PWR REMOVED FROM THE ACFT AND SYS. AGAIN AT THE DIRECTION OF MAINT PERSONNEL THE ACFT WAS THEN ONCE AGAIN STARTED AND PROGRAMMED FOR DEP. MAINT BELIEVED THIS COULD SOLVE THE PROB. ALL CHKLISTS WERE COMPLETED AND A NORMAL AND UNEVENTFUL TKOF WAS MADE OFF XXR WITH NO ABNORMALITIES OBSERVED.